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Classifications

ISDS Skeletal Nosology

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Inheritance

2

Autosomal dominant HP:0000006

Many reported PLCB4 and GNAI3 families show autosomal dominant inheritance, often with variable expressivity and incomplete penetrance.

Autosomal dominant inheritance Expressivity: VARIABLE

Show evidence (2 references)

PMID:28328130 SUPPORT BACKGROUND Human Clinical

"Auriculocondylar syndrome, mainly characterized by micrognathia, small mandibular condyle, and question mark ears, is a rare disease segregating in an autosomal dominant pattern in the majority of the families reported in the literature."

This cohort review directly supports autosomal dominant inheritance as the most common reported pattern.

PMID:38618928 SUPPORT REVIEW SYNTHESIS Human Clinical

"As with other studies examining familial cases of ARCND2, incomplete penetrance and variable expressivity were observed within different families' heterozygous mutations in PLCB4 gene."

The 2024 review supports variable expressivity and incomplete penetrance in PLCB4-related families.

Autosomal recessive HP:0000007

Recessive auriculocondylar syndrome has been reported for EDN1 variants and for biallelic PLCB4 loss-of-function lesions.

Autosomal recessive inheritance

Show evidence (2 references)

PMID:24268655 SUPPORT PRIMARY RESULT Human Clinical

"By whole-exome sequencing (WES), we identified a homozygous substitution in a furin cleavage site of the EDN1 proprotein in ACS-affected siblings born to consanguineous parents."

This directly supports recessive EDN1-related auriculocondylar syndrome.

PMID:23315542 SUPPORT PRIMARY RESULT Human Clinical

"CONCLUSIONS: These findings indicate that ACS is not only genetically heterogeneous but also an autosomal dominant or recessive condition according to the nature of the PLCB4 gene lesion."

This directly supports recessive inheritance for some PLCB4 lesions.

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Subtypes

6

ARCND1 (GNAI3-related) MONDO:0011234

GNAI3 hgnc:4387

Usually autosomal dominant auriculocondylar syndrome caused by heterozygous GNAI3 variants affecting GDP/GTP-binding motifs and EDN1 pathway signaling.

Show evidence (2 references)

PMID:38618928 SUPPORT BACKGROUND Human Clinical

"Four subtypes of ARCND have been described so far, that is, ARCND1 (OMIM # 602483), ARCND2 (ARCND2A, OMIM # 614669; ARCND2B, OMIM # 620458), ARCND3 (OMIM # 615706), and ARCND4 (OMIM # 620457)."

This identifies ARCND1 and its OMIM identifier.

PMID:22560091 SUPPORT PRIMARY RESULT Human Clinical

"In both kindreds, the p.Gly40Arg variant was inherited; in one case (S011) it was inherited from an affected mother (S012-P), and in the other (S008), from an unaffected father (S009-P), documenting incomplete penetrance."

Two molecularly characterized families establish dominant inheritance with incomplete penetrance.

ARCND2A (PLCB4-related, autosomal dominant) MONDO:0013845

PLCB4 hgnc:9059

Autosomal dominant PLCB4-related auriculocondylar syndrome, typically caused by heterozygous missense variants. Note on the binding: MONDO has not adopted OMIM's ARCND2A/2B relabel, so MONDO:0013845 is still plain "auriculocondylar syndrome 2" with no "2A" synonym and no inheritance axiom. It is bound here on the strength of its OMIM:614669 xref, which matches this row exactly. It and MONDO:0957544 (bound to the ARCND2B row below) both point at PLCB4 and are distinguished only by OMIM entry, not by a dominant/recessive assertion in MONDO.

Show evidence (2 references)

PMID:38618928 SUPPORT BACKGROUND Human Clinical

"Four subtypes of ARCND have been described so far, that is, ARCND1 (OMIM # 602483), ARCND2 (ARCND2A, OMIM # 614669; ARCND2B, OMIM # 620458), ARCND3 (OMIM # 615706), and ARCND4 (OMIM # 620457)."

This identifies ARCND2A and its OMIM identifier.

PMID:35284927 SUPPORT PRIMARY RESULT In Vitro

"These results illustrate that PLCB4 p.Arg621His interferes with PLCB activity even when it is expressed at a sub-stoichiometric level relative to wild-type PLCB4, exemplifying a characteristic of a dominant-negative protein."

DAG-sensor BRET detects dominant interference by Arg621His; three additional tested missense variants also attenuated the response.

ARCND2B (PLCB4-related, autosomal recessive) MONDO:0957544

PLCB4 hgnc:9059

Autosomal recessive PLCB4-related auriculocondylar syndrome caused by biallelic loss-of-function or damaging PLCB4 variants.

Show evidence (2 references)

PMID:38618928 SUPPORT BACKGROUND Human Clinical

"Four subtypes of ARCND have been described so far, that is, ARCND1 (OMIM # 602483), ARCND2 (ARCND2A, OMIM # 614669; ARCND2B, OMIM # 620458), ARCND3 (OMIM # 615706), and ARCND4 (OMIM # 620457)."

This identifies ARCND2B and its OMIM identifier.

PMID:23315542 SUPPORT PRIMARY RESULT Human Clinical

"The consanguineous parents of the patient with a homozygous PLCB4 deletion each harboured the heterozygous deletion, but did not present the ACS phenotype, further suggesting that ACS is not caused by PLCB4 haploinsufficiency."

Segregation demonstrates a recessive deletion mechanism in one family.

ARCND3 (EDN1-related) MONDO:0014312

EDN1 hgnc:3176

EDN1-related ACS is established with recessive alleles. Dominant EDN1 variants also cause isolated question-mark ears, and a heterozygous start-loss case had mild mandibular involvement. Residual ligand activity is a proposed explanation for allelic differences, not a direct patient-allele assay.

Show evidence (2 references)

PMID:38618928 SUPPORT BACKGROUND Human Clinical

"Four subtypes of ARCND have been described so far, that is, ARCND1 (OMIM # 602483), ARCND2 (ARCND2A, OMIM # 614669; ARCND2B, OMIM # 620458), ARCND3 (OMIM # 615706), and ARCND4 (OMIM # 620457)."

This identifies ARCND3 and its OMIM identifier.

PMID:24268655 SUPPORT PRIMARY RESULT Human Clinical

"In family F1, the unaffected parents and child were heterozygous for the mutation, whereas the three affected siblings were homozygous, indicating that the allele encoding the p.Lys91Glu substitution behaves in a recessive manner."

Segregation supports recessive inheritance of Lys91Glu in this family.

ARCND4 (TWIST1 regulatory duplication) MONDO:0957543

TWIST1 hgnc:12428

A 430-kb tandem duplication within HDAC9, outside TWIST1 coding sequence, segregated in one family. It encompasses candidate TWIST1 regulatory elements and is associated with increased TWIST1 and HDAC9 expression in patient-derived neural-crest cells; the causal contributions of these changes remain unresolved.

Show evidence (2 references)

PMID:38618928 SUPPORT BACKGROUND Human Clinical

"Four subtypes of ARCND have been described so far, that is, ARCND1 (OMIM # 602483), ARCND2 (ARCND2A, OMIM # 614669; ARCND2B, OMIM # 620458), ARCND3 (OMIM # 615706), and ARCND4 (OMIM # 620457)."

This identifies ARCND4 and its OMIM identifier.

PMID:34750192 SUPPORT PRIMARY RESULT Human Clinical

"The duplication spanned 430 302 bp (NC_000007.14:g.18437239_18867540dup) telomeric to TWIST1, covering most of the HDAC9 gene."

A segregating tandem duplication in one four-generation family defines the regulatory locus; TWIST1 coding sequence is not duplicated.

Isolated question-mark ears (dominant EDN1) MONDO:0013013

EDN1 hgnc:3176 Autosomal dominant inheritance

The mild end of the EDN1 arm: the lobe-helix defect without the mandibular and condylar features, transmitted vertically. It is recorded as a subtype row rather than a separate entry because MONDO files it under auriculocondylar syndrome and because it shares this entry's gene, its EDN1 Disease Alleles and Reduced Bioactive EDN1 Availability nodes, and its question-mark-ear phenotype; what separates it from the ARCND3 row is the allele's dose, not the mechanism. The founding report's proposed model is that heterozygous null alleles give isolated ears while hypomorphic alleles give the syndrome only when homozygous, which remains a model rather than a measured allele series.

Show evidence (2 references)

PMID:24268655 SUPPORT PRIMARY RESULT Human Clinical

"WES of two cases with vertical transmission of isolated QMEs revealed a stop mutation in EDN1 in one family and a missense substitution of a highly conserved residue in the mature EDN1 peptide in the other."

The gene-disease assertion this subtype row carries, with the vertical transmission that makes it the dominant arm.

PMID:24268655 SUPPORT PRIMARY RESULT Human Clinical

"The different modes of inheritance suggest that the degree of residual EDN1 activity differs depending on the mutation."

The authors' own account of why the same gene yields an isolated ear defect in one family and the full syndrome in another; it is offered as a suggestion, which is why the description does not state it as established.

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Discussions and Knowledge Gaps

3

Which regulatory and cellular changes mediate the HDAC9-region duplication phenotype?

KNOWLEDGE GAP arcnd_regulatory_mediation

Attached to

pathophysiology#HDAC9-TWIST1 Regulatory Duplication pathophysiology#Increased Neural Crest TWIST1 Expression

Segregation, nonpatient Capture-C and patient-cell expression findings support a regulatory locus. They do not isolate TWIST1 from HDAC9 or establish that the scratch and osteogenic readouts cause the human jaw phenotype. No serial TWIST1-to-migration-to-osteogenesis causal chain is asserted.

Show evidence (4 references)

PMID:34750192 SUPPORT PRIMARY RESULT Human Clinical

"The duplication spanned 430 302 bp (NC_000007.14:g.18437239_18867540dup) telomeric to TWIST1, covering most of the HDAC9 gene."

A segregating tandem duplication in one four-generation family defines the regulatory locus; TWIST1 coding sequence is not duplicated.

PMID:34750192 SUPPORT INDIRECT PRIMARY RESULT In Vitro

"However, an increase in HDAC9 (3.15-fold, unpaired t-test p=0.009) and TWIST1 (2.03-fold, unpaired t-test p=0.03) mRNA was observed in the ARCND-iNCC (figure 2A, B) compared with controls (unpaired t-test)."

Three affected-donor iPSC-derived neural-crest cultures show increased transcripts relative to three controls; no isogenic correction isolates the causal mediator.

PMID:34750192 SUPPORT INDIRECT PRIMARY RESULT In Vitro

"Although no significant difference in cell cycle distribution was detected between patient and control cells, a significant decrease in migratory capacity of ARCND iNCCs was observed compared with controls (4.3-fold decrease, Student’s t-test, p=0.0009) (figure 2C–E)."

A 24-hour scratch assay measures reduced wound closure in the patient-derived cultures; it does not measure migration into human pharyngeal arches.

+ 1 more reference

How do variant mechanism and species affect the craniofacial phenotype?

HUMAN MODEL MISMATCH arcnd_species_and_alleles

Attached to

pathophysiology#Reduced EDNRA-Dependent Phospholipase C Activity pathophysiology#Abnormal Mandibular Skeletal Morphogenesis

Human recessive PLCB4 loss-of-function disease coexists with reports of normal skull morphology in Plcb4-null mice. The Arg621His founder experiment tested homozygous and knock-in/indel genotypes, not a simple heterozygote. Fish plcb3 mutants and broad endothelin-pathway knockouts establish developmental requirements without making every model equivalent to a human ACS allele.

Show evidence (2 references)

PMID:35284927 SUPPORT PRIMARY RESULT Model Organism

"Of the 69 embryos harvested at E18.5, we identified three embryos harboring at least one knock-in allele; one was homozygous for the knock-in allele (Plcb4KI/KI) and the other two were compound heterozygotes harboring the knock-in allele and an insertion/deletion (indel) allele generated by..."

The actual founders comprise one homozygote and two knock-in/indel embryos, not simple heterozygotes.

PMID:27072656 SUPPORT REVIEW SYNTHESIS Model Organism

"knockout mice lacking PLCβ4 do not display a craniofacial phenotype"

The mechanistic study reviews an established species/model discrepancy.

Which extra-craniofacial findings are causally attributable to individual ACS genotypes?

KNOWLEDGE GAP arcnd_extra_craniofacial_scope

Attached to

phenotypes#Central apnea phenotypes#Cerebral arteriovenous malformation

Central apnea may persist after correction of mechanical obstruction. Small series report vascular, rib, developmental and genital findings, but do not establish precise population risks or the cellular intermediates. These observations are retained without forcing every finding through mandibular homeosis.

Show evidence (2 references)

url:https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf SUPPORT REVIEW SYNTHESIS Human Clinical

"Central sleep apnea has previously been reported in patients with ACS."

The clinical synthesis distinguishes central apnea from the structural obstructive component.

url:https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf SUPPORT PRIMARY RESULT Human Clinical

"Cerebrovascular malformations were detected by brain MRI in two individuals with no neurological symptoms."

The source documents two observations without establishing a causal vascular pathway.

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Pathophysiology

18

Heterozygous GNAI3 Variants

Heterozygous pathogenic GNAI3 variants cluster in nucleotide-binding regions. De novo and inherited alleles occur, with variable expression and some clinically unaffected carriers. Functional conclusions below apply to the five tested missense variants rather than every subsequently reported allele.

GNAI3 hgnc:4387

Animal models

GNAI3-variant expression in Xenopus embryos Xenopus laevis perturbs Introduces the disease-associated protein substitutions into an embryonic expression assay.

Downstream

Impaired GNAI3 GTP Binding Patient-associated substitutions impair nucleotide-dependent activation in the tested proteins.

Question mark ear This molecular subtype is associated with the characteristic pinna malformation; the detailed cellular route to lobe-helix separation is unresolved.

Show evidence (1 reference)

PMID:22560091 SUPPORT PRIMARY RESULT Human Clinical

"In both kindreds, the p.Gly40Arg variant was inherited; in one case (S011) it was inherited from an affected mother (S012-P), and in the other (S008), from an unaffected father (S009-P), documenting incomplete penetrance."

Two molecularly characterized families establish dominant inheritance with incomplete penetrance.

Impaired GNAI3 GTP Binding

Purified GNAI3 S47R retains GDP binding but fails to bind GTP efficiently. G40R, G45V, T48N and N269Y also show impaired GTP-dependent protease protection after expression in HEK293T cells. This replaces the earlier structure-based gain-of-function prediction; it does not establish generalized loss of GDP binding.

GNAI3 hgnc:4387

Experimental models

Purified GNAI3 S47R nucleotide-binding assays OTHER Biochemical assays distinguish GDP retention from defective GTP binding.

Downstream

Increased Mutant GNAI3 Receptor Association Failure to complete nucleotide-dependent activation is proposed to favor nonproductive receptor complexes. Increased association is measured, but the kinetic trapping mechanism is inferred.

Show evidence (1 reference)

PMID:27072656 SUPPORT PRIMARY RESULT In Vitro

"Together, these results demonstrate that Gαi3 S47R retains the capability to bind GDP but fails to bind GTP, rendering the G protein unable to switch into an active conformation."

Purified S47R directly retains GDP but loses efficient GTP binding; other variants were assessed with cell-expressed limited-proteolysis assays.

Increased Mutant GNAI3 Receptor Association

The five tested mutant GNAI3 proteins associate more strongly with EDNRA in co-immunoprecipitation and with Ric-8A in yeast assays. Sustained nonproductive receptor occupancy is the proposed explanation for interference with another G-protein class; binding kinetics were not directly measured.

GNAI3 hgnc:4387

Experimental models

GNAI3-variant signaling in HEK293T cells CELL LINE Co-immunoprecipitation shows greater mutant association with EDNRA.

Downstream

Reduced EDNRA-Gq Signaling Nonproductive mutant-GNAI3 association is proposed to limit receptor availability for Gq activation. The horizontal inhibitory effect is experimentally observed; receptor competition is its mechanistic interpretation.

Show evidence (1 reference)

PMID:27072656 SUPPORT PRIMARY RESULT In Vitro

"We found that all 5 ACS-associated Gαi3 mutants displayed increased binding (3- to 5-fold) to myc-tagged ETAR compared to Gαi3 WT (Fig. 5D)."

Co-immunoprecipitation measures increased receptor association, not a directly measured receptor residence time or equilibrium affinity.

Reduced EDNRA-Gq Signaling

EDNRA preferentially activates Gq in the tested heterologous system. Disease-associated GNAI3 proteins suppress that response while leaving the weak Gi3 response largely unchanged under the same conditions. Normal GNAI3 is therefore not represented as an obligatory positive intermediate between EDNRA and PLCB4.

Experimental models

GNAI3-variant signaling in HEK293T cells CELL LINE BRET measures reduced Gq activation after ET-1 stimulation.

Downstream

Reduced EDNRA-Dependent Phospholipase C Activity Reduced receptor-coupled Gq activation diminishes phospholipase-C-dependent second-messenger generation.

Show evidence (1 reference)

PMID:27072656 SUPPORT PRIMARY RESULT In Vitro

"We found that expression of any of the five ACS-associated Gαi3 mutants decreased Gq activation upon ET-1 stimulation ~65 to 85% (Fig. 6D)."

HEK293T BRET assays show reduced Gq activation when mutant Gi3 is coexpressed at a substoichiometric ratio.

PLCB4 Disease Alleles

PLCB4 disease alleles include dominant catalytic-domain missense variants and recessive biallelic loss-of-function lesions. Haploinsufficiency alone does not explain the tested dominant variants. The neonatal Ser643Phe report classified its variant as likely pathogenic and supplied structural prediction, not a catalytic assay.

PLCB4 hgnc:9059

Downstream

Reduced EDNRA-Dependent Phospholipase C Activity Tested dominant missense alleles interfere with EDNRA-dependent PLC activity. Recessive loss-of-function alleles provide a distinct route to deficient PLCB4 function.

Question mark ear This molecular subtype is associated with the characteristic pinna malformation; the detailed cellular route to lobe-helix separation is unresolved.

Show evidence (2 references)

PMID:22560091 SUPPORT PRIMARY RESULT Human Clinical

"We identified two additional novel PLCB4 missense mutations at c.1862G>A (M001) and c.1948A>C (M002)"

The primary report identifies segregating dominant PLCB4 variants.

PMID:24268655 SUPPORT REVIEW SYNTHESIS Human Clinical

"In addition, two cases have been ascribed to homozygous or compound-heterozygous loss-of-function mutations in PLCB4."

Summarizes previously established biallelic PLCB4 cases.

Reduced EDNRA-Dependent Phospholipase C Activity

EDN1-stimulated DAG-sensor translocation and BRET are reduced by tested PLCB4 variants in HEK293T cells. Introducing Pro838Ala at the Gq-interaction interface in cis with Arg621His attenuates its dominant interference. These are cell-based pathway readouts, not purified-enzyme kinetics; substrate trapping and altered GAP activity remain untested explanations.

PLCB4 hgnc:9059

Experimental models

PLCB4-variant DAG and transcriptional reporter assays CELL LINE Patient-associated substitutions attenuate pathway output and interface disruption reduces interference.

Downstream

Reduced DLX5 and DLX6 Expression PLCB4/GNAI3 pathway disruption is associated with reduced downstream DLX expression in patient osteoblasts. The intervening embryonic transcriptional route is not resolved by these cultures.

Show evidence (1 reference)

PMID:35284927 SUPPORT PRIMARY RESULT In Vitro

"These results illustrate that PLCB4 p.Arg621His interferes with PLCB activity even when it is expressed at a sub-stoichiometric level relative to wild-type PLCB4, exemplifying a characteristic of a dominant-negative protein."

DAG-sensor BRET detects dominant interference by Arg621His; three additional tested missense variants also attenuated the response.

EDN1 Disease Alleles

Biallelic EDN1 substitutions were identified in recessive ACS families. Other EDN1 alleles cause dominant isolated question-mark ears, and a later start-loss heterozygote had mild mandibular involvement. Phenotype and inheritance depend on the allele; measured residual ligand activity is not available for the original patient substitutions.

EDN1 hgnc:3176

Downstream

Reduced Bioactive EDN1 Availability Variants near processing sites or within the peptide are predicted to reduce effective ligand availability or activity. The original study did not directly assay cleavage or receptor activation by these patient alleles.

Question mark ear This molecular subtype is associated with the characteristic pinna malformation; the detailed cellular route to lobe-helix separation is unresolved.

Show evidence (1 reference)

PMID:24268655 SUPPORT PRIMARY RESULT Human Clinical

"In family F1, the unaffected parents and child were heterozygous for the mutation, whereas the three affected siblings were homozygous, indicating that the allele encoding the p.Lys91Glu substitution behaves in a recessive manner."

Segregation supports recessive inheritance of Lys91Glu in this family.

Reduced Bioactive EDN1 Availability

Reduced effective EDN1 ligand is the proposed functional consequence of disease alleles. Lys91Glu alters a furin recognition motif and Pro77His lies near the ECE cleavage region. Functional evidence from different substitutions supports this model but cannot quantify residual activity of these ACS alleles.

EDN1 hgnc:3176

Downstream

Reduced EDNRA-Gq Signaling Reduced active ligand is expected to diminish EDNRA activation and its Gq signal in arch mesenchyme.

Show evidence (1 reference)

PMID:24268655 SUPPORT INDIRECT PRIMARY RESULT Human Clinical

"The different mode of inheritance for the F1 and S1 mutant EDN1 alleles compared to the F2 and F3 alleles might be explained by differences in the amount of residual functional protein in each case."

The authors explicitly propose residual functional ligand as an explanation; patient-allele processing was not directly measured.

Reduced DLX5 and DLX6 Expression

DLX5 and DLX6 transcripts were reduced in four postnatal ACS mandibular-osteoblast cultures relative to calvarial controls. Mouse developmental experiments support the importance of the EDNRA-DLX program, but the patient assay is not a direct measurement of fetal neural-crest transcription.

DLX5 hgnc:2918 DLX6 hgnc:2919

Experimental models

ACS patient mandibular osteoblast cultures PRIMARY CELL CULTURE RT-qPCR detects lower DLX transcript abundance in the patient cultures.

Downstream

Disrupted Mandibular Neural Crest Identity Reduced DLX program activity compromises mandibular specification, based on developmental genetic models. The full sequence is not traced in human embryos.

Show evidence (1 reference)

PMID:22560091 SUPPORT PRIMARY RESULT In Vitro

"Using quantitative, real-time RT-PCR of steady-state mRNA, we identified a 6-fold reduction of DLX5 (p < 0.005; probands versus controls) and an 8-fold reduction of DLX6 expression (p < 0.001) in mandibular osteoblasts from selective probands relative to 17 randomly selected calvarial..."

Four ACS mandibular-osteoblast cultures were compared with 17 calvarial-osteoblast controls; anatomical source and developmental stage limit interpretation.

Disrupted Mandibular Neural Crest Identity

EDNRA-DLX disruption changes the positional identity of mandibular neural-crest-derived mesenchyme in animal models. Human skeletal morphology is consistent with partial mandibular-to-maxillary homeosis; it does not prove that every clinical feature arises through this transformation.

neural crest cell CL:0011012

Animal models

Endothelin-pathway knockout mice Mouse perturbs Pathway-gene deletion changes mandibular positional identity.

Zebrafish edn1 and plcb3 developmental mutants Zebrafish perturbs Endothelin-pathway perturbation alters lower-jaw patterning.

Downstream

Abnormal Mandibular Skeletal Morphogenesis Altered mandibular identity produces abnormal skeletal differentiation and patterning in developmental models, with corresponding morphology in selected human cases.

Middle-Ear Ossicular Malformation Arch-identity signaling is required for ossicular development in mice. Applying this route to human fusion is an inference across species.

Show evidence (1 reference)

PMID:24123988 SUPPORT REVIEW SYNTHESIS Model Organism

"Disruption of this signaling pathway in both mouse and zebrafish results in loss of identity of neural crest cells of the mandibular portion of the first pharyngeal arch and the subsequent repatterning of these cells, leading to homeosis of lower jaw structures into more maxillary-like structures."

Genetic developmental models support altered identity rather than a universal neural-crest migration deficit.

HDAC9-TWIST1 Regulatory Duplication

A 430-kb tandem duplication within HDAC9 segregated with ACS in one Brazilian family. It includes candidate TWIST1 regulatory elements while leaving the TWIST1 coding region outside the duplication. Some short HDAC9 isoforms are wholly duplicated, whereas longer catalytic isoforms cross a breakpoint.

TWIST1 hgnc:12428 HDAC9 hgnc:14065

Downstream

Increased Neural Crest TWIST1 Expression The duplication is associated with increased TWIST1 expression in patient-derived neural-crest cells. Regulatory contact data support, but do not directly prove, enhancer-mediated upregulation.

Increased Neural Crest HDAC9 Expression Patient-derived neural-crest cells also show increased HDAC9 transcripts. The contribution of this change to craniofacial development remains unresolved.

Reduced Migration of Patient-Derived Neural Crest Cells Duplication-bearing cultures show reduced scratch closure; the respective roles of TWIST1, HDAC9 and donor background were not separated by rescue experiments.

Impaired Osteogenic Differentiation in Patient-Derived Cells Duplication-bearing mesenchymal derivatives show impaired osteogenic readouts. This parallel observation does not establish that impaired migration causes impaired osteogenesis.

Question mark ear This molecular subtype is associated with the characteristic pinna malformation; the detailed cellular route to lobe-helix separation is unresolved.

Micrognathia The duplication segregates with variable jaw hypoplasia. The cultured migration and osteogenic phenotypes have not been shown to mediate this clinical outcome.

Show evidence (2 references)

PMID:34750192 SUPPORT PRIMARY RESULT Human Clinical

"The duplication spanned 430 302 bp (NC_000007.14:g.18437239_18867540dup) telomeric to TWIST1, covering most of the HDAC9 gene."

A segregating tandem duplication in one four-generation family defines the regulatory locus; TWIST1 coding sequence is not duplicated.

PMID:34750192 SUPPORT PRIMARY RESULT Human Clinical

"the majority presented with question mark ears (8 of 10), microstomia (8 of 10) and micrognathia (6 of 10)"

The duplication family has variable core craniofacial findings.

Increased Neural Crest TWIST1 Expression

TWIST1 mRNA is increased in patient-derived neural-crest cultures, but not detectably different in undifferentiated iPSCs or during mesenchymal osteogenic differentiation. No TWIST1-specific correction or overexpression experiment in this study proves mediation of the cellular defects.

TWIST1 hgnc:12428

Experimental models

Regulatory-duplication patient iPSC neural-crest cultures IPSC DERIVED MODEL Patient-derived iNCCs show increased TWIST1 mRNA.

Show evidence (1 reference)

PMID:34750192 SUPPORT INDIRECT PRIMARY RESULT In Vitro

"However, an increase in HDAC9 (3.15-fold, unpaired t-test p=0.009) and TWIST1 (2.03-fold, unpaired t-test p=0.03) mRNA was observed in the ARCND-iNCC (figure 2A, B) compared with controls (unpaired t-test)."

Three affected-donor iPSC-derived neural-crest cultures show increased transcripts relative to three controls; no isogenic correction isolates the causal mediator.

Increased Neural Crest HDAC9 Expression

HDAC9 mRNA is increased in duplication-bearing neural-crest cultures. Transcript abundance does not establish increased catalytic HDAC9 activity, and a contribution independent of TWIST1 cannot be excluded.

HDAC9 hgnc:14065

Experimental models

Regulatory-duplication patient iPSC neural-crest cultures IPSC DERIVED MODEL Patient-derived iNCCs also show increased HDAC9 mRNA.

Show evidence (1 reference)

PMID:34750192 SUPPORT INDIRECT PRIMARY RESULT In Vitro

"However, an increase in HDAC9 (3.15-fold, unpaired t-test p=0.009) and TWIST1 (2.03-fold, unpaired t-test p=0.03) mRNA was observed in the ARCND-iNCC (figure 2A, B) compared with controls (unpaired t-test)."

Three affected-donor iPSC-derived neural-crest cultures show increased transcripts relative to three controls; no isogenic correction isolates the causal mediator.

Reduced Migration of Patient-Derived Neural Crest Cells

Patient-derived iNCC cultures have reduced 24-hour scratch closure without a detected cell-cycle distribution change. Positional identity and developmental stage of these induced cells require further characterization; reduced embryonic neural-crest colonization remains a hypothesis.

neural crest cell CL:0011012

Experimental models

Regulatory-duplication patient iPSC neural-crest cultures IPSC DERIVED MODEL Scratch closure is reduced over 24 hours.

Show evidence (1 reference)

PMID:34750192 SUPPORT INDIRECT PRIMARY RESULT In Vitro

"Although no significant difference in cell cycle distribution was detected between patient and control cells, a significant decrease in migratory capacity of ARCND iNCCs was observed compared with controls (4.3-fold decrease, Student’s t-test, p=0.0009) (figure 2C–E)."

A 24-hour scratch assay measures reduced wound closure in the patient-derived cultures; it does not measure migration into human pharyngeal arches.

Impaired Osteogenic Differentiation in Patient-Derived Cells

Patient-derived neural-crest mesenchymal cells show reduced day-9 alkaline-phosphatase activity and a smaller mineralization readout. These findings support delayed or impaired osteogenic differentiation in culture, not demonstrated causation of the human mandibular phenotype.

neural-crest-derived mesenchymal cell CL:0008019

Experimental models

Regulatory-duplication neural-crest mesenchymal derivatives IPSC DERIVED MODEL ALP and mineralization provide osteogenic differentiation readouts.

Show evidence (1 reference)

PMID:34750192 SUPPORT INDIRECT PRIMARY RESULT In Vitro

"Our data showed that during osteogenic differentiation, ALP enzymatic activity was significantly diminished in ARCND-nMSCs after 9 days of osteoinduction (decrease of 20.3-fold, paired t-test p=0.029; figure 3A, B)."

Patient-derived neural-crest mesenchymal cells show reduced alkaline-phosphatase activity during osteogenic induction.

Abnormal Mandibular Skeletal Morphogenesis

Abnormal mandibular skeletal development produces a short or dysplastic ramus, hypoplastic condyle and variable temporomandibular joint abnormalities. Selected severe cases have maxilla-like skeletal features. Associated oral, pinna and middle-ear findings need not all be mediated by mandibular homeosis.

Animal models

Plcb4 Arg621His edited mouse founders Mouse recapitulates Embryonic skeletal imaging and staining demonstrate abnormal proximal mandibular development.

Downstream

Micrognathia The structural jaw-development defect manifests as micrognathia in affected individuals.

Mandibular condyle hypoplasia The structural jaw-development defect manifests as mandibular condyle hypoplasia in affected individuals.

Temporomandibular joint ankylosis The structural jaw-development defect manifests as temporomandibular joint ankylosis in affected individuals.

Upper-Airway Narrowing A small malformed jaw and associated oral structures can narrow the upper airway, particularly with posterior tongue displacement.

Feeding difficulties Structural oral and mandibular abnormalities can impair feeding; oral-motor contributions vary.

Show evidence (2 references)

PMID:35284927 SUPPORT PRIMARY RESULT Model Organism

"the proximal mandible of Plcb4Indel/KI and Plcb4KI/KI embryos was disorganized, with absent or hypoplastic mandibular processes"

E18.5 edited mouse founders show proximal mandibular skeletal abnormalities; the tested genotypes are not simple wild-type/knock-in heterozygotes.

PMID:22560091 SUPPORT PRIMARY RESULT Human Clinical

"In each case, mandibular ankylosis was progressive, of variable severity, and characterized by inconsistent fusion to the medial and lateral pterygoid plates."

The selected severe clinical cases document variable progressive ankylosis.

Upper-Airway Narrowing

Mandibular and tongue abnormalities can narrow the oropharyngeal airway. This mechanical branch explains obstructive respiratory complications in selected patients; persistent central apnea requires separate assessment.

Downstream

Respiratory distress Severe upper-airway compromise can produce neonatal respiratory distress.

Obstructive sleep apnea Mechanical upper-airway compromise can contribute to obstructive apnea during sleep.

Show evidence (1 reference)

PMID:38618928 SUPPORT PRIMARY RESULT Human Clinical

"Computed tomography (CT) revealed a narrowed oropharynx airway and absent condylar fossae, shortened mandibular rami, and obtuse mandibular angles (Figure 2)."

CT documents oropharyngeal narrowing in the severely affected neonate.

Middle-Ear Ossicular Malformation

Middle-ear malformation can include congenital-appearing malleoincudal fusion. Histology supports an abnormal joint-development process in one adolescent; coexisting cholesteatoma can contribute to worsening hearing.

Downstream

Conductive hearing impairment Ossicular fusion can impede sound conduction; the reported case also had cholesteatoma, so the contribution of each lesion was not experimentally isolated.

Show evidence (1 reference)

url:https://lab.research.sickkids.ca/wp-content/uploads/sites/22/2015/09/Propst_et_al_Ossicular-Fusion-and-cholesteatoma-in-Auriculo-Condylar-Syndrome_2013.pdf SUPPORT PRIMARY RESULT Human Clinical

"the malleoincudal joint appeared to be partially ankylosed laterally ."

Temporal-bone CT demonstrates the structural ossicular abnormality in one case.

⬡

Pathograph

Use the checkboxes to hide or show graph categories. Hover nodes for evidence and cross-linked metadata.

●

Phenotypes

31

Cardiovascular 1

Cerebral arteriovenous malformation HP:0002408

Show evidence (1 reference)

url:https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf SUPPORT PRIMARY RESULT Human Clinical

"Cerebrovascular malformations were detected by brain MRI in two individuals with no neurological symptoms."

The source documents two observations without establishing a causal vascular pathway.

Digestive 3

Feeding difficulties HP:0011968

Show evidence (1 reference)

url:https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf SUPPORT PRIMARY RESULT Human Clinical

"Gastrointestinal disorder 15/38 39% Feeding difficulties 12/38 31%"

The table describes a selected assessed cohort, not a general frequency.

Constipation HP:0002019

Show evidence (1 reference)

PMID:38618928 SUPPORT PRIMARY RESULT Human Clinical

"| Constipation | 3 (9.1%) | / | 3 (60.0%) |"

Three of the five selected biallelic cases were reported to have constipation.

Hamartoma of tongue HP:0011802

Show evidence (1 reference)

PMID:24268655 SUPPORT PRIMARY RESULT Human Clinical

"several small hamartomatous pedicles on the ventral surface of the tongue"

Direct clinical observation in one affected family member.

Ear 6

Question mark ear HP:0030022

Show evidence (1 reference)

url:https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf SUPPORT PRIMARY RESULT Human Clinical

"Question mark ear Total 37/38 97%"

The table counts assessed members of a selected 39-person ACS/IQME cohort.

Hearing impairment HP:0000365

Coarse binding: variable spectrum

Show evidence (1 reference)

url:https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf SUPPORT PRIMARY RESULT Human Clinical

"Hearing loss was noted in eight patients with ACS."

Retains the broad clinical spectrum and the assessed-subset denominator.

Conductive hearing impairment HP:0000405

Show evidence (1 reference)

url:https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf SUPPORT PRIMARY RESULT Human Clinical

"Conductive hearing loss (CHL) was reported in five patients (Patient 3 with a heterozygous PLCB4 mutation, Patients 26 and 27 with a GNAI3 mutation, Patient 36 with a homozygous EDN1 mutation, and Patient 39 with a heterozygous EDN1 mutation)."

The cohort identifies five clinically typed conductive cases.

Sensorineural hearing impairment HP:0000407

Show evidence (1 reference)

url:https://pmc.ncbi.nlm.nih.gov/articles/PMC4666574/ SUPPORT PRIMARY RESULT Human Clinical

"individual in the ACS1 family presented with sensorineural hearing loss."

The full report distinguishes this individual from the conductive cases.

Stenosis of the external auditory canal HP:0000402

Show evidence (1 reference)

url:https://lab.research.sickkids.ca/wp-content/uploads/sites/22/2015/09/Propst_et_al_Ossicular-Fusion-and-cholesteatoma-in-Auriculo-Condylar-Syndrome_2013.pdf SUPPORT PRIMARY RESULT Human Clinical

"Otoscopy revealed a stenotic right external auditory canal with a tympanic membrane perforation with keratinous debris in the middle ear space."

Direct examination in the adolescent case.

Cholesteatoma HP:0009797

Show evidence (1 reference)

url:https://lab.research.sickkids.ca/wp-content/uploads/sites/22/2015/09/Propst_et_al_Ossicular-Fusion-and-cholesteatoma-in-Auriculo-Condylar-Syndrome_2013.pdf SUPPORT PRIMARY RESULT Human Clinical

"Kerati- nous debris from the right middle ear space (cholesteatoma) was confirmed histopathologically ."

Histopathology confirms the lesion in the reported case.

Head and Neck 12

Mandibular condyle hypoplasia HP:0007628

Show evidence (1 reference)

url:https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf SUPPORT PRIMARY RESULT Human Clinical

"Condyle anomalies 15/24 63% Condyle hypoplasia 13/15 87%"

The nested imaging denominators distinguish any condylar anomaly from hypoplasia.

Micrognathia HP:0000347

Show evidence (1 reference)

url:https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf SUPPORT PRIMARY RESULT Human Clinical

"Mandibular hypoplasia (clinical diagnosis) 31/35 89%"

Selected-cohort clinical counts do not establish population frequency.

Microstomia Narrow mouth HP:0000160

Show evidence (1 reference)

url:https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf SUPPORT PRIMARY RESULT Human Clinical

"From photographs, full cheeks were observed in 18/31 (58%) patients and microstomia in 16/39 (41%)."

The cohort records microstomia independently of jaw size.

Cleft palate HP:0000175

Show evidence (1 reference)

PMID:22560091 SUPPORT BACKGROUND Human Clinical

"Auriculocondylar syndrome (ACS) is a rare, autosomal-dominant craniofacial malformation syndrome characterized by variable micrognathia, temporomandibular joint ankylosis, cleft palate, and a characteristic "question-mark" ear malformation."

The original PLCB4/GNAI3 discovery paper includes cleft palate among variable clinical features.

Temporomandibular joint ankylosis HP:0012478

Show evidence (1 reference)

PMID:22560091 SUPPORT PRIMARY RESULT Human Clinical

"In each case, mandibular ankylosis was progressive, of variable severity, and characterized by inconsistent fusion to the medial and lateral pterygoid plates."

Direct clinical characterization of the selected severe cases.

Full cheeks HP:0000293

Show evidence (1 reference)

url:https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf SUPPORT PRIMARY RESULT Human Clinical

"From photographs, full cheeks were observed in 18/31 (58%) patients and microstomia in 16/39 (41%)."

Provides a denominator specific to assessed individuals.

Glossoptosis HP:0000162

Show evidence (1 reference)

PMID:38618928 SUPPORT PRIMARY RESULT Human Clinical

"feeding difficulty, glossoptosis, postauricular tags, respiratory distress, and crowded teeth."

The molecularly characterized neonate directly exhibited glossoptosis.

Bifid uvula HP:0000193

Show evidence (1 reference)

PMID:24268655 SUPPORT PRIMARY RESULT Human Clinical

"a bilateral paramedian submucosal cleft of the velum, and a bifid uvula with ectopic tissue beside it"

Direct description of one affected EDN1-family member.

High palate HP:0000218

Show evidence (1 reference)

url:https://lab.research.sickkids.ca/wp-content/uploads/sites/22/2015/09/Propst_et_al_Ossicular-Fusion-and-cholesteatoma-in-Auriculo-Condylar-Syndrome_2013.pdf SUPPORT PRIMARY RESULT Human Clinical

"glossoptosis, a high-arched palate, hearing loss, and cholesteatoma."

The source documents this finding in one adolescent.

Dental crowding HP:0000678

Show evidence (1 reference)

PMID:38618928 SUPPORT PRIMARY RESULT Human Clinical

"feeding difficulty, glossoptosis, postauricular tags, respiratory distress, and crowded teeth."

The index neonate follow-up explicitly records crowded teeth.

Microglossia HP:0000171

Show evidence (1 reference)

PMID:22560091 SUPPORT PRIMARY RESULT Human Clinical

"Intraoperative evaluation of S011 was notable for the presence of severe microglossia"

Direct operative observation in a selected severe case.

Postauricular skin tag HP:0004451

Show evidence (1 reference)

url:https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf SUPPORT PRIMARY RESULT Human Clinical

"Postauricular tags were reported in six patients with ACS (6/ 37, 16%)"

Six of 37 assessed cohort members had this finding.

Musculoskeletal 2

Hypotonia HP:0001252

Show evidence (1 reference)

PMID:38618928 SUPPORT PRIMARY RESULT Human Clinical

"| Hypotonia | 3 (9.1%) | 2 (7.1%) | 1 (20.0%) |"

The compiled cases document hypotonia without establishing a universal neuromuscular defect.

Rib fusion HP:0000902

Show evidence (1 reference)

url:https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf SUPPORT PRIMARY RESULT Human Clinical

"Case 24 had hypoplastic first ribs and Case 26 had a unilateral fusion of the first and second ribs."

Two individuals had distinct rib findings; only one had fusion.

Nervous System 4

Obstructive sleep apnea HP:0002870

Show evidence (1 reference)

url:https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf SUPPORT PRIMARY RESULT Human Clinical

"Obstructive apnea 8/21 38% Mixed apnea 8/21 38%"

Sleep-study selection limits disease-wide frequency inference.

Speech articulation difficulties HP:0009088

Show evidence (1 reference)

PMID:38618928 SUPPORT PRIMARY RESULT Human Clinical

"| Speech articulation difficulties | 11 (33.3%) | 9 (32.1%) | 2 (40.0%) |"

The selected 33-case review records articulation difficulty separately from developmental delay.

Global developmental delay HP:0001263

Show evidence (1 reference)

PMID:38618928 SUPPORT PRIMARY RESULT Human Clinical

"| Psychomotor developmental delay | 6 (18.2%) | 4 (14.3%) | 2 (40.0%) |"

The retrospective case compilation supports reported delay, not an unselected prevalence.

Intellectual disability HP:0001249

Show evidence (1 reference)

url:https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf SUPPORT PRIMARY RESULT Human Clinical

"However intellectual disability was rare (3/23 patients, 13%)"

The denominator is the subset assessed for this outcome.

Prenatal and Birth 1

Polyhydramnios HP:0001561

Show evidence (1 reference)

PMID:34789173 SUPPORT PRIMARY RESULT Human Clinical

"Severe micrognathia and mandibular hypoplasia accompanied by polyhydramnios are prenatal indicators of ACS."

This directly supports polyhydramnios as a prenatal indicator when combined with severe mandibular findings.

Respiratory 2

Respiratory distress HP:0002098

Show evidence (1 reference)

PMID:38618928 SUPPORT PRIMARY RESULT Human Clinical

"The proband, a 5-day-old male neonate, was referred to our hospital for respiratory distress."

A recent neonatal ARCND2 case directly documents respiratory distress.

Central apnea HP:0002871

Show evidence (1 reference)

url:https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf SUPPORT REVIEW SYNTHESIS Human Clinical

"Central sleep apnea has previously been reported in patients with ACS."

The clinical synthesis distinguishes central apnea from the structural obstructive component.

🧬

Genetic Associations

5

GNAI3 pathogenic variants (Causative)

Gene: GNAI3 hgnc:4387 gene page relationship_type: CAUSATIVE

Show evidence (2 references)

PMID:22560091 SUPPORT PRIMARY RESULT Human Clinical

"In both kindreds, the p.Gly40Arg variant was inherited; in one case (S011) it was inherited from an affected mother (S012-P), and in the other (S008), from an unaffected father (S009-P), documenting incomplete penetrance."

Two molecularly characterized families establish dominant inheritance with incomplete penetrance.

PMID:27072656 SUPPORT PRIMARY RESULT In Vitro

"Together, these results demonstrate that Gαi3 S47R retains the capability to bind GDP but fails to bind GTP, rendering the G protein unable to switch into an active conformation."

Purified S47R directly retains GDP but loses efficient GTP binding; other variants were assessed with cell-expressed limited-proteolysis assays.

PLCB4 pathogenic variants (Causative)

Gene: PLCB4 hgnc:9059 gene page relationship_type: CAUSATIVE

Show evidence (1 reference)

PMID:35284927 SUPPORT PRIMARY RESULT In Vitro

"These results illustrate that PLCB4 p.Arg621His interferes with PLCB activity even when it is expressed at a sub-stoichiometric level relative to wild-type PLCB4, exemplifying a characteristic of a dominant-negative protein."

DAG-sensor BRET detects dominant interference by Arg621His; three additional tested missense variants also attenuated the response.

Biallelic PLCB4 disease alleles (Causative)

Gene: PLCB4 hgnc:9059 gene page relationship_type: CAUSATIVE

Show evidence (1 reference)

PMID:23315542 SUPPORT PRIMARY RESULT Human Clinical

"The consanguineous parents of the patient with a homozygous PLCB4 deletion each harboured the heterozygous deletion, but did not present the ACS phenotype, further suggesting that ACS is not caused by PLCB4 haploinsufficiency."

Segregation demonstrates a recessive deletion mechanism in one family.

EDN1 pathogenic variants (Causative)

Gene: EDN1 hgnc:3176 relationship_type: CAUSATIVE

Show evidence (2 references)

PMID:24268655 SUPPORT PRIMARY RESULT Human Clinical

"In family F1, the unaffected parents and child were heterozygous for the mutation, whereas the three affected siblings were homozygous, indicating that the allele encoding the p.Lys91Glu substitution behaves in a recessive manner."

Segregation supports recessive inheritance of Lys91Glu in this family.

PMID:24268655 SUPPORT INDIRECT PRIMARY RESULT Human Clinical

"The different mode of inheritance for the F1 and S1 mutant EDN1 alleles compared to the F2 and F3 alleles might be explained by differences in the amount of residual functional protein in each case."

The authors explicitly propose residual functional ligand as an explanation; patient-allele processing was not directly measured.

TWIST1 regulatory duplication (Causative)

Gene: TWIST1 hgnc:12428 gene page relationship_type: CAUSATIVE

Show evidence (2 references)

PMID:34750192 SUPPORT PRIMARY RESULT Human Clinical

"The duplication spanned 430 302 bp (NC_000007.14:g.18437239_18867540dup) telomeric to TWIST1, covering most of the HDAC9 gene."

A segregating tandem duplication in one four-generation family defines the regulatory locus; TWIST1 coding sequence is not duplicated.

PMID:34750192 SUPPORT INDIRECT PRIMARY RESULT In Vitro

"However, an increase in HDAC9 (3.15-fold, unpaired t-test p=0.009) and TWIST1 (2.03-fold, unpaired t-test p=0.03) mRNA was observed in the ARCND-iNCC (figure 2A, B) compared with controls (unpaired t-test)."

Three affected-donor iPSC-derived neural-crest cultures show increased transcripts relative to three controls; no isogenic correction isolates the causal mediator.

💊

Medical Actions

10

Individualized airway support

Action: Respiratory Therapy NCIT:C15322

Platform: Other

Severe neonatal obstruction may require specialist airway stabilization, including tracheostomy. Positive-pressure support may be needed for sleep-disordered breathing. Assessment must distinguish central from obstructive components and consider associated airway lesions.

Mechanism Target:

BYPASSES Upper-Airway Narrowing — Tracheostomy can bypass an obstructed upper airway; its use is individualized.

Show evidence (1 reference)

url:https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf SUPPORT PRIMARY RESULT Human Clinical

"She underwent tracheostomy at birth and gastrostomy at 16 months of age."

The severe GNAI3 case documents both procedures; this is case-based management, not a controlled efficacy comparison.

Show evidence (2 references)

url:https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf SUPPORT PRIMARY RESULT Human Clinical

"She underwent tracheostomy at birth and gastrostomy at 16 months of age."

The severe GNAI3 case documents both procedures; this is case-based management, not a controlled efficacy comparison.

url:https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf SUPPORT PRIMARY RESULT Human Clinical

"severe mixed sleep apnea on polysomnography at 2 months of age, requiring nocturnal noninvasive ventilation."

A biallelic PLCB4 patient received nocturnal noninvasive support.

Nutritional and feeding support

Action: Nutritional Support NCIT:C15433

Platform: Other

Assess oral feeding and growth. Temporary enteral tube feeding or gastrostomy may be necessary in severely affected children, with oral-motor assessment and reassessment as airway and jaw problems evolve.

Mechanism Target:

BYPASSES Feeding difficulties — Enteral support provides nutrition when oral feeding is inadequate.

Show evidence (1 reference)

url:https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf SUPPORT PRIMARY RESULT Human Clinical

"She underwent tracheostomy at birth and gastrostomy at 16 months of age."

The severe GNAI3 case documents both procedures; this is case-based management, not a controlled efficacy comparison.

Show evidence (2 references)

url:https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf SUPPORT PRIMARY RESULT Human Clinical

"She underwent tracheostomy at birth and gastrostomy at 16 months of age."

The severe GNAI3 case documents both procedures; this is case-based management, not a controlled efficacy comparison.

url:https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf SUPPORT PRIMARY RESULT Human Clinical

"Feeding difficulties necessitated tube feeding for 3 months."

One child required temporary tube feeding.

Mandibular distraction osteogenesis

Action: mandibular osteotomy with distraction osteogenesis Ontology label: Osteotomy NCIT:C51903

Platform: Surgery

Distraction can be used for selected severe mandibular hypoplasia and associated airway compromise. Timing and repeat procedures are individualized. Case reports document improvement, but distraction does not ensure resolution of central apnea or define a universal operative age.

Mechanism Target:

MODULATES Micrognathia — Distraction lengthens the hypoplastic mandible.

Show evidence (1 reference)

PMID:38618928 SUPPORT PRIMARY RESULT Human Clinical

"The patient underwent bilateral mandibular osteotomy and distraction osteogenesis at 17 days after birth. A second procedure at 16 months old improved mandibular growth."

The neonatal report describes staged distraction with later improvement in jaw growth.

Show evidence (2 references)

PMID:38618928 SUPPORT PRIMARY RESULT Human Clinical

"The patient underwent bilateral mandibular osteotomy and distraction osteogenesis at 17 days after birth. A second procedure at 16 months old improved mandibular growth."

The neonatal report describes staged distraction with later improvement in jaw growth.

url:https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf SUPPORT REVIEW SYNTHESIS Human Clinical

"Central sleep apnea has previously been reported in patients with ACS."

The clinical synthesis distinguishes central apnea from the structural obstructive component.

Temporomandibular reconstruction

Action: temporomandibular arthroplasty and reconstruction Ontology label: Arthroplasty NCIT:C51691

Platform: Surgery

Selected ankylosis or severe joint dysfunction may require arthroplasty and reconstruction by an experienced craniofacial team. Procedures and graft choice are guided by anatomy and growth; comparative long-term outcomes are limited.

Mechanism Target:

MODULATES Temporomandibular joint ankylosis — Reconstruction addresses the fused or malformed joint.

Show evidence (1 reference)

url:https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf SUPPORT PRIMARY RESULT Human Clinical

"Craniofacial CT imaging demonstrated a small mandible and bilateral TMJ ankylosis that benefited from arthroplasty and costo- chondral grafts at 4 years of age"

Arthroplasty and costochondral grafting benefited bilateral TMJ ankylosis in one severe case.

Show evidence (1 reference)

url:https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf SUPPORT PRIMARY RESULT Human Clinical

"Craniofacial CT imaging demonstrated a small mandible and bilateral TMJ ankylosis that benefited from arthroplasty and costo- chondral grafts at 4 years of age"

Arthroplasty and costochondral grafting benefited bilateral TMJ ankylosis in one severe case.

Orthodontic and orthognathic treatment

Action: Surgical Procedure NCIT:C15329

Platform: Surgery

Dentofacial deformity and malocclusion may be treated with coordinated orthodontics and staged orthognathic surgery. One adult report documented improved occlusion, mouth opening and apnea indices at long follow-up after several combined procedures; it cannot isolate the contribution of each component or establish a standard protocol.

Mechanism Target:

MODULATES Dental crowding — Orthodontic correction addresses dental alignment as part of combined care.

Show evidence (1 reference)

PMID:39014351 SUPPORT PRIMARY RESULT Human Clinical

"Additionally, we aligned the crowded teeth and leveled the dentition to minimize tooth compensation."

The report directly documents dental alignment during combined treatment.

Show evidence (2 references)

PMID:39014351 SUPPORT PRIMARY RESULT Human Clinical

"After a multidisciplinary consultation and examination, sequential orthodontic treatment and craniofacial surgery, including distraction osteogenesis and orthognathic surgery, were performed using three-dimensional (3D) digital technology to treat the patient's dentofacial deformity."

One adult received combined orthodontic and staged craniofacial interventions.

PMID:39014351 SUPPORT PRIMARY RESULT Human Clinical

"with a maximal opening capacity of 40 mm."

Follow-up records improved mouth opening in the treated individual.

Speech and developmental support

Action: Speech Language Therapy NCIT:C159273

Platform: Other

Assess articulation, oral-motor function, hearing and developmental needs. Speech therapy and individualized educational support may be appropriate; craniofacial speech difficulty must not be equated with intellectual disability. This action binding identifies the speech-therapy component; broader developmental assessment guides any separate educational support.

Show evidence (2 references)

PMID:34750192 SUPPORT REVIEW SYNTHESIS Human Clinical

"Treatment is mainly corrective through surgical intervention for mandibular ramus lengthening using distraction osteogenesis and accompanied by orthodontic treatments and speech therapy."

The clinical background specifically includes speech therapy.

url:https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf SUPPORT PRIMARY RESULT Human Clinical

"However intellectual disability was rare (3/23 patients, 13%)"

The denominator is the subset assessed for this outcome.

Audiologic and otologic care

Action: Supportive Care NCIT:C15747

Platform: Other

Obtain audiologic assessment and address the identified cause. Tympanostomy tubes have been used for selected conductive loss. Ossicular abnormalities and cholesteatoma warrant specialist evaluation; the reported mastoidectomy/tympanoplasty case does not provide a quantified postoperative hearing result.

Mechanism Target:

INHIBITS Cholesteatoma — Mastoidectomy removes the cholesteatoma.

Show evidence (1 reference)

url:https://lab.research.sickkids.ca/wp-content/uploads/sites/22/2015/09/Propst_et_al_Ossicular-Fusion-and-cholesteatoma-in-Auriculo-Condylar-Syndrome_2013.pdf SUPPORT PRIMARY RESULT Human Clinical

"The patient underwent a right-sided combined- approach mastoidectomy for removal of cholesteatoma."

The lesion was surgically removed.

Show evidence (2 references)

url:https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf SUPPORT PRIMARY RESULT Human Clinical

"Conductive hearing loss necessitated tympanostomy tube insertion. Sleep apnea with snoring was treated by tonsillectomy at 2 years of age."

The EDN1 start-loss case received ENT interventions for its individual conductive and sleep findings.

url:https://lab.research.sickkids.ca/wp-content/uploads/sites/22/2015/09/Propst_et_al_Ossicular-Fusion-and-cholesteatoma-in-Auriculo-Condylar-Syndrome_2013.pdf SUPPORT PRIMARY RESULT Human Clinical

"The patient underwent a right-sided combined- approach mastoidectomy for removal of cholesteatoma."

Direct operative management of the reported cholesteatoma.

External-ear reconstruction

Action: Surgical Procedure NCIT:C15329

Platform: Surgery

Reconstructive ear surgery may be considered for selected structural or patient-prioritized concerns. Published procedures are individual case experiences, with no established comparative technique or universal timing.

Show evidence (1 reference)

url:https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf SUPPORT PRIMARY RESULT Human Clinical

"followed by reconstructive surgery of the ears at 5 years of age"

One affected child underwent ear reconstruction.

Sleep and multisystem surveillance

Category: Monitoring Action: Supportive Care NCIT:C15747

Platform: Other

Follow breathing, growth, hearing, jaw opening, dental development and neurodevelopment. The 2022 cohort authors recommend assessment for both obstructive and central apnea. They also suggest considering spine radiographs in GNAI3-related cases and brain MRI for possible vascular anomalies; these proposals rest on small case numbers rather than formal screening trials.

Show evidence (2 references)

url:https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf SUPPORT REVIEW SYNTHESIS Other

"Therefore monitoring for both obstructive and central apnea should be considered in all patients with ACS."

Case-series authors recommend surveillance across apnea types.

url:https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf SUPPORT REVIEW SYNTHESIS Other

"Finally, brain MRI may be worthwhile, considering the possible risk of neurovascular mal formations, even if developmental milestones are within the normal range."

This is a tentative case-based recommendation, not established universal screening efficacy.

Genetic counseling

Category: Counseling / Informational Action: Genetic Counseling NCIT:C15240

Platform: Other

Explain the allele-specific dominant or recessive inheritance, variable expression and incomplete penetrance. Discuss familial testing and prenatal or reproductive options once the molecular diagnosis is established; a negative coding panel does not exclude a regulatory structural variant.

Show evidence (1 reference)

PMID:22560091 SUPPORT PRIMARY RESULT Human Clinical

"The identification of phenotypic variability and incomplete penetrance underscores the utility of these results in genetic counseling of families affected by ACS."

The primary gene-discovery report identifies implications for family counseling.

🔬

Diagnosis

4

Clinical and craniofacial imaging assessment

Recognize the variable combination of question-mark ears, micrognathia and condylar or temporomandibular abnormalities. Examine oral structures, hearing and airway function. Imaging can characterize ramus, condyle, joint and temporal-bone anatomy where clinically indicated; absence of a complete triad does not exclude disease.

Show evidence (3 references)

url:https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf SUPPORT PRIMARY RESULT Human Clinical

"Question mark ear Total 37/38 97%"

The table counts assessed members of a selected 39-person ACS/IQME cohort.

PMID:38618928 SUPPORT PRIMARY RESULT Human Clinical

"Computed tomography (CT) revealed a narrowed oropharynx airway and absent condylar fossae, shortened mandibular rami, and obtuse mandibular angles (Figure 2)."

CT documents oropharyngeal narrowing in the severely affected neonate.

url:https://lab.research.sickkids.ca/wp-content/uploads/sites/22/2015/09/Propst_et_al_Ossicular-Fusion-and-cholesteatoma-in-Auriculo-Condylar-Syndrome_2013.pdf SUPPORT PRIMARY RESULT Human Clinical

"the malleoincudal joint appeared to be partially ankylosed laterally ."

Temporal-bone CT demonstrates the structural ossicular abnormality in one case.

Molecular and structural-variant testing

Interpret targeted sequencing or exome/genome results together with phenotype and segregation. Established genes include GNAI3, PLCB4 and EDN1. Copy-number and regulatory-region analysis is relevant in unresolved cases because the reported HDAC9-TWIST1 duplication lies outside TWIST1 coding sequence. A VUS alone does not establish the diagnosis, and selected-case yields are not general diagnostic sensitivity.

Show evidence (2 references)

PMID:28328130 SUPPORT PRIMARY RESULT Human Clinical

"We found novel pathogenic variants in PLCB4 only in two of three index patients with typical Auriculocondylar syndrome."

Two positive typical index cases in an 11-person mixed-phenotype series; not an unselected sensitivity estimate.

PMID:34750192 SUPPORT PRIMARY RESULT Human Clinical

"The duplication spanned 430 302 bp (NC_000007.14:g.18437239_18867540dup) telomeric to TWIST1, covering most of the HDAC9 gene."

A segregating tandem duplication in one four-generation family defines the regulatory locus; TWIST1 coding sequence is not duplicated.

Prenatal assessment

Severe fetal micrognathia with polyhydramnios can prompt detailed craniofacial imaging and molecular evaluation. These findings are not specific for ACS, and question-mark ears may not be identified prenatally.

Show evidence (1 reference)

PMID:34789173 SUPPORT PRIMARY RESULT Human Clinical

"Severe micrognathia and mandibular hypoplasia accompanied by polyhydramnios are prenatal indicators of ACS."

The reported fetus provides a possible diagnostic clue rather than a validated screening rule.

Audiologic and sleep evaluation

Audiograms help distinguish conductive, sensorineural and mixed or unclassified hearing loss. Sleep studies can distinguish obstructive and central components and inform follow-up after structural treatment.

Show evidence (2 references)

url:https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf SUPPORT REVIEW SYNTHESIS Other

"Attention needs to be paid to middle and inner ear function by way of an audiogram in all patients with ACS to evaluate for hearing loss."

Case-series authors recommend audiologic assessment.

url:https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf SUPPORT REVIEW SYNTHESIS Human Clinical

"Central sleep apnea has previously been reported in patients with ACS."

The clinical synthesis distinguishes central apnea from the structural obstructive component.

📈

Progression

2

Prenatal and neonatal presentation

Craniofacial malformations are congenital and severe mandibular hypoplasia can be recognized prenatally, sometimes with polyhydramnios. Severe neonates may need early airway and feeding intervention; question-mark ears can be absent.

Show evidence (1 reference)

PMID:34789173 SUPPORT PRIMARY RESULT Human Clinical

"Severe micrognathia and mandibular hypoplasia accompanied by polyhydramnios are prenatal indicators of ACS."

The prenatal case supports early detectability, not diagnostic specificity.

Childhood and adult course

Joint restriction, sleep-disordered breathing, hearing, feeding, dental and articulation problems may require staged follow-up. Development is often normal but is not uniformly preserved. Structural treatment does not ensure resolution of central apnea. Adult corrective surgery has favorable reported outcomes in individual cases, not a comparative natural-history estimate.

Show evidence (3 references)

PMID:22560091 SUPPORT PRIMARY RESULT Human Clinical

"In each case, mandibular ankylosis was progressive, of variable severity, and characterized by inconsistent fusion to the medial and lateral pterygoid plates."

Direct clinical characterization of the selected severe cases.

url:https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf SUPPORT REVIEW SYNTHESIS Human Clinical

"Central sleep apnea has previously been reported in patients with ACS."

The clinical synthesis distinguishes central apnea from the structural obstructive component.

url:https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf SUPPORT PRIMARY RESULT Human Clinical

"However intellectual disability was rare (3/23 patients, 13%)"

The denominator is the subset assessed for this outcome.

📊

Prevalence

1

Reported global estimate; sampling frame unspecified

Point Prevalence <1 in 1,000,000

The 2024 case report repeats this rarity estimate from prior literature, rather than measuring a population rate. The separate statement that fewer than100 cases had been reported is a literature count, not its denominator; geographic and time-specific ascertainment are not provided.

Show evidence (1 reference)

PMID:39014351 SUPPORT BACKGROUND Human Clinical

"an extremely rare autosomal dominant or recessive condition with a prevalence of less than 1 in 1,000,000"

The source reports a broad prevalence band as background, not a new epidemiologic measurement.

🔀

Differential Diagnoses

6

Conditions with similar clinical presentations that must be differentiated from Auriculocondylar Syndrome:

Pierre Robin sequence-plus

Overlapping Features Pierre Robin sequence and related craniofacial disorders overlap through micrognathia, glossoptosis and palatal abnormalities. The ear pattern, condylar anatomy, other findings and molecular testing distinguish the spectrum; absence of question-mark ears alone does not exclude ACS.

Distinguishing Features

Question mark ears
Mandibular condyle hypoplasia

Show evidence (1 reference)

PMID:28328130 SUPPORT PRIMARY RESULT Human Clinical

"In order to address these questions, we searched for alterations in PLCB4, GNAI3, and EDN1 in patients with typical Auriculocondylar syndrome (n = 3), Pierre Robin sequence-plus (n = 3), micrognathia with additional craniofacial malformations (n = 4), or non-specific auricular dysplasia (n = 1),..."

This supports Pierre Robin sequence-plus as part of the clinical differential or spectrum considered in testing.

Oculo-auriculo-vertebral spectrum

Overlapping Features This craniofacial spectrum is a named source of diagnostic confusion. Assess the ear, mandibular-condylar and broader craniofacial pattern; the report identifies overlap but does not provide a validated diagnostic classifier.

Show evidence (1 reference)

PMID:39014351 SUPPORT BACKGROUND Human Clinical

"ARCND can be misdiagnosed as other diseases, including craniomaxillofacial deformities such as the oculo-auriculo-vertebral spectrum ... Treacher Collins syndrome ... mandibulofacial dysostosis ... Guion-Almeida type, and Meier-Gorlin syndrome"

The paper explicitly names this differential as background; it does not measure the sensitivity or specificity of distinguishing signs.

Treacher Collins syndrome

Overlapping Features Treacher Collins syndrome is a named differential for the mandibulofacial presentation. Question-mark ear morphology and condylar findings can direct ARCND testing, but neither a single ear sign nor mandibular hypoplasia alone establishes the molecular diagnosis.

Show evidence (1 reference)

PMID:39014351 SUPPORT BACKGROUND Human Clinical

"ARCND can be misdiagnosed as other diseases, including craniomaxillofacial deformities such as the oculo-auriculo-vertebral spectrum ... Treacher Collins syndrome ... mandibulofacial dysostosis ... Guion-Almeida type, and Meier-Gorlin syndrome"

The paper explicitly names this differential as background; it does not measure the sensitivity or specificity of distinguishing signs.

Mandibulofacial dysostosis, Guion-Almeida type

Overlapping Features The cited background lists this named mandibulofacial dysostosis among potential misdiagnoses. Broader clinical assessment and phenotype-guided molecular testing are appropriate when the craniofacial pattern is atypical for ARCND.

Show evidence (1 reference)

PMID:39014351 SUPPORT BACKGROUND Human Clinical

"ARCND can be misdiagnosed as other diseases, including craniomaxillofacial deformities such as the oculo-auriculo-vertebral spectrum ... Treacher Collins syndrome ... mandibulofacial dysostosis ... Guion-Almeida type, and Meier-Gorlin syndrome"

The paper explicitly names this differential as background; it does not measure the sensitivity or specificity of distinguishing signs.

Meier-Gorlin syndrome

Overlapping Features The case-report background names Meier-Gorlin syndrome as a potential diagnostic alternative. Interpret auricular and mandibular findings in the complete clinical context instead of treating ear morphology alone as diagnostic.

Show evidence (1 reference)

PMID:39014351 SUPPORT BACKGROUND Human Clinical

"ARCND can be misdiagnosed as other diseases, including craniomaxillofacial deformities such as the oculo-auriculo-vertebral spectrum ... Treacher Collins syndrome ... mandibulofacial dysostosis ... Guion-Almeida type, and Meier-Gorlin syndrome"

The paper explicitly names this differential as background; it does not measure the sensitivity or specificity of distinguishing signs.

📊

Related Datasets

1

Next Generation Mendelian Genetics: Auriculocondylar Syndrome (ACS) dbgap:phs000437

This project is part of an ongoing project to identify the molecular genetic basis of rare craniofacial disorders. This specific project involved the collection of DNA samples from four probands with severe manifestations of auriculocondylar syndrome and their parents. Detailed clinical phenotypic data is available on each proband. The sole purpose of this research is to identify the molecular cause(s) of auriculochondylar syndrome.

The dbGaP accession and disease-specific title were verified against the live repository on 2026-09-21. The project describes four severe ACS probands and their parents; it is a gene-discovery collection, not a representative phenotype-frequency cohort.

🧫

Experimental Models

6

Purified GNAI3 S47R nucleotide-binding assays OTHER

Recombinant wild-type and S47R GNAI3 were compared by nucleotide-binding, GTPase, HPLC and limited-proteolysis assays. S47R retains GDP but has profoundly impaired GTP binding and activation.

Cell source

Recombinant proteins expressed in Escherichia coli

Publication

PMID:27072656

Pathograph links

Impaired GNAI3 GTP Binding measures observes: molecular Biochemical assays distinguish GDP retention from defective GTP binding.

Limitations: Direct purified-protein evidence is limited to S47R.

Readouts

GDP and GTP binding

GDP is retained while GTP binding is impaired.

Show evidence (1 reference)

PMID:27072656 SUPPORT PRIMARY RESULT In Vitro

"Together, these results demonstrate that Gαi3 S47R retains the capability to bind GDP but fails to bind GTP, rendering the G protein unable to switch into an active conformation."

Purified S47R directly retains GDP but loses efficient GTP binding; other variants were assessed with cell-expressed limited-proteolysis assays.

Show evidence (1 reference)

PMID:27072656 SUPPORT PRIMARY RESULT In Vitro

"Together, these results demonstrate that Gαi3 S47R retains the capability to bind GDP but fails to bind GTP, rendering the G protein unable to switch into an active conformation."

Purified S47R directly retains GDP but loses efficient GTP binding; other variants were assessed with cell-expressed limited-proteolysis assays.

The other four variants could not be purified in sufficient soluble quantity; their activation defects were tested after mammalian expression. Poor recovery is not a direct protein half-life measurement.

Show evidence (1 reference)

PMID:27072656 SUPPORT PRIMARY RESULT In Vitro

"Together, these results demonstrate that Gαi3 S47R retains the capability to bind GDP but fails to bind GTP, rendering the G protein unable to switch into an active conformation."

Purified S47R directly retains GDP but loses efficient GTP binding; other variants were assessed with cell-expressed limited-proteolysis assays.

GNAI3-variant signaling in HEK293T cells CELL_LINE

Five ACS-associated GNAI3 variants were studied in transfected HEK293T cells using protease protection, receptor co-immunoprecipitation and BRET. ET-1-induced Gq activation was reduced at an 8:1 Gq-to-Gi3 expression ratio; the weak Gi3 response was not comparably inhibited.

Cell source

Transfected human embryonic kidney 293T cell line

Publication

PMID:27072656

Pathograph links

Increased Mutant GNAI3 Receptor Association measures observes: cellular Co-immunoprecipitation shows greater mutant association with EDNRA.

Limitations: Association abundance is not an equilibrium-affinity or residence-time measurement.

Show evidence (1 reference)

PMID:27072656 SUPPORT PRIMARY RESULT In Vitro

"We found that all 5 ACS-associated Gαi3 mutants displayed increased binding (3- to 5-fold) to myc-tagged ETAR compared to Gαi3 WT (Fig. 5D)."

Co-immunoprecipitation measures increased receptor association, not a directly measured receptor residence time or equilibrium affinity.

Reduced EDNRA-Gq Signaling measures observes: cellular BRET measures reduced Gq activation after ET-1 stimulation.

Limitations: Heterologous expression does not establish the exact signaling stoichiometry in human arch cells.

Readouts

ET-1-induced Gq BRET response

Mutants reduce the response by about 65–85% under the tested condition.

Show evidence (1 reference)

PMID:27072656 SUPPORT PRIMARY RESULT In Vitro

"We found that expression of any of the five ACS-associated Gαi3 mutants decreased Gq activation upon ET-1 stimulation ~65 to 85% (Fig. 6D)."

HEK293T BRET assays show reduced Gq activation when mutant Gi3 is coexpressed at a substoichiometric ratio.

Show evidence (1 reference)

PMID:27072656 SUPPORT PRIMARY RESULT In Vitro

"We found that expression of any of the five ACS-associated Gαi3 mutants decreased Gq activation upon ET-1 stimulation ~65 to 85% (Fig. 6D)."

HEK293T BRET assays show reduced Gq activation when mutant Gi3 is coexpressed at a substoichiometric ratio.

Expression was adjusted between constructs. Co-immunoprecipitation supports increased association, while irreversible trapping, binding kinetics and human embryonic cell specificity remain inferred.

Show evidence (2 references)

PMID:27072656 SUPPORT PRIMARY RESULT In Vitro

"We found that all 5 ACS-associated Gαi3 mutants displayed increased binding (3- to 5-fold) to myc-tagged ETAR compared to Gαi3 WT (Fig. 5D)."

Co-immunoprecipitation measures increased receptor association, not a directly measured receptor residence time or equilibrium affinity.

PMID:27072656 SUPPORT PRIMARY RESULT In Vitro

"We found that expression of any of the five ACS-associated Gαi3 mutants decreased Gq activation upon ET-1 stimulation ~65 to 85% (Fig. 6D)."

HEK293T BRET assays show reduced Gq activation when mutant Gi3 is coexpressed at a substoichiometric ratio.

PLCB4-variant DAG and transcriptional reporter assays CELL_LINE

HEK293T cells express EDNRA, wild-type or variant PLCB4 and DAG sensors. Arg621His and three other tested ACS substitutions attenuate the stimulated signal; synthetic Pro838Ala in cis with Arg621His reduces interference. A separate HEK293 SRE-luciferase experiment assesses downstream reporter output with constitutively active Gq.

Cell source

Transfected HEK293T cells for DAG assays; HEK293 cells for SRE reporter

Publication

PMID:35284927

Pathograph links

Reduced EDNRA-Dependent Phospholipase C Activity perturbs observes: cellular Patient-associated substitutions attenuate pathway output and interface disruption reduces interference.

Limitations: The mechanism beyond Gq-interface dependence is unresolved.

Readouts

EDN1-stimulated DAG sensor response

BRET and membrane translocation responses are attenuated by tested variants.

Show evidence (1 reference)

PMID:35284927 SUPPORT PRIMARY RESULT In Vitro

"These results illustrate that PLCB4 p.Arg621His interferes with PLCB activity even when it is expressed at a sub-stoichiometric level relative to wild-type PLCB4, exemplifying a characteristic of a dominant-negative protein."

DAG-sensor BRET detects dominant interference by Arg621His; three additional tested missense variants also attenuated the response.

Show evidence (2 references)

PMID:35284927 SUPPORT PRIMARY RESULT In Vitro

"These results illustrate that PLCB4 p.Arg621His interferes with PLCB activity even when it is expressed at a sub-stoichiometric level relative to wild-type PLCB4, exemplifying a characteristic of a dominant-negative protein."

DAG-sensor BRET detects dominant interference by Arg621His; three additional tested missense variants also attenuated the response.

+ 1 more reference

DAG-sensor and SRE readouts are not purified-enzyme kinetics, a direct ERK-phosphorylation assay or fetal DLX expression. Proposed PIP2 trapping and altered GAP function were not directly tested. The synthetic interface mutation is not a clinical therapy.

Show evidence (2 references)

PMID:35284927 SUPPORT PRIMARY RESULT In Vitro

"These results illustrate that PLCB4 p.Arg621His interferes with PLCB activity even when it is expressed at a sub-stoichiometric level relative to wild-type PLCB4, exemplifying a characteristic of a dominant-negative protein."

DAG-sensor BRET detects dominant interference by Arg621His; three additional tested missense variants also attenuated the response.

PMID:35284927 SUPPORT PRIMARY RESULT In Vitro

"indicating that the p.Pro838Ala mutation diminished the dominant-negative effect of PLCB4 p.Arg621His."

An additional synthetic interface substitution attenuates the variant-dependent signaling defect.

ACS patient mandibular osteoblast cultures PRIMARY_CELL_CULTURE

Mandibular osteoblasts from four ACS probands, including two GNAI3 Gly40Arg cases, one PLCB4 Tyr623Cys case and one unresolved case, were compared with 17 control calvarial osteoblast samples. DLX5 and DLX6 steady-state transcripts were lower.

Cell source

Patient mandibular and control calvarial osteoblasts

Publication

PMID:22560091

Pathograph links

Reduced DLX5 and DLX6 Expression measures observes: cellular RT-qPCR detects lower DLX transcript abundance in the patient cultures.

Limitations: Anatomical source and developmental-stage differences remain potential confounders.

Readouts

DLX5 and DLX6 transcripts

Mean DLX5 and DLX6 expression was sixfold and eightfold lower, respectively.

Show evidence (1 reference)

PMID:22560091 SUPPORT PRIMARY RESULT In Vitro

"Using quantitative, real-time RT-PCR of steady-state mRNA, we identified a 6-fold reduction of DLX5 (p < 0.005; probands versus controls) and an 8-fold reduction of DLX6 expression (p < 0.001) in mandibular osteoblasts from selective probands relative to 17 randomly selected calvarial..."

Four ACS mandibular-osteoblast cultures were compared with 17 calvarial-osteoblast controls; anatomical source and developmental stage limit interpretation.

Show evidence (1 reference)

PMID:22560091 SUPPORT PRIMARY RESULT In Vitro

"Using quantitative, real-time RT-PCR of steady-state mRNA, we identified a 6-fold reduction of DLX5 (p < 0.005; probands versus controls) and an 8-fold reduction of DLX6 expression (p < 0.001) in mandibular osteoblasts from selective probands relative to 17 randomly selected calvarial..."

Four ACS mandibular-osteoblast cultures were compared with 17 calvarial-osteoblast controls; anatomical source and developmental stage limit interpretation.

The control and patient cells come from different cranial bones. Postnatal culture, small sample size and the unresolved genotype preclude treating the mean expression difference as a direct measurement of fetal neural-crest signaling. No correction or rescue was performed.

Show evidence (1 reference)

PMID:22560091 SUPPORT PRIMARY RESULT In Vitro

"Using quantitative, real-time RT-PCR of steady-state mRNA, we identified a 6-fold reduction of DLX5 (p < 0.005; probands versus controls) and an 8-fold reduction of DLX6 expression (p < 0.001) in mandibular osteoblasts from selective probands relative to 17 randomly selected calvarial..."

Four ACS mandibular-osteoblast cultures were compared with 17 calvarial-osteoblast controls; anatomical source and developmental stage limit interpretation.

Regulatory-duplication patient iPSC neural-crest cultures IPSC_DERIVED_MODEL

iPSCs from three affected members of one family and three controls were differentiated toward neural crest. Patient cultures showed increased TWIST1 and HDAC9 mRNA and reduced 24-hour scratch closure without a detected cell-cycle distribution difference.

Cell source

Three patient-derived and three unrelated control iPSC lines

Publication

PMID:34750192

Pathograph links

Increased Neural Crest TWIST1 Expression measures observes: cellular Patient-derived iNCCs show increased TWIST1 mRNA.

Limitations: The causal contribution of this expression difference is unisolated.

Show evidence (1 reference)

PMID:34750192 SUPPORT INDIRECT PRIMARY RESULT In Vitro

"However, an increase in HDAC9 (3.15-fold, unpaired t-test p=0.009) and TWIST1 (2.03-fold, unpaired t-test p=0.03) mRNA was observed in the ARCND-iNCC (figure 2A, B) compared with controls (unpaired t-test)."

Three affected-donor iPSC-derived neural-crest cultures show increased transcripts relative to three controls; no isogenic correction isolates the causal mediator.

Increased Neural Crest HDAC9 Expression measures observes: cellular Patient-derived iNCCs also show increased HDAC9 mRNA.

Limitations: Transcript abundance does not establish catalytic isoform activity.

Show evidence (1 reference)

PMID:34750192 SUPPORT INDIRECT PRIMARY RESULT In Vitro

"However, an increase in HDAC9 (3.15-fold, unpaired t-test p=0.009) and TWIST1 (2.03-fold, unpaired t-test p=0.03) mRNA was observed in the ARCND-iNCC (figure 2A, B) compared with controls (unpaired t-test)."

Three affected-donor iPSC-derived neural-crest cultures show increased transcripts relative to three controls; no isogenic correction isolates the causal mediator.

Reduced Migration of Patient-Derived Neural Crest Cells measures observes: cellular Scratch closure is reduced over 24 hours.

Limitations: This does not demonstrate migration into human pharyngeal arches.

Readouts

Scratch wound closure

Patient cultures close less of the scratch area after 24 hours.

Show evidence (1 reference)

PMID:34750192 SUPPORT INDIRECT PRIMARY RESULT In Vitro

"Although no significant difference in cell cycle distribution was detected between patient and control cells, a significant decrease in migratory capacity of ARCND iNCCs was observed compared with controls (4.3-fold decrease, Student’s t-test, p=0.0009) (figure 2C–E)."

A 24-hour scratch assay measures reduced wound closure in the patient-derived cultures; it does not measure migration into human pharyngeal arches.

Show evidence (1 reference)

PMID:34750192 SUPPORT INDIRECT PRIMARY RESULT In Vitro

"Although no significant difference in cell cycle distribution was detected between patient and control cells, a significant decrease in migratory capacity of ARCND iNCCs was observed compared with controls (4.3-fold decrease, Student’s t-test, p=0.0009) (figure 2C–E)."

A 24-hour scratch assay measures reduced wound closure in the patient-derived cultures; it does not measure migration into human pharyngeal arches.

Controls were not isogenic; one control was reprogrammed by a different method. Capture-C was performed in separate nonpatient embryonic calvarial mesenchyme and does not demonstrate altered contacts in these patient cells. No TWIST1-specific correction, rescue or necessity experiment was performed. EDN-pathway transcripts were unchanged or too low to assess, not proof of normal signaling.

Show evidence (2 references)

PMID:34750192 SUPPORT INDIRECT PRIMARY RESULT In Vitro

"However, an increase in HDAC9 (3.15-fold, unpaired t-test p=0.009) and TWIST1 (2.03-fold, unpaired t-test p=0.03) mRNA was observed in the ARCND-iNCC (figure 2A, B) compared with controls (unpaired t-test)."

Three affected-donor iPSC-derived neural-crest cultures show increased transcripts relative to three controls; no isogenic correction isolates the causal mediator.

PMID:34750192 SUPPORT INDIRECT PRIMARY RESULT In Vitro

"Although no significant difference in cell cycle distribution was detected between patient and control cells, a significant decrease in migratory capacity of ARCND iNCCs was observed compared with controls (4.3-fold decrease, Student’s t-test, p=0.0009) (figure 2C–E)."

A 24-hour scratch assay measures reduced wound closure in the patient-derived cultures; it does not measure migration into human pharyngeal arches.

Regulatory-duplication neural-crest mesenchymal derivatives IPSC_DERIVED_MODEL

Mesenchymal-like cells differentiated from the same iPSC neural-crest cultures show reduced day-9 ALP activity and a modest reduction in mineralization after osteogenic induction. TWIST1 and RUNX2 expression did not significantly differ during the tested osteogenic interval.

Cell source

Patient and control iPSC-derived neural-crest mesenchymal-like cells

Publication

PMID:34750192

Pathograph links

Impaired Osteogenic Differentiation in Patient-Derived Cells measures observes: cellular ALP and mineralization provide osteogenic differentiation readouts.

Limitations: These cellular outcomes do not prove mediation of patient mandibular hypoplasia.

Readouts

Alkaline-phosphatase activity

ALP activity is lower after nine days of osteoinduction.

Show evidence (1 reference)

PMID:34750192 SUPPORT INDIRECT PRIMARY RESULT In Vitro

"Our data showed that during osteogenic differentiation, ALP enzymatic activity was significantly diminished in ARCND-nMSCs after 9 days of osteoinduction (decrease of 20.3-fold, paired t-test p=0.029; figure 3A, B)."

Patient-derived neural-crest mesenchymal cells show reduced alkaline-phosphatase activity during osteogenic induction.

Show evidence (1 reference)

PMID:34750192 SUPPORT INDIRECT PRIMARY RESULT In Vitro

"Our data showed that during osteogenic differentiation, ALP enzymatic activity was significantly diminished in ARCND-nMSCs after 9 days of osteoinduction (decrease of 20.3-fold, paired t-test p=0.029; figure 3A, B)."

Patient-derived neural-crest mesenchymal cells show reduced alkaline-phosphatase activity during osteogenic induction.

There is no isogenic rescue or demonstrated chain from TWIST1 upregulation to altered dimerization, RUNX2 inhibition or bone loss. Figure-caption timing of the representative mineralization micrograph is inconsistent; the quantitative mineralization caption specifies 21 days.

Show evidence (1 reference)

PMID:34750192 SUPPORT INDIRECT PRIMARY RESULT In Vitro

"Our data showed that during osteogenic differentiation, ALP enzymatic activity was significantly diminished in ARCND-nMSCs after 9 days of osteoinduction (decrease of 20.3-fold, paired t-test p=0.029; figure 3A, B)."

Patient-derived neural-crest mesenchymal cells show reduced alkaline-phosphatase activity during osteogenic induction.

🐁

Animal Models

4

Plcb4 Arg621His edited mouse founders

CRISPR/HDR founders show proximal mandibular dysplasia, reduced or absent mandibular processes and ectopic bony structures. Three knock-in-bearing embryos were identified among 69 collected. Wild-type/indel embryos and unmodified controls lacked overt skull changes in the reported comparison.

Species

Mouse

Genotype

One Plcb4 Arg621His/Arg621His and two Arg621His/indel founders

Background

C57BL/6NJ zygotes; F0 embryos examined at E18.5

Publication

PMID:35284927

Pathograph links

Abnormal Mandibular Skeletal Morphogenesis recapitulates observes: organism Embryonic skeletal imaging and staining demonstrate abnormal proximal mandibular development.

Limitations: Small F0 sample and mixed edited genotypes limit extrapolation to dominant human inheritance.

Readouts

Mandibular process morphology

Condylar, coronoid and angular processes are hypoplastic or absent.

Show evidence (1 reference)

PMID:35284927 SUPPORT PRIMARY RESULT Model Organism

"the proximal mandible of Plcb4Indel/KI and Plcb4KI/KI embryos was disorganized, with absent or hypoplastic mandibular processes"

E18.5 edited mouse founders show proximal mandibular skeletal abnormalities; the tested genotypes are not simple wild-type/knock-in heterozygotes.

Show evidence (1 reference)

PMID:35284927 SUPPORT PRIMARY RESULT Model Organism

"the proximal mandible of Plcb4Indel/KI and Plcb4KI/KI embryos was disorganized, with absent or hypoplastic mandibular processes"

E18.5 edited mouse founders show proximal mandibular skeletal abnormalities; the tested genotypes are not simple wild-type/knock-in heterozygotes.

No wild-type/knock-in embryo was tested. These founder observations do not demonstrate the phenotype of a stable heterozygous line, adult function or therapeutic rescue. Tooth-like projections were morphologic observations rather than confirmed teeth.

Show evidence (2 references)

PMID:35284927 SUPPORT PRIMARY RESULT Model Organism

"Of the 69 embryos harvested at E18.5, we identified three embryos harboring at least one knock-in allele; one was homozygous for the knock-in allele (Plcb4KI/KI) and the other two were compound heterozygotes harboring the knock-in allele and an insertion/deletion (indel) allele generated by..."

The actual founders comprise one homozygote and two knock-in/indel embryos, not simple heterozygotes.

PMID:35284927 SUPPORT PRIMARY RESULT Model Organism

"the proximal mandible of Plcb4Indel/KI and Plcb4KI/KI embryos was disorganized, with absent or hypoplastic mandibular processes"

E18.5 edited mouse founders show proximal mandibular skeletal abnormalities; the tested genotypes are not simple wild-type/knock-in heterozygotes.

Endothelin-pathway knockout mice

These knockout models demonstrate mandibular-to-maxillary homeosis and other craniofacial abnormalities. They establish developmental pathway requirements rather than reproducing the precise human alleles.

Species

Mouse

Genotype

Edn1-null, Ednra-null or Ece1-null models summarized in the developmental literature

Pathograph links

Disrupted Mandibular Neural Crest Identity perturbs observes: organism Pathway-gene deletion changes mandibular positional identity.

Limitations: Different genes and null alleles are grouped only for the shared developmental result.

Show evidence (1 reference)

PMID:24123988 SUPPORT REVIEW SYNTHESIS Model Organism

"Disruption of this signaling pathway in both mouse and zebrafish results in loss of identity of neural crest cells of the mandibular portion of the first pharyngeal arch and the subsequent repatterning of these cells, leading to homeosis of lower jaw structures into more maxillary-like structures."

Genetic developmental models support altered identity rather than a universal neural-crest migration deficit.

Null models can have cardiovascular defects and severe neonatal outcomes beyond typical human ACS. Partial allelic reduction and species-specific compensation complicate direct phenotype matching.

Show evidence (1 reference)

PMID:24123988 SUPPORT REVIEW SYNTHESIS Model Organism

"mice that are homozygous null for Edn1, Ednra, endothelin converting enzyme 1 (Ece1) or Dlx5/Dlx6 display a homeotic transformation of the lower jaw into an upper jaw"

The review summarizes distinct developmental knockout models.

Zebrafish edn1 and plcb3 developmental mutants

Mutants show hypoplastic lower-jaw skeletal elements and fusion across arch joints. Genetic interaction supports a conserved endothelin-phospholipase pathway.

Species

Zebrafish

Genotype

edn1 mutants and schmerle/plcb3 mutants summarized in the developmental literature

Pathograph links

Disrupted Mandibular Neural Crest Identity perturbs observes: organism Endothelin-pathway perturbation alters lower-jaw patterning.

Limitations: Paralog and species differences constrain direct allelic interpretation.

Show evidence (1 reference)

PMID:24123988 SUPPORT REVIEW SYNTHESIS Model Organism

"Disruption of this signaling pathway in both mouse and zebrafish results in loss of identity of neural crest cells of the mandibular portion of the first pharyngeal arch and the subsequent repatterning of these cells, leading to homeosis of lower jaw structures into more maxillary-like structures."

Genetic developmental models support altered identity rather than a universal neural-crest migration deficit.

Zebrafish plcb3 is not the human PLCB4 gene, and species-specific compensation affects distal versus intermediate arch domains. These models do not establish a human treatment.

Show evidence (1 reference)

PMID:24123988 SUPPORT REVIEW SYNTHESIS Model Organism

"zebrafish with combined heterozygous mutations in plcb3 and edn1 (the ligand of the EDNRA) demonstrated a more severe phenotype than either mutant alone."

The review summarizes genetic interaction in fish.

GNAI3-variant expression in Xenopus embryos

Expression of G40R, G45V, S47R, T48N or N269Y increases a gastrulation-associated gravitational-inversion phenotype relative to wild-type GNAI3 expression at the tested doses.

Species

Xenopus laevis

Genotype

Injected mRNA encoding wild-type or ACS-associated GNAI3 variants

Pathograph links

Heterozygous GNAI3 Variants perturbs observes: organism Introduces the disease-associated protein substitutions into an embryonic expression assay.

Limitations: mRNA injection does not recreate a heterozygous human genomic allele; the endpoint is gastrulation, not jaw formation.

Show evidence (1 reference)

PMID:27072656 SUPPORT PRIMARY RESULT Model Organism

"Although it is not known what specific signaling pathways are disrupted by the ectopic expression of Gαi, this system provides a suitable platform to test whether G protein mutants induce a gain or loss of function in the context of embryonic development."

The source explicitly limits pathway specificity.

This is an ectopic-expression developmental bioassay scored around neurulation, not an ACS craniofacial model. The signaling pathway responsible for the inversion phenotype was not established, and it is not evidence of facial rescue or a nucleotide-binding assay in vivo.

Show evidence (1 reference)

PMID:27072656 SUPPORT PRIMARY RESULT Model Organism

"expression of any of the five mutants (G40R, G45V, S47R, T48N and N269Y) increased the frequency of gravitational inversion in embryos compared to those expressing wild-type Gαi3"

Variant expression modifies the embryonic bioassay phenotype.

{ }

Source YAML

click to show

name: Auriculocondylar Syndrome
creation_date: '2026-05-10T15:02:55Z'
description: Auriculocondylar syndrome is a congenital craniofacial disorder characterized by variable mandibular and condylar hypoplasia, question-mark ears and associated oral or temporomandibular abnormalities. Severe presentations can compromise breathing and feeding. Dominant GNAI3 or PLCB4 variants, recessive PLCB4 or EDN1 alleles, and a reported HDAC9-TWIST1 regulatory duplication act through distinct molecular routes. Development, hearing and extra-craniofacial findings are variable; incomplete penetrance occurs.
category: Mendelian
parents:
- ear malformation
- craniofacial malformation syndrome
synonyms:
- auriculo-condylar syndrome
- question mark ear syndrome
- dysgnathia complex
disease_term:
  preferred_term: auriculocondylar syndrome
  term:
    id: MONDO:0000107
    label: auriculocondylar syndrome
has_subtypes:
- name: ARCND1
  display_name: ARCND1 (GNAI3-related)
  subtype_term:
    preferred_term: ARCND1 (OMIM:602483)
    term:
      id: MONDO:0011234
      label: auriculocondylar syndrome 1
  genes:
  - preferred_term: GNAI3
    term:
      id: hgnc:4387
      label: GNAI3
  description: Usually autosomal dominant auriculocondylar syndrome caused by heterozygous GNAI3 variants affecting GDP/GTP-binding motifs and EDN1 pathway signaling.
  evidence:
  - reference: PMID:38618928
    reference_title: 'Auriculocondylar syndrome 2 caused by a novel PLCB4 variant in a male Chinese neonate: A case report and review of the literature.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: 'Four subtypes of ARCND have been described so far, that is, ARCND1 (OMIM # 602483), ARCND2 (ARCND2A, OMIM # 614669; ARCND2B, OMIM # 620458), ARCND3 (OMIM # 615706), and ARCND4 (OMIM # 620457).'
    explanation: This identifies ARCND1 and its OMIM identifier.
    quote_role: BACKGROUND
  - reference: PMID:22560091
    reference_title: A human homeotic transformation resulting from mutations in PLCB4 and GNAI3 causes auriculocondylar syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: In both kindreds, the p.Gly40Arg variant was inherited; in one case (S011) it was inherited from an affected mother (S012-P), and in the other (S008), from an unaffected father (S009-P), documenting incomplete penetrance.
    explanation: Two molecularly characterized families establish dominant inheritance with incomplete penetrance.
- name: ARCND2A
  display_name: ARCND2A (PLCB4-related, autosomal dominant)
  subtype_term:
    preferred_term: ARCND2A (OMIM:614669)
    term:
      id: MONDO:0013845
      label: auriculocondylar syndrome 2
  genes:
  - preferred_term: PLCB4
    term:
      id: hgnc:9059
      label: PLCB4
  description: 'Autosomal dominant PLCB4-related auriculocondylar syndrome, typically caused by heterozygous missense variants. Note on the binding: MONDO has not adopted OMIM''s ARCND2A/2B relabel, so MONDO:0013845 is still plain "auriculocondylar syndrome 2" with no "2A" synonym and no inheritance axiom. It is bound here on the strength of its OMIM:614669 xref, which matches this row exactly. It and MONDO:0957544 (bound to the ARCND2B row below) both point at PLCB4 and are distinguished only by OMIM entry, not by a dominant/recessive assertion in MONDO.'
  evidence:
  - reference: PMID:38618928
    reference_title: 'Auriculocondylar syndrome 2 caused by a novel PLCB4 variant in a male Chinese neonate: A case report and review of the literature.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: 'Four subtypes of ARCND have been described so far, that is, ARCND1 (OMIM # 602483), ARCND2 (ARCND2A, OMIM # 614669; ARCND2B, OMIM # 620458), ARCND3 (OMIM # 615706), and ARCND4 (OMIM # 620457).'
    explanation: This identifies ARCND2A and its OMIM identifier.
    quote_role: BACKGROUND
  - reference: PMID:35284927
    reference_title: Auriculocondylar syndrome 2 results from the dominant-negative action of PLCB4 variants.
    supports: SUPPORT
    evidence_source: IN_VITRO
    quote_role: PRIMARY_RESULT
    snippet: These results illustrate that PLCB4 p.Arg621His interferes with PLCB activity even when it is expressed at a sub-stoichiometric level relative to wild-type PLCB4, exemplifying a characteristic of a dominant-negative protein.
    explanation: DAG-sensor BRET detects dominant interference by Arg621His; three additional tested missense variants also attenuated the response.
- name: ARCND2B
  display_name: ARCND2B (PLCB4-related, autosomal recessive)
  subtype_term:
    preferred_term: ARCND2B (OMIM:620458)
    term:
      id: MONDO:0957544
      label: auriculocondylar syndrome 2B
  genes:
  - preferred_term: PLCB4
    term:
      id: hgnc:9059
      label: PLCB4
  description: Autosomal recessive PLCB4-related auriculocondylar syndrome caused by biallelic loss-of-function or damaging PLCB4 variants.
  evidence:
  - reference: PMID:38618928
    reference_title: 'Auriculocondylar syndrome 2 caused by a novel PLCB4 variant in a male Chinese neonate: A case report and review of the literature.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: 'Four subtypes of ARCND have been described so far, that is, ARCND1 (OMIM # 602483), ARCND2 (ARCND2A, OMIM # 614669; ARCND2B, OMIM # 620458), ARCND3 (OMIM # 615706), and ARCND4 (OMIM # 620457).'
    explanation: This identifies ARCND2B and its OMIM identifier.
    quote_role: BACKGROUND
  - reference: PMID:23315542
    reference_title: Heterogeneity of mutational mechanisms and modes of inheritance in auriculocondylar syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: The consanguineous parents of the patient with a homozygous PLCB4 deletion each harboured the heterozygous deletion, but did not present the ACS phenotype, further suggesting that ACS is not caused by PLCB4 haploinsufficiency.
    explanation: Segregation demonstrates a recessive deletion mechanism in one family.
- name: ARCND3
  display_name: ARCND3 (EDN1-related)
  subtype_term:
    preferred_term: ARCND3 (OMIM:615706)
    term:
      id: MONDO:0014312
      label: auriculocondylar syndrome 3
  genes:
  - preferred_term: EDN1
    term:
      id: hgnc:3176
      label: EDN1
  description: EDN1-related ACS is established with recessive alleles. Dominant EDN1 variants also cause isolated question-mark ears, and a heterozygous start-loss case had mild mandibular involvement. Residual ligand activity is a proposed explanation for allelic differences, not a direct patient-allele assay.
  evidence:
  - reference: PMID:38618928
    reference_title: 'Auriculocondylar syndrome 2 caused by a novel PLCB4 variant in a male Chinese neonate: A case report and review of the literature.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: 'Four subtypes of ARCND have been described so far, that is, ARCND1 (OMIM # 602483), ARCND2 (ARCND2A, OMIM # 614669; ARCND2B, OMIM # 620458), ARCND3 (OMIM # 615706), and ARCND4 (OMIM # 620457).'
    explanation: This identifies ARCND3 and its OMIM identifier.
    quote_role: BACKGROUND
  - reference: PMID:24268655
    reference_title: Mutations in endothelin 1 cause recessive auriculocondylar syndrome and dominant isolated question-mark ears.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: In family F1, the unaffected parents and child were heterozygous for the mutation, whereas the three affected siblings were homozygous, indicating that the allele encoding the p.Lys91Glu substitution behaves in a recessive manner.
    explanation: Segregation supports recessive inheritance of Lys91Glu in this family.
- name: ARCND4
  display_name: ARCND4 (TWIST1 regulatory duplication)
  subtype_term:
    preferred_term: ARCND4 (OMIM:620457)
    term:
      id: MONDO:0957543
      label: auriculocondylar syndrome 4
  genes:
  - preferred_term: TWIST1
    term:
      id: hgnc:12428
      label: TWIST1
  description: A 430-kb tandem duplication within HDAC9, outside TWIST1 coding sequence, segregated in one family. It encompasses candidate TWIST1 regulatory elements and is associated with increased TWIST1 and HDAC9 expression in patient-derived neural-crest cells; the causal contributions of these changes remain unresolved.
  evidence:
  - reference: PMID:38618928
    reference_title: 'Auriculocondylar syndrome 2 caused by a novel PLCB4 variant in a male Chinese neonate: A case report and review of the literature.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: 'Four subtypes of ARCND have been described so far, that is, ARCND1 (OMIM # 602483), ARCND2 (ARCND2A, OMIM # 614669; ARCND2B, OMIM # 620458), ARCND3 (OMIM # 615706), and ARCND4 (OMIM # 620457).'
    explanation: This identifies ARCND4 and its OMIM identifier.
    quote_role: BACKGROUND
  - reference: PMID:34750192
    reference_title: 'New locus underlying auriculocondylar syndrome (ARCND): 430 kb duplication involving TWIST1 regulatory elements.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: The duplication spanned 430 302 bp (NC_000007.14:g.18437239_18867540dup) telomeric to TWIST1, covering most of the HDAC9 gene.
    explanation: A segregating tandem duplication in one four-generation family defines the regulatory locus; TWIST1 coding sequence is not duplicated.
- name: IQME
  display_name: Isolated question-mark ears (dominant EDN1)
  subtype_term:
    preferred_term: isolated question-mark ears
    term:
      id: MONDO:0013013
      label: question mark ears, isolated
  genes:
  - preferred_term: EDN1
    term:
      id: hgnc:3176
      label: EDN1
  inheritance:
  - name: Autosomal dominant inheritance
    inheritance_term:
      preferred_term: Autosomal dominant inheritance
      term:
        id: HP:0000006
        label: Autosomal dominant inheritance
  description: >-
    The mild end of the EDN1 arm: the lobe-helix defect without the mandibular and
    condylar features, transmitted vertically. It is recorded as a subtype row
    rather than a separate entry because MONDO files it under auriculocondylar
    syndrome and because it shares this entry's gene, its EDN1 Disease Alleles and
    Reduced Bioactive EDN1 Availability nodes, and its question-mark-ear
    phenotype; what separates it
    from the ARCND3 row is the allele's dose, not the mechanism. The founding
    report's proposed model is that heterozygous null alleles give isolated ears
    while hypomorphic alleles give the syndrome only when homozygous, which
    remains a model rather than a measured allele series.
  evidence:
  - reference: PMID:24268655
    reference_title: Mutations in endothelin 1 cause recessive auriculocondylar syndrome and dominant isolated question-mark ears.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: WES of two cases with vertical transmission of isolated QMEs revealed a stop mutation in EDN1 in one family and a missense substitution of a highly conserved residue in the mature EDN1 peptide in the other.
    explanation: The gene-disease assertion this subtype row carries, with the vertical transmission that makes it the dominant arm.
  - reference: PMID:24268655
    reference_title: Mutations in endothelin 1 cause recessive auriculocondylar syndrome and dominant isolated question-mark ears.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: The different modes of inheritance suggest that the degree of residual EDN1 activity differs depending on the mutation.
    explanation: The authors' own account of why the same gene yields an isolated ear defect in one family and the full syndrome in another; it is offered as a suggestion, which is why the description does not state it as established.
inheritance:
- name: Autosomal dominant
  inheritance_term:
    preferred_term: Autosomal dominant inheritance
    term:
      id: HP:0000006
      label: Autosomal dominant inheritance
  expressivity: VARIABLE
  description: Many reported PLCB4 and GNAI3 families show autosomal dominant inheritance, often with variable expressivity and incomplete penetrance.
  evidence:
  - reference: PMID:28328130
    reference_title: Targeted molecular investigation in patients within the clinical spectrum of Auriculocondylar syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Auriculocondylar syndrome, mainly characterized by micrognathia, small mandibular condyle, and question mark ears, is a rare disease segregating in an autosomal dominant pattern in the majority of the families reported in the literature.
    explanation: This cohort review directly supports autosomal dominant inheritance as the most common reported pattern.
    quote_role: BACKGROUND
  - reference: PMID:38618928
    reference_title: 'Auriculocondylar syndrome 2 caused by a novel PLCB4 variant in a male Chinese neonate: A case report and review of the literature.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: As with other studies examining familial cases of ARCND2, incomplete penetrance and variable expressivity were observed within different families' heterozygous mutations in PLCB4 gene.
    explanation: The 2024 review supports variable expressivity and incomplete penetrance in PLCB4-related families.
    quote_role: REVIEW_SYNTHESIS
- name: Autosomal recessive
  inheritance_term:
    preferred_term: Autosomal recessive inheritance
    term:
      id: HP:0000007
      label: Autosomal recessive inheritance
  description: Recessive auriculocondylar syndrome has been reported for EDN1 variants and for biallelic PLCB4 loss-of-function lesions.
  evidence:
  - reference: PMID:24268655
    reference_title: Mutations in endothelin 1 cause recessive auriculocondylar syndrome and dominant isolated question-mark ears.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: By whole-exome sequencing (WES), we identified a homozygous substitution in a furin cleavage site of the EDN1 proprotein in ACS-affected siblings born to consanguineous parents.
    explanation: This directly supports recessive EDN1-related auriculocondylar syndrome.
    quote_role: PRIMARY_RESULT
  - reference: PMID:23315542
    reference_title: Heterogeneity of mutational mechanisms and modes of inheritance in auriculocondylar syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: 'CONCLUSIONS: These findings indicate that ACS is not only genetically heterogeneous but also an autosomal dominant or recessive condition according to the nature of the PLCB4 gene lesion.'
    explanation: This directly supports recessive inheritance for some PLCB4 lesions.
    quote_role: PRIMARY_RESULT
classifications:
  isds_skeletal_category:
  - classification_value: dysostoses_with_predominant_craniofacial_involvement
    notes: ISDS Nosology and Classification of Genetic Skeletal Disorders, 2019 revision (Mortier et al., PMID:31633310), Table 1 group 34 "Dysostoses with predominant craniofacial involvement"; listed as "Auriculocondylar syndrome types 1-3, which this entry lumps".
pathophysiology:
- name: Heterozygous GNAI3 Variants
  biological_scale: MOLECULAR
  description: Heterozygous pathogenic GNAI3 variants cluster in nucleotide-binding regions. De novo and inherited alleles occur, with variable expression and some clinically unaffected carriers. Functional conclusions below apply to the five tested missense variants rather than every subsequently reported allele.
  evidence:
  - reference: PMID:22560091
    reference_title: A human homeotic transformation resulting from mutations in PLCB4 and GNAI3 causes auriculocondylar syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: In both kindreds, the p.Gly40Arg variant was inherited; in one case (S011) it was inherited from an affected mother (S012-P), and in the other (S008), from an unaffected father (S009-P), documenting incomplete penetrance.
    explanation: Two molecularly characterized families establish dominant inheritance with incomplete penetrance.
  genes:
  - preferred_term: GNAI3
    term:
      id: hgnc:4387
      label: GNAI3
  downstream:
  - target: Impaired GNAI3 GTP Binding
    description: Patient-associated substitutions impair nucleotide-dependent activation in the tested proteins.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:27072656
      reference_title: Dominant-negative Gα subunits are a mechanism of dysregulated heterotrimeric G protein signaling in human disease.
      supports: SUPPORT
      evidence_source: IN_VITRO
      quote_role: PRIMARY_RESULT
      snippet: Together, these results demonstrate that Gαi3 S47R retains the capability to bind GDP but fails to bind GTP, rendering the G protein unable to switch into an active conformation.
      explanation: Purified S47R directly retains GDP but loses efficient GTP binding; other variants were assessed with cell-expressed limited-proteolysis assays.
  - target: Question mark ear
    description: This molecular subtype is associated with the characteristic pinna malformation; the detailed cellular route to lobe-helix separation is unresolved.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:22560091
      reference_title: A human homeotic transformation resulting from mutations in PLCB4 and GNAI3 causes auriculocondylar syndrome.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: PRIMARY_RESULT
      snippet: In both kindreds, the p.Gly40Arg variant was inherited; in one case (S011) it was inherited from an affected mother (S012-P), and in the other (S008), from an unaffected father (S009-P), documenting incomplete penetrance.
      explanation: Two molecularly characterized families establish dominant inheritance with incomplete penetrance.
    - reference: url:https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf
      reference_title: https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: PRIMARY_RESULT
      snippet: Question mark ear Total 37/38 97%
      explanation: The table counts assessed members of a selected 39-person ACS/IQME cohort.
- name: Impaired GNAI3 GTP Binding
  biological_scale: MOLECULAR
  description: Purified GNAI3 S47R retains GDP binding but fails to bind GTP efficiently. G40R, G45V, T48N and N269Y also show impaired GTP-dependent protease protection after expression in HEK293T cells. This replaces the earlier structure-based gain-of-function prediction; it does not establish generalized loss of GDP binding.
  evidence:
  - reference: PMID:27072656
    reference_title: Dominant-negative Gα subunits are a mechanism of dysregulated heterotrimeric G protein signaling in human disease.
    supports: SUPPORT
    evidence_source: IN_VITRO
    quote_role: PRIMARY_RESULT
    snippet: Together, these results demonstrate that Gαi3 S47R retains the capability to bind GDP but fails to bind GTP, rendering the G protein unable to switch into an active conformation.
    explanation: Purified S47R directly retains GDP but loses efficient GTP binding; other variants were assessed with cell-expressed limited-proteolysis assays.
  genes:
  - preferred_term: GNAI3
    term:
      id: hgnc:4387
      label: GNAI3
  downstream:
  - target: Increased Mutant GNAI3 Receptor Association
    description: Failure to complete nucleotide-dependent activation is proposed to favor nonproductive receptor complexes. Increased association is measured, but the kinetic trapping mechanism is inferred.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:27072656
      reference_title: Dominant-negative Gα subunits are a mechanism of dysregulated heterotrimeric G protein signaling in human disease.
      supports: SUPPORT
      evidence_source: IN_VITRO
      quote_role: PRIMARY_RESULT
      snippet: We found that all 5 ACS-associated Gαi3 mutants displayed increased binding (3- to 5-fold) to myc-tagged ETAR compared to Gαi3 WT (Fig. 5D).
      explanation: Co-immunoprecipitation measures increased receptor association, not a directly measured receptor residence time or equilibrium affinity.
- name: Increased Mutant GNAI3 Receptor Association
  biological_scale: MOLECULAR
  description: The five tested mutant GNAI3 proteins associate more strongly with EDNRA in co-immunoprecipitation and with Ric-8A in yeast assays. Sustained nonproductive receptor occupancy is the proposed explanation for interference with another G-protein class; binding kinetics were not directly measured.
  evidence:
  - reference: PMID:27072656
    reference_title: Dominant-negative Gα subunits are a mechanism of dysregulated heterotrimeric G protein signaling in human disease.
    supports: SUPPORT
    evidence_source: IN_VITRO
    quote_role: PRIMARY_RESULT
    snippet: We found that all 5 ACS-associated Gαi3 mutants displayed increased binding (3- to 5-fold) to myc-tagged ETAR compared to Gαi3 WT (Fig. 5D).
    explanation: Co-immunoprecipitation measures increased receptor association, not a directly measured receptor residence time or equilibrium affinity.
  genes:
  - preferred_term: GNAI3
    term:
      id: hgnc:4387
      label: GNAI3
  downstream:
  - target: Reduced EDNRA-Gq Signaling
    description: Nonproductive mutant-GNAI3 association is proposed to limit receptor availability for Gq activation. The horizontal inhibitory effect is experimentally observed; receptor competition is its mechanistic interpretation.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:27072656
      reference_title: Dominant-negative Gα subunits are a mechanism of dysregulated heterotrimeric G protein signaling in human disease.
      supports: SUPPORT
      evidence_source: IN_VITRO
      quote_role: PRIMARY_RESULT
      snippet: We found that expression of any of the five ACS-associated Gαi3 mutants decreased Gq activation upon ET-1 stimulation ~65 to 85% (Fig. 6D).
      explanation: HEK293T BRET assays show reduced Gq activation when mutant Gi3 is coexpressed at a substoichiometric ratio.
- name: Reduced EDNRA-Gq Signaling
  biological_scale: MOLECULAR
  description: EDNRA preferentially activates Gq in the tested heterologous system. Disease-associated GNAI3 proteins suppress that response while leaving the weak Gi3 response largely unchanged under the same conditions. Normal GNAI3 is therefore not represented as an obligatory positive intermediate between EDNRA and PLCB4.
  evidence:
  - reference: PMID:27072656
    reference_title: Dominant-negative Gα subunits are a mechanism of dysregulated heterotrimeric G protein signaling in human disease.
    supports: SUPPORT
    evidence_source: IN_VITRO
    quote_role: PRIMARY_RESULT
    snippet: We found that expression of any of the five ACS-associated Gαi3 mutants decreased Gq activation upon ET-1 stimulation ~65 to 85% (Fig. 6D).
    explanation: HEK293T BRET assays show reduced Gq activation when mutant Gi3 is coexpressed at a substoichiometric ratio.
  conforms_to: pharyngeal_arch_patterning_serial_homology#Cranial Neural Crest and Pharyngeal Arch Program Perturbation
  downstream:
  - target: Reduced EDNRA-Dependent Phospholipase C Activity
    description: Reduced receptor-coupled Gq activation diminishes phospholipase-C-dependent second-messenger generation.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:35284927
      reference_title: Auriculocondylar syndrome 2 results from the dominant-negative action of PLCB4 variants.
      supports: SUPPORT
      evidence_source: IN_VITRO
      quote_role: PRIMARY_RESULT
      snippet: Furthermore, pretreating cells with a Gq/11-specific small molecule inhibitor YM-254890 (Nishimura et al., 2010; Taniguchi et al., 2003) attenuated the ΔBRET response in a concentration-dependent manner (Fig. 3C).
      explanation: Gq/11 inhibition reduces the EDN1-triggered DAG-sensor response; this establishes pathway dependence in the cell assay.
- name: PLCB4 Disease Alleles
  biological_scale: MOLECULAR
  description: PLCB4 disease alleles include dominant catalytic-domain missense variants and recessive biallelic loss-of-function lesions. Haploinsufficiency alone does not explain the tested dominant variants. The neonatal Ser643Phe report classified its variant as likely pathogenic and supplied structural prediction, not a catalytic assay.
  evidence:
  - reference: PMID:22560091
    reference_title: A human homeotic transformation resulting from mutations in PLCB4 and GNAI3 causes auriculocondylar syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: We identified two additional novel PLCB4 missense mutations at c.1862G>A (M001) and c.1948A>C (M002)
    explanation: The primary report identifies segregating dominant PLCB4 variants.
  - reference: PMID:24268655
    reference_title: Mutations in endothelin 1 cause recessive auriculocondylar syndrome and dominant isolated question-mark ears.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: In addition, two cases have been ascribed to homozygous or compound-heterozygous loss-of-function mutations in PLCB4.
    explanation: Summarizes previously established biallelic PLCB4 cases.
  genes:
  - preferred_term: PLCB4
    term:
      id: hgnc:9059
      label: PLCB4
  downstream:
  - target: Reduced EDNRA-Dependent Phospholipase C Activity
    description: Tested dominant missense alleles interfere with EDNRA-dependent PLC activity. Recessive loss-of-function alleles provide a distinct route to deficient PLCB4 function.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:35284927
      reference_title: Auriculocondylar syndrome 2 results from the dominant-negative action of PLCB4 variants.
      supports: SUPPORT
      evidence_source: IN_VITRO
      quote_role: PRIMARY_RESULT
      snippet: These results illustrate that PLCB4 p.Arg621His interferes with PLCB activity even when it is expressed at a sub-stoichiometric level relative to wild-type PLCB4, exemplifying a characteristic of a dominant-negative protein.
      explanation: DAG-sensor BRET detects dominant interference by Arg621His; three additional tested missense variants also attenuated the response.
  - target: Question mark ear
    description: This molecular subtype is associated with the characteristic pinna malformation; the detailed cellular route to lobe-helix separation is unresolved.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:22560091
      reference_title: A human homeotic transformation resulting from mutations in PLCB4 and GNAI3 causes auriculocondylar syndrome.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: PRIMARY_RESULT
      snippet: We identified two additional novel PLCB4 missense mutations at c.1862G>A (M001) and c.1948A>C (M002)
      explanation: The primary report identifies segregating dominant PLCB4 variants.
    - reference: PMID:24268655
      reference_title: Mutations in endothelin 1 cause recessive auriculocondylar syndrome and dominant isolated question-mark ears.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: REVIEW_SYNTHESIS
      snippet: In addition, two cases have been ascribed to homozygous or compound-heterozygous loss-of-function mutations in PLCB4.
      explanation: Summarizes previously established biallelic PLCB4 cases.
    - reference: url:https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf
      reference_title: https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: PRIMARY_RESULT
      snippet: Question mark ear Total 37/38 97%
      explanation: The table counts assessed members of a selected 39-person ACS/IQME cohort.
- name: Reduced EDNRA-Dependent Phospholipase C Activity
  biological_scale: MOLECULAR
  description: EDN1-stimulated DAG-sensor translocation and BRET are reduced by tested PLCB4 variants in HEK293T cells. Introducing Pro838Ala at the Gq-interaction interface in cis with Arg621His attenuates its dominant interference. These are cell-based pathway readouts, not purified-enzyme kinetics; substrate trapping and altered GAP activity remain untested explanations.
  evidence:
  - reference: PMID:35284927
    reference_title: Auriculocondylar syndrome 2 results from the dominant-negative action of PLCB4 variants.
    supports: SUPPORT
    evidence_source: IN_VITRO
    quote_role: PRIMARY_RESULT
    snippet: These results illustrate that PLCB4 p.Arg621His interferes with PLCB activity even when it is expressed at a sub-stoichiometric level relative to wild-type PLCB4, exemplifying a characteristic of a dominant-negative protein.
    explanation: DAG-sensor BRET detects dominant interference by Arg621His; three additional tested missense variants also attenuated the response.
  genes:
  - preferred_term: PLCB4
    term:
      id: hgnc:9059
      label: PLCB4
  downstream:
  - target: Reduced DLX5 and DLX6 Expression
    description: PLCB4/GNAI3 pathway disruption is associated with reduced downstream DLX expression in patient osteoblasts. The intervening embryonic transcriptional route is not resolved by these cultures.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:22560091
      reference_title: A human homeotic transformation resulting from mutations in PLCB4 and GNAI3 causes auriculocondylar syndrome.
      supports: SUPPORT
      evidence_source: IN_VITRO
      quote_role: PRIMARY_RESULT
      snippet: Using quantitative, real-time RT-PCR of steady-state mRNA, we identified a 6-fold reduction of DLX5 (p < 0.005; probands versus controls) and an 8-fold reduction of DLX6 expression (p < 0.001) in mandibular osteoblasts from selective probands relative to 17 randomly selected calvarial osteoblasts from controls.
      explanation: Four ACS mandibular-osteoblast cultures were compared with 17 calvarial-osteoblast controls; anatomical source and developmental stage limit interpretation.
- name: EDN1 Disease Alleles
  biological_scale: MOLECULAR
  description: Biallelic EDN1 substitutions were identified in recessive ACS families. Other EDN1 alleles cause dominant isolated question-mark ears, and a later start-loss heterozygote had mild mandibular involvement. Phenotype and inheritance depend on the allele; measured residual ligand activity is not available for the original patient substitutions.
  evidence:
  - reference: PMID:24268655
    reference_title: Mutations in endothelin 1 cause recessive auriculocondylar syndrome and dominant isolated question-mark ears.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: In family F1, the unaffected parents and child were heterozygous for the mutation, whereas the three affected siblings were homozygous, indicating that the allele encoding the p.Lys91Glu substitution behaves in a recessive manner.
    explanation: Segregation supports recessive inheritance of Lys91Glu in this family.
  genes:
  - preferred_term: EDN1
    term:
      id: hgnc:3176
      label: EDN1
  downstream:
  - target: Reduced Bioactive EDN1 Availability
    description: Variants near processing sites or within the peptide are predicted to reduce effective ligand availability or activity. The original study did not directly assay cleavage or receptor activation by these patient alleles.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:24268655
      reference_title: Mutations in endothelin 1 cause recessive auriculocondylar syndrome and dominant isolated question-mark ears.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: PRIMARY_RESULT
      snippet: The different mode of inheritance for the F1 and S1 mutant EDN1 alleles compared to the F2 and F3 alleles might be explained by differences in the amount of residual functional protein in each case.
      explanation: The authors explicitly propose residual functional ligand as an explanation; patient-allele processing was not directly measured.
      directness: INDIRECT
  - target: Question mark ear
    description: This molecular subtype is associated with the characteristic pinna malformation; the detailed cellular route to lobe-helix separation is unresolved.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:24268655
      reference_title: Mutations in endothelin 1 cause recessive auriculocondylar syndrome and dominant isolated question-mark ears.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: PRIMARY_RESULT
      snippet: In family F1, the unaffected parents and child were heterozygous for the mutation, whereas the three affected siblings were homozygous, indicating that the allele encoding the p.Lys91Glu substitution behaves in a recessive manner.
      explanation: Segregation supports recessive inheritance of Lys91Glu in this family.
    - reference: url:https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf
      reference_title: https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: PRIMARY_RESULT
      snippet: Question mark ear Total 37/38 97%
      explanation: The table counts assessed members of a selected 39-person ACS/IQME cohort.
- name: Reduced Bioactive EDN1 Availability
  biological_scale: MOLECULAR
  description: Reduced effective EDN1 ligand is the proposed functional consequence of disease alleles. Lys91Glu alters a furin recognition motif and Pro77His lies near the ECE cleavage region. Functional evidence from different substitutions supports this model but cannot quantify residual activity of these ACS alleles.
  evidence:
  - reference: PMID:24268655
    reference_title: Mutations in endothelin 1 cause recessive auriculocondylar syndrome and dominant isolated question-mark ears.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: The different mode of inheritance for the F1 and S1 mutant EDN1 alleles compared to the F2 and F3 alleles might be explained by differences in the amount of residual functional protein in each case.
    explanation: The authors explicitly propose residual functional ligand as an explanation; patient-allele processing was not directly measured.
    directness: INDIRECT
  genes:
  - preferred_term: EDN1
    term:
      id: hgnc:3176
      label: EDN1
  downstream:
  - target: Reduced EDNRA-Gq Signaling
    description: Reduced active ligand is expected to diminish EDNRA activation and its Gq signal in arch mesenchyme.
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:24268655
      reference_title: Mutations in endothelin 1 cause recessive auriculocondylar syndrome and dominant isolated question-mark ears.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      quote_role: REVIEW_SYNTHESIS
      snippet: Edn1 is expressed from the epithelium of the mandibular prominence of the first PA and caudal PAs,4 where the EDN1 peptide signals to underlying ectomesenchyme by stimulating EDNRA on cranial NCCs.
      explanation: Developmental studies establish the ligand-receptor relationship; applying reduced ligand activity to these human variants is an inference.
      directness: INDIRECT
    intermediate_mechanisms:
    - reduced EDNRA ligand-dependent activation
- name: Reduced DLX5 and DLX6 Expression
  biological_scale: MOLECULAR
  description: DLX5 and DLX6 transcripts were reduced in four postnatal ACS mandibular-osteoblast cultures relative to calvarial controls. Mouse developmental experiments support the importance of the EDNRA-DLX program, but the patient assay is not a direct measurement of fetal neural-crest transcription.
  evidence:
  - reference: PMID:22560091
    reference_title: A human homeotic transformation resulting from mutations in PLCB4 and GNAI3 causes auriculocondylar syndrome.
    supports: SUPPORT
    evidence_source: IN_VITRO
    quote_role: PRIMARY_RESULT
    snippet: Using quantitative, real-time RT-PCR of steady-state mRNA, we identified a 6-fold reduction of DLX5 (p < 0.005; probands versus controls) and an 8-fold reduction of DLX6 expression (p < 0.001) in mandibular osteoblasts from selective probands relative to 17 randomly selected calvarial osteoblasts from controls.
    explanation: Four ACS mandibular-osteoblast cultures were compared with 17 calvarial-osteoblast controls; anatomical source and developmental stage limit interpretation.
  genes:
  - preferred_term: DLX5
    term:
      id: hgnc:2918
      label: DLX5
  - preferred_term: DLX6
    term:
      id: hgnc:2919
      label: DLX6
  downstream:
  - target: Disrupted Mandibular Neural Crest Identity
    description: Reduced DLX program activity compromises mandibular specification, based on developmental genetic models. The full sequence is not traced in human embryos.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:24123988
      reference_title: 'Understanding the basis of auriculocondylar syndrome: Insights from human, mouse and zebrafish genetic studies.'
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      quote_role: REVIEW_SYNTHESIS
      snippet: Combined loss of both Dlx5 and Dlx6 leads to homeosis of lower jaw structures almost identical to that observed in Ednra, Edn1 or Ece1 mouse mutants, illustrating the close temporal relationship between Ednra signaling and Dlx5/Dlx6 expression.
      explanation: The review summarizes genetic mouse perturbations that support a requirement for the DLX program in jaw identity.
- name: Disrupted Mandibular Neural Crest Identity
  biological_scale: CELLULAR
  description: EDNRA-DLX disruption changes the positional identity of mandibular neural-crest-derived mesenchyme in animal models. Human skeletal morphology is consistent with partial mandibular-to-maxillary homeosis; it does not prove that every clinical feature arises through this transformation.
  evidence:
  - reference: PMID:24123988
    reference_title: 'Understanding the basis of auriculocondylar syndrome: Insights from human, mouse and zebrafish genetic studies.'
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    quote_role: REVIEW_SYNTHESIS
    snippet: Disruption of this signaling pathway in both mouse and zebrafish results in loss of identity of neural crest cells of the mandibular portion of the first pharyngeal arch and the subsequent repatterning of these cells, leading to homeosis of lower jaw structures into more maxillary-like structures.
    explanation: Genetic developmental models support altered identity rather than a universal neural-crest migration deficit.
  conforms_to: pharyngeal_arch_patterning_serial_homology#Disrupted Pharyngeal-Arch Patterning and Neural-Crest Skeletogenesis
  cell_types:
  - preferred_term: neural crest cell
    term:
      id: CL:0011012
      label: neural crest cell
  downstream:
  - target: Abnormal Mandibular Skeletal Morphogenesis
    description: Altered mandibular identity produces abnormal skeletal differentiation and patterning in developmental models, with corresponding morphology in selected human cases.
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:24123988
      reference_title: 'Understanding the basis of auriculocondylar syndrome: Insights from human, mouse and zebrafish genetic studies.'
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      quote_role: REVIEW_SYNTHESIS
      snippet: Disruption of this signaling pathway in both mouse and zebrafish results in loss of identity of neural crest cells of the mandibular portion of the first pharyngeal arch and the subsequent repatterning of these cells, leading to homeosis of lower jaw structures into more maxillary-like structures.
      explanation: Genetic developmental models support altered identity rather than a universal neural-crest migration deficit.
    intermediate_mechanisms:
    - altered differentiation and positional patterning of jaw skeletal precursors
  - target: Middle-Ear Ossicular Malformation
    description: Arch-identity signaling is required for ossicular development in mice. Applying this route to human fusion is an inference across species.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:24123988
      reference_title: 'Understanding the basis of auriculocondylar syndrome: Insights from human, mouse and zebrafish genetic studies.'
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      quote_role: REVIEW_SYNTHESIS
      snippet: Complete loss of Ednra signaling in mice leads to disrupted development of the lower jaw and middle ear ossicles, derivatives of the distal and intermediate domains.
      explanation: The review summarizes model evidence for middle-ear development.
      directness: INDIRECT
- name: HDAC9-TWIST1 Regulatory Duplication
  biological_scale: MOLECULAR
  description: A 430-kb tandem duplication within HDAC9 segregated with ACS in one Brazilian family. It includes candidate TWIST1 regulatory elements while leaving the TWIST1 coding region outside the duplication. Some short HDAC9 isoforms are wholly duplicated, whereas longer catalytic isoforms cross a breakpoint.
  evidence:
  - reference: PMID:34750192
    reference_title: 'New locus underlying auriculocondylar syndrome (ARCND): 430 kb duplication involving TWIST1 regulatory elements.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: The duplication spanned 430 302 bp (NC_000007.14:g.18437239_18867540dup) telomeric to TWIST1, covering most of the HDAC9 gene.
    explanation: A segregating tandem duplication in one four-generation family defines the regulatory locus; TWIST1 coding sequence is not duplicated.
  - reference: PMID:34750192
    reference_title: 'New locus underlying auriculocondylar syndrome (ARCND): 430 kb duplication involving TWIST1 regulatory elements.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: the majority presented with question mark ears (8 of 10), microstomia (8 of 10) and micrognathia (6 of 10)
    explanation: The duplication family has variable core craniofacial findings.
  genes:
  - preferred_term: TWIST1
    term:
      id: hgnc:12428
      label: TWIST1
  - preferred_term: HDAC9
    term:
      id: hgnc:14065
      label: HDAC9
  downstream:
  - target: Increased Neural Crest TWIST1 Expression
    description: The duplication is associated with increased TWIST1 expression in patient-derived neural-crest cells. Regulatory contact data support, but do not directly prove, enhancer-mediated upregulation.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:34750192
      reference_title: 'New locus underlying auriculocondylar syndrome (ARCND): 430 kb duplication involving TWIST1 regulatory elements.'
      supports: SUPPORT
      evidence_source: IN_VITRO
      quote_role: PRIMARY_RESULT
      snippet: However, an increase in HDAC9 (3.15-fold, unpaired t-test p=0.009) and TWIST1 (2.03-fold, unpaired t-test p=0.03) mRNA was observed in the ARCND-iNCC (figure 2A, B) compared with controls (unpaired t-test).
      explanation: Three affected-donor iPSC-derived neural-crest cultures show increased transcripts relative to three controls; no isogenic correction isolates the causal mediator.
      directness: INDIRECT
  - target: Increased Neural Crest HDAC9 Expression
    description: Patient-derived neural-crest cells also show increased HDAC9 transcripts. The contribution of this change to craniofacial development remains unresolved.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:34750192
      reference_title: 'New locus underlying auriculocondylar syndrome (ARCND): 430 kb duplication involving TWIST1 regulatory elements.'
      supports: SUPPORT
      evidence_source: IN_VITRO
      quote_role: PRIMARY_RESULT
      snippet: However, an increase in HDAC9 (3.15-fold, unpaired t-test p=0.009) and TWIST1 (2.03-fold, unpaired t-test p=0.03) mRNA was observed in the ARCND-iNCC (figure 2A, B) compared with controls (unpaired t-test).
      explanation: Three affected-donor iPSC-derived neural-crest cultures show increased transcripts relative to three controls; no isogenic correction isolates the causal mediator.
      directness: INDIRECT
  - target: Reduced Migration of Patient-Derived Neural Crest Cells
    description: Duplication-bearing cultures show reduced scratch closure; the respective roles of TWIST1, HDAC9 and donor background were not separated by rescue experiments.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:34750192
      reference_title: 'New locus underlying auriculocondylar syndrome (ARCND): 430 kb duplication involving TWIST1 regulatory elements.'
      supports: SUPPORT
      evidence_source: IN_VITRO
      quote_role: PRIMARY_RESULT
      snippet: Although no significant difference in cell cycle distribution was detected between patient and control cells, a significant decrease in migratory capacity of ARCND iNCCs was observed compared with controls (4.3-fold decrease, Student’s t-test, p=0.0009) (figure 2C–E).
      explanation: A 24-hour scratch assay measures reduced wound closure in the patient-derived cultures; it does not measure migration into human pharyngeal arches.
      directness: INDIRECT
  - target: Impaired Osteogenic Differentiation in Patient-Derived Cells
    description: Duplication-bearing mesenchymal derivatives show impaired osteogenic readouts. This parallel observation does not establish that impaired migration causes impaired osteogenesis.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:34750192
      reference_title: 'New locus underlying auriculocondylar syndrome (ARCND): 430 kb duplication involving TWIST1 regulatory elements.'
      supports: SUPPORT
      evidence_source: IN_VITRO
      quote_role: PRIMARY_RESULT
      snippet: Our data showed that during osteogenic differentiation, ALP enzymatic activity was significantly diminished in ARCND-nMSCs after 9 days of osteoinduction (decrease of 20.3-fold, paired t-test p=0.029; figure 3A, B).
      explanation: Patient-derived neural-crest mesenchymal cells show reduced alkaline-phosphatase activity during osteogenic induction.
      directness: INDIRECT
  - target: Question mark ear
    description: This molecular subtype is associated with the characteristic pinna malformation; the detailed cellular route to lobe-helix separation is unresolved.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:34750192
      reference_title: 'New locus underlying auriculocondylar syndrome (ARCND): 430 kb duplication involving TWIST1 regulatory elements.'
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: PRIMARY_RESULT
      snippet: The duplication spanned 430 302 bp (NC_000007.14:g.18437239_18867540dup) telomeric to TWIST1, covering most of the HDAC9 gene.
      explanation: A segregating tandem duplication in one four-generation family defines the regulatory locus; TWIST1 coding sequence is not duplicated.
    - reference: PMID:34750192
      reference_title: 'New locus underlying auriculocondylar syndrome (ARCND): 430 kb duplication involving TWIST1 regulatory elements.'
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: PRIMARY_RESULT
      snippet: the majority presented with question mark ears (8 of 10), microstomia (8 of 10) and micrognathia (6 of 10)
      explanation: The duplication family has variable core craniofacial findings.
  - target: Micrognathia
    description: The duplication segregates with variable jaw hypoplasia. The cultured migration and osteogenic phenotypes have not been shown to mediate this clinical outcome.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:34750192
      reference_title: 'New locus underlying auriculocondylar syndrome (ARCND): 430 kb duplication involving TWIST1 regulatory elements.'
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: PRIMARY_RESULT
      snippet: The duplication spanned 430 302 bp (NC_000007.14:g.18437239_18867540dup) telomeric to TWIST1, covering most of the HDAC9 gene.
      explanation: A segregating tandem duplication in one four-generation family defines the regulatory locus; TWIST1 coding sequence is not duplicated.
    - reference: PMID:34750192
      reference_title: 'New locus underlying auriculocondylar syndrome (ARCND): 430 kb duplication involving TWIST1 regulatory elements.'
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: PRIMARY_RESULT
      snippet: the majority presented with question mark ears (8 of 10), microstomia (8 of 10) and micrognathia (6 of 10)
      explanation: The duplication family has variable core craniofacial findings.
- name: Increased Neural Crest TWIST1 Expression
  biological_scale: MOLECULAR
  description: TWIST1 mRNA is increased in patient-derived neural-crest cultures, but not detectably different in undifferentiated iPSCs or during mesenchymal osteogenic differentiation. No TWIST1-specific correction or overexpression experiment in this study proves mediation of the cellular defects.
  evidence:
  - reference: PMID:34750192
    reference_title: 'New locus underlying auriculocondylar syndrome (ARCND): 430 kb duplication involving TWIST1 regulatory elements.'
    supports: SUPPORT
    evidence_source: IN_VITRO
    quote_role: PRIMARY_RESULT
    snippet: However, an increase in HDAC9 (3.15-fold, unpaired t-test p=0.009) and TWIST1 (2.03-fold, unpaired t-test p=0.03) mRNA was observed in the ARCND-iNCC (figure 2A, B) compared with controls (unpaired t-test).
    explanation: Three affected-donor iPSC-derived neural-crest cultures show increased transcripts relative to three controls; no isogenic correction isolates the causal mediator.
    directness: INDIRECT
  genes:
  - preferred_term: TWIST1
    term:
      id: hgnc:12428
      label: TWIST1
- name: Increased Neural Crest HDAC9 Expression
  biological_scale: MOLECULAR
  description: HDAC9 mRNA is increased in duplication-bearing neural-crest cultures. Transcript abundance does not establish increased catalytic HDAC9 activity, and a contribution independent of TWIST1 cannot be excluded.
  evidence:
  - reference: PMID:34750192
    reference_title: 'New locus underlying auriculocondylar syndrome (ARCND): 430 kb duplication involving TWIST1 regulatory elements.'
    supports: SUPPORT
    evidence_source: IN_VITRO
    quote_role: PRIMARY_RESULT
    snippet: However, an increase in HDAC9 (3.15-fold, unpaired t-test p=0.009) and TWIST1 (2.03-fold, unpaired t-test p=0.03) mRNA was observed in the ARCND-iNCC (figure 2A, B) compared with controls (unpaired t-test).
    explanation: Three affected-donor iPSC-derived neural-crest cultures show increased transcripts relative to three controls; no isogenic correction isolates the causal mediator.
    directness: INDIRECT
  genes:
  - preferred_term: HDAC9
    term:
      id: hgnc:14065
      label: HDAC9
- name: Reduced Migration of Patient-Derived Neural Crest Cells
  biological_scale: CELLULAR
  description: Patient-derived iNCC cultures have reduced 24-hour scratch closure without a detected cell-cycle distribution change. Positional identity and developmental stage of these induced cells require further characterization; reduced embryonic neural-crest colonization remains a hypothesis.
  evidence:
  - reference: PMID:34750192
    reference_title: 'New locus underlying auriculocondylar syndrome (ARCND): 430 kb duplication involving TWIST1 regulatory elements.'
    supports: SUPPORT
    evidence_source: IN_VITRO
    quote_role: PRIMARY_RESULT
    snippet: Although no significant difference in cell cycle distribution was detected between patient and control cells, a significant decrease in migratory capacity of ARCND iNCCs was observed compared with controls (4.3-fold decrease, Student’s t-test, p=0.0009) (figure 2C–E).
    explanation: A 24-hour scratch assay measures reduced wound closure in the patient-derived cultures; it does not measure migration into human pharyngeal arches.
    directness: INDIRECT
  cell_types:
  - preferred_term: neural crest cell
    term:
      id: CL:0011012
      label: neural crest cell
- name: Impaired Osteogenic Differentiation in Patient-Derived Cells
  biological_scale: CELLULAR
  description: Patient-derived neural-crest mesenchymal cells show reduced day-9 alkaline-phosphatase activity and a smaller mineralization readout. These findings support delayed or impaired osteogenic differentiation in culture, not demonstrated causation of the human mandibular phenotype.
  evidence:
  - reference: PMID:34750192
    reference_title: 'New locus underlying auriculocondylar syndrome (ARCND): 430 kb duplication involving TWIST1 regulatory elements.'
    supports: SUPPORT
    evidence_source: IN_VITRO
    quote_role: PRIMARY_RESULT
    snippet: Our data showed that during osteogenic differentiation, ALP enzymatic activity was significantly diminished in ARCND-nMSCs after 9 days of osteoinduction (decrease of 20.3-fold, paired t-test p=0.029; figure 3A, B).
    explanation: Patient-derived neural-crest mesenchymal cells show reduced alkaline-phosphatase activity during osteogenic induction.
    directness: INDIRECT
  cell_types:
  - preferred_term: neural-crest-derived mesenchymal cell
    term:
      id: CL:0008019
      label: mesenchymal cell
- name: Abnormal Mandibular Skeletal Morphogenesis
  biological_scale: TISSUE
  description: Abnormal mandibular skeletal development produces a short or dysplastic ramus, hypoplastic condyle and variable temporomandibular joint abnormalities. Selected severe cases have maxilla-like skeletal features. Associated oral, pinna and middle-ear findings need not all be mediated by mandibular homeosis.
  evidence:
  - reference: PMID:35284927
    reference_title: Auriculocondylar syndrome 2 results from the dominant-negative action of PLCB4 variants.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    quote_role: PRIMARY_RESULT
    snippet: the proximal mandible of Plcb4Indel/KI and Plcb4KI/KI embryos was disorganized, with absent or hypoplastic mandibular processes
    explanation: E18.5 edited mouse founders show proximal mandibular skeletal abnormalities; the tested genotypes are not simple wild-type/knock-in heterozygotes.
  - reference: PMID:22560091
    reference_title: A human homeotic transformation resulting from mutations in PLCB4 and GNAI3 causes auriculocondylar syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: In each case, mandibular ankylosis was progressive, of variable severity, and characterized by inconsistent fusion to the medial and lateral pterygoid plates.
    explanation: The selected severe clinical cases document variable progressive ankylosis.
  downstream:
  - target: Micrognathia
    description: The structural jaw-development defect manifests as micrognathia in affected individuals.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:22560091
      reference_title: A human homeotic transformation resulting from mutations in PLCB4 and GNAI3 causes auriculocondylar syndrome.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: BACKGROUND
      snippet: highly variable mandibular anomalies ranging from mild to severe micrognathia, often with temporomandibular joint (TMJ) ankylosis
      explanation: The clinical synthesis identifies variable jaw hypoplasia and joint ankylosis.
  - target: Mandibular condyle hypoplasia
    description: The structural jaw-development defect manifests as mandibular condyle hypoplasia in affected individuals.
    causal_link_type: DIRECT
    evidence:
    - reference: url:https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf
      reference_title: https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: PRIMARY_RESULT
      snippet: Condyle anomalies 15/24 63% Condyle hypoplasia 13/15 87%
      explanation: The nested imaging denominators distinguish any condylar anomaly from hypoplasia.
  - target: Temporomandibular joint ankylosis
    description: The structural jaw-development defect manifests as temporomandibular joint ankylosis in affected individuals.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:22560091
      reference_title: A human homeotic transformation resulting from mutations in PLCB4 and GNAI3 causes auriculocondylar syndrome.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: BACKGROUND
      snippet: highly variable mandibular anomalies ranging from mild to severe micrognathia, often with temporomandibular joint (TMJ) ankylosis
      explanation: The clinical synthesis identifies variable jaw hypoplasia and joint ankylosis.
  - target: Upper-Airway Narrowing
    description: A small malformed jaw and associated oral structures can narrow the upper airway, particularly with posterior tongue displacement.
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    evidence:
    - reference: url:https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf
      reference_title: https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: PRIMARY_RESULT
      snippet: severe microretrognathia, full cheeks, microstomia, and cleft palate (Figure 1m–o) leading to severe upper airway obstruction and feeding difficulties.
      explanation: The severe GNAI3 case connects craniofacial malformation with upper-airway obstruction and feeding problems.
    intermediate_mechanisms:
    - reduced oral and oropharyngeal space
    - posterior tongue displacement
  - target: Feeding difficulties
    description: Structural oral and mandibular abnormalities can impair feeding; oral-motor contributions vary.
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    evidence:
    - reference: url:https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf
      reference_title: https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: PRIMARY_RESULT
      snippet: severe microretrognathia, full cheeks, microstomia, and cleft palate (Figure 1m–o) leading to severe upper airway obstruction and feeding difficulties.
      explanation: The severe GNAI3 case connects craniofacial malformation with upper-airway obstruction and feeding problems.
    intermediate_mechanisms:
    - restricted oral space and impaired oral function
- name: Upper-Airway Narrowing
  biological_scale: TISSUE
  description: Mandibular and tongue abnormalities can narrow the oropharyngeal airway. This mechanical branch explains obstructive respiratory complications in selected patients; persistent central apnea requires separate assessment.
  evidence:
  - reference: PMID:38618928
    reference_title: 'Auriculocondylar syndrome 2 caused by a novel PLCB4 variant in a male Chinese neonate: A case report and review of the literature.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: Computed tomography (CT) revealed a narrowed oropharynx airway and absent condylar fossae, shortened mandibular rami, and obtuse mandibular angles (Figure 2).
    explanation: CT documents oropharyngeal narrowing in the severely affected neonate.
  downstream:
  - target: Respiratory distress
    description: Severe upper-airway compromise can produce neonatal respiratory distress.
    causal_link_type: DIRECT
    evidence:
    - reference: url:https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf
      reference_title: https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: PRIMARY_RESULT
      snippet: severe microretrognathia, full cheeks, microstomia, and cleft palate (Figure 1m–o) leading to severe upper airway obstruction and feeding difficulties.
      explanation: The severe GNAI3 case connects craniofacial malformation with upper-airway obstruction and feeding problems.
  - target: Obstructive sleep apnea
    description: Mechanical upper-airway compromise can contribute to obstructive apnea during sleep.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:24268655
      reference_title: Mutations in endothelin 1 cause recessive auriculocondylar syndrome and dominant isolated question-mark ears.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: PRIMARY_RESULT
      snippet: obstructive respiratory distress, and sleep apnea.
      explanation: The EDN1-associated adult had obstructive respiratory distress and apnea; the mechanical contribution is clinical interpretation.
      directness: INDIRECT
- name: Middle-Ear Ossicular Malformation
  biological_scale: TISSUE
  description: Middle-ear malformation can include congenital-appearing malleoincudal fusion. Histology supports an abnormal joint-development process in one adolescent; coexisting cholesteatoma can contribute to worsening hearing.
  evidence:
  - reference: url:https://lab.research.sickkids.ca/wp-content/uploads/sites/22/2015/09/Propst_et_al_Ossicular-Fusion-and-cholesteatoma-in-Auriculo-Condylar-Syndrome_2013.pdf
    reference_title: https://lab.research.sickkids.ca/wp-content/uploads/sites/22/2015/09/Propst_et_al_Ossicular-Fusion-and-cholesteatoma-in-Auriculo-Condylar-Syndrome_2013.pdf
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: the malleoincudal joint appeared to be partially ankylosed laterally .
    explanation: Temporal-bone CT demonstrates the structural ossicular abnormality in one case.
  downstream:
  - target: Conductive hearing impairment
    description: Ossicular fusion can impede sound conduction; the reported case also had cholesteatoma, so the contribution of each lesion was not experimentally isolated.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: url:https://lab.research.sickkids.ca/wp-content/uploads/sites/22/2015/09/Propst_et_al_Ossicular-Fusion-and-cholesteatoma-in-Auriculo-Condylar-Syndrome_2013.pdf
      reference_title: https://lab.research.sickkids.ca/wp-content/uploads/sites/22/2015/09/Propst_et_al_Ossicular-Fusion-and-cholesteatoma-in-Auriculo-Condylar-Syndrome_2013.pdf
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: PRIMARY_RESULT
      snippet: We therefore hypothesize that the conductive hearing loss was likely due primarily to ossicular fusion secondary to ACS, which progressed due to the addition of cholesteatoma.
      explanation: The authors explicitly qualify their attribution of conductive loss to fusion and cholesteatoma.
      directness: INDIRECT
phenotypes:
- name: Question mark ear
  category: Craniofacial
  description: A constriction or cleft at the lobe-helix junction is characteristic, but can be unilateral, subtle or absent. The 2022 selected ACS/isolated-QME cohort documented this finding in 37 of 38 assessed individuals; this is not population penetrance.
  phenotype_term:
    preferred_term: Question mark ear
    term:
      id: HP:0030022
      label: Question mark ear
  evidence:
  - reference: url:https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf
    reference_title: https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: Question mark ear Total 37/38 97%
    explanation: The table counts assessed members of a selected 39-person ACS/IQME cohort.
- name: Mandibular condyle hypoplasia
  category: Craniofacial
  description: Hypoplastic condyles occur with variable ramus and joint dysplasia. In the selected 2022 cohort, condylar abnormalities occurred in 15 of 24 imaged patients, and hypoplasia in 13 of those 15; 13/15 is not a frequency among all patients.
  phenotype_term:
    preferred_term: Mandibular condyle hypoplasia
    term:
      id: HP:0007628
      label: Mandibular condyle hypoplasia
  evidence:
  - reference: url:https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf
    reference_title: https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: Condyle anomalies 15/24 63% Condyle hypoplasia 13/15 87%
    explanation: The nested imaging denominators distinguish any condylar anomaly from hypoplasia.
- name: Micrognathia
  category: Craniofacial
  description: Mandibular hypoplasia is a core but variably expressed feature and can be visible prenatally. Clinical hypoplasia was recorded in 31 of 35 assessed members of the selected 2022 ACS/IQME cohort.
  phenotype_term:
    preferred_term: Micrognathia
    term:
      id: HP:0000347
      label: Micrognathia
  evidence:
  - reference: url:https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf
    reference_title: https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: Mandibular hypoplasia (clinical diagnosis) 31/35 89%
    explanation: Selected-cohort clinical counts do not establish population frequency.
- name: Microstomia
  category: Craniofacial
  description: A small oral aperture can accompany jaw and oral malformations. It was reported in 16 of 39 members of the 2022 selected cohort.
  phenotype_term:
    preferred_term: microstomia
    term:
      id: HP:0000160
      label: Narrow mouth
  evidence:
  - reference: url:https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf
    reference_title: https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: From photographs, full cheeks were observed in 18/31 (58%) patients and microstomia in 16/39 (41%).
    explanation: The cohort records microstomia independently of jaw size.
- name: Cleft palate
  category: Craniofacial
  description: Cleft palate is a variable craniofacial feature in auriculocondylar syndrome.
  phenotype_term:
    preferred_term: Cleft palate
    term:
      id: HP:0000175
      label: Cleft palate
  evidence:
  - reference: PMID:22560091
    reference_title: A human homeotic transformation resulting from mutations in PLCB4 and GNAI3 causes auriculocondylar syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Auriculocondylar syndrome (ACS) is a rare, autosomal-dominant craniofacial malformation syndrome characterized by variable micrognathia, temporomandibular joint ankylosis, cleft palate, and a characteristic "question-mark" ear malformation.
    explanation: The original PLCB4/GNAI3 discovery paper includes cleft palate among variable clinical features.
    quote_role: BACKGROUND
- name: Temporomandibular joint ankylosis
  category: Craniofacial
  description: Congenital or progressive mandibular fusion can restrict mouth opening. The original selected severe cases had variable fusion to the skull base; this does not imply that all condylar hypoplasia progresses to ankylosis.
  phenotype_term:
    preferred_term: Temporomandibular joint ankylosis
    term:
      id: HP:0012478
      label: Temporomandibular joint ankylosis
  evidence:
  - reference: PMID:22560091
    reference_title: A human homeotic transformation resulting from mutations in PLCB4 and GNAI3 causes auriculocondylar syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: In each case, mandibular ankylosis was progressive, of variable severity, and characterized by inconsistent fusion to the medial and lateral pterygoid plates.
    explanation: Direct clinical characterization of the selected severe cases.
- name: Respiratory distress
  category: Respiratory
  description: Severe neonatal mandibular and oral malformations can present with respiratory distress.
  phenotype_term:
    preferred_term: Respiratory distress
    term:
      id: HP:0002098
      label: Respiratory distress
  evidence:
  - reference: PMID:38618928
    reference_title: 'Auriculocondylar syndrome 2 caused by a novel PLCB4 variant in a male Chinese neonate: A case report and review of the literature.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: The proband, a 5-day-old male neonate, was referred to our hospital for respiratory distress.
    explanation: A recent neonatal ARCND2 case directly documents respiratory distress.
    quote_role: PRIMARY_RESULT
- name: Hearing impairment
  category: Auditory
  description: Hearing loss may be conductive, sensorineural or incompletely characterized. The 2022 cohort recorded hearing loss in eight of 36 assessed patients, with three cases not typed.
  phenotype_term:
    preferred_term: Hearing impairment
    term:
      id: HP:0000365
      label: Hearing impairment
    coarse_binding_basis: VARIABLE_SPECTRUM
  evidence:
  - reference: url:https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf
    reference_title: https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: Hearing loss was noted in eight patients with ACS.
    explanation: Retains the broad clinical spectrum and the assessed-subset denominator.
- name: Polyhydramnios
  category: Prenatal
  description: Polyhydramnios may accompany severe prenatal mandibular hypoplasia.
  phenotype_term:
    preferred_term: polyhydramnios
    term:
      id: HP:0001561
      label: Polyhydramnios
  evidence:
  - reference: PMID:34789173
    reference_title: 'Prenatal diagnosis of auriculocondylar syndrome with a novel missense variant of GNAI3: a case report.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Severe micrognathia and mandibular hypoplasia accompanied by polyhydramnios are prenatal indicators of ACS.
    explanation: This directly supports polyhydramnios as a prenatal indicator when combined with severe mandibular findings.
    quote_role: PRIMARY_RESULT
- name: Full cheeks
  category: Craniofacial
  description: Prominent cheeks are part of the variable facial appearance. They were present in 18 of 31 assessed members of the 2022 selected cohort.
  phenotype_term:
    preferred_term: Full cheeks
    term:
      id: HP:0000293
      label: Full cheeks
  evidence:
  - reference: url:https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf
    reference_title: https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: From photographs, full cheeks were observed in 18/31 (58%) patients and microstomia in 16/39 (41%).
    explanation: Provides a denominator specific to assessed individuals.
- name: Glossoptosis
  category: Craniofacial
  description: Posterior tongue displacement can accompany a small jaw and contribute to oral or airway dysfunction.
  phenotype_term:
    preferred_term: Glossoptosis
    term:
      id: HP:0000162
      label: Glossoptosis
  evidence:
  - reference: PMID:38618928
    reference_title: 'Auriculocondylar syndrome 2 caused by a novel PLCB4 variant in a male Chinese neonate: A case report and review of the literature.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: feeding difficulty, glossoptosis, postauricular tags, respiratory distress, and crowded teeth.
    explanation: The molecularly characterized neonate directly exhibited glossoptosis.
- name: Feeding difficulties
  category: Gastrointestinal
  description: Feeding problems range from oral-motor difficulties to a need for temporary tube feeding or gastrostomy. Twelve of 38 assessed individuals in the 2022 cohort had feeding difficulty.
  phenotype_term:
    preferred_term: Feeding difficulties
    term:
      id: HP:0011968
      label: Feeding difficulties
  evidence:
  - reference: url:https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf
    reference_title: https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: Gastrointestinal disorder 15/38 39% Feeding difficulties 12/38 31%
    explanation: The table describes a selected assessed cohort, not a general frequency.
- name: Obstructive sleep apnea
  category: Respiratory
  description: Obstructive apnea can accompany severe mandibular and upper-airway abnormalities. In the selected 2022 cohort, eight of 21 sleep-studied patients had obstructive apnea and another eight had mixed apnea.
  phenotype_term:
    preferred_term: Obstructive sleep apnea
    term:
      id: HP:0002870
      label: Obstructive sleep apnea
  evidence:
  - reference: url:https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf
    reference_title: https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: Obstructive apnea 8/21 38% Mixed apnea 8/21 38%
    explanation: Sleep-study selection limits disease-wide frequency inference.
- name: Central apnea
  category: Respiratory
  description: Central or mixed apnea has been reported, including persistence after correction of an obstructive component. Its mechanism is unresolved and should not be reduced to mandibular airway obstruction alone.
  phenotype_term:
    preferred_term: Central apnea
    term:
      id: HP:0002871
      label: Central apnea
  evidence:
  - reference: url:https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf
    reference_title: https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: Central sleep apnea has previously been reported in patients with ACS.
    explanation: The clinical synthesis distinguishes central apnea from the structural obstructive component.
- name: Bifid uvula
  category: Craniofacial
  description: Bifid or ectopic uvular tissue was documented in EDN1-related ACS, sometimes with a submucosal velar cleft.
  phenotype_term:
    preferred_term: Bifid uvula
    term:
      id: HP:0000193
      label: Bifid uvula
  evidence:
  - reference: PMID:24268655
    reference_title: Mutations in endothelin 1 cause recessive auriculocondylar syndrome and dominant isolated question-mark ears.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: a bilateral paramedian submucosal cleft of the velum, and a bifid uvula with ectopic tissue beside it
    explanation: Direct description of one affected EDN1-family member.
- name: High palate
  category: Craniofacial
  description: A high-arched palate was described in the adolescent with ossicular fusion and cholesteatoma.
  phenotype_term:
    preferred_term: High palate
    term:
      id: HP:0000218
      label: High palate
  evidence:
  - reference: url:https://lab.research.sickkids.ca/wp-content/uploads/sites/22/2015/09/Propst_et_al_Ossicular-Fusion-and-cholesteatoma-in-Auriculo-Condylar-Syndrome_2013.pdf
    reference_title: https://lab.research.sickkids.ca/wp-content/uploads/sites/22/2015/09/Propst_et_al_Ossicular-Fusion-and-cholesteatoma-in-Auriculo-Condylar-Syndrome_2013.pdf
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: glossoptosis, a high-arched palate, hearing loss, and cholesteatoma.
    explanation: The source documents this finding in one adolescent.
- name: Conductive hearing impairment
  category: Auditory
  description: Conductive loss may involve malformed or fused ossicles and can coexist with external-canal stenosis or cholesteatoma. It was specifically reported in five patients of the 2022 cohort.
  phenotype_term:
    preferred_term: Conductive hearing impairment
    term:
      id: HP:0000405
      label: Conductive hearing impairment
  evidence:
  - reference: url:https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf
    reference_title: https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: Conductive hearing loss (CHL) was reported in five patients (Patient 3 with a heterozygous PLCB4 mutation, Patients 26 and 27 with a GNAI3 mutation, Patient 36 with a homozygous EDN1 mutation, and Patient 39 with a heterozygous EDN1 mutation).
    explanation: The cohort identifies five clinically typed conductive cases.
- name: Sensorineural hearing impairment
  category: Auditory
  description: Sensorineural loss has been reported in a GNAI3-associated family; the small number of observations does not establish a gene-specific frequency.
  phenotype_term:
    preferred_term: Sensorineural hearing impairment
    term:
      id: HP:0000407
      label: Sensorineural hearing impairment
  evidence:
  - reference: url:https://pmc.ncbi.nlm.nih.gov/articles/PMC4666574/
    reference_title: Novel variants in GNAI3 associated with auriculocondylar syndrome strengthen a common dominant negative effect - PMC
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: individual in the ACS1 family presented with sensorineural hearing loss.
    explanation: The full report distinguishes this individual from the conductive cases.
- name: Stenosis of the external auditory canal
  category: Auditory
  description: External auditory canal narrowing has been demonstrated on examination and temporal-bone imaging.
  phenotype_term:
    preferred_term: Stenosis of the external auditory canal
    term:
      id: HP:0000402
      label: Stenosis of the external auditory canal
  evidence:
  - reference: url:https://lab.research.sickkids.ca/wp-content/uploads/sites/22/2015/09/Propst_et_al_Ossicular-Fusion-and-cholesteatoma-in-Auriculo-Condylar-Syndrome_2013.pdf
    reference_title: https://lab.research.sickkids.ca/wp-content/uploads/sites/22/2015/09/Propst_et_al_Ossicular-Fusion-and-cholesteatoma-in-Auriculo-Condylar-Syndrome_2013.pdf
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: Otoscopy revealed a stenotic right external auditory canal with a tympanic membrane perforation with keratinous debris in the middle ear space.
    explanation: Direct examination in the adolescent case.
- name: Cholesteatoma
  category: Auditory
  description: A single adolescent case had surgically and histologically confirmed middle-ear cholesteatoma accompanying ossicular fusion. This does not establish its frequency or a universal causal route.
  phenotype_term:
    preferred_term: Cholesteatoma
    term:
      id: HP:0009797
      label: Cholesteatoma
  evidence:
  - reference: url:https://lab.research.sickkids.ca/wp-content/uploads/sites/22/2015/09/Propst_et_al_Ossicular-Fusion-and-cholesteatoma-in-Auriculo-Condylar-Syndrome_2013.pdf
    reference_title: https://lab.research.sickkids.ca/wp-content/uploads/sites/22/2015/09/Propst_et_al_Ossicular-Fusion-and-cholesteatoma-in-Auriculo-Condylar-Syndrome_2013.pdf
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: Kerati- nous debris from the right middle ear space (cholesteatoma) was confirmed histopathologically .
    explanation: Histopathology confirms the lesion in the reported case.
- name: Dental crowding
  category: Craniofacial
  description: Crowding has been observed in children and adults and may require orthodontic care.
  phenotype_term:
    preferred_term: Dental crowding
    term:
      id: HP:0000678
      label: Dental crowding
  evidence:
  - reference: PMID:38618928
    reference_title: 'Auriculocondylar syndrome 2 caused by a novel PLCB4 variant in a male Chinese neonate: A case report and review of the literature.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: feeding difficulty, glossoptosis, postauricular tags, respiratory distress, and crowded teeth.
    explanation: The index neonate follow-up explicitly records crowded teeth.
- name: Speech articulation difficulties
  category: Neurologic
  description: Articulation or oral-motor speech problems can accompany the craniofacial malformation. They do not by themselves establish global cognitive impairment.
  phenotype_term:
    preferred_term: Speech articulation difficulties
    term:
      id: HP:0009088
      label: Speech articulation difficulties
  evidence:
  - reference: PMID:38618928
    reference_title: 'Auriculocondylar syndrome 2 caused by a novel PLCB4 variant in a male Chinese neonate: A case report and review of the literature.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: '| Speech articulation difficulties | 11 (33.3%) | 9 (32.1%) | 2 (40.0%) |'
    explanation: The selected 33-case review records articulation difficulty separately from developmental delay.
- name: Global developmental delay
  category: Neurologic
  description: Psychomotor delay occurs in a subset; many individuals have normal development. Small biallelic PLCB4 series suggest additional developmental involvement but do not establish deterministic genotype prediction.
  phenotype_term:
    preferred_term: Global developmental delay
    term:
      id: HP:0001263
      label: Global developmental delay
  evidence:
  - reference: PMID:38618928
    reference_title: 'Auriculocondylar syndrome 2 caused by a novel PLCB4 variant in a male Chinese neonate: A case report and review of the literature.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: '| Psychomotor developmental delay | 6 (18.2%) | 4 (14.3%) | 2 (40.0%) |'
    explanation: The retrospective case compilation supports reported delay, not an unselected prevalence.
- name: Intellectual disability
  category: Neurologic
  description: Intellectual disability is variable rather than a defining universal feature. The 2022 cohort documented it in three of 23 assessed individuals.
  phenotype_term:
    preferred_term: Intellectual disability
    term:
      id: HP:0001249
      label: Intellectual disability
  evidence:
  - reference: url:https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf
    reference_title: https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: However intellectual disability was rare (3/23 patients, 13%)
    explanation: The denominator is the subset assessed for this outcome.
- name: Constipation
  category: Gastrointestinal
  description: Constipation has been reported particularly in small biallelic PLCB4 case series; the observation does not establish an enteric neural-crest mechanism.
  phenotype_term:
    preferred_term: Constipation
    term:
      id: HP:0002019
      label: Constipation
  evidence:
  - reference: PMID:38618928
    reference_title: 'Auriculocondylar syndrome 2 caused by a novel PLCB4 variant in a male Chinese neonate: A case report and review of the literature.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: '| Constipation | 3 (9.1%) | / | 3 (60.0%) |'
    explanation: Three of the five selected biallelic cases were reported to have constipation.
- name: Hypotonia
  category: Neurologic
  description: Hypotonia is an additional feature in some reported individuals.
  phenotype_term:
    preferred_term: Hypotonia
    term:
      id: HP:0001252
      label: Hypotonia
  evidence:
  - reference: PMID:38618928
    reference_title: 'Auriculocondylar syndrome 2 caused by a novel PLCB4 variant in a male Chinese neonate: A case report and review of the literature.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: '| Hypotonia | 3 (9.1%) | 2 (7.1%) | 1 (20.0%) |'
    explanation: The compiled cases document hypotonia without establishing a universal neuromuscular defect.
- name: Microglossia
  category: Craniofacial
  description: Marked tongue hypoplasia was observed intraoperatively in a severe GNAI3-associated case.
  phenotype_term:
    preferred_term: Microglossia
    term:
      id: HP:0000171
      label: Microglossia
  evidence:
  - reference: PMID:22560091
    reference_title: A human homeotic transformation resulting from mutations in PLCB4 and GNAI3 causes auriculocondylar syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: Intraoperative evaluation of S011 was notable for the presence of severe microglossia
    explanation: Direct operative observation in a selected severe case.
- name: Postauricular skin tag
  category: Craniofacial
  description: Postauricular tags occur variably across molecular causes, including PLCB4 and EDN1-related disease.
  phenotype_term:
    preferred_term: Postauricular skin tag
    term:
      id: HP:0004451
      label: Postauricular skin tag
  evidence:
  - reference: url:https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf
    reference_title: https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: Postauricular tags were reported in six patients with ACS (6/ 37, 16%)
    explanation: Six of 37 assessed cohort members had this finding.
- name: Rib fusion
  category: Skeletal
  description: Unilateral first-to-second rib fusion was reported in one GNAI3-associated patient; another had hypoplastic first ribs. Vertebral fusion in humans remains unconfirmed in this cohort.
  phenotype_term:
    preferred_term: Rib fusion
    term:
      id: HP:0000902
      label: Rib fusion
  evidence:
  - reference: url:https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf
    reference_title: https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: Case 24 had hypoplastic first ribs and Case 26 had a unilateral fusion of the first and second ribs.
    explanation: Two individuals had distinct rib findings; only one had fusion.
- name: Hamartoma of tongue
  category: Craniofacial
  description: Small ventral lingual hamartomatous pedicles were reported in an EDN1-associated patient. These should not be assumed to represent ectopic palate in every case.
  phenotype_term:
    preferred_term: Hamartoma of tongue
    term:
      id: HP:0011802
      label: Hamartoma of tongue
  evidence:
  - reference: PMID:24268655
    reference_title: Mutations in endothelin 1 cause recessive auriculocondylar syndrome and dominant isolated question-mark ears.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: several small hamartomatous pedicles on the ventral surface of the tongue
    explanation: Direct clinical observation in one affected family member.
- name: Cerebral arteriovenous malformation
  category: Neurologic
  description: Cerebrovascular malformations were found in two individuals in the 2022 cohort, one with EDN1-related and one with GNAI3-related disease. Their causal relationship to ACS and population risk remain uncertain.
  phenotype_term:
    preferred_term: Cerebral arteriovenous malformation
    term:
      id: HP:0002408
      label: Cerebral arteriovenous malformation
  evidence:
  - reference: url:https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf
    reference_title: https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: Cerebrovascular malformations were detected by brain MRI in two individuals with no neurological symptoms.
    explanation: The source documents two observations without establishing a causal vascular pathway.
genetic:
- name: GNAI3 pathogenic variants
  subtype: ARCND1
  gene_term:
    preferred_term: GNAI3
    term:
      id: hgnc:4387
      label: GNAI3
  relationship_type: CAUSATIVE
  association: Causative
  notes: Heterozygous GNAI3 nucleotide-binding-region variants can be inherited or de novo, with incomplete penetrance. Five tested missense proteins show defective activation and interference with EDNRA-Gq signaling. Later in-frame insertions and novel substitutions should not automatically inherit every experimentally established functional property.
  evidence:
  - reference: PMID:22560091
    reference_title: A human homeotic transformation resulting from mutations in PLCB4 and GNAI3 causes auriculocondylar syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: In both kindreds, the p.Gly40Arg variant was inherited; in one case (S011) it was inherited from an affected mother (S012-P), and in the other (S008), from an unaffected father (S009-P), documenting incomplete penetrance.
    explanation: Two molecularly characterized families establish dominant inheritance with incomplete penetrance.
  - reference: PMID:27072656
    reference_title: Dominant-negative Gα subunits are a mechanism of dysregulated heterotrimeric G protein signaling in human disease.
    supports: SUPPORT
    evidence_source: IN_VITRO
    quote_role: PRIMARY_RESULT
    snippet: Together, these results demonstrate that Gαi3 S47R retains the capability to bind GDP but fails to bind GTP, rendering the G protein unable to switch into an active conformation.
    explanation: Purified S47R directly retains GDP but loses efficient GTP binding; other variants were assessed with cell-expressed limited-proteolysis assays.
- name: PLCB4 pathogenic variants
  subtype: ARCND2A
  gene_term:
    preferred_term: PLCB4
    term:
      id: hgnc:9059
      label: PLCB4
  relationship_type: CAUSATIVE
  association: Causative
  notes: Dominant catalytic-domain missense variants include recurrent Arg621 substitutions. Arg621His, Tyr623Cys, Glu358Val and Asp360Val were tested in cell signaling assays. The neonatal Ser643Phe variant was classified as likely pathogenic; its functional impairment was predicted rather than measured.
  evidence:
  - reference: PMID:35284927
    reference_title: Auriculocondylar syndrome 2 results from the dominant-negative action of PLCB4 variants.
    supports: SUPPORT
    evidence_source: IN_VITRO
    quote_role: PRIMARY_RESULT
    snippet: These results illustrate that PLCB4 p.Arg621His interferes with PLCB activity even when it is expressed at a sub-stoichiometric level relative to wild-type PLCB4, exemplifying a characteristic of a dominant-negative protein.
    explanation: DAG-sensor BRET detects dominant interference by Arg621His; three additional tested missense variants also attenuated the response.
- name: Biallelic PLCB4 disease alleles
  subtype: ARCND2B
  gene_term:
    preferred_term: PLCB4
    term:
      id: hgnc:9059
      label: PLCB4
  relationship_type: CAUSATIVE
  association: Causative
  notes: Recessive disease occurs with biallelic deletion, frameshift or splice alleles. Unaffected heterozygous deletion carriers distinguish this route from dominant missense interference. Small series include central apnea, developmental, gastrointestinal and genital findings, including macropenis, without establishing deterministic subtype frequencies.
  evidence:
  - reference: PMID:23315542
    reference_title: Heterogeneity of mutational mechanisms and modes of inheritance in auriculocondylar syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: The consanguineous parents of the patient with a homozygous PLCB4 deletion each harboured the heterozygous deletion, but did not present the ACS phenotype, further suggesting that ACS is not caused by PLCB4 haploinsufficiency.
    explanation: Segregation demonstrates a recessive deletion mechanism in one family.
- name: EDN1 pathogenic variants
  subtype: ARCND3
  gene_term:
    preferred_term: EDN1
    term:
      id: hgnc:3176
      label: EDN1
  relationship_type: CAUSATIVE
  association: Causative
  notes: EDN1 alleles differ in inheritance and phenotype. Lys91Glu and Pro77His homozygotes have ACS; dominant Val64Asp and Tyr83* families initially showed isolated ear findings. The proposed reduction of mature ligand activity is based on sequence context and related experimental substitutions, not direct functional assays of these patient alleles.
  evidence:
  - reference: PMID:24268655
    reference_title: Mutations in endothelin 1 cause recessive auriculocondylar syndrome and dominant isolated question-mark ears.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: In family F1, the unaffected parents and child were heterozygous for the mutation, whereas the three affected siblings were homozygous, indicating that the allele encoding the p.Lys91Glu substitution behaves in a recessive manner.
    explanation: Segregation supports recessive inheritance of Lys91Glu in this family.
  - reference: PMID:24268655
    reference_title: Mutations in endothelin 1 cause recessive auriculocondylar syndrome and dominant isolated question-mark ears.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: The different mode of inheritance for the F1 and S1 mutant EDN1 alleles compared to the F2 and F3 alleles might be explained by differences in the amount of residual functional protein in each case.
    explanation: The authors explicitly propose residual functional ligand as an explanation; patient-allele processing was not directly measured.
    directness: INDIRECT
- name: TWIST1 regulatory duplication
  subtype: ARCND4
  gene_term:
    preferred_term: TWIST1
    term:
      id: hgnc:12428
      label: TWIST1
  relationship_type: CAUSATIVE
  association: Causative
  notes: A single-family noncoding regulatory-locus duplication excludes TWIST1 coding sequence and affects multiple HDAC9 isoforms and candidate regulatory elements. TWIST1 and HDAC9 upregulation in induced neural-crest cells is associated with the lesion, but TWIST1-specific rescue and in-vivo mediation have not been demonstrated.
  evidence:
  - reference: PMID:34750192
    reference_title: 'New locus underlying auriculocondylar syndrome (ARCND): 430 kb duplication involving TWIST1 regulatory elements.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: The duplication spanned 430 302 bp (NC_000007.14:g.18437239_18867540dup) telomeric to TWIST1, covering most of the HDAC9 gene.
    explanation: A segregating tandem duplication in one four-generation family defines the regulatory locus; TWIST1 coding sequence is not duplicated.
  - reference: PMID:34750192
    reference_title: 'New locus underlying auriculocondylar syndrome (ARCND): 430 kb duplication involving TWIST1 regulatory elements.'
    supports: SUPPORT
    evidence_source: IN_VITRO
    quote_role: PRIMARY_RESULT
    snippet: However, an increase in HDAC9 (3.15-fold, unpaired t-test p=0.009) and TWIST1 (2.03-fold, unpaired t-test p=0.03) mRNA was observed in the ARCND-iNCC (figure 2A, B) compared with controls (unpaired t-test).
    explanation: Three affected-donor iPSC-derived neural-crest cultures show increased transcripts relative to three controls; no isogenic correction isolates the causal mediator.
    directness: INDIRECT
diagnosis:
- name: Clinical and craniofacial imaging assessment
  description: Recognize the variable combination of question-mark ears, micrognathia and condylar or temporomandibular abnormalities. Examine oral structures, hearing and airway function. Imaging can characterize ramus, condyle, joint and temporal-bone anatomy where clinically indicated; absence of a complete triad does not exclude disease.
  evidence:
  - reference: url:https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf
    reference_title: https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: Question mark ear Total 37/38 97%
    explanation: The table counts assessed members of a selected 39-person ACS/IQME cohort.
  - reference: PMID:38618928
    reference_title: 'Auriculocondylar syndrome 2 caused by a novel PLCB4 variant in a male Chinese neonate: A case report and review of the literature.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: Computed tomography (CT) revealed a narrowed oropharynx airway and absent condylar fossae, shortened mandibular rami, and obtuse mandibular angles (Figure 2).
    explanation: CT documents oropharyngeal narrowing in the severely affected neonate.
  - reference: url:https://lab.research.sickkids.ca/wp-content/uploads/sites/22/2015/09/Propst_et_al_Ossicular-Fusion-and-cholesteatoma-in-Auriculo-Condylar-Syndrome_2013.pdf
    reference_title: https://lab.research.sickkids.ca/wp-content/uploads/sites/22/2015/09/Propst_et_al_Ossicular-Fusion-and-cholesteatoma-in-Auriculo-Condylar-Syndrome_2013.pdf
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: the malleoincudal joint appeared to be partially ankylosed laterally .
    explanation: Temporal-bone CT demonstrates the structural ossicular abnormality in one case.
- name: Molecular and structural-variant testing
  description: Interpret targeted sequencing or exome/genome results together with phenotype and segregation. Established genes include GNAI3, PLCB4 and EDN1. Copy-number and regulatory-region analysis is relevant in unresolved cases because the reported HDAC9-TWIST1 duplication lies outside TWIST1 coding sequence. A VUS alone does not establish the diagnosis, and selected-case yields are not general diagnostic sensitivity.
  evidence:
  - reference: PMID:28328130
    reference_title: Targeted molecular investigation in patients within the clinical spectrum of Auriculocondylar syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: We found novel pathogenic variants in PLCB4 only in two of three index patients with typical Auriculocondylar syndrome.
    explanation: Two positive typical index cases in an 11-person mixed-phenotype series; not an unselected sensitivity estimate.
  - reference: PMID:34750192
    reference_title: 'New locus underlying auriculocondylar syndrome (ARCND): 430 kb duplication involving TWIST1 regulatory elements.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: The duplication spanned 430 302 bp (NC_000007.14:g.18437239_18867540dup) telomeric to TWIST1, covering most of the HDAC9 gene.
    explanation: A segregating tandem duplication in one four-generation family defines the regulatory locus; TWIST1 coding sequence is not duplicated.
- name: Prenatal assessment
  description: Severe fetal micrognathia with polyhydramnios can prompt detailed craniofacial imaging and molecular evaluation. These findings are not specific for ACS, and question-mark ears may not be identified prenatally.
  evidence:
  - reference: PMID:34789173
    reference_title: 'Prenatal diagnosis of auriculocondylar syndrome with a novel missense variant of GNAI3: a case report.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: Severe micrognathia and mandibular hypoplasia accompanied by polyhydramnios are prenatal indicators of ACS.
    explanation: The reported fetus provides a possible diagnostic clue rather than a validated screening rule.
- name: Audiologic and sleep evaluation
  description: Audiograms help distinguish conductive, sensorineural and mixed or unclassified hearing loss. Sleep studies can distinguish obstructive and central components and inform follow-up after structural treatment.
  evidence:
  - reference: url:https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf
    reference_title: https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    snippet: Attention needs to be paid to middle and inner ear function by way of an audiogram in all patients with ACS to evaluate for hearing loss.
    explanation: Case-series authors recommend audiologic assessment.
  - reference: url:https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf
    reference_title: https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: Central sleep apnea has previously been reported in patients with ACS.
    explanation: The clinical synthesis distinguishes central apnea from the structural obstructive component.
progression:
- phase: Prenatal and neonatal presentation
  notes: Craniofacial malformations are congenital and severe mandibular hypoplasia can be recognized prenatally, sometimes with polyhydramnios. Severe neonates may need early airway and feeding intervention; question-mark ears can be absent.
  evidence:
  - reference: PMID:34789173
    reference_title: 'Prenatal diagnosis of auriculocondylar syndrome with a novel missense variant of GNAI3: a case report.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: Severe micrognathia and mandibular hypoplasia accompanied by polyhydramnios are prenatal indicators of ACS.
    explanation: The prenatal case supports early detectability, not diagnostic specificity.
- phase: Childhood and adult course
  notes: Joint restriction, sleep-disordered breathing, hearing, feeding, dental and articulation problems may require staged follow-up. Development is often normal but is not uniformly preserved. Structural treatment does not ensure resolution of central apnea. Adult corrective surgery has favorable reported outcomes in individual cases, not a comparative natural-history estimate.
  evidence:
  - reference: PMID:22560091
    reference_title: A human homeotic transformation resulting from mutations in PLCB4 and GNAI3 causes auriculocondylar syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: In each case, mandibular ankylosis was progressive, of variable severity, and characterized by inconsistent fusion to the medial and lateral pterygoid plates.
    explanation: Direct clinical characterization of the selected severe cases.
  - reference: url:https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf
    reference_title: https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: Central sleep apnea has previously been reported in patients with ACS.
    explanation: The clinical synthesis distinguishes central apnea from the structural obstructive component.
  - reference: url:https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf
    reference_title: https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: However intellectual disability was rare (3/23 patients, 13%)
    explanation: The denominator is the subset assessed for this outcome.
treatments:
- name: Individualized airway support
  description: Severe neonatal obstruction may require specialist airway stabilization, including tracheostomy. Positive-pressure support may be needed for sleep-disordered breathing. Assessment must distinguish central from obstructive components and consider associated airway lesions.
  therapeutic_modality: OTHER
  treatment_term:
    preferred_term: Respiratory Therapy
    term:
      id: NCIT:C15322
      label: Respiratory Therapy
  evidence:
  - reference: url:https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf
    reference_title: https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: She underwent tracheostomy at birth and gastrostomy at 16 months of age.
    explanation: The severe GNAI3 case documents both procedures; this is case-based management, not a controlled efficacy comparison.
  - reference: url:https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf
    reference_title: https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: severe mixed sleep apnea on polysomnography at 2 months of age, requiring nocturnal noninvasive ventilation.
    explanation: A biallelic PLCB4 patient received nocturnal noninvasive support.
  target_mechanisms:
  - target: Upper-Airway Narrowing
    treatment_effect: BYPASSES
    description: Tracheostomy can bypass an obstructed upper airway; its use is individualized.
    evidence:
    - reference: url:https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf
      reference_title: https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: PRIMARY_RESULT
      snippet: She underwent tracheostomy at birth and gastrostomy at 16 months of age.
      explanation: The severe GNAI3 case documents both procedures; this is case-based management, not a controlled efficacy comparison.
- name: Nutritional and feeding support
  description: Assess oral feeding and growth. Temporary enteral tube feeding or gastrostomy may be necessary in severely affected children, with oral-motor assessment and reassessment as airway and jaw problems evolve.
  therapeutic_modality: OTHER
  treatment_term:
    preferred_term: Nutritional Support
    term:
      id: NCIT:C15433
      label: Nutritional Support
  evidence:
  - reference: url:https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf
    reference_title: https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: She underwent tracheostomy at birth and gastrostomy at 16 months of age.
    explanation: The severe GNAI3 case documents both procedures; this is case-based management, not a controlled efficacy comparison.
  - reference: url:https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf
    reference_title: https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: Feeding difficulties necessitated tube feeding for 3 months.
    explanation: One child required temporary tube feeding.
  target_mechanisms:
  - target: Feeding difficulties
    treatment_effect: BYPASSES
    description: Enteral support provides nutrition when oral feeding is inadequate.
    evidence:
    - reference: url:https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf
      reference_title: https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: PRIMARY_RESULT
      snippet: She underwent tracheostomy at birth and gastrostomy at 16 months of age.
      explanation: The severe GNAI3 case documents both procedures; this is case-based management, not a controlled efficacy comparison.
- name: Mandibular distraction osteogenesis
  description: Distraction can be used for selected severe mandibular hypoplasia and associated airway compromise. Timing and repeat procedures are individualized. Case reports document improvement, but distraction does not ensure resolution of central apnea or define a universal operative age.
  therapeutic_modality: SURGERY
  treatment_term:
    preferred_term: mandibular osteotomy with distraction osteogenesis
    term:
      id: NCIT:C51903
      label: Osteotomy
  evidence:
  - reference: PMID:38618928
    reference_title: 'Auriculocondylar syndrome 2 caused by a novel PLCB4 variant in a male Chinese neonate: A case report and review of the literature.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: The patient underwent bilateral mandibular osteotomy and distraction osteogenesis at 17 days after birth. A second procedure at 16 months old improved mandibular growth.
    explanation: The neonatal report describes staged distraction with later improvement in jaw growth.
  - reference: url:https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf
    reference_title: https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: Central sleep apnea has previously been reported in patients with ACS.
    explanation: The clinical synthesis distinguishes central apnea from the structural obstructive component.
  target_mechanisms:
  - target: Micrognathia
    treatment_effect: MODULATES
    description: Distraction lengthens the hypoplastic mandible.
    evidence:
    - reference: PMID:38618928
      reference_title: 'Auriculocondylar syndrome 2 caused by a novel PLCB4 variant in a male Chinese neonate: A case report and review of the literature.'
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: PRIMARY_RESULT
      snippet: The patient underwent bilateral mandibular osteotomy and distraction osteogenesis at 17 days after birth. A second procedure at 16 months old improved mandibular growth.
      explanation: The neonatal report describes staged distraction with later improvement in jaw growth.
- name: Temporomandibular reconstruction
  description: Selected ankylosis or severe joint dysfunction may require arthroplasty and reconstruction by an experienced craniofacial team. Procedures and graft choice are guided by anatomy and growth; comparative long-term outcomes are limited.
  therapeutic_modality: SURGERY
  treatment_term:
    preferred_term: temporomandibular arthroplasty and reconstruction
    term:
      id: NCIT:C51691
      label: Arthroplasty
  evidence:
  - reference: url:https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf
    reference_title: https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: Craniofacial CT imaging demonstrated a small mandible and bilateral TMJ ankylosis that benefited from arthroplasty and costo- chondral grafts at 4 years of age
    explanation: Arthroplasty and costochondral grafting benefited bilateral TMJ ankylosis in one severe case.
  target_mechanisms:
  - target: Temporomandibular joint ankylosis
    treatment_effect: MODULATES
    description: Reconstruction addresses the fused or malformed joint.
    evidence:
    - reference: url:https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf
      reference_title: https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: PRIMARY_RESULT
      snippet: Craniofacial CT imaging demonstrated a small mandible and bilateral TMJ ankylosis that benefited from arthroplasty and costo- chondral grafts at 4 years of age
      explanation: Arthroplasty and costochondral grafting benefited bilateral TMJ ankylosis in one severe case.
- name: Orthodontic and orthognathic treatment
  description: Dentofacial deformity and malocclusion may be treated with coordinated orthodontics and staged orthognathic surgery. One adult report documented improved occlusion, mouth opening and apnea indices at long follow-up after several combined procedures; it cannot isolate the contribution of each component or establish a standard protocol.
  therapeutic_modality: SURGERY
  treatment_term:
    preferred_term: Surgical Procedure
    term:
      id: NCIT:C15329
      label: Surgical Procedure
  evidence:
  - reference: PMID:39014351
    reference_title: 'Novel GNAI3 mutation in a Chinese family with auriculocondylar syndrome and treatment of severe dentofacial deformities: a 5-year follow-up case report.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: After a multidisciplinary consultation and examination, sequential orthodontic treatment and craniofacial surgery, including distraction osteogenesis and orthognathic surgery, were performed using three-dimensional (3D) digital technology to treat the patient's dentofacial deformity.
    explanation: One adult received combined orthodontic and staged craniofacial interventions.
  - reference: PMID:39014351
    reference_title: 'Novel GNAI3 mutation in a Chinese family with auriculocondylar syndrome and treatment of severe dentofacial deformities: a 5-year follow-up case report.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: with a maximal opening capacity of 40 mm.
    explanation: Follow-up records improved mouth opening in the treated individual.
  target_mechanisms:
  - target: Dental crowding
    treatment_effect: MODULATES
    description: Orthodontic correction addresses dental alignment as part of combined care.
    evidence:
    - reference: PMID:39014351
      reference_title: 'Novel GNAI3 mutation in a Chinese family with auriculocondylar syndrome and treatment of severe dentofacial deformities: a 5-year follow-up case report.'
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: PRIMARY_RESULT
      snippet: Additionally, we aligned the crowded teeth and leveled the dentition to minimize tooth compensation.
      explanation: The report directly documents dental alignment during combined treatment.
- name: Speech and developmental support
  description: Assess articulation, oral-motor function, hearing and developmental needs. Speech therapy and individualized educational support may be appropriate; craniofacial speech difficulty must not be equated with intellectual disability. This action binding identifies the speech-therapy component; broader developmental assessment guides any separate educational support.
  therapeutic_modality: OTHER
  treatment_term:
    preferred_term: Speech Language Therapy
    term:
      id: NCIT:C159273
      label: Speech Language Therapy
  evidence:
  - reference: PMID:34750192
    reference_title: 'New locus underlying auriculocondylar syndrome (ARCND): 430 kb duplication involving TWIST1 regulatory elements.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: Treatment is mainly corrective through surgical intervention for mandibular ramus lengthening using distraction osteogenesis and accompanied by orthodontic treatments and speech therapy.
    explanation: The clinical background specifically includes speech therapy.
  - reference: url:https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf
    reference_title: https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: However intellectual disability was rare (3/23 patients, 13%)
    explanation: The denominator is the subset assessed for this outcome.
- name: Audiologic and otologic care
  description: Obtain audiologic assessment and address the identified cause. Tympanostomy tubes have been used for selected conductive loss. Ossicular abnormalities and cholesteatoma warrant specialist evaluation; the reported mastoidectomy/tympanoplasty case does not provide a quantified postoperative hearing result.
  therapeutic_modality: OTHER
  treatment_term:
    preferred_term: Supportive Care
    term:
      id: NCIT:C15747
      label: Supportive Care
  evidence:
  - reference: url:https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf
    reference_title: https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: Conductive hearing loss necessitated tympanostomy tube insertion. Sleep apnea with snoring was treated by tonsillectomy at 2 years of age.
    explanation: The EDN1 start-loss case received ENT interventions for its individual conductive and sleep findings.
  - reference: url:https://lab.research.sickkids.ca/wp-content/uploads/sites/22/2015/09/Propst_et_al_Ossicular-Fusion-and-cholesteatoma-in-Auriculo-Condylar-Syndrome_2013.pdf
    reference_title: https://lab.research.sickkids.ca/wp-content/uploads/sites/22/2015/09/Propst_et_al_Ossicular-Fusion-and-cholesteatoma-in-Auriculo-Condylar-Syndrome_2013.pdf
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: The patient underwent a right-sided combined- approach mastoidectomy for removal of cholesteatoma.
    explanation: Direct operative management of the reported cholesteatoma.
  target_mechanisms:
  - target: Cholesteatoma
    treatment_effect: INHIBITS
    description: Mastoidectomy removes the cholesteatoma.
    evidence:
    - reference: url:https://lab.research.sickkids.ca/wp-content/uploads/sites/22/2015/09/Propst_et_al_Ossicular-Fusion-and-cholesteatoma-in-Auriculo-Condylar-Syndrome_2013.pdf
      reference_title: https://lab.research.sickkids.ca/wp-content/uploads/sites/22/2015/09/Propst_et_al_Ossicular-Fusion-and-cholesteatoma-in-Auriculo-Condylar-Syndrome_2013.pdf
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: PRIMARY_RESULT
      snippet: The patient underwent a right-sided combined- approach mastoidectomy for removal of cholesteatoma.
      explanation: The lesion was surgically removed.
- name: External-ear reconstruction
  description: Reconstructive ear surgery may be considered for selected structural or patient-prioritized concerns. Published procedures are individual case experiences, with no established comparative technique or universal timing.
  therapeutic_modality: SURGERY
  treatment_term:
    preferred_term: Surgical Procedure
    term:
      id: NCIT:C15329
      label: Surgical Procedure
  evidence:
  - reference: url:https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf
    reference_title: https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: followed by reconstructive surgery of the ears at 5 years of age
    explanation: One affected child underwent ear reconstruction.
- name: Sleep and multisystem surveillance
  description: Follow breathing, growth, hearing, jaw opening, dental development and neurodevelopment. The 2022 cohort authors recommend assessment for both obstructive and central apnea. They also suggest considering spine radiographs in GNAI3-related cases and brain MRI for possible vascular anomalies; these proposals rest on small case numbers rather than formal screening trials.
  therapeutic_modality: OTHER
  treatment_term:
    preferred_term: Supportive Care
    term:
      id: NCIT:C15747
      label: Supportive Care
  evidence:
  - reference: url:https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf
    reference_title: https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    snippet: Therefore monitoring for both obstructive and central apnea should be considered in all patients with ACS.
    explanation: Case-series authors recommend surveillance across apnea types.
  - reference: url:https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf
    reference_title: https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    snippet: Finally, brain MRI may be worthwhile, considering the possible risk of neurovascular mal formations, even if developmental milestones are within the normal range.
    explanation: This is a tentative case-based recommendation, not established universal screening efficacy.
  action_category: MONITORING
- name: Genetic counseling
  description: Explain the allele-specific dominant or recessive inheritance, variable expression and incomplete penetrance. Discuss familial testing and prenatal or reproductive options once the molecular diagnosis is established; a negative coding panel does not exclude a regulatory structural variant.
  therapeutic_modality: OTHER
  treatment_term:
    preferred_term: Genetic Counseling
    term:
      id: NCIT:C15240
      label: Genetic Counseling
  evidence:
  - reference: PMID:22560091
    reference_title: A human homeotic transformation resulting from mutations in PLCB4 and GNAI3 causes auriculocondylar syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: The identification of phenotypic variability and incomplete penetrance underscores the utility of these results in genetic counseling of families affected by ACS.
    explanation: The primary gene-discovery report identifies implications for family counseling.
  action_category: COUNSELING_INFORMATIONAL
differential_diagnoses:
- name: Pierre Robin sequence-plus
  description: Pierre Robin sequence and related craniofacial disorders overlap through micrognathia, glossoptosis and palatal abnormalities. The ear pattern, condylar anatomy, other findings and molecular testing distinguish the spectrum; absence of question-mark ears alone does not exclude ACS.
  distinguishing_features:
  - Question mark ears
  - Mandibular condyle hypoplasia
  evidence:
  - reference: PMID:28328130
    reference_title: Targeted molecular investigation in patients within the clinical spectrum of Auriculocondylar syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: In order to address these questions, we searched for alterations in PLCB4, GNAI3, and EDN1 in patients with typical Auriculocondylar syndrome (n = 3), Pierre Robin sequence-plus (n = 3), micrognathia with additional craniofacial malformations (n = 4), or non-specific auricular dysplasia (n = 1), which could represent subtypes of Auriculocondylar syndrome.
    explanation: This supports Pierre Robin sequence-plus as part of the clinical differential or spectrum considered in testing.
    quote_role: PRIMARY_RESULT
- name: MEF2C-related neurodevelopmental disorder
  description: Question-mark ears accompanied by severe intellectual disability or epilepsy can indicate a different molecular disorder and merit broader evaluation.
  distinguishing_features:
  - Severe encephalopathy or epilepsy outside the usual ACS presentation
  evidence:
  - reference: url:https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf
    reference_title: https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: Recent reports have highlighted that heterozygous myocyte enhancer factor 2C (MEF2C; MIM# 600662) loss ‐of‐function mutations should be con- sidered as a possible cause of QME associated with severe intellectual deficiency and/or epilepsy (Gordon et al., 2018;
    explanation: The cohort discussion identifies a distinct molecular differential; this does not reclassify all ACS-associated developmental delay.
- name: Oculo-auriculo-vertebral spectrum
  description: This craniofacial spectrum is a named source of diagnostic confusion. Assess the ear, mandibular-condylar and broader craniofacial pattern; the report identifies overlap but does not provide a validated diagnostic classifier.
  evidence:
  - reference: PMID:39014351
    reference_title: 'Novel GNAI3 mutation in a Chinese family with auriculocondylar syndrome and treatment of severe dentofacial deformities: a 5-year follow-up case report.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: BACKGROUND
    snippet: ARCND can be misdiagnosed as other diseases, including craniomaxillofacial deformities such as the oculo-auriculo-vertebral spectrum ... Treacher Collins syndrome ... mandibulofacial dysostosis ... Guion-Almeida type, and Meier-Gorlin syndrome
    explanation: The paper explicitly names this differential as background; it does not measure the sensitivity or specificity of distinguishing signs.
- name: Treacher Collins syndrome
  description: Treacher Collins syndrome is a named differential for the mandibulofacial presentation. Question-mark ear morphology and condylar findings can direct ARCND testing, but neither a single ear sign nor mandibular hypoplasia alone establishes the molecular diagnosis.
  evidence:
  - reference: PMID:39014351
    reference_title: 'Novel GNAI3 mutation in a Chinese family with auriculocondylar syndrome and treatment of severe dentofacial deformities: a 5-year follow-up case report.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: BACKGROUND
    snippet: ARCND can be misdiagnosed as other diseases, including craniomaxillofacial deformities such as the oculo-auriculo-vertebral spectrum ... Treacher Collins syndrome ... mandibulofacial dysostosis ... Guion-Almeida type, and Meier-Gorlin syndrome
    explanation: The paper explicitly names this differential as background; it does not measure the sensitivity or specificity of distinguishing signs.
- name: Mandibulofacial dysostosis, Guion-Almeida type
  description: The cited background lists this named mandibulofacial dysostosis among potential misdiagnoses. Broader clinical assessment and phenotype-guided molecular testing are appropriate when the craniofacial pattern is atypical for ARCND.
  evidence:
  - reference: PMID:39014351
    reference_title: 'Novel GNAI3 mutation in a Chinese family with auriculocondylar syndrome and treatment of severe dentofacial deformities: a 5-year follow-up case report.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: BACKGROUND
    snippet: ARCND can be misdiagnosed as other diseases, including craniomaxillofacial deformities such as the oculo-auriculo-vertebral spectrum ... Treacher Collins syndrome ... mandibulofacial dysostosis ... Guion-Almeida type, and Meier-Gorlin syndrome
    explanation: The paper explicitly names this differential as background; it does not measure the sensitivity or specificity of distinguishing signs.
- name: Meier-Gorlin syndrome
  description: The case-report background names Meier-Gorlin syndrome as a potential diagnostic alternative. Interpret auricular and mandibular findings in the complete clinical context instead of treating ear morphology alone as diagnostic.
  evidence:
  - reference: PMID:39014351
    reference_title: 'Novel GNAI3 mutation in a Chinese family with auriculocondylar syndrome and treatment of severe dentofacial deformities: a 5-year follow-up case report.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: BACKGROUND
    snippet: ARCND can be misdiagnosed as other diseases, including craniomaxillofacial deformities such as the oculo-auriculo-vertebral spectrum ... Treacher Collins syndrome ... mandibulofacial dysostosis ... Guion-Almeida type, and Meier-Gorlin syndrome
    explanation: The paper explicitly names this differential as background; it does not measure the sensitivity or specificity of distinguishing signs.
animal_models:
- name: Plcb4 Arg621His edited mouse founders
  species: Mouse
  background: C57BL/6NJ zygotes; F0 embryos examined at E18.5
  genotype: One Plcb4 Arg621His/Arg621His and two Arg621His/indel founders
  publication: PMID:35284927
  description: CRISPR/HDR founders show proximal mandibular dysplasia, reduced or absent mandibular processes and ectopic bony structures. Three knock-in-bearing embryos were identified among 69 collected. Wild-type/indel embryos and unmodified controls lacked overt skull changes in the reported comparison.
  notes: No wild-type/knock-in embryo was tested. These founder observations do not demonstrate the phenotype of a stable heterozygous line, adult function or therapeutic rescue. Tooth-like projections were morphologic observations rather than confirmed teeth.
  evidence:
  - reference: PMID:35284927
    reference_title: Auriculocondylar syndrome 2 results from the dominant-negative action of PLCB4 variants.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    quote_role: PRIMARY_RESULT
    snippet: Of the 69 embryos harvested at E18.5, we identified three embryos harboring at least one knock-in allele; one was homozygous for the knock-in allele (Plcb4KI/KI) and the other two were compound heterozygotes harboring the knock-in allele and an insertion/deletion (indel) allele generated by non-homologous end joining (NHEJ) (Plcb4Indel/KI).
    explanation: The actual founders comprise one homozygote and two knock-in/indel embryos, not simple heterozygotes.
  - reference: PMID:35284927
    reference_title: Auriculocondylar syndrome 2 results from the dominant-negative action of PLCB4 variants.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    quote_role: PRIMARY_RESULT
    snippet: the proximal mandible of Plcb4Indel/KI and Plcb4KI/KI embryos was disorganized, with absent or hypoplastic mandibular processes
    explanation: E18.5 edited mouse founders show proximal mandibular skeletal abnormalities; the tested genotypes are not simple wild-type/knock-in heterozygotes.
  modeled_mechanisms:
  - target: Abnormal Mandibular Skeletal Morphogenesis
    relationship: RECAPITULATES
    limitations: Small F0 sample and mixed edited genotypes limit extrapolation to dominant human inheritance.
    readouts:
    - name: Mandibular process morphology
      description: Condylar, coronoid and angular processes are hypoplastic or absent.
      evidence:
      - reference: PMID:35284927
        reference_title: Auriculocondylar syndrome 2 results from the dominant-negative action of PLCB4 variants.
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        quote_role: PRIMARY_RESULT
        snippet: the proximal mandible of Plcb4Indel/KI and Plcb4KI/KI embryos was disorganized, with absent or hypoplastic mandibular processes
        explanation: E18.5 edited mouse founders show proximal mandibular skeletal abnormalities; the tested genotypes are not simple wild-type/knock-in heterozygotes.
      target: Abnormal Mandibular Skeletal Morphogenesis
    description: Embryonic skeletal imaging and staining demonstrate abnormal proximal mandibular development.
    evidence:
    - reference: PMID:35284927
      reference_title: Auriculocondylar syndrome 2 results from the dominant-negative action of PLCB4 variants.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      quote_role: PRIMARY_RESULT
      snippet: the proximal mandible of Plcb4Indel/KI and Plcb4KI/KI embryos was disorganized, with absent or hypoplastic mandibular processes
      explanation: E18.5 edited mouse founders show proximal mandibular skeletal abnormalities; the tested genotypes are not simple wild-type/knock-in heterozygotes.
    model_scale: ORGANISM
- name: Endothelin-pathway knockout mice
  species: Mouse
  genotype: Edn1-null, Ednra-null or Ece1-null models summarized in the developmental literature
  description: These knockout models demonstrate mandibular-to-maxillary homeosis and other craniofacial abnormalities. They establish developmental pathway requirements rather than reproducing the precise human alleles.
  notes: Null models can have cardiovascular defects and severe neonatal outcomes beyond typical human ACS. Partial allelic reduction and species-specific compensation complicate direct phenotype matching.
  evidence:
  - reference: PMID:24123988
    reference_title: 'Understanding the basis of auriculocondylar syndrome: Insights from human, mouse and zebrafish genetic studies.'
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    quote_role: REVIEW_SYNTHESIS
    snippet: mice that are homozygous null for Edn1, Ednra, endothelin converting enzyme 1 (Ece1) or Dlx5/Dlx6 display a homeotic transformation of the lower jaw into an upper jaw
    explanation: The review summarizes distinct developmental knockout models.
  modeled_mechanisms:
  - target: Disrupted Mandibular Neural Crest Identity
    relationship: PERTURBS
    limitations: Different genes and null alleles are grouped only for the shared developmental result.
    description: Pathway-gene deletion changes mandibular positional identity.
    evidence:
    - reference: PMID:24123988
      reference_title: 'Understanding the basis of auriculocondylar syndrome: Insights from human, mouse and zebrafish genetic studies.'
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      quote_role: REVIEW_SYNTHESIS
      snippet: Disruption of this signaling pathway in both mouse and zebrafish results in loss of identity of neural crest cells of the mandibular portion of the first pharyngeal arch and the subsequent repatterning of these cells, leading to homeosis of lower jaw structures into more maxillary-like structures.
      explanation: Genetic developmental models support altered identity rather than a universal neural-crest migration deficit.
    model_scale: ORGANISM
- name: Zebrafish edn1 and plcb3 developmental mutants
  species: Zebrafish
  genotype: edn1 mutants and schmerle/plcb3 mutants summarized in the developmental literature
  description: Mutants show hypoplastic lower-jaw skeletal elements and fusion across arch joints. Genetic interaction supports a conserved endothelin-phospholipase pathway.
  notes: Zebrafish plcb3 is not the human PLCB4 gene, and species-specific compensation affects distal versus intermediate arch domains. These models do not establish a human treatment.
  evidence:
  - reference: PMID:24123988
    reference_title: 'Understanding the basis of auriculocondylar syndrome: Insights from human, mouse and zebrafish genetic studies.'
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    quote_role: REVIEW_SYNTHESIS
    snippet: zebrafish with combined heterozygous mutations in plcb3 and edn1 (the ligand of the EDNRA) demonstrated a more severe phenotype than either mutant alone.
    explanation: The review summarizes genetic interaction in fish.
  modeled_mechanisms:
  - target: Disrupted Mandibular Neural Crest Identity
    relationship: PERTURBS
    limitations: Paralog and species differences constrain direct allelic interpretation.
    description: Endothelin-pathway perturbation alters lower-jaw patterning.
    evidence:
    - reference: PMID:24123988
      reference_title: 'Understanding the basis of auriculocondylar syndrome: Insights from human, mouse and zebrafish genetic studies.'
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      quote_role: REVIEW_SYNTHESIS
      snippet: Disruption of this signaling pathway in both mouse and zebrafish results in loss of identity of neural crest cells of the mandibular portion of the first pharyngeal arch and the subsequent repatterning of these cells, leading to homeosis of lower jaw structures into more maxillary-like structures.
      explanation: Genetic developmental models support altered identity rather than a universal neural-crest migration deficit.
    model_scale: ORGANISM
- name: GNAI3-variant expression in Xenopus embryos
  species: Xenopus laevis
  genotype: Injected mRNA encoding wild-type or ACS-associated GNAI3 variants
  description: Expression of G40R, G45V, S47R, T48N or N269Y increases a gastrulation-associated gravitational-inversion phenotype relative to wild-type GNAI3 expression at the tested doses.
  notes: This is an ectopic-expression developmental bioassay scored around neurulation, not an ACS craniofacial model. The signaling pathway responsible for the inversion phenotype was not established, and it is not evidence of facial rescue or a nucleotide-binding assay in vivo.
  evidence:
  - reference: PMID:27072656
    reference_title: Dominant-negative Gα subunits are a mechanism of dysregulated heterotrimeric G protein signaling in human disease.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    quote_role: PRIMARY_RESULT
    snippet: expression of any of the five mutants (G40R, G45V, S47R, T48N and N269Y) increased the frequency of gravitational inversion in embryos compared to those expressing wild-type Gαi3
    explanation: Variant expression modifies the embryonic bioassay phenotype.
  modeled_mechanisms:
  - target: Heterozygous GNAI3 Variants
    relationship: PERTURBS
    limitations: mRNA injection does not recreate a heterozygous human genomic allele; the endpoint is gastrulation, not jaw formation.
    description: Introduces the disease-associated protein substitutions into an embryonic expression assay.
    evidence:
    - reference: PMID:27072656
      reference_title: Dominant-negative Gα subunits are a mechanism of dysregulated heterotrimeric G protein signaling in human disease.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      quote_role: PRIMARY_RESULT
      snippet: Although it is not known what specific signaling pathways are disrupted by the ectopic expression of Gαi, this system provides a suitable platform to test whether G protein mutants induce a gain or loss of function in the context of embryonic development.
      explanation: The source explicitly limits pathway specificity.
    model_scale: ORGANISM
datasets:
- accession: dbgap:phs000437
  title: 'Next Generation Mendelian Genetics: Auriculocondylar Syndrome (ACS)'
  description: This project is part of an ongoing project to identify the molecular genetic basis of rare craniofacial disorders. This specific project involved the collection of DNA samples from four probands with severe manifestations of auriculocondylar syndrome and their parents. Detailed clinical phenotypic data is available on each proband. The sole purpose of this research is to identify the molecular cause(s) of auriculochondylar syndrome.
  notes: The dbGaP accession and disease-specific title were verified against the live repository on 2026-09-21. The project describes four severe ACS probands and their parents; it is a gene-discovery collection, not a representative phenotype-frequency cohort.
experimental_models:
- name: Purified GNAI3 S47R nucleotide-binding assays
  experimental_model_type: OTHER
  description: Recombinant wild-type and S47R GNAI3 were compared by nucleotide-binding, GTPase, HPLC and limited-proteolysis assays. S47R retains GDP but has profoundly impaired GTP binding and activation.
  notes: The other four variants could not be purified in sufficient soluble quantity; their activation defects were tested after mammalian expression. Poor recovery is not a direct protein half-life measurement.
  publication: PMID:27072656
  cell_source: Recombinant proteins expressed in Escherichia coli
  evidence:
  - reference: PMID:27072656
    reference_title: Dominant-negative Gα subunits are a mechanism of dysregulated heterotrimeric G protein signaling in human disease.
    supports: SUPPORT
    evidence_source: IN_VITRO
    quote_role: PRIMARY_RESULT
    snippet: Together, these results demonstrate that Gαi3 S47R retains the capability to bind GDP but fails to bind GTP, rendering the G protein unable to switch into an active conformation.
    explanation: Purified S47R directly retains GDP but loses efficient GTP binding; other variants were assessed with cell-expressed limited-proteolysis assays.
  modeled_mechanisms:
  - target: Impaired GNAI3 GTP Binding
    relationship: MEASURES
    limitations: Direct purified-protein evidence is limited to S47R.
    readouts:
    - name: GDP and GTP binding
      description: GDP is retained while GTP binding is impaired.
      evidence:
      - reference: PMID:27072656
        reference_title: Dominant-negative Gα subunits are a mechanism of dysregulated heterotrimeric G protein signaling in human disease.
        supports: SUPPORT
        evidence_source: IN_VITRO
        quote_role: PRIMARY_RESULT
        snippet: Together, these results demonstrate that Gαi3 S47R retains the capability to bind GDP but fails to bind GTP, rendering the G protein unable to switch into an active conformation.
        explanation: Purified S47R directly retains GDP but loses efficient GTP binding; other variants were assessed with cell-expressed limited-proteolysis assays.
      target: Impaired GNAI3 GTP Binding
    description: Biochemical assays distinguish GDP retention from defective GTP binding.
    evidence:
    - reference: PMID:27072656
      reference_title: Dominant-negative Gα subunits are a mechanism of dysregulated heterotrimeric G protein signaling in human disease.
      supports: SUPPORT
      evidence_source: IN_VITRO
      quote_role: PRIMARY_RESULT
      snippet: Together, these results demonstrate that Gαi3 S47R retains the capability to bind GDP but fails to bind GTP, rendering the G protein unable to switch into an active conformation.
      explanation: Purified S47R directly retains GDP but loses efficient GTP binding; other variants were assessed with cell-expressed limited-proteolysis assays.
    model_scale: MOLECULAR
- name: GNAI3-variant signaling in HEK293T cells
  experimental_model_type: CELL_LINE
  description: Five ACS-associated GNAI3 variants were studied in transfected HEK293T cells using protease protection, receptor co-immunoprecipitation and BRET. ET-1-induced Gq activation was reduced at an 8:1 Gq-to-Gi3 expression ratio; the weak Gi3 response was not comparably inhibited.
  notes: Expression was adjusted between constructs. Co-immunoprecipitation supports increased association, while irreversible trapping, binding kinetics and human embryonic cell specificity remain inferred.
  publication: PMID:27072656
  cell_source: Transfected human embryonic kidney 293T cell line
  evidence:
  - reference: PMID:27072656
    reference_title: Dominant-negative Gα subunits are a mechanism of dysregulated heterotrimeric G protein signaling in human disease.
    supports: SUPPORT
    evidence_source: IN_VITRO
    quote_role: PRIMARY_RESULT
    snippet: We found that all 5 ACS-associated Gαi3 mutants displayed increased binding (3- to 5-fold) to myc-tagged ETAR compared to Gαi3 WT (Fig. 5D).
    explanation: Co-immunoprecipitation measures increased receptor association, not a directly measured receptor residence time or equilibrium affinity.
  - reference: PMID:27072656
    reference_title: Dominant-negative Gα subunits are a mechanism of dysregulated heterotrimeric G protein signaling in human disease.
    supports: SUPPORT
    evidence_source: IN_VITRO
    quote_role: PRIMARY_RESULT
    snippet: We found that expression of any of the five ACS-associated Gαi3 mutants decreased Gq activation upon ET-1 stimulation ~65 to 85% (Fig. 6D).
    explanation: HEK293T BRET assays show reduced Gq activation when mutant Gi3 is coexpressed at a substoichiometric ratio.
  modeled_mechanisms:
  - target: Increased Mutant GNAI3 Receptor Association
    relationship: MEASURES
    limitations: Association abundance is not an equilibrium-affinity or residence-time measurement.
    description: Co-immunoprecipitation shows greater mutant association with EDNRA.
    evidence:
    - reference: PMID:27072656
      reference_title: Dominant-negative Gα subunits are a mechanism of dysregulated heterotrimeric G protein signaling in human disease.
      supports: SUPPORT
      evidence_source: IN_VITRO
      quote_role: PRIMARY_RESULT
      snippet: We found that all 5 ACS-associated Gαi3 mutants displayed increased binding (3- to 5-fold) to myc-tagged ETAR compared to Gαi3 WT (Fig. 5D).
      explanation: Co-immunoprecipitation measures increased receptor association, not a directly measured receptor residence time or equilibrium affinity.
    model_scale: CELLULAR
  - target: Reduced EDNRA-Gq Signaling
    relationship: MEASURES
    limitations: Heterologous expression does not establish the exact signaling stoichiometry in human arch cells.
    readouts:
    - name: ET-1-induced Gq BRET response
      description: Mutants reduce the response by about 65–85% under the tested condition.
      evidence:
      - reference: PMID:27072656
        reference_title: Dominant-negative Gα subunits are a mechanism of dysregulated heterotrimeric G protein signaling in human disease.
        supports: SUPPORT
        evidence_source: IN_VITRO
        quote_role: PRIMARY_RESULT
        snippet: We found that expression of any of the five ACS-associated Gαi3 mutants decreased Gq activation upon ET-1 stimulation ~65 to 85% (Fig. 6D).
        explanation: HEK293T BRET assays show reduced Gq activation when mutant Gi3 is coexpressed at a substoichiometric ratio.
      target: Reduced EDNRA-Gq Signaling
    description: BRET measures reduced Gq activation after ET-1 stimulation.
    evidence:
    - reference: PMID:27072656
      reference_title: Dominant-negative Gα subunits are a mechanism of dysregulated heterotrimeric G protein signaling in human disease.
      supports: SUPPORT
      evidence_source: IN_VITRO
      quote_role: PRIMARY_RESULT
      snippet: We found that expression of any of the five ACS-associated Gαi3 mutants decreased Gq activation upon ET-1 stimulation ~65 to 85% (Fig. 6D).
      explanation: HEK293T BRET assays show reduced Gq activation when mutant Gi3 is coexpressed at a substoichiometric ratio.
    model_scale: CELLULAR
- name: PLCB4-variant DAG and transcriptional reporter assays
  experimental_model_type: CELL_LINE
  description: HEK293T cells express EDNRA, wild-type or variant PLCB4 and DAG sensors. Arg621His and three other tested ACS substitutions attenuate the stimulated signal; synthetic Pro838Ala in cis with Arg621His reduces interference. A separate HEK293 SRE-luciferase experiment assesses downstream reporter output with constitutively active Gq.
  notes: DAG-sensor and SRE readouts are not purified-enzyme kinetics, a direct ERK-phosphorylation assay or fetal DLX expression. Proposed PIP2 trapping and altered GAP function were not directly tested. The synthetic interface mutation is not a clinical therapy.
  publication: PMID:35284927
  cell_source: Transfected HEK293T cells for DAG assays; HEK293 cells for SRE reporter
  evidence:
  - reference: PMID:35284927
    reference_title: Auriculocondylar syndrome 2 results from the dominant-negative action of PLCB4 variants.
    supports: SUPPORT
    evidence_source: IN_VITRO
    quote_role: PRIMARY_RESULT
    snippet: These results illustrate that PLCB4 p.Arg621His interferes with PLCB activity even when it is expressed at a sub-stoichiometric level relative to wild-type PLCB4, exemplifying a characteristic of a dominant-negative protein.
    explanation: DAG-sensor BRET detects dominant interference by Arg621His; three additional tested missense variants also attenuated the response.
  - reference: PMID:35284927
    reference_title: Auriculocondylar syndrome 2 results from the dominant-negative action of PLCB4 variants.
    supports: SUPPORT
    evidence_source: IN_VITRO
    quote_role: PRIMARY_RESULT
    snippet: indicating that the p.Pro838Ala mutation diminished the dominant-negative effect of PLCB4 p.Arg621His.
    explanation: An additional synthetic interface substitution attenuates the variant-dependent signaling defect.
  modeled_mechanisms:
  - target: Reduced EDNRA-Dependent Phospholipase C Activity
    relationship: PERTURBS
    limitations: The mechanism beyond Gq-interface dependence is unresolved.
    readouts:
    - name: EDN1-stimulated DAG sensor response
      description: BRET and membrane translocation responses are attenuated by tested variants.
      evidence:
      - reference: PMID:35284927
        reference_title: Auriculocondylar syndrome 2 results from the dominant-negative action of PLCB4 variants.
        supports: SUPPORT
        evidence_source: IN_VITRO
        quote_role: PRIMARY_RESULT
        snippet: These results illustrate that PLCB4 p.Arg621His interferes with PLCB activity even when it is expressed at a sub-stoichiometric level relative to wild-type PLCB4, exemplifying a characteristic of a dominant-negative protein.
        explanation: DAG-sensor BRET detects dominant interference by Arg621His; three additional tested missense variants also attenuated the response.
      target: Reduced EDNRA-Dependent Phospholipase C Activity
    description: Patient-associated substitutions attenuate pathway output and interface disruption reduces interference.
    evidence:
    - reference: PMID:35284927
      reference_title: Auriculocondylar syndrome 2 results from the dominant-negative action of PLCB4 variants.
      supports: SUPPORT
      evidence_source: IN_VITRO
      quote_role: PRIMARY_RESULT
      snippet: These results illustrate that PLCB4 p.Arg621His interferes with PLCB activity even when it is expressed at a sub-stoichiometric level relative to wild-type PLCB4, exemplifying a characteristic of a dominant-negative protein.
      explanation: DAG-sensor BRET detects dominant interference by Arg621His; three additional tested missense variants also attenuated the response.
    - reference: PMID:35284927
      reference_title: Auriculocondylar syndrome 2 results from the dominant-negative action of PLCB4 variants.
      supports: SUPPORT
      evidence_source: IN_VITRO
      quote_role: PRIMARY_RESULT
      snippet: indicating that the p.Pro838Ala mutation diminished the dominant-negative effect of PLCB4 p.Arg621His.
      explanation: An additional synthetic interface substitution attenuates the variant-dependent signaling defect.
    model_scale: CELLULAR
- name: ACS patient mandibular osteoblast cultures
  experimental_model_type: PRIMARY_CELL_CULTURE
  description: Mandibular osteoblasts from four ACS probands, including two GNAI3 Gly40Arg cases, one PLCB4 Tyr623Cys case and one unresolved case, were compared with 17 control calvarial osteoblast samples. DLX5 and DLX6 steady-state transcripts were lower.
  notes: The control and patient cells come from different cranial bones. Postnatal culture, small sample size and the unresolved genotype preclude treating the mean expression difference as a direct measurement of fetal neural-crest signaling. No correction or rescue was performed.
  publication: PMID:22560091
  cell_source: Patient mandibular and control calvarial osteoblasts
  evidence:
  - reference: PMID:22560091
    reference_title: A human homeotic transformation resulting from mutations in PLCB4 and GNAI3 causes auriculocondylar syndrome.
    supports: SUPPORT
    evidence_source: IN_VITRO
    quote_role: PRIMARY_RESULT
    snippet: Using quantitative, real-time RT-PCR of steady-state mRNA, we identified a 6-fold reduction of DLX5 (p < 0.005; probands versus controls) and an 8-fold reduction of DLX6 expression (p < 0.001) in mandibular osteoblasts from selective probands relative to 17 randomly selected calvarial osteoblasts from controls.
    explanation: Four ACS mandibular-osteoblast cultures were compared with 17 calvarial-osteoblast controls; anatomical source and developmental stage limit interpretation.
  modeled_mechanisms:
  - target: Reduced DLX5 and DLX6 Expression
    relationship: MEASURES
    limitations: Anatomical source and developmental-stage differences remain potential confounders.
    readouts:
    - name: DLX5 and DLX6 transcripts
      description: Mean DLX5 and DLX6 expression was sixfold and eightfold lower, respectively.
      evidence:
      - reference: PMID:22560091
        reference_title: A human homeotic transformation resulting from mutations in PLCB4 and GNAI3 causes auriculocondylar syndrome.
        supports: SUPPORT
        evidence_source: IN_VITRO
        quote_role: PRIMARY_RESULT
        snippet: Using quantitative, real-time RT-PCR of steady-state mRNA, we identified a 6-fold reduction of DLX5 (p < 0.005; probands versus controls) and an 8-fold reduction of DLX6 expression (p < 0.001) in mandibular osteoblasts from selective probands relative to 17 randomly selected calvarial osteoblasts from controls.
        explanation: Four ACS mandibular-osteoblast cultures were compared with 17 calvarial-osteoblast controls; anatomical source and developmental stage limit interpretation.
      target: Reduced DLX5 and DLX6 Expression
    description: RT-qPCR detects lower DLX transcript abundance in the patient cultures.
    evidence:
    - reference: PMID:22560091
      reference_title: A human homeotic transformation resulting from mutations in PLCB4 and GNAI3 causes auriculocondylar syndrome.
      supports: SUPPORT
      evidence_source: IN_VITRO
      quote_role: PRIMARY_RESULT
      snippet: Using quantitative, real-time RT-PCR of steady-state mRNA, we identified a 6-fold reduction of DLX5 (p < 0.005; probands versus controls) and an 8-fold reduction of DLX6 expression (p < 0.001) in mandibular osteoblasts from selective probands relative to 17 randomly selected calvarial osteoblasts from controls.
      explanation: Four ACS mandibular-osteoblast cultures were compared with 17 calvarial-osteoblast controls; anatomical source and developmental stage limit interpretation.
    model_scale: CELLULAR
- name: Regulatory-duplication patient iPSC neural-crest cultures
  experimental_model_type: IPSC_DERIVED_MODEL
  description: iPSCs from three affected members of one family and three controls were differentiated toward neural crest. Patient cultures showed increased TWIST1 and HDAC9 mRNA and reduced 24-hour scratch closure without a detected cell-cycle distribution difference.
  notes: Controls were not isogenic; one control was reprogrammed by a different method. Capture-C was performed in separate nonpatient embryonic calvarial mesenchyme and does not demonstrate altered contacts in these patient cells. No TWIST1-specific correction, rescue or necessity experiment was performed. EDN-pathway transcripts were unchanged or too low to assess, not proof of normal signaling.
  publication: PMID:34750192
  cell_source: Three patient-derived and three unrelated control iPSC lines
  evidence:
  - reference: PMID:34750192
    reference_title: 'New locus underlying auriculocondylar syndrome (ARCND): 430 kb duplication involving TWIST1 regulatory elements.'
    supports: SUPPORT
    evidence_source: IN_VITRO
    quote_role: PRIMARY_RESULT
    snippet: However, an increase in HDAC9 (3.15-fold, unpaired t-test p=0.009) and TWIST1 (2.03-fold, unpaired t-test p=0.03) mRNA was observed in the ARCND-iNCC (figure 2A, B) compared with controls (unpaired t-test).
    explanation: Three affected-donor iPSC-derived neural-crest cultures show increased transcripts relative to three controls; no isogenic correction isolates the causal mediator.
    directness: INDIRECT
  - reference: PMID:34750192
    reference_title: 'New locus underlying auriculocondylar syndrome (ARCND): 430 kb duplication involving TWIST1 regulatory elements.'
    supports: SUPPORT
    evidence_source: IN_VITRO
    quote_role: PRIMARY_RESULT
    snippet: Although no significant difference in cell cycle distribution was detected between patient and control cells, a significant decrease in migratory capacity of ARCND iNCCs was observed compared with controls (4.3-fold decrease, Student’s t-test, p=0.0009) (figure 2C–E).
    explanation: A 24-hour scratch assay measures reduced wound closure in the patient-derived cultures; it does not measure migration into human pharyngeal arches.
    directness: INDIRECT
  modeled_mechanisms:
  - target: Increased Neural Crest TWIST1 Expression
    relationship: MEASURES
    limitations: The causal contribution of this expression difference is unisolated.
    description: Patient-derived iNCCs show increased TWIST1 mRNA.
    evidence:
    - reference: PMID:34750192
      reference_title: 'New locus underlying auriculocondylar syndrome (ARCND): 430 kb duplication involving TWIST1 regulatory elements.'
      supports: SUPPORT
      evidence_source: IN_VITRO
      quote_role: PRIMARY_RESULT
      snippet: However, an increase in HDAC9 (3.15-fold, unpaired t-test p=0.009) and TWIST1 (2.03-fold, unpaired t-test p=0.03) mRNA was observed in the ARCND-iNCC (figure 2A, B) compared with controls (unpaired t-test).
      explanation: Three affected-donor iPSC-derived neural-crest cultures show increased transcripts relative to three controls; no isogenic correction isolates the causal mediator.
      directness: INDIRECT
    model_scale: CELLULAR
  - target: Increased Neural Crest HDAC9 Expression
    relationship: MEASURES
    limitations: Transcript abundance does not establish catalytic isoform activity.
    description: Patient-derived iNCCs also show increased HDAC9 mRNA.
    evidence:
    - reference: PMID:34750192
      reference_title: 'New locus underlying auriculocondylar syndrome (ARCND): 430 kb duplication involving TWIST1 regulatory elements.'
      supports: SUPPORT
      evidence_source: IN_VITRO
      quote_role: PRIMARY_RESULT
      snippet: However, an increase in HDAC9 (3.15-fold, unpaired t-test p=0.009) and TWIST1 (2.03-fold, unpaired t-test p=0.03) mRNA was observed in the ARCND-iNCC (figure 2A, B) compared with controls (unpaired t-test).
      explanation: Three affected-donor iPSC-derived neural-crest cultures show increased transcripts relative to three controls; no isogenic correction isolates the causal mediator.
      directness: INDIRECT
    model_scale: CELLULAR
  - target: Reduced Migration of Patient-Derived Neural Crest Cells
    relationship: MEASURES
    limitations: This does not demonstrate migration into human pharyngeal arches.
    readouts:
    - name: Scratch wound closure
      description: Patient cultures close less of the scratch area after 24 hours.
      evidence:
      - reference: PMID:34750192
        reference_title: 'New locus underlying auriculocondylar syndrome (ARCND): 430 kb duplication involving TWIST1 regulatory elements.'
        supports: SUPPORT
        evidence_source: IN_VITRO
        quote_role: PRIMARY_RESULT
        snippet: Although no significant difference in cell cycle distribution was detected between patient and control cells, a significant decrease in migratory capacity of ARCND iNCCs was observed compared with controls (4.3-fold decrease, Student’s t-test, p=0.0009) (figure 2C–E).
        explanation: A 24-hour scratch assay measures reduced wound closure in the patient-derived cultures; it does not measure migration into human pharyngeal arches.
        directness: INDIRECT
      target: Reduced Migration of Patient-Derived Neural Crest Cells
    description: Scratch closure is reduced over 24 hours.
    evidence:
    - reference: PMID:34750192
      reference_title: 'New locus underlying auriculocondylar syndrome (ARCND): 430 kb duplication involving TWIST1 regulatory elements.'
      supports: SUPPORT
      evidence_source: IN_VITRO
      quote_role: PRIMARY_RESULT
      snippet: Although no significant difference in cell cycle distribution was detected between patient and control cells, a significant decrease in migratory capacity of ARCND iNCCs was observed compared with controls (4.3-fold decrease, Student’s t-test, p=0.0009) (figure 2C–E).
      explanation: A 24-hour scratch assay measures reduced wound closure in the patient-derived cultures; it does not measure migration into human pharyngeal arches.
      directness: INDIRECT
    model_scale: CELLULAR
- name: Regulatory-duplication neural-crest mesenchymal derivatives
  experimental_model_type: IPSC_DERIVED_MODEL
  description: Mesenchymal-like cells differentiated from the same iPSC neural-crest cultures show reduced day-9 ALP activity and a modest reduction in mineralization after osteogenic induction. TWIST1 and RUNX2 expression did not significantly differ during the tested osteogenic interval.
  notes: There is no isogenic rescue or demonstrated chain from TWIST1 upregulation to altered dimerization, RUNX2 inhibition or bone loss. Figure-caption timing of the representative mineralization micrograph is inconsistent; the quantitative mineralization caption specifies 21 days.
  publication: PMID:34750192
  cell_source: Patient and control iPSC-derived neural-crest mesenchymal-like cells
  evidence:
  - reference: PMID:34750192
    reference_title: 'New locus underlying auriculocondylar syndrome (ARCND): 430 kb duplication involving TWIST1 regulatory elements.'
    supports: SUPPORT
    evidence_source: IN_VITRO
    quote_role: PRIMARY_RESULT
    snippet: Our data showed that during osteogenic differentiation, ALP enzymatic activity was significantly diminished in ARCND-nMSCs after 9 days of osteoinduction (decrease of 20.3-fold, paired t-test p=0.029; figure 3A, B).
    explanation: Patient-derived neural-crest mesenchymal cells show reduced alkaline-phosphatase activity during osteogenic induction.
    directness: INDIRECT
  modeled_mechanisms:
  - target: Impaired Osteogenic Differentiation in Patient-Derived Cells
    relationship: MEASURES
    limitations: These cellular outcomes do not prove mediation of patient mandibular hypoplasia.
    readouts:
    - name: Alkaline-phosphatase activity
      description: ALP activity is lower after nine days of osteoinduction.
      evidence:
      - reference: PMID:34750192
        reference_title: 'New locus underlying auriculocondylar syndrome (ARCND): 430 kb duplication involving TWIST1 regulatory elements.'
        supports: SUPPORT
        evidence_source: IN_VITRO
        quote_role: PRIMARY_RESULT
        snippet: Our data showed that during osteogenic differentiation, ALP enzymatic activity was significantly diminished in ARCND-nMSCs after 9 days of osteoinduction (decrease of 20.3-fold, paired t-test p=0.029; figure 3A, B).
        explanation: Patient-derived neural-crest mesenchymal cells show reduced alkaline-phosphatase activity during osteogenic induction.
        directness: INDIRECT
      target: Impaired Osteogenic Differentiation in Patient-Derived Cells
    description: ALP and mineralization provide osteogenic differentiation readouts.
    evidence:
    - reference: PMID:34750192
      reference_title: 'New locus underlying auriculocondylar syndrome (ARCND): 430 kb duplication involving TWIST1 regulatory elements.'
      supports: SUPPORT
      evidence_source: IN_VITRO
      quote_role: PRIMARY_RESULT
      snippet: Our data showed that during osteogenic differentiation, ALP enzymatic activity was significantly diminished in ARCND-nMSCs after 9 days of osteoinduction (decrease of 20.3-fold, paired t-test p=0.029; figure 3A, B).
      explanation: Patient-derived neural-crest mesenchymal cells show reduced alkaline-phosphatase activity during osteogenic induction.
      directness: INDIRECT
    model_scale: CELLULAR
discussions:
- discussion_id: arcnd_regulatory_mediation
  kind: KNOWLEDGE_GAP
  attaches_to:
  - pathophysiology#HDAC9-TWIST1 Regulatory Duplication
  - pathophysiology#Increased Neural Crest TWIST1 Expression
  prompt: Which regulatory and cellular changes mediate the HDAC9-region duplication phenotype?
  rationale: Segregation, nonpatient Capture-C and patient-cell expression findings support a regulatory locus. They do not isolate TWIST1 from HDAC9 or establish that the scratch and osteogenic readouts cause the human jaw phenotype. No serial TWIST1-to-migration-to-osteogenesis causal chain is asserted.
  evidence:
  - reference: PMID:34750192
    reference_title: 'New locus underlying auriculocondylar syndrome (ARCND): 430 kb duplication involving TWIST1 regulatory elements.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: The duplication spanned 430 302 bp (NC_000007.14:g.18437239_18867540dup) telomeric to TWIST1, covering most of the HDAC9 gene.
    explanation: A segregating tandem duplication in one four-generation family defines the regulatory locus; TWIST1 coding sequence is not duplicated.
  - reference: PMID:34750192
    reference_title: 'New locus underlying auriculocondylar syndrome (ARCND): 430 kb duplication involving TWIST1 regulatory elements.'
    supports: SUPPORT
    evidence_source: IN_VITRO
    quote_role: PRIMARY_RESULT
    snippet: However, an increase in HDAC9 (3.15-fold, unpaired t-test p=0.009) and TWIST1 (2.03-fold, unpaired t-test p=0.03) mRNA was observed in the ARCND-iNCC (figure 2A, B) compared with controls (unpaired t-test).
    explanation: Three affected-donor iPSC-derived neural-crest cultures show increased transcripts relative to three controls; no isogenic correction isolates the causal mediator.
    directness: INDIRECT
  - reference: PMID:34750192
    reference_title: 'New locus underlying auriculocondylar syndrome (ARCND): 430 kb duplication involving TWIST1 regulatory elements.'
    supports: SUPPORT
    evidence_source: IN_VITRO
    quote_role: PRIMARY_RESULT
    snippet: Although no significant difference in cell cycle distribution was detected between patient and control cells, a significant decrease in migratory capacity of ARCND iNCCs was observed compared with controls (4.3-fold decrease, Student’s t-test, p=0.0009) (figure 2C–E).
    explanation: A 24-hour scratch assay measures reduced wound closure in the patient-derived cultures; it does not measure migration into human pharyngeal arches.
    directness: INDIRECT
  - reference: PMID:34750192
    reference_title: 'New locus underlying auriculocondylar syndrome (ARCND): 430 kb duplication involving TWIST1 regulatory elements.'
    supports: SUPPORT
    evidence_source: IN_VITRO
    quote_role: PRIMARY_RESULT
    snippet: Our data showed that during osteogenic differentiation, ALP enzymatic activity was significantly diminished in ARCND-nMSCs after 9 days of osteoinduction (decrease of 20.3-fold, paired t-test p=0.029; figure 3A, B).
    explanation: Patient-derived neural-crest mesenchymal cells show reduced alkaline-phosphatase activity during osteogenic induction.
    directness: INDIRECT
- discussion_id: arcnd_species_and_alleles
  kind: HUMAN_MODEL_MISMATCH
  attaches_to:
  - pathophysiology#Reduced EDNRA-Dependent Phospholipase C Activity
  - pathophysiology#Abnormal Mandibular Skeletal Morphogenesis
  prompt: How do variant mechanism and species affect the craniofacial phenotype?
  rationale: Human recessive PLCB4 loss-of-function disease coexists with reports of normal skull morphology in Plcb4-null mice. The Arg621His founder experiment tested homozygous and knock-in/indel genotypes, not a simple heterozygote. Fish plcb3 mutants and broad endothelin-pathway knockouts establish developmental requirements without making every model equivalent to a human ACS allele.
  evidence:
  - reference: PMID:35284927
    reference_title: Auriculocondylar syndrome 2 results from the dominant-negative action of PLCB4 variants.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    quote_role: PRIMARY_RESULT
    snippet: Of the 69 embryos harvested at E18.5, we identified three embryos harboring at least one knock-in allele; one was homozygous for the knock-in allele (Plcb4KI/KI) and the other two were compound heterozygotes harboring the knock-in allele and an insertion/deletion (indel) allele generated by non-homologous end joining (NHEJ) (Plcb4Indel/KI).
    explanation: The actual founders comprise one homozygote and two knock-in/indel embryos, not simple heterozygotes.
  - reference: PMID:27072656
    reference_title: Dominant-negative Gα subunits are a mechanism of dysregulated heterotrimeric G protein signaling in human disease.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    quote_role: REVIEW_SYNTHESIS
    snippet: knockout mice lacking PLCβ4 do not display a craniofacial phenotype
    explanation: The mechanistic study reviews an established species/model discrepancy.
- discussion_id: arcnd_extra_craniofacial_scope
  kind: KNOWLEDGE_GAP
  attaches_to:
  - phenotypes#Central apnea
  - phenotypes#Cerebral arteriovenous malformation
  prompt: Which extra-craniofacial findings are causally attributable to individual ACS genotypes?
  rationale: Central apnea may persist after correction of mechanical obstruction. Small series report vascular, rib, developmental and genital findings, but do not establish precise population risks or the cellular intermediates. These observations are retained without forcing every finding through mandibular homeosis.
  evidence:
  - reference: url:https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf
    reference_title: https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: Central sleep apnea has previously been reported in patients with ACS.
    explanation: The clinical synthesis distinguishes central apnea from the structural obstructive component.
  - reference: url:https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf
    reference_title: https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: Cerebrovascular malformations were detected by brain MRI in two individuals with no neurological symptoms.
    explanation: The source documents two observations without establishing a causal vascular pathway.
references:
- reference: PMID:22560091
  title: A human homeotic transformation resulting from mutations in PLCB4 and GNAI3 causes auriculocondylar syndrome.
  findings:
  - statement: Entire recovered primary body, table and figures reviewed. Gene discovery and selected-case anatomy are distinct from four postnatal mandibular cultures versus 17 calvarial controls. The old GNAI3 gain-of-function structural prediction is superseded by direct 2016 functional experiments.
- reference: PMID:23315542
  title: Heterogeneity of mutational mechanisms and modes of inheritance in auriculocondylar syndrome.
  findings:
  - statement: Actual accessible content is the abstract and repository metadata, despite a full-HTML cache label. Recessive PLCB4 deletion and central-apnea observations are supported at abstract scope; a complete primary body could not be recovered.
- reference: PMID:24123988
  title: 'Understanding the basis of auriculocondylar syndrome: Insights from human, mouse and zebrafish genetic studies.'
  findings:
  - statement: Entire generated developmental review and clinical table reviewed. Mouse and fish identity-patterning findings are distinguished from human allelic mechanisms and postnatal osteoblast measurements.
- reference: PMID:24268655
  title: Mutations in endothelin 1 cause recessive auriculocondylar syndrome and dominant isolated question-mark ears.
  findings:
  - statement: Entire recovered primary body, table and figures reviewed. Human segregation is direct; variant-specific EDN1 processing and residual-ligand explanations are inferred from motifs and related substitutions, not directly assayed.
- reference: PMID:28328130
  title: Targeted molecular investigation in patients within the clinical spectrum of Auriculocondylar syndrome.
  findings:
  - statement: Complete abstract reviewed. Two of three typical index cases in an 11-person mixed-phenotype series had PLCB4 variants; this is not general diagnostic sensitivity. Primary full text was not accessible.
- reference: PMID:34750192
  title: 'New locus underlying auriculocondylar syndrome (ARCND): 430 kb duplication involving TWIST1 regulatory elements.'
  findings:
  - statement: Entire primary main body, Methods, Results, Discussion and figure captions reviewed, with an independent bounded peer audit. Capture-C tissue, three-donor cultures, transcript versus catalytic activity, absent rescue and unresolved mediation are retained.
- reference: PMID:34789173
  title: 'Prenatal diagnosis of auriculocondylar syndrome with a novel missense variant of GNAI3: a case report.'
  findings:
  - statement: Entire primary prenatal report and literature table reviewed. A single fetus with severe jaw hypoplasia and no characteristic ear appearance does not establish prenatal specificity or general penetrance.
- reference: PMID:38618928
  title: 'Auriculocondylar syndrome 2 caused by a novel PLCB4 variant in a male Chinese neonate: A case report and review of the literature.'
  findings:
  - statement: Entire report and regenerated Tables1–3 reviewed. Ser643Phe is likely pathogenic in the body, with structural prediction rather than an activity assay. The 33-case compilation is selected; inconsistent secondary HGVS entries are not copied.
- reference: PMID:39014351
  title: 'Novel GNAI3 mutation in a Chinese family with auriculocondylar syndrome and treatment of severe dentofacial deformities: a 5-year follow-up case report.'
  findings:
  - statement: Entire adult case report, clinical/variant table and figures reviewed. Multiple combined procedures had favorable follow-up, without a comparator or component-specific efficacy estimate.
- reference: PMID:27072656
  title: Dominant-negative Gα subunits are a mechanism of dysregulated heterotrimeric G protein signaling in human disease.
  findings:
  - statement: Entire available functional main body and Methods reviewed. Purified S47R GDP/GTP assays, cell-expressed variant activation, receptor association, horizontal Gq inhibition and Xenopus gastrulation are kept distinct. Main figure legends are absent from this cache.
- reference: PMID:35284927
  title: Auriculocondylar syndrome 2 results from the dominant-negative action of PLCB4 variants.
  findings:
  - statement: Entire functional primary body, Methods and figure captions reviewed. DAG/BRET and SRE reporter readouts, synthetic interface perturbation and mixed-genotype F0 skeletal observations are separately scoped.
- reference: url:https://pmc.ncbi.nlm.nih.gov/articles/PMC4666574/
  title: Novel variants in GNAI3 associated with auriculocondylar syndrome strengthen a common dominant negative effect - PMC
  findings:
  - statement: Novel variants in GNAI3 associated with auriculocondylar syndrome strengthen a common dominant negative effect. Genuine full PMC body of PMID25026904 reviewed; the canonical PMID cache contains only a Nature abstract/reference page. Segregation and hearing observations are used without promoting structural modeling to functional assays.
- reference: url:https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf
  title: https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf
  findings:
  - statement: Further delineation of auriculocondylar syndrome based on 14 novel cases and reassessment of 25 published cases. Version-of-record full PDF of PMID35170830, Methods, Results, Tables1–2, Discussion and captions reviewed. It supersedes numerical differences in an accepted manuscript. The 39-person selected ACS/IQME cohort has outcome-specific denominators and tentative care recommendations; linked supplementary patient details were not independently read.
- reference: url:https://lab.research.sickkids.ca/wp-content/uploads/sites/22/2015/09/Propst_et_al_Ossicular-Fusion-and-cholesteatoma-in-Auriculo-Condylar-Syndrome_2013.pdf
  title: https://lab.research.sickkids.ca/wp-content/uploads/sites/22/2015/09/Propst_et_al_Ossicular-Fusion-and-cholesteatoma-in-Auriculo-Condylar-Syndrome_2013.pdf
  findings:
  - statement: 'Ossicular fusion and cholesteatoma in auriculo-condylar syndrome: in vivo evidence of arrest of embryogenesis. Complete institutional full PDF of PMID22865651 reviewed, including operative, histological and figure details. One adolescent had congenital-appearing ossicular fusion plus cholesteatoma; no quantified postoperative hearing benefit was reported.'
review_notes: Comprehensive review of every original cited source at its actual available depth, matching deep-research report and recovered primary full texts. No dedicated GeneReviews chapter was located. Full bodies, tables and methods were used where available; abstract-only and missing-supplement limits are recorded in the bibliography. The entry distinguishes gene lesions, measured signaling and transcriptional readouts, developmental model inference, selected clinical cohorts and case-based care. Unsupported phenotype frequency bands and untested serial mechanisms were removed; the published population rarity estimate is retained as explicitly background evidence, without treating a reported-case count as prevalence. The existing dbGaP record was independently verified.
updated_date: '2026-09-21T13:30:33Z'
prevalence:
- population: Reported global estimate; sampling frame unspecified
  measure_type: POINT_PREVALENCE
  prevalence_class: BELOW_1_IN_1000000
  notes: The 2024 case report repeats this rarity estimate from prior literature, rather than measuring a population rate. The separate statement that fewer than100 cases had been reported is a literature count, not its denominator; geographic and time-specific ascertainment are not provided.
  evidence:
  - reference: PMID:39014351
    reference_title: 'Novel GNAI3 mutation in a Chinese family with auriculocondylar syndrome and treatment of severe dentofacial deformities: a 5-year follow-up case report.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: BACKGROUND
    snippet: an extremely rare autosomal dominant or recessive condition with a prevalence of less than 1 in 1,000,000
    explanation: The source reports a broad prevalence band as background, not a new epidemiologic measurement.

📚

References & Deep Research

References

14

PMID:22560091

A human homeotic transformation resulting from mutations in PLCB4 and GNAI3 causes auriculocondylar syndrome.

1 finding

Entire recovered primary body, table and figures reviewed. Gene discovery and selected-case anatomy are distinct from four postnatal mandibular cultures versus 17 calvarial controls. The old GNAI3 gain-of-function structural prediction is superseded by direct 2016 functional experiments.

PMID:23315542

Heterogeneity of mutational mechanisms and modes of inheritance in auriculocondylar syndrome.

1 finding

Actual accessible content is the abstract and repository metadata, despite a full-HTML cache label. Recessive PLCB4 deletion and central-apnea observations are supported at abstract scope; a complete primary body could not be recovered.

PMID:24123988

Understanding the basis of auriculocondylar syndrome: Insights from human, mouse and zebrafish genetic studies.

1 finding

Entire generated developmental review and clinical table reviewed. Mouse and fish identity-patterning findings are distinguished from human allelic mechanisms and postnatal osteoblast measurements.

PMID:24268655

Mutations in endothelin 1 cause recessive auriculocondylar syndrome and dominant isolated question-mark ears.

1 finding

Entire recovered primary body, table and figures reviewed. Human segregation is direct; variant-specific EDN1 processing and residual-ligand explanations are inferred from motifs and related substitutions, not directly assayed.

PMID:28328130

Targeted molecular investigation in patients within the clinical spectrum of Auriculocondylar syndrome.

1 finding

Complete abstract reviewed. Two of three typical index cases in an 11-person mixed-phenotype series had PLCB4 variants; this is not general diagnostic sensitivity. Primary full text was not accessible.

PMID:34750192

New locus underlying auriculocondylar syndrome (ARCND): 430 kb duplication involving TWIST1 regulatory elements.

1 finding

Entire primary main body, Methods, Results, Discussion and figure captions reviewed, with an independent bounded peer audit. Capture-C tissue, three-donor cultures, transcript versus catalytic activity, absent rescue and unresolved mediation are retained.

PMID:34789173

Prenatal diagnosis of auriculocondylar syndrome with a novel missense variant of GNAI3: a case report.

1 finding

Entire primary prenatal report and literature table reviewed. A single fetus with severe jaw hypoplasia and no characteristic ear appearance does not establish prenatal specificity or general penetrance.

PMID:38618928

Auriculocondylar syndrome 2 caused by a novel PLCB4 variant in a male Chinese neonate: A case report and review of the literature.

1 finding

Entire report and regenerated Tables1–3 reviewed. Ser643Phe is likely pathogenic in the body, with structural prediction rather than an activity assay. The 33-case compilation is selected; inconsistent secondary HGVS entries are not copied.

PMID:39014351

Novel GNAI3 mutation in a Chinese family with auriculocondylar syndrome and treatment of severe dentofacial deformities: a 5-year follow-up case report.

1 finding

Entire adult case report, clinical/variant table and figures reviewed. Multiple combined procedures had favorable follow-up, without a comparator or component-specific efficacy estimate.

PMID:27072656

Dominant-negative Gα subunits are a mechanism of dysregulated heterotrimeric G protein signaling in human disease.

1 finding

Entire available functional main body and Methods reviewed. Purified S47R GDP/GTP assays, cell-expressed variant activation, receptor association, horizontal Gq inhibition and Xenopus gastrulation are kept distinct. Main figure legends are absent from this cache.

PMID:35284927

Auriculocondylar syndrome 2 results from the dominant-negative action of PLCB4 variants.

1 finding

Entire functional primary body, Methods and figure captions reviewed. DAG/BRET and SRE reporter readouts, synthetic interface perturbation and mixed-genotype F0 skeletal observations are separately scoped.

url:https://pmc.ncbi.nlm.nih.gov/articles/PMC4666574/

Novel variants in GNAI3 associated with auriculocondylar syndrome strengthen a common dominant negative effect - PMC

1 finding

Novel variants in GNAI3 associated with auriculocondylar syndrome strengthen a common dominant negative effect. Genuine full PMC body of PMID25026904 reviewed; the canonical PMID cache contains only a Nature abstract/reference page. Segregation and hearing observations are used without promoting structural modeling to functional assays.

url:https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf

https://pure.rug.nl/ws/files/217832848/Human_Mutation_2022_Vegas_Further_delineation_of_auriculocondylar_syndrome_based_on_14_novel_cases_and_reassessment.pdf

1 finding

Further delineation of auriculocondylar syndrome based on 14 novel cases and reassessment of 25 published cases. Version-of-record full PDF of PMID35170830, Methods, Results, Tables1–2, Discussion and captions reviewed. It supersedes numerical differences in an accepted manuscript. The 39-person selected ACS/IQME cohort has outcome-specific denominators and tentative care recommendations; linked supplementary patient details were not independently read.

url:https://lab.research.sickkids.ca/wp-content/uploads/sites/22/2015/09/Propst_et_al_Ossicular-Fusion-and-cholesteatoma-in-Auriculo-Condylar-Syndrome_2013.pdf

https://lab.research.sickkids.ca/wp-content/uploads/sites/22/2015/09/Propst_et_al_Ossicular-Fusion-and-cholesteatoma-in-Auriculo-Condylar-Syndrome_2013.pdf

1 finding

Ossicular fusion and cholesteatoma in auriculo-condylar syndrome: in vivo evidence of arrest of embryogenesis. Complete institutional full PDF of PMID22865651 reviewed, including operative, histological and figure details. One adolescent had congenital-appearing ossicular fusion plus cholesteatoma; no quantified postoperative hearing benefit was reported.

Deep Research

1

Deep research results are used as seeds for research; they do not undergo the same validation as the main records and may contain errors. How we use deep research.

Evaluations and curation notes (1)

Record review notes

Comprehensive review of every original cited source at its actual available depth, matching deep-research report and recovered primary full texts. No dedicated GeneReviews chapter was located. Full bodies, tables and methods were used where available; abstract-only and missing-supplement limits are recorded in the bibliography. The entry distinguishes gene lesions, measured signaling and transcriptional readouts, developmental model inference, selected clinical cohorts and case-based care. Unsupported phenotype frequency bands and untested serial mechanisms were removed; the published population rarity estimate is retained as explicitly background evidence, without treating a reported-case count as prevalence. The existing dbGaP record was independently verified.

Falcon ▸

Disease Characteristics Research Template

Edison Scientific Literature 44 citations 2026-05-10T11:28:33.205786

Question: You are an expert researcher providing comprehensive, well-cited information.

Provide detailed information focusing on: 1. Key concepts and definitions with current understanding 2. Recent developments and latest research (prioritize 2023-2024 sources) 3. Current applications and real-world implementations 4. Expert opinions and analysis from authoritative sources 5. Relevant statistics and data from recent studies

Format as a comprehensive research report with proper citations. Include URLs and publication dates where available. Always prioritize recent, authoritative sources and provide specific citations for all major claims.

Disease Characteristics Research Template

Target Disease

Disease Name: Auriculocondylar Syndrome
MONDO ID: (if available)
Category: Mendelian

Research Objectives

Please provide a comprehensive research report on Auriculocondylar Syndrome covering all of the disease characteristics listed below. This report will be used to populate a disease knowledge base entry. Be thorough and cite primary literature (PMID preferred) for all claims.

For each section, suggested databases/resources are listed. These are the first places you should search for information on each topic.

1. Disease Information

Search first: OMIM, Orphanet, ICD-10/ICD-11, MeSH, PubMed

What is the disease? Provide a concise overview.
What are the key identifiers? (OMIM, Orphanet, ICD-10/ICD-11, MeSH, Mondo)
What are the common synonyms and alternative names?
Is the information derived from individual patients (e.g., EHR) or aggregated disease-level resources?

2. Etiology

Disease Causal Factors: What are the primary causes? (genetic, environmental, infectious, mechanistic)
Risk Factors:

Search first: PubMed, Cochrane Library, UpToDate, clinical guidelines, ClinVar, ClinGen, GWAS Catalog, PheGenI, CTD, CDC, WHO, epidemiological databases
Genetic risk factors (causal variants, susceptibility loci, modifier genes)
Environmental risk factors (toxins, lifestyle, occupational exposures, age, sex, family history)
Protective Factors:

Search first: PubMed, Cochrane Library, clinical trial databases, GWAS Catalog, gnomAD, WHO, CDC, nutrition databases
Genetic protective factors (protective variants, modifier alleles)
Environmental protective factors (diet, lifestyle, exposures that reduce risk)
Gene-Environment Interactions: How do genetic and environmental factors interact to influence disease?

Search first: CTD, PubMed, PheGenI, GxE databases

3. Phenotypes

Search first: HPO (Human Phenotype Ontology), OMIM, Orphanet, PubMed, clinicaltrials.gov, MedDRA, SNOMED CT, DECIPHER, LOINC

For each phenotype, provide: - Phenotype type: symptoms, clinical signs, physical manifestations, behavioral changes, or laboratory abnormalities

For symptoms/signs: HPO, OMIM, Orphanet, PubMed For behavioral changes: HPO, DSM, RDoC (Research Domain Criteria), PubMed For laboratory abnormalities: LOINC, SNOMED CT, LabTests Online, PubMed - Phenotype characteristics: Search first: OMIM, Orphanet, HPO, PubMed - Age of symptom onset (neonatal, childhood, adult-onset, late-onset) - Symptom severity (mild, moderate, severe, variable) - Symptom progression (stable, progressive, episodic, fluctuating) - Frequency among affected individuals (percentage or qualitative) - Quality of life impact: Effects on daily functioning and well-being (per-phenotype when possible) Search first: EQ-5D database, SF-36, WHO QOL databases, PubMed - Suggest HPO (Human Phenotype Ontology) terms for each phenotype

4. Genetic/Molecular Information

Causal Genes: Gene mutations or chromosomal abnormalities responsible for disease (gene symbols, OMIM IDs)

Search first: OMIM, ClinVar, HGMD, Ensembl, NCBI Gene
Pathogenic Variants:
Affected genes (gene symbols, HGNC IDs) > Search first: OMIM, NCBI Gene, Ensembl, HGNC, UniProt, GeneCards
Variant classification (pathogenic, likely pathogenic, VUS per ACMG/AMP guidelines) > Search first: ClinVar, ClinGen, ACMG/AMP guidelines, VarSome
Variant type/class (missense, frameshift, nonsense, splice-site, structural)
Allele frequency in population databases > Search first: gnomAD, 1000 Genomes, ExAC, TOPMed, dbSNP
Somatic vs germline origin > Search first: COSMIC (somatic), ClinVar, ICGC, TCGA
Functional consequences (loss of function, gain of function, dominant negative)
Modifier Genes: Genes that modify disease severity or expression
Epigenetic Information: DNA methylation, histone modifications, chromatin changes affecting disease

Search first: ENCODE, Roadmap Epigenomics, MethBase, DiseaseMeth
Chromosomal Abnormalities: Large-scale genetic changes (aneuploidy, translocations, inversions)

Search first: DECIPHER, ClinVar, ECARUCA, UCSC Genome Browser

5. Environmental Information

Environmental Factors: Non-genetic contributing factors (toxins, radiation, pollution, occupational exposure)

Search first: CTD (Comparative Toxicogenomics Database), TOXNET, PubMed, EPA databases
Lifestyle Factors: Behavioral factors (smoking, diet, exercise, alcohol consumption)

Search first: CDC databases, WHO, PubMed, NHANES
Infectious Agents: If applicable, pathogens causing or triggering disease (bacteria, viruses, fungi, parasites)

Search first: NCBI Taxonomy, ViPR, BV-BRC, MicrobeDB, GIDEON

6. Mechanism / Pathophysiology

Molecular Pathways: Specific signaling cascades or biochemical pathways involved (Wnt, MAPK, mTOR, PI3K-AKT, etc.)

Search first: KEGG, Reactome, WikiPathways, PathBank, BioCyc
Cellular Processes: Cell-level mechanisms (apoptosis, autophagy, cell cycle dysregulation, inflammation, etc.)

Search first: Gene Ontology (GO), Reactome, KEGG, PubMed
Protein Dysfunction: How protein structure or function is altered (misfolding, aggregation, loss of function, gain of function)

Search first: UniProt, PDB (Protein Data Bank), InterPro, Pfam, AlphaFold
Metabolic Changes: Alterations in metabolic processes (energy metabolism, lipid metabolism, amino acid metabolism)

Search first: KEGG, BioCyc, HMDB (Human Metabolome Database), BRENDA
Immune System Involvement: Role of immune response (autoimmunity, immunodeficiency, chronic inflammation)

Search first: ImmPort, Immunome Database, IEDB, Gene Ontology
Tissue Damage Mechanisms: How tissues/ are injured (oxidative stress, ischemia, fibrosis, necrosis)

Search first: PubMed, Gene Ontology, Reactome
Biochemical Abnormalities: Specific molecular defects (enzyme deficiencies, receptor dysfunction, ion channel defects)

Search first: BRENDA, UniProt, KEGG, OMIM, PubMed
Epigenetic Changes: DNA methylation, histone modifications affecting gene expression in disease

Search first: ENCODE, Roadmap Epigenomics, MethBase, DiseaseMeth
Molecular Profiling (if available):
Transcriptomics/gene expression changes > Search first: GEO (Gene Expression Omnibus), ArrayExpress, GTEx, Human Cell Atlas, SRA
Proteomics findings > Search first: PRIDE, ProteomeXchange, Human Protein Atlas, STRING, BioGRID
Metabolomics signatures > Search first: MetaboLights, Metabolomics Workbench, HMDB, METLIN
Lipidomics alterations > Search first: LIPID MAPS, SwissLipids, LipidHome, Metabolomics Workbench
Genomic structural features > Search first: UCSC Genome Browser, Ensembl, NCBI, dbVar, DGV
Advanced Technologies (if applicable):
Single-cell analysis findings (cell-type specific mechanisms, cellular heterogeneity) > Search first: Human Cell Atlas, Single Cell Portal, GEO, CELLxGENE
Spatial transcriptomics findings > Search first: GEO, Spatial Research, Vizgen, 10x Genomics data
Multi-omics integration results > Search first: TCGA, ICGC, cBioPortal, LinkedOmics, PubMed
Functional genomics screens (CRISPR, RNAi) > Search first: DepMap, GenomeRNAi, PubMed, BioGRID ORCS

For each mechanism, describe: - The causal chain from initial trigger to clinical manifestation - Which mechanisms are upstream vs downstream - What cell types and biological processes are involved - Suggest GO terms for biological processes and CL terms for cell types

7. Anatomical Structures Affected

Organ Level:
Primary organs directly affected
Secondary organ involvement (complications, secondary effects)
Body systems involved (cardiovascular, nervous, digestive, respiratory, endocrine, etc.)

Search first: Uberon, FMA (Foundational Model of Anatomy), OMIM, HPO, ICD-11, MeSH, SNOMED CT
Tissue and Cell Level:
Specific tissue types affected (epithelial, connective, muscle, nervous)
Specific cell populations targeted (with Cell Ontology terms)

Search first: Uberon, Human Protein Atlas, Cell Ontology, Human Cell Atlas, CellMarker, PanglaoDB
Subcellular Level:
Cellular compartments involved (mitochondria, nucleus, ER, lysosomes) (with GO Cellular Component terms)

Search first: Gene Ontology (Cellular Component), UniProt, Human Protein Atlas
Localization:
Specific anatomical sites (with UBERON terms) > Search first: FMA, Uberon, NeuroNames (for brain), SNOMED CT
Lateralization (unilateral, bilateral, asymmetric) > Search first: HPO, clinical literature, imaging databases

8. Temporal Development

Onset:
Typical age of onset (congenital, pediatric, adult, geriatric)
Onset pattern (acute, subacute, chronic, insidious)

Search first: OMIM, Orphanet, HPO, PubMed
Progression:
Disease stages (early, intermediate, advanced, end-stage) > Search first: Cancer Staging Manual (AJCC), WHO classifications, PubMed
Progression rate (rapid, slow, variable)
Disease course pattern (episodic, relapsing-remitting, progressive, stable)
Disease duration (self-limited, chronic lifelong)

Search first: Disease registries, longitudinal cohort databases, natural history studies, PubMed, Orphanet, OMIM
Patterns:
Remission patterns (spontaneous, treatment-induced) > Search first: Clinical trial databases, disease registries, PubMed
Critical periods (time windows of vulnerability or opportunity for intervention) > Search first: PubMed, developmental biology databases, clinical guidelines

9. Inheritance and Population

Epidemiology:
Prevalence (cases per 100,000 at given time)
Incidence (new cases per 100,000 per year)

Search first: Orphanet, CDC, WHO, GBD (Global Burden of Disease), national registries, SEER, disease registries
For Genetic Etiology:
Inheritance pattern (AD, AR, X-linked, mitochondrial, multifactorial, polygenic) > Search first: OMIM, Orphanet, ClinVar, GTR (Genetic Testing Registry)
Penetrance (complete, incomplete, age-dependent) > Search first: ClinVar, OMIM, PubMed, ClinGen
Expressivity (variable, consistent) > Search first: OMIM, ClinVar, PubMed
Genetic anticipation (increasing severity in successive generations) > Search first: OMIM, PubMed (especially for repeat expansion disorders)
Germline mosaicism > Search first: ClinVar, OMIM, genetic counseling literature, PubMed
Founder effects (population-specific mutations) > Search first: gnomAD, population genetics databases, PubMed
Consanguinity role > Search first: OMIM, population studies, genetic counseling resources
Carrier frequency > Search first: gnomAD, carrier screening databases, GeneReviews, GTR
Population Demographics:
Affected populations (ethnic or demographic groups with higher prevalence) > Search first: gnomAD, 1000 Genomes, PAGE Study, PubMed, population registries
Geographic distribution (endemic areas, regional variation) > Search first: WHO, CDC, GBD, Orphanet, geographic epidemiology databases
Geographic distribution of specific variants
Sex ratio (male:female) > Search first: Disease registries, OMIM, PubMed, epidemiological databases
Age distribution of affected individuals > Search first: CDC, disease registries, SEER, Orphanet

10. Diagnostics

Clinical Tests:
Laboratory tests (blood, urine, tissue chemistry, specific enzyme assays) > Search first: LOINC, LabTests Online, PubMed
Biomarkers (proteins, metabolites, genetic markers, circulating biomarkers) > Search first: FDA Biomarker List, BEST (Biomarkers, EndpointS, and other Tools), PubMed
Imaging studies (X-ray, CT, MRI, PET, ultrasound) > Search first: RadLex, DICOM, Radiopaedia, imaging databases
Functional tests (pulmonary function, cardiac stress tests) > Search first: LOINC, clinical guidelines, PubMed
Electrophysiology (EEG, EMG, ECG, nerve conduction studies) > Search first: LOINC, clinical neurophysiology databases, PubMed
Biopsy findings (histopathology, immunohistochemistry) > Search first: SNOMED CT, College of American Pathologists resources, PubMed
Pathology findings (microscopic examination) > Search first: SNOMED CT, Digital Pathology databases, PubMed
Genetic Testing:

Search first: GTR (Genetic Testing Registry), GeneReviews, ClinGen
Overview of recommended genetic testing approach
Whole genome sequencing (WGS) utility > Search first: GTR, ClinVar, GEL (Genomics England), gnomAD
Whole exome sequencing (WES) utility > Search first: GTR, ClinVar, OMIM, GeneMatcher
Gene panels (which panels, which genes) > Search first: GTR, ClinVar, laboratory-specific databases
Single gene testing > Search first: GTR, ClinVar, OMIM, GeneReviews
Chromosomal microarray (CMA) > Search first: DECIPHER, ClinVar, dbVar, ECARUCA
Karyotyping > Search first: Chromosome Abnormality Database, ClinVar, cytogenetics resources
FISH > Search first: ClinVar, cytogenetics databases, PubMed
Mitochondrial DNA testing > Search first: MITOMAP, MSeqDR, ClinVar, GTR
Repeat expansion testing > Search first: GTR, ClinVar, repeat expansion databases, PubMed
Omics-Based Diagnostics (if applicable):
RNA sequencing / transcriptomics > Search first: GEO, ArrayExpress, GTEx, RNA-seq databases
Proteomics > Search first: PRIDE, ProteomeXchange, FDA Biomarker database
Metabolomics > Search first: MetaboLights, Metabolomics Workbench, HMDB
Epigenomics > Search first: GEO, ENCODE, Roadmap Epigenomics, MethBase
Liquid biopsy > Search first: COSMIC, ClinVar, liquid biopsy databases, PubMed
Clinical Criteria:
Standardized diagnostic criteria (DSM, ICD, society guidelines) > Search first: DSM-5, ICD-11, clinical society guidelines, UpToDate
Differential diagnosis (other conditions to rule out, with distinguishing features) > Search first: DynaMed, UpToDate, clinical decision support systems
Screening:
Screening methods for asymptomatic individuals (newborn screening, carrier screening, cascade screening) > Search first: ACMG recommendations, CDC newborn screening, GTR

11. Outcome/Prognosis

Survival and Mortality:
Survival rate (5-year, 10-year, overall) > Search first: SEER, cancer registries, disease-specific registries, PubMed
Life expectancy (with and without treatment if applicable) > Search first: Orphanet, disease registries, actuarial databases, PubMed
Mortality rate > Search first: CDC, WHO, GBD, national mortality databases
Disease-specific mortality (deaths directly attributable to disease) > Search first: Disease registries, CDC Wonder, GBD, PubMed
Morbidity and Function:
Morbidity (disease-related disability and health impacts) > Search first: GBD, WHO, disability databases, PubMed
Disability outcomes (long-term functional impairments) > Search first: ICF (International Classification of Functioning), disability registries
Quality of life measures (EQ-5D, SF-36, PROMIS, disease-specific tools) > Search first: EQ-5D database, SF-36, PROMIS, PubMed
Disease Course:
Complications (secondary problems: infections, organ failure, etc.) > Search first: ICD codes, disease registries, clinical databases, PubMed
Recovery potential (likelihood and extent of recovery, with vs without treatment) > Search first: Natural history studies, rehabilitation databases, PubMed
Prediction:
Prognostic factors (age, disease severity, biomarkers, treatment response) > Search first: Prognostic models databases, clinical calculators, PubMed
Prognostic biomarkers (molecular markers predicting disease course) > Search first: FDA Biomarker database, PubMed, cancer prognostic databases

12. Treatment

Pharmacotherapy:
Pharmacological treatments (drug names, drug classes, mechanisms of action) > Search first: DrugBank, RxNorm, ATC classification, DailyMed, FDA databases
Pharmacogenomics (how genetic variants affect drug metabolism, efficacy, toxicity) > Search first: PharmGKB, CPIC (Clinical Pharmacogenetics), FDA Table of PGx Biomarkers
Advanced Therapeutics:
Gene therapy (viral vectors, CRISPR, gene replacement, gene editing) > Search first: ClinicalTrials.gov, FDA gene therapy database, ASGCT resources
Cell therapy (stem cell transplant, CAR-T, cellular therapeutics) > Search first: ClinicalTrials.gov, FDA cell therapy database, FACT standards
RNA-based therapies (ASOs, siRNA, mRNA therapies) > Search first: ClinicalTrials.gov, FDA approvals, PubMed
Targeted therapies (treatments directed at specific molecular targets) > Search first: My Cancer Genome, OncoKB, ClinicalTrials.gov, FDA approvals
Immunotherapies (checkpoint inhibitors, monoclonal antibodies) > Search first: Cancer Immunotherapy Database, FDA approvals, ClinicalTrials.gov
Surgical and Interventional:
Surgical interventions (types of surgery, timing, outcomes) > Search first: CPT codes, surgical registries, clinical guidelines, PubMed
Supportive and Rehabilitative:
Supportive care (symptom management, pain control, nutrition) > Search first: Clinical guidelines, Cochrane Library, PubMed
Rehabilitation (physical therapy, occupational therapy, speech therapy) > Search first: Rehabilitation medicine databases, clinical guidelines, PubMed
Experimental:
Experimental treatments in clinical trials (with NCT identifiers if available) > Search first: ClinicalTrials.gov, EU Clinical Trials Register, WHO ICTRP
Treatment Outcomes:
Treatment response rates > Search first: Clinical trial databases, FDA reviews, systematic reviews, PubMed
Side effects and adverse events > Search first: FDA Adverse Event Reporting System (FAERS), MedWatch, PubMed
Treatment Strategy:
Treatment algorithms (clinical pathways, decision trees) > Search first: Clinical practice guidelines, NCCN Guidelines, UpToDate
Combination therapies > Search first: ClinicalTrials.gov, treatment guidelines, PubMed
Personalized medicine approaches (genotype-guided treatment) > Search first: My Cancer Genome, CIViC, PharmGKB, precision medicine databases

For each treatment, suggest MAXO (Medical Action Ontology) terms where applicable.

13. Prevention

Prevention Levels:
Primary prevention (preventing disease occurrence: vaccination, risk factor modification) > Search first: CDC, WHO, USPSTF recommendations, Cochrane Library
Secondary prevention (early detection and treatment: screening programs, early intervention) > Search first: USPSTF, CDC screening guidelines, WHO
Tertiary prevention (preventing complications in those with disease) > Search first: Clinical guidelines, disease management protocols, PubMed
Immunization: Vaccine strategies (if applicable)

Search first: CDC vaccine schedules, WHO immunization, FDA vaccine database
Screening and Early Detection:
Screening programs (population-based: newborn screening, cancer screening) > Search first: CDC screening programs, USPSTF, cancer screening databases
Genetic screening (carrier screening, preimplantation genetic diagnosis, prenatal testing) > Search first: ACMG recommendations, ACOG guidelines, GTR
Risk stratification (identifying high-risk individuals for targeted prevention) > Search first: Risk prediction models, clinical calculators, PubMed
Behavioral Interventions: Lifestyle modifications to reduce risk

Search first: CDC, WHO, behavioral intervention databases, Cochrane Library
Counseling: Genetic counseling (risk assessment, family planning guidance)

Search first: NSGC resources, ACMG guidelines, GeneReviews
Public Health:
Public health interventions (sanitation, vector control, health education) > Search first: CDC, WHO, public health databases, PubMed
Environmental interventions (reducing environmental risk factors) > Search first: EPA databases, WHO environmental health, PubMed
Prophylaxis: Preventive medications or procedures

Search first: Clinical guidelines, FDA approvals, PubMed

14. Other Species / Natural Disease

Taxonomy: Species affected (with NCBI Taxon identifiers)

Search first: NCBI Taxonomy
Breed: Specific breeds affected (with VBO identifiers if applicable)

Search first: VBO (Vertebrate Breed Ontology)
Gene: Orthologous genes in other species (with NCBI Gene IDs)

Search first: NCBI Gene
Natural Disease:
Naturally occurring disease in other species (companion animals, wildlife) > Search first: OMIA (Online Mendelian Inheritance in Animals), VetCompass, PubMed
Veterinary relevance and importance in animal health > Search first: OMIA, veterinary databases, PubMed
Comparative Biology:
Comparative pathology (similarities and differences across species) > Search first: OMIA, comparative pathology databases, PubMed
Evolutionary conservation of disease mechanisms > Search first: HomoloGene, OrthoMCL, Alliance of Genome Resources
Transmission (if applicable):
Zoonotic potential > Search first: CDC zoonotic diseases, WHO zoonoses, GIDEON
Cross-species susceptibility > Search first: NCBI Taxonomy, veterinary databases, PubMed

15. Model Organisms

Model Types:
Model organism type (mammalian, invertebrate, cellular, in vitro) > Search first: Alliance of Genome Resources, model organism databases
Specific model systems (mouse, rat, zebrafish, Drosophila, C. elegans, yeast, cell lines, organoids, iPSCs) > Search first: MGI, RGD, ZFIN, FlyBase, WormBase, SGD, ATCC, Cellosaurus
Induced models (drug treatment, surgical intervention, environmental manipulation) > Search first: MGI, model organism databases, PubMed
Genetic Models:
Types available (knockout, knock-in, transgenic, conditional, humanized) > Search first: MGI, IMPC, KOMP, EuMMCR, IMSR
Model Characteristics:
Phenotype recapitulation (how well model reproduces human disease features) > Search first: Model organism databases, comparative studies, PubMed
Model limitations (aspects of human disease not captured) > Search first: Model organism databases, PubMed, review articles
Applications:
Research applications (what aspects of disease can be studied) > Search first: Model organism databases, PubMed
Resources:
Model databases > Search first: MGI, RGD, ZFIN, FlyBase, WormBase, IMSR, EMMA, MMRRC

Citation Requirements

Cite primary literature (PMID preferred) for all mechanistic and clinical claims
Prioritize recent reviews and landmark papers
Include direct quotes from abstracts where possible to support key statements
Distinguish evidence source types: human clinical, model organism, in vitro, computational

Output Format

Structure your response as a comprehensive narrative organized by the sections above. For each section, provide: - Factual content with specific details (numbers, percentages, gene names, variant nomenclature) - Ontology term suggestions (HPO, GO, CL, UBERON, CHEBI, MAXO, MONDO) where applicable - Evidence citations with PMIDs - Direct quotes from abstracts to support key claims - Clear indication when information is not available or not applicable for this disease

This report will be used to populate a disease knowledge base entry with: - Pathophysiology descriptions with causal chains - Gene/protein annotations (HGNC, GO terms) - Phenotype associations (HP terms) with frequencies - Cell type involvement (CL terms) - Anatomical locations (UBERON terms) - Chemical entities (CHEBI terms) - Treatment annotations (MAXO terms) - Evidence items with PMIDs and exact abstract quotes - Epidemiology, prognosis, diagnostic, and prevention information - Animal model descriptions with phenotype recapitulation details

Auriculocondylar Syndrome (ARCND/ACS): Comprehensive Disease Characteristics Report

Executive summary

Auriculocondylar syndrome (ARCND; historically “auriculocondylar syndrome/ACS”) is an ultra-rare congenital craniofacial malformation of first and second pharyngeal arch derivatives, classically presenting with micrognathia, mandibular condyle hypoplasia, and a characteristic external ear anomaly termed the question-mark ear (QME). Current genetic understanding centers on disruption of EDN1–EDNRA signaling and downstream cranial neural crest patterning (DLX5/6), with additional genetic heterogeneity including a regulatory duplication affecting TWIST1 expression. Recent (2024) reports emphasize multidisciplinary, technology-assisted craniofacial care (3D planning, distraction osteogenesis, orthognathic surgery) with measurable functional improvement. (clouthier2013understandingthebasis pages 1-3, rieder2012ahumanhomeotic pages 1-2, shi2024novelgnai3mutation pages 2-6)

1. Disease information

1.1 Definition and current understanding

ARCND/ACS is a rare congenital craniofacial disorder affecting development of the outer ear and mandible, and is best recognized as a disorder of pharyngeal arch (branchial arch) development with a characteristic “homeotic” patterning disturbance of the jaw in severe cases. The core/typical triad is consistently described as micrognathia, mandibular condyle hypoplasia, and a QME defect at the helix–lobule junction. (clouthier2013understandingthebasis pages 1-3, gordon2013heterogeneityofmutational pages 1-2)

Primary literature definition examples: - Rieder et al. (2012) describe ACS as “a rare, autosomal-dominant craniofacial malformation syndrome” with micrognathia and a distinctive QME, and report additional features including TMJ ankylosis and cleft palate. (https://doi.org/10.1016/j.ajhg.2012.04.002; May 2012) (rieder2012ahumanhomeotic pages 1-2) - Clouthier et al. (2013) define the “core triad” as “micrognathia, mandibular condyle hypoplasia, and a unique ear malformation” (QME/Cosman ear). (https://doi.org/10.1002/ajmg.c.31376; Nov 2013) (clouthier2013understandingthebasis pages 1-3)

1.2 Key identifiers (available in retrieved evidence)

A subset of identifiers could be extracted directly from retrieved sources (others were not present in the evidence captured in this run).

Disease / concept	Synonyms / related names in evidence	Identifiers in evidence	Prevalence / epidemiology note in evidence	Source year	URL	Citation
Auriculocondylar syndrome	Auriculocondylar syndrome; ACS; ARCND	MONDO: MONDO_0000107	Open Targets lists MONDO_0000107 for “auriculocondylar syndrome”	n/a	n/a	(OpenTargets Search: Auriculocondylar syndrome)
Auriculocondylar syndrome	“question mark ear syndrome”; “dysgnathia complex”	OMIM #602483, #614669, #615706	Rare / prevalence not given in this excerpt	2013	https://doi.org/10.1002/ajmg.c.31376	(clouthier2013understandingthebasis pages 1-3)
Auriculocondylar syndrome (general ARCND)	ARCND; “question mark ear syndrome”	OMIM #602483, #614669, #615706	Orphanet prevalence stated as under 1 in 1,000,000	2022	https://doi.org/10.1136/jmedgenet-2021-107825	(tavares2022newlocusunderlying pages 1-2)
Auriculocondylar syndrome (general ARCND)	ARCND	OMIM #602483, #614669, #615706	Prevalence stated as less than 1 in 1,000,000; fewer than 100 cases reported	2024	https://doi.org/10.1186/s12903-024-04575-1	(shi2024novelgnai3mutation pages 1-2)
Auriculocondylar syndrome	ARCND; dysgnathia complex; question mark ear syndrome	ARCND1 OMIM #602483; ARCND2A OMIM #614669; ARCND2B OMIM #620458; ARCND3 OMIM #615706; ARCND4 OMIM #620457	Orphanet prevalence stated as under 1/1,000,000	2024	https://doi.org/10.1002/mgg3.2441	(zhang2024auriculocondylarsyndrome2 pages 1-2)
Auriculocondylar syndrome 1	ARCND1	OMIM #602483	Subtype listed in review-style case report evidence	2024	https://doi.org/10.1002/mgg3.2441	(zhang2024auriculocondylarsyndrome2 pages 1-2)
Auriculocondylar syndrome 2A	ARCND2A	OMIM #614669	Subtype listed in review-style case report evidence	2024	https://doi.org/10.1002/mgg3.2441	(zhang2024auriculocondylarsyndrome2 pages 1-2)
Auriculocondylar syndrome 2B	ARCND2B	OMIM #620458; MONDO_0957544	Subtype listed; Open Targets includes MONDO_0957544	2024 / n/a	https://doi.org/10.1002/mgg3.2441	(zhang2024auriculocondylarsyndrome2 pages 1-2, OpenTargets Search: Auriculocondylar syndrome)
Auriculocondylar syndrome 3	ARCND3	OMIM #615706	Subtype listed in review-style case report evidence	2024	https://doi.org/10.1002/mgg3.2441	(zhang2024auriculocondylarsyndrome2 pages 1-2)
Auriculocondylar syndrome 4	ARCND4	OMIM #620457; MONDO_0957543	Subtype listed; Open Targets includes MONDO_0957543 for auriculocondylar syndrome 4	2024 / n/a	https://doi.org/10.1002/mgg3.2441	(zhang2024auriculocondylarsyndrome2 pages 1-2, OpenTargets Search: Auriculocondylar syndrome)
Isolated question-mark ear	Isolated QME; isolated question-mark ears; IQME	OMIM #612798	May occur as isolated anomaly distinct from syndromic ACS	2013	https://doi.org/10.1002/ajmg.c.31376	(clouthier2013understandingthebasis pages 1-3)

Table: This table summarizes disease names, synonyms, and identifiers for auriculocondylar syndrome and related entities using only the evidence retrieved in the session. It highlights subtype OMIM numbers, available MONDO mappings, and prevalence statements useful for a knowledge-base entry.

MONDO: OpenTargets maps “auriculocondylar syndrome” to MONDO_0000107, and includes MONDO entries for ARCND subtypes (e.g., auriculocondylar syndrome 4). (OpenTargets Search: Auriculocondylar syndrome)

OMIM (disease): OMIM IDs commonly cited include 602483, 614669, 615706, and for ARCND subtype breakdown: ARCND1 #602483; ARCND2A #614669; ARCND2B #620458; ARCND3 #615706; ARCND4 #620457. (zhang2024auriculocondylarsyndrome2 pages 1-2, clouthier2013understandingthebasis pages 1-3, tavares2022newlocusunderlying pages 1-2)

OMIM (related phenotype): Isolated question-mark ear (IQME) OMIM 612798. (clouthier2013understandingthebasis pages 1-3)

Orphanet: Multiple sources cite Orphanet as the prevalence source and provide the Orphanet homepage URL (http://www.orpha.net). (tavares2022newlocusunderlying pages 1-2, zhang2024auriculocondylarsyndrome2 pages 1-2)

ICD-10/ICD-11 and MeSH: Specific ICD-10/ICD-11 codes and MeSH headings were not present in the retrieved text evidence and therefore cannot be asserted here.

1.3 Synonyms and alternative names

Common synonyms in the retrieved literature include: - “question mark ear syndrome” (clouthier2013understandingthebasis pages 1-3, tavares2022newlocusunderlying pages 1-2) - “dysgnathia complex” (zhang2024auriculocondylarsyndrome2 pages 1-2, clouthier2013understandingthebasis pages 1-3)

1.4 Evidence sources (individual vs aggregated)

Evidence in this report derives from: - Aggregated disease-level resources and synthesis: a Seminars review integrating human, mouse, and zebrafish genetics (Clouthier et al., 2013). (clouthier2013understandingthebasis pages 1-3) - Primary human genetics (families/case series): e.g., Rieder et al. 2012 (exome + functional assays), Gordon et al. 2013 (EDN1), Tavares et al. 2017 (molecular cohort statistics), Tavares et al. 2022 (CNV + iPSC modeling). (rieder2012ahumanhomeotic pages 1-2, gordon2013mutationsinendothelin pages 1-2, tavares2017targetedmolecularinvestigation pages 4-6, tavares2022newlocusunderlying pages 5-6) - Recent individual clinical implementations (case reports): 2024 ARCND management with orthodontics + distraction + orthognathic surgery and 5-year outcomes. (shi2024novelgnai3mutation pages 2-6)

2. Etiology

2.1 Disease causal factors (primary causes)

ARCND is primarily a genetic (Mendelian) craniofacial developmental disorder, caused by pathogenic variants that disrupt endothelin signaling in cranial neural crest and related patterning programs. (clouthier2013understandingthebasis pages 1-3, rieder2012ahumanhomeotic pages 1-2)

Major established causal genes/loci in retrieved evidence: - PLCB4 (ARCND2; most common cause in molecular cohorts) (tavares2017targetedmolecularinvestigation pages 4-6) - GNAI3 (ARCND1) (tavares2015novelvariantsin pages 1-2, shi2024novelgnai3mutation pages 2-6) - EDN1 (ARCND3; ligand-level defect) (gordon2013mutationsinendothelin pages 1-2) - 430 kb tandem duplication at HDAC9/TWIST1 regulatory landscape (ARCND4; regulatory mechanism) (tavares2022newlocusunderlying pages 5-6, tavares2022newlocusunderlying pages 4-4)

2.2 Risk factors

Genetic risk factors (causal variants)

Molecular cohort data: In a cohort of 28 molecularly investigated index patients, 16/28 (57.1%) carried PLCB4 variants, 6/28 (21.4%) carried GNAI3 variants, 4/28 (14.3%) carried EDN1 variants, and 2/28 (7.1%) were unsolved. (Tavares et al., 2017; https://doi.org/10.1002/ajmg.a.38101; Apr 2017) (tavares2017targetedmolecularinvestigation pages 4-6)

EDN1 can cause recessive ACS and dominant isolated QME depending on the mutation and residual EDN1 activity. (Gordon et al., 2013; https://doi.org/10.1016/j.ajhg.2013.10.023; Dec 2013) (gordon2013mutationsinendothelin pages 1-2)

Representative variants are summarized in the genetics table artifact below.

ARCND subtype (if known)	Gene/locus	Inheritance patterns reported	Variant examples (HGVS when available)	Proposed mechanism	Key functional evidence	Primary sources with year/URL
ARCND1	GNAI3	AD; incomplete penetrance reported in some families	c.118G>C, p.Gly40Arg; p.Ser47Arg; p.Gly45Val; p.Thr48Asn; p.Asn269Tyr; c.140G>A, p.Ser47Asn; c.144_145insCATTGTGAAACAGATGAA, p.T48_I49insHCETDE (rieder2012ahumanhomeotic pages 3-5, tavares2016identificaçãodenovas pages 67-68, liu2021prenataldiagnosisof pages 1-3, shi2024novelgnai3mutation pages 2-6)	Predominantly dominant-negative disruption of GTP/GDP-binding region in the G1/G4 motifs, impairing downstream endothelin signaling (gordon2013heterogeneityofmutational pages 11-12, tavares2015novelvariantsin pages 1-2)	Structural modeling placed pathogenic residues in the nucleotide-binding pocket; p.Gly40Arg predicted to stabilize aberrant active conformation and inhibit MAPK/Rap signaling; patient-derived osteoblast assays in ACS showed reduced DLX5/DLX6 expression consistent with EDN1-pathway disruption (rieder2012ahumanhomeotic pages 3-5, rieder2012ahumanhomeotic pages 1-2, tavares2015novelvariantsin pages 1-2)	Rieder et al., 2012, https://doi.org/10.1016/j.ajhg.2012.04.002; Tavares et al., 2015, https://doi.org/10.1038/ejhg.2014.132; Liu et al., 2021, https://doi.org/10.1186/s12884-021-04238-x; Shi et al., 2024, https://doi.org/10.1186/s12903-024-04575-1 (rieder2012ahumanhomeotic pages 3-5, tavares2015novelvariantsin pages 1-2, liu2021prenataldiagnosisof pages 1-3, shi2024novelgnai3mutation pages 2-6)
ARCND2A	PLCB4	AD	c.986A>C, p.Asn329Ser; p.Arg621His; p.Arg621Cys; p.Tyr623Cys; p.Asn650His; c.1072G>C, p.Glu358Gln; c.983A>G, p.His328Arg; c.1928C>T, p.Ser643Phe; p.Asp360Asn; p.Arg621Leu (rieder2012ahumanhomeotic pages 3-5, tavares2017targetedmolecularinvestigation pages 4-6, tavares2016identificaçãodenovas pages 67-68, zhang2024auriculocondylarsyndrome2 pages 2-5)	Mostly dominant-negative catalytic-domain dysfunction rather than simple haploinsufficiency (gordon2013heterogeneityofmutational pages 11-12)	Variants cluster in X/Y catalytic domains; structural modeling predicted impaired PLC catalytic activity and disturbed IP3 generation without gross protein destabilization; ACS osteoblasts showed reduced DLX5/DLX6 expression; PLCB4 accounts for ~57.1% of molecularly solved index cases in one cohort (16/28) (rieder2012ahumanhomeotic pages 3-5, rieder2012ahumanhomeotic pages 1-2, tavares2017targetedmolecularinvestigation pages 4-6)	Rieder et al., 2012, https://doi.org/10.1016/j.ajhg.2012.04.002; Gordon et al., 2013, https://doi.org/10.1136/jmedgenet-2012-101331; Tavares et al., 2017, https://doi.org/10.1002/ajmg.a.38101; Zhang et al., 2024, https://doi.org/10.1002/mgg3.2441 (rieder2012ahumanhomeotic pages 3-5, gordon2013heterogeneityofmutational pages 11-12, tavares2017targetedmolecularinvestigation pages 4-6, zhang2024auriculocondylarsyndrome2 pages 2-5)
ARCND2B	PLCB4	AR	Intragenic homozygous deletion; compound heterozygous splice variants c.854-1G>A and c.1238+1G>C; homozygous loss-of-function PLCB4 alleles also reported in review tables (tavares2016identificaçãodenovas pages 67-68, tavares2016identificaçãodenovas pages 68-72)	Loss-of-function / splice-null mechanism (tavares2016identificaçãodenovas pages 68-72, gordon2013heterogeneityofmutational pages 11-12)	Human recessive cases demonstrate that complete PLCB4 loss can produce classical ACS craniofacial features, contrasting with lack of craniofacial phenotype in some mouse null models; 13.3% (2/15) of PLCB4 variants in one summary were homozygous predicted LoF (gordon2013heterogeneityofmutational pages 11-12, tavares2016identificaçãodenovas pages 68-72)	Gordon et al., 2013, https://doi.org/10.1136/jmedgenet-2012-101331; Tavares thesis, 2016, https://doi.org/10.11606/t.41.2016.tde-14072016-142513 (gordon2013heterogeneityofmutational pages 11-12, tavares2016identificaçãodenovas pages 68-72, tavares2016identificaçãodenovas pages 67-68)
ARCND3	EDN1	AR for syndromic ACS; AD for isolated question-mark ears	Homozygous proprotein cleavage-site substitutions in ACS; AD EDN1 variants reported include p.Val64Asp and p.Tyr83*; homozygous c.271A>G, p.Lys91Glu reported in consanguineous ACS cases (gordon2013mutationsinendothelin pages 1-2, tavares2016identificaçãodenovas pages 67-68)	Reduced or altered EDN1 ligand activity with mutation-dependent residual function; upstream endothelin-pathway defect (gordon2013mutationsinendothelin pages 1-2)	Mouse data show Edn1/Ednra/Ece1 loss causes severe mandibular defects; human EDN1 mutations establish ligand-level causation upstream of PLCB4/GNAI3; differing inheritance for ACS vs isolated QME likely reflects residual EDN1 activity (gordon2013mutationsinendothelin pages 1-2)	Gordon et al., 2013, https://doi.org/10.1016/j.ajhg.2013.10.023 (gordon2013mutationsinendothelin pages 1-2)
ARCND4	7p locus involving HDAC9/TWIST1 regulatory elements	AD in reported pedigree	Tandem duplication NC_000007.14:g.18437239_18867540dup (430,302 bp), telomeric to TWIST1 and covering most of HDAC9 (tavares2022newlocusunderlying pages 4-4)	Regulatory mechanism: altered cis-regulation of TWIST1 and disruption/duplication of HDAC9 isoforms rather than coding mutation in known ARCND genes (tavares2022newlocusunderlying pages 1-1, tavares2022newlocusunderlying pages 4-4)	Capture-C showed duplicated region contacts the TWIST1 promoter; patient iPSC-derived neural crest cells had increased HDAC9 (3.15-fold) and TWIST1 (2.03-fold), ~4.3-fold reduced NCC migration, and impaired osteogenic differentiation with ~20.3-fold reduced ALP activity and reduced matrix mineralization; linkage LOD 2.88 (tavares2022newlocusunderlying pages 5-6, tavares2022newlocusunderlying pages 6-7, tavares2022newlocusunderlying pages 4-4)	Tavares et al., 2022, https://doi.org/10.1136/jmedgenet-2021-107825 (tavares2022newlocusunderlying pages 1-1, tavares2022newlocusunderlying pages 5-6, tavares2022newlocusunderlying pages 6-7, tavares2022newlocusunderlying pages 4-4)
Unsolved / residual ARCND fraction	Unknown locus/loci	Likely mixed	No pathogenic variants found in known genes in 2/28 index patients in one cohort; historical reports also noted unsolved families before discovery of the HDAC9/TWIST1 duplication (tavares2017targetedmolecularinvestigation pages 4-6, tavares2022newlocusunderlying pages 1-1)	Genetic heterogeneity; additional loci remain plausible (tavares2017targetedmolecularinvestigation pages 4-6)	Cohort data: 16/28 PLCB4, 6/28 GNAI3, 4/28 EDN1, and 2/28 unexplained; discovery of ARCND4 reduced but did not eliminate unsolved disease fraction (tavares2017targetedmolecularinvestigation pages 4-6, tavares2022newlocusunderlying pages 1-1)	Tavares et al., 2017, https://doi.org/10.1002/ajmg.a.38101; Tavares et al., 2022, https://doi.org/10.1136/jmedgenet-2021-107825 (tavares2017targetedmolecularinvestigation pages 4-6, tavares2022newlocusunderlying pages 1-1)

Table: This table summarizes the currently reported genetic causes and loci for auriculocondylar syndrome, linking subtypes to representative variants, inheritance, and proposed molecular mechanisms. It is useful for quickly comparing coding-gene causes in the EDN1 pathway with the newer regulatory ARCND4 locus involving TWIST1/HDAC9.

Environmental risk factors

No validated environmental risk factors were identified in the retrieved evidence for ARCND. Given the congenital Mendelian etiology, environmental modifiers may exist but are not established here.

2.3 Protective factors

No protective genetic or environmental factors were identified in the retrieved evidence.

2.4 Gene–environment interactions

No gene–environment interaction evidence was identified in the retrieved materials.

3. Phenotypes

3.1 Core phenotype (triad)

The core clinical triad is consistently stated as: - Question-mark ears (QME) - Mandibular condyle hypoplasia - Micrognathia

This is explicitly stated in a 2024 clinical report: “The typical triad manifestations of ARCND include question mark ears (QMEs), mandibular condyle hypoplasia, and micrognathia.” (Shi et al., 2024; https://doi.org/10.1186/s12903-024-04575-1; Jul 2024) (shi2024novelgnai3mutation pages 1-2)

3.2 Additional phenotypes and frequencies/statistics

ARCND shows broad inter- and intra-familial variability and incomplete penetrance in some dominant families. (clouthier2013understandingthebasis pages 1-3, rieder2012ahumanhomeotic pages 3-5)

Features beyond the triad reported across sources include: microstomia/narrow mouth, prominent/full cheeks, glossoptosis, palatal anomalies (including cleft palate), facial asymmetry, pre/postauricular tags, hearing loss, feeding difficulties, respiratory distress/airway obstruction, dental crowding/malocclusion, and TMJ pathology (including ankylosis). (clouthier2013understandingthebasis pages 1-3, rieder2012ahumanhomeotic pages 1-2, tavares2017targetedmolecularinvestigation pages 4-6)

Phenotype frequencies/statistics from retrieved cohort tables and analyses: - Full cheeks and QME association: In one study, full cheeks were significantly overrepresented (P = 0.0026) and QME was strongly associated with ACS (P = 0.0001). (tavares2017targetedmolecularinvestigation pages 4-6) - Selected frequency examples summarized in a literature table include microstomia 10/11 and prominent cheeks 10/11 in one reported group, and respiratory distress 6/10 in one group (noting small denominators and missing reporting). (tavares2016identificaçãodenovas pages 67-68)

3.3 Age of onset, severity, progression

Onset: congenital / prenatal developmental.
Severity: variable, from isolated ear findings (IQME) to severe mandibular hypoplasia with airway compromise.
Progression: TMJ ankylosis can be progressive and severe cases may cause airway obstruction requiring tracheostomy (reported in earlier primary literature). (rieder2012ahumanhomeotic pages 1-2)

3.4 Quality-of-life impact

Quantitative QOL instruments were not found in retrieved evidence. However, severe dentofacial deformities are described as “present[ing] considerable challenges in patients’ lives and clinical treatment.” (shi2024novelgnai3mutation pages 1-2)

3.5 Suggested HPO terms (non-exhaustive)

Based on phenotypes described in retrieved evidence: - Question mark ear / auricular clefting: HP:0009907 (Question mark ear; commonly used HPO term for QME) - Micrognathia: HP:0000347 - Mandibular condyle hypoplasia: HP:0009119 (Mandibular condyle hypoplasia) - Microstomia: HP:0000174 - Glossoptosis: HP:0000162 - Cleft palate: HP:0000175 - Hearing impairment: HP:0000365 - Facial asymmetry: HP:0000324 - Malocclusion/crowded teeth: HP:0000689 (Crowding of teeth), HP:0000688 (Malocclusion)

(These HPO identifiers are standard ontology mappings; the evidence for the underlying phenotypes is in the cited papers.) (clouthier2013understandingthebasis pages 1-3, tavares2017targetedmolecularinvestigation pages 4-6, shi2024novelgnai3mutation pages 2-6)

4. Genetic / molecular information

4.1 Causal genes and loci

Causal genes/locus in retrieved evidence include PLCB4, GNAI3, EDN1, and a 7p duplication affecting regulatory elements interacting with TWIST1 (HDAC9/TWIST1 region). (tavares2017targetedmolecularinvestigation pages 4-6, gordon2013mutationsinendothelin pages 1-2, tavares2022newlocusunderlying pages 5-6)

4.2 Pathogenic variants: types and functional consequences

PLCB4: predominantly missense variants in catalytic domains (X/Y), with evidence suggesting dominant-negative action for many heterozygous missense alleles; additionally, biallelic loss-of-function (deletions/splice) can cause recessive disease (ARCND2B). (gordon2013heterogeneityofmutational pages 11-12, tavares2016identificaçãodenovas pages 67-68)
GNAI3: multiple variants cluster in GDP/GTP-binding motifs; multiple sources argue for a dominant-negative mechanism affecting EDN1 pathway signaling. (tavares2015novelvariantsin pages 1-2, gordon2013heterogeneityofmutational pages 11-12)
EDN1: homozygous mutations affecting processing/peptide can cause recessive ACS; other mutations can cause dominant isolated QME, consistent with mutation-dependent residual ligand activity. (gordon2013mutationsinendothelin pages 1-2)
HDAC9/TWIST1 regulatory duplication (ARCND4): a 430 kb tandem duplication with functional evidence for altered TWIST1 regulation and neural crest cell migration/osteogenesis effects in iPSC-derived models. (tavares2022newlocusunderlying pages 5-6, tavares2022newlocusunderlying pages 4-4)

4.3 Allele frequencies

Population-database frequency statements were limited in retrieved excerpts. Example: GNAI3 p.Gly40Arg was “not observed in 10,758 control chromosomes” in Rieder et al. (2012). (rieder2012ahumanhomeotic pages 3-5)

4.4 Modifier genes / epigenetics / chromosomal abnormalities

No validated modifier genes or epigenetic signatures specific to ARCND were found in retrieved evidence.

5. Environmental information

No ARCND-specific environmental, lifestyle, or infectious contributors were identified in retrieved evidence.

6. Mechanism / pathophysiology

6.1 Molecular pathway: EDN1–EDNRA–(GNAI3/PLCB4)–DLX5/6 craniofacial patterning

A central mechanistic model supported by human genetics, functional assays, and animal studies is disruption of endothelin-1 signaling in cranial neural crest: - EDN1 is a ligand critical for patterning the mandibular portion of the first pharyngeal arch via EDNRA signaling; murine deletion of Edn1/Ednra/Ece1 causes severe mandibular defects. (gordon2013mutationsinendothelin pages 1-2) - In human ACS, mutations in PLCB4 and GNAI3 are proposed to act as core intracellular effectors downstream of endothelin receptor signaling; patient-derived osteoblast assays showed significantly reduced DLX5 and DLX6 expression, consistent with impaired mandibular identity specification. (rieder2012ahumanhomeotic pages 1-2) - Clouthier et al. (2013) synthesize that loss of EDN1/EDNRA signaling causes “loss of mandibular neural crest cell identity and repatterning,” producing a homeotic shift toward maxillary-like morphology. (clouthier2013understandingthebasis pages 1-3)

6.2 Regulatory mechanism: TWIST1 dosage and neural crest migration (ARCND4)

Tavares et al. (2022) established a fourth locus involving a 430 kb tandem duplication in the HDAC9 region with regulatory contacts to TWIST1: - Capture-C revealed multiple cis interactions between the TWIST1 promoter and regulatory elements in the duplicated region. (tavares2022newlocusunderlying pages 1-1) - Patient iPSC-derived neural crest cells (iNCCs) showed HDAC9 upregulation (3.15-fold; p=0.009) and TWIST1 upregulation (2.03-fold; p=0.03), with ~4.3-fold reduced migratory capacity (p=0.0009). (tavares2022newlocusunderlying pages 5-6) - NCC-derived mesenchymal cells showed impaired osteogenic differentiation (e.g., markedly reduced ALP activity and reduced mineralization). (tavares2022newlocusunderlying pages 5-6)

6.3 Suggested GO biological process terms (examples)

Neural crest cell migration: GO:0001755
Craniofacial morphogenesis: GO:0060325
Pharyngeal arch development: GO:0060034
Endothelin receptor signaling pathway: GO:0072000 (related terms depending on curation)
Osteoblast differentiation / ossification: GO:0001649, GO:0001503

6.4 Suggested cell types (Cell Ontology; examples)

Cranial neural crest cell: CL:0002638 (commonly used for neural crest lineage)
Mesenchymal stem cell: CL:0000134
Osteoblast: CL:0000062

(Functional evidence for NCC involvement and osteogenic defects is supported by iPSC-derived NCC and nMSC assays in Tavares et al. 2022.) (tavares2022newlocusunderlying pages 5-6)

7. Anatomical structures affected

7.1 Organ/tissue level (with UBERON suggestions)

Primary structures: - External ear / pinna (UBERON:0001690) — QME malformation at helix–lobule junction. (clouthier2013understandingthebasis pages 1-3) - Mandible (UBERON:0001684) — micrognathia, mandibular hypoplasia. (clouthier2013understandingthebasis pages 1-3, shi2024novelgnai3mutation pages 2-6) - Temporomandibular joint (UBERON:0002388) — condylar hypoplasia; ankylosis in some cases. (rieder2012ahumanhomeotic pages 1-2) - First/second pharyngeal arches (UBERON:0004456, UBERON:0004457; developmental structures) (tavares2022newlocusunderlying pages 1-2)

Secondary/associated: - Upper airway/oropharynx (UBERON:0001723 pharynx; airway volumes) in severe micrognathia/OSA. (shi2024novelgnai3mutation pages 2-6)

8. Temporal development (natural history)

ARCND is a congenital developmental disorder, sometimes detectable prenatally by ultrasound when severe micrognathia/mandibular hypoplasia is present.

Prenatal case evidence: Liu et al. (2021) report prenatal ultrasound identification of severe micrognathia and mandibular hypoplasia with polyhydramnios, followed by WES identification of a de novo GNAI3 variant (p.Ser47Asn). The abstract states: “Severe micrognathia and mandibular hypoplasia accompanied by polyhydramnios are prenatal indicators of ACS.” (https://doi.org/10.1186/s12884-021-04238-x; Nov 2021) (liu2021prenataldiagnosisof pages 1-3)

9. Inheritance and population

9.1 Inheritance

ARCND can be autosomal dominant or autosomal recessive, depending on gene and variant class: - Dominant inheritance with variable expressivity and occasional non-penetrance is widely noted (e.g., GNAI3/PLCB4 families). (clouthier2013understandingthebasis pages 1-3, rieder2012ahumanhomeotic pages 3-5) - EDN1 can cause recessive ACS and dominant isolated QME. (gordon2013mutationsinendothelin pages 1-2) - ARCND2 includes dominant ARCND2A and recessive ARCND2B. (zhang2024auriculocondylarsyndrome2 pages 1-2)

9.2 Epidemiology

ARCND is repeatedly described as extremely rare: - Orphanet-cited prevalence “under 1 in 1,000,000.” (tavares2022newlocusunderlying pages 1-2) - “Fewer than 100 cases” reported is stated in a 2024 case report background. (shi2024novelgnai3mutation pages 1-2)

Robust population prevalence/incidence estimates were not provided in the retrieved primary texts.

10. Diagnostics

10.1 Clinical diagnosis

The clinical triad is emphasized as the diagnostic anchor, with recognition that incomplete presentations occur and can lead to misdiagnosis.

Direct abstract quote (2024): “ARCND is a monogenic and rare condition that can be diagnosed based on its clinical triad of core features.” (Shi et al., 2024; https://doi.org/10.1186/s12903-024-04575-1) (shi2024novelgnai3mutation pages 1-2)

10.2 Differential diagnosis

A 2024 clinical report lists potential misdiagnoses including: - Oculo-auriculo-vertebral spectrum - Treacher Collins syndrome - Mandibulofacial dysostosis - Guion-Almeida type - Meier-Gorlin syndrome

(shi2024novelgnai3mutation pages 1-2)

10.3 Genetic testing and real-world implementation

WES is repeatedly used in modern diagnosis and case resolution (including prenatal and postnatal), identifying novel GNAI3 insertions/missense changes. (shi2024novelgnai3mutation pages 1-2, liu2021prenataldiagnosisof pages 1-3)
Targeted sequencing of PLCB4, GNAI3, EDN1 is used for patients in the clinical spectrum and supports genotype–phenotype correlation work. (tavares2017targetedmolecularinvestigation pages 4-6)

In prenatal settings, WES has been used as confirmatory testing when ultrasound indicates severe mandibular anomalies. (liu2021prenataldiagnosisof pages 1-3)

10.4 Suggested diagnostic workflow (evidence-based synthesis)

1) Recognize craniofacial pattern consistent with ARCND (QME + micrognathia + condylar hypoplasia) (clouthier2013understandingthebasis pages 1-3, tavares2017targetedmolecularinvestigation pages 4-6) 2) Molecular testing: targeted ARCND genes (PLCB4, GNAI3, EDN1) or WES; consider CNV analysis if negative (HDAC9/TWIST1 duplication) (tavares2017targetedmolecularinvestigation pages 4-6, tavares2022newlocusunderlying pages 4-4) 3) Multidisciplinary craniofacial and airway evaluation in severe cases (sleep study/OSA assessment when indicated) (shi2024novelgnai3mutation pages 2-6)

11. Outcomes / prognosis

ARCND outcomes depend on severity (airway compromise, feeding difficulties, craniofacial growth, TMJ involvement). Quantitative survival data were not found in the retrieved evidence.

Functional outcome example (2024, 5-year follow-up): A patient with ARCND treated with sequential orthodontics, distraction osteogenesis, and orthognathic surgery had measurable improvements in airway and sleep-disordered breathing: airway volume increased from 18,672 mm³ to 32,880 mm³, AHI improved to 0.5 with SpO2 97%, maximal mouth opening 40 mm, and stability maintained at follow-up with return to normal life. (shi2024novelgnai3mutation pages 2-6)

12. Treatment

12.1 Current applications and real-world implementations

There are no disease-specific pharmacotherapies in the retrieved evidence; management is primarily craniofacial, orthodontic, and surgical, tailored to severity.

A detailed modern treatment implementation (Shi et al., 2024) included: - Multidisciplinary planning and 3D digital technology guidance - Preoperative orthodontic treatment with extractions and alignment - Mandibular distraction osteogenesis (bilateral distractors) - Orthognathic surgery (e.g., Le Fort I, BSSRO, genioplasty) - Demonstrated 5-year stable functional improvement (airway metrics, OSA resolution) (shi2024novelgnai3mutation pages 2-6)

12.2 MAXO (Medical Action Ontology) term suggestions

Mandibular distraction osteogenesis: MAXO:0001170 (Distraction osteogenesis; exact ID may vary by MAXO version)
Orthognathic surgery / corrective jaw surgery: MAXO:0000127 (Surgical procedure) with more specific jaw surgery subclass if available
Genetic testing / exome sequencing: MAXO:0000120 (Genetic testing)
Polysomnography / sleep study: MAXO:0000537 (Sleep study; exact ID may vary)

(These MAXO mappings are suggestions; evidence of the interventions is in the cited case report.) (shi2024novelgnai3mutation pages 2-6)

12.3 Clinical trials

ClinicalTrials.gov search in this run did not identify ARCND-specific interventional trials; retrieved trials related to orthognathic surgery or dysgnathic patients appear generic rather than syndrome-specific. (clinical trial metadata returned; no ARCND-targeted NCT found) (shi2024novelgnai3mutation pages 2-6)

13. Prevention

Primary prevention is not established because ARCND is genetic and typically congenital.

Potential prevention/mitigation strategies in practice include: - Genetic counseling and recurrence risk assessment for families with known pathogenic variants (implied by Mendelian inheritance patterns and use of prenatal molecular testing). (liu2021prenataldiagnosisof pages 1-3, gordon2013mutationsinendothelin pages 1-2) - Prenatal diagnosis when familial pathogenic variants are known or when severe mandibular anomalies are detected by ultrasound, followed by confirmatory molecular testing. (liu2021prenataldiagnosisof pages 1-3)

14. Other species / natural disease

Natural disease analogs in other species were not identified in retrieved evidence. However, mechanistic insights rely on vertebrate developmental models: - Mouse loss-of-function of Edn1/Ednra/Ece1 produces mandibular patterning defects, supporting causality of the endothelin pathway in jaw identity specification. (gordon2013mutationsinendothelin pages 1-2)

15. Model organisms

ARCND mechanisms are informed by mouse and zebrafish craniofacial development studies summarized in the 2013 Seminars review, alongside human genetics. (clouthier2013understandingthebasis pages 1-3)

A human stem-cell/iPSC model has been used as a complementary system for ARCND4, demonstrating altered gene expression and functional deficits in iPSC-derived cranial neural crest migration and osteogenic differentiation. (tavares2022newlocusunderlying pages 5-6)

Recent developments (prioritizing 2023–2024)

1) 2024: Longitudinal treatment outcomes and digital surgical workflows - BMC Oral Health (Jul 2024) reports a novel inherited GNAI3 insertion and detailed multi-stage orthodontic + surgical treatment with quantitative improvements in airway volume and sleep apnea metrics at 5 years. (https://doi.org/10.1186/s12903-024-04575-1) (shi2024novelgnai3mutation pages 2-6) - Visual evidence of phenotype and treatment planning (Figures showing micrognathia/condylar hypoplasia and digital workflow) was retrieved. (shi2024novelgnai3mutation media 1e0f905a, shi2024novelgnai3mutation media 063b200e)

2) 2024: Expanded PLCB4 variant spectrum and neonatal presentation - Molecular Genetics & Genomic Medicine (Apr 2024) reports a de novo PLCB4 variant and consolidates subtype nomenclature and prevalence statements, including ARCND subtype OMIM numbers and literature counts (36 PLCB4-mutant patients retrieved). (https://doi.org/10.1002/mgg3.2441) (zhang2024auriculocondylarsyndrome2 pages 2-5, zhang2024auriculocondylarsyndrome2 pages 1-2)

3) 2023: Continued mechanistic refinement in endothelin receptor signaling (related craniofacial endothelin disorders) - Although focused on EDNRA gain-of-function in mandibulofacial dysostosis with alopecia (MFDA), JCI 2023 provides modern GPCR allostery/ligand affinity mechanistic analysis relevant to endothelin receptor biology broadly. (https://doi.org/10.1172/jci151536; Feb 2023) (tavares2022newlocusunderlying pages 1-2)

Expert opinion / authoritative synthesis

The 2013 Seminars review (Clouthier et al.) remains an authoritative synthesis linking human genetics to mouse/zebrafish developmental biology and framing ARCND as a neural crest patterning disorder driven by loss of mandibular identity cues in EDN1/EDNRA signaling. (clouthier2013understandingthebasis pages 1-3)

A 2022 J Med Genet study provides authoritative locus-level expansion beyond the classic EDN1 pathway genes by demonstrating a regulatory duplication affecting TWIST1 control elements and measurable NCC migration defects in iPSC-derived models—supporting the view that ARCND includes both signal-transduction and regulatory/cranial neural crest migration etiologies. (tavares2022newlocusunderlying pages 5-6)

Visual evidence (phenotype and management)

Patient craniofacial phenotype and mandibular condyle hypoplasia on 3D CT reconstructions (Figure 1) and digital treatment workflow (Figure 4) from the 2024 ARCND case report. (shi2024novelgnai3mutation media 1e0f905a, shi2024novelgnai3mutation media 063b200e)

Key limitations of this report (evidence gaps)

Specific ICD-10/ICD-11 and MeSH identifiers were not present in the retrieved evidence.
Systematic, population-based epidemiology (incidence/prevalence by region) and formal QOL measures were not found in the retrieved primary texts.
ARCND-specific interventional clinical trials were not identified in the clinical trials search results during this run.

References (URLs and publication dates)

Rieder MJ et al. Am J Hum Genet. May 2012. https://doi.org/10.1016/j.ajhg.2012.04.002 (rieder2012ahumanhomeotic pages 1-2, rieder2012ahumanhomeotic pages 3-5)
Gordon CT et al. Am J Hum Genet. Dec 2013. https://doi.org/10.1016/j.ajhg.2013.10.023 (gordon2013mutationsinendothelin pages 1-2)
Clouthier DE et al. Am J Med Genet C Semin Med Genet. Nov 2013. https://doi.org/10.1002/ajmg.c.31376 (clouthier2013understandingthebasis pages 1-3)
Tavares VLR et al. Am J Med Genet A. Apr 2017. https://doi.org/10.1002/ajmg.a.38101 (tavares2017targetedmolecularinvestigation pages 4-6)
Tavares VLR et al. J Med Genet. Nov 2022. https://doi.org/10.1136/jmedgenet-2021-107825 (tavares2022newlocusunderlying pages 5-6, tavares2022newlocusunderlying pages 4-4)
Zhang Y et al. Mol Genet Genomic Med. Apr 2024. https://doi.org/10.1002/mgg3.2441 (zhang2024auriculocondylarsyndrome2 pages 2-5, zhang2024auriculocondylarsyndrome2 pages 1-2)
Shi Y et al. BMC Oral Health. Jul 2024. https://doi.org/10.1186/s12903-024-04575-1 (shi2024novelgnai3mutation pages 2-6, shi2024novelgnai3mutation media 1e0f905a)
OpenTargets disease-target mapping (MONDO mapping). (OpenTargets Search: Auriculocondylar syndrome)

References

(clouthier2013understandingthebasis pages 1-3): David E. Clouthier, Maria Rita Passos‐Bueno, Andre L.P. Tavares, Stanislas Lyonnet, Jeanne Amiel, and Christopher T. Gordon. Understanding the basis of auriculocondylar syndrome: insights from human, mouse and zebrafish genetic studies. American Journal of Medical Genetics Part C: Seminars in Medical Genetics, 163:306-317, Nov 2013. URL: https://doi.org/10.1002/ajmg.c.31376, doi:10.1002/ajmg.c.31376. This article has 69 citations.
(rieder2012ahumanhomeotic pages 1-2): Mark J. Rieder, Glenn E. Green, Sarah S. Park, Brendan D. Stamper, Christopher T. Gordon, Jason M. Johnson, Christopher M. Cunniff, Joshua D. Smith, Sarah B. Emery, Stanislas Lyonnet, Jeanne Amiel, Muriel Holder, Andrew A. Heggie, Michael J. Bamshad, Deborah A. Nickerson, Timothy C. Cox, Anne V. Hing, Jeremy A. Horst, and Michael L. Cunningham. A human homeotic transformation resulting from mutations in plcb4 and gnai3 causes auriculocondylar syndrome. American journal of human genetics, 90 5:907-14, May 2012. URL: https://doi.org/10.1016/j.ajhg.2012.04.002, doi:10.1016/j.ajhg.2012.04.002. This article has 114 citations and is from a highest quality peer-reviewed journal.
(shi2024novelgnai3mutation pages 2-6): Yulin Shi, Liang Rong, Siying Liu, Yiwen Liu, Chunlin Zong, Jinbiao Lu, Hongtao Shang, Yang Xue, and Lei Tian. Novel gnai3 mutation in a chinese family with auriculocondylar syndrome and treatment of severe dentofacial deformities: a 5-year follow-up case report. BMC Oral Health, Jul 2024. URL: https://doi.org/10.1186/s12903-024-04575-1, doi:10.1186/s12903-024-04575-1. This article has 2 citations and is from a peer-reviewed journal.
(gordon2013heterogeneityofmutational pages 1-2): Christopher T Gordon, Alice Vuillot, Sandrine Marlin, Erica Gerkes, Alex Henderson, Adila AlKindy, Muriel Holder-Espinasse, Sarah S Park, Asma Omarjee, Mateo Sanchis-Borja, Eya Ben Bdira, Myriam Oufadem, Birgit Sikkema-Raddatz, Alison Stewart, Rodger Palmer, Ruth McGowan, Florence Petit, Bruno Delobel, Michael R Speicher, Paul Aurora, David Kilner, Philippe Pellerin, Marie Simon, Jean-Paul Bonnefont, Edward S Tobias, Sixto García-Miñaúr, Maria Bitner-Glindzicz, Pernille Lindholm, Brigitte A Meijer, Véronique Abadie, Françoise Denoyelle, Marie-Paule Vazquez, Christa Rotky-Fast, Vincent Couloigner, Sébastien Pierrot, Yves Manach, Sylvain Breton, Yvonne M C Hendriks, Arnold Munnich, Linda Jakobsen, Peter Kroisel, Angela Lin, Leonard B Kaban, Lina Basel-Vanagaite, Louise Wilson, Michael L Cunningham, Stanislas Lyonnet, and Jeanne Amiel. Heterogeneity of mutational mechanisms and modes of inheritance in auriculocondylar syndrome. Journal of Medical Genetics, 50:174-186, Jan 2013. URL: https://doi.org/10.1136/jmedgenet-2012-101331, doi:10.1136/jmedgenet-2012-101331. This article has 58 citations and is from a domain leading peer-reviewed journal.
(OpenTargets Search: Auriculocondylar syndrome): Open Targets Query (Auriculocondylar syndrome, 6 results). Buniello, A. et al. (2025). Open Targets Platform: facilitating therapeutic hypotheses building in drug discovery. Nucleic Acids Research.
(tavares2022newlocusunderlying pages 1-2): Vanessa Luiza Romanelli Tavares, Sofia Ligia Guimarães-Ramos, Yan Zhou, Cibele Masotti, Suzana Ezquina, Danielle de Paula Moreira, Henk Buermans, Renato S Freitas, Johan T Den Dunnen, Stephen R F Twigg, and Maria Rita Passos-Bueno. New locus underlying auriculocondylar syndrome (arcnd): 430 kb duplication involving twist1 regulatory elements. Journal of Medical Genetics, 59:895-905, Nov 2022. URL: https://doi.org/10.1136/jmedgenet-2021-107825, doi:10.1136/jmedgenet-2021-107825. This article has 9 citations and is from a domain leading peer-reviewed journal.
(shi2024novelgnai3mutation pages 1-2): Yulin Shi, Liang Rong, Siying Liu, Yiwen Liu, Chunlin Zong, Jinbiao Lu, Hongtao Shang, Yang Xue, and Lei Tian. Novel gnai3 mutation in a chinese family with auriculocondylar syndrome and treatment of severe dentofacial deformities: a 5-year follow-up case report. BMC Oral Health, Jul 2024. URL: https://doi.org/10.1186/s12903-024-04575-1, doi:10.1186/s12903-024-04575-1. This article has 2 citations and is from a peer-reviewed journal.
(zhang2024auriculocondylarsyndrome2 pages 1-2): Yongli Zhang, Yuwei Zhao, Liying Dai, Yu Liu, and Zifeng Shi. Auriculocondylar syndrome 2 caused by a novel plcb4 variant in a male chinese neonate: a case report and review of the literature. Molecular Genetics & Genomic Medicine, Apr 2024. URL: https://doi.org/10.1002/mgg3.2441, doi:10.1002/mgg3.2441. This article has 3 citations and is from a peer-reviewed journal.
(gordon2013mutationsinendothelin pages 1-2): Christopher T. Gordon, Florence Petit, Peter M. Kroisel, Linda Jakobsen, Roseli Maria Zechi-Ceide, Myriam Oufadem, Christine Bole-Feysot, Solenn Pruvost, Cécile Masson, Frédéric Tores, Thierry Hieu, Patrick Nitschké, Pernille Lindholm, Philippe Pellerin, Maria Leine Guion-Almeida, Nancy Mizue Kokitsu-Nakata, Siulan Vendramini-Pittoli, Arnold Munnich, Stanislas Lyonnet, Muriel Holder-Espinasse, and Jeanne Amiel. Mutations in endothelin 1 cause recessive auriculocondylar syndrome and dominant isolated question-mark ears. American journal of human genetics, 93 6:1118-25, Dec 2013. URL: https://doi.org/10.1016/j.ajhg.2013.10.023, doi:10.1016/j.ajhg.2013.10.023. This article has 86 citations and is from a highest quality peer-reviewed journal.
(tavares2017targetedmolecularinvestigation pages 4-6): Vanessa L. Romanelli Tavares, Roseli M. Zechi‐Ceide, Debora R. Bertola, Christopher T. Gordon, Simone G. Ferreira, Gabriella S. P. Hsia, Guilherme L. Yamamoto, Suzana A. M. Ezquina, Nancy M. Kokitsu‐Nakata, Siulan Vendramini‐Pittoli, Renato S. Freitas, Josiane Souza, Cesar A. Raposo‐Amaral, Mayana Zatz, Jeanne Amiel, Maria L. Guion‐Almeida, and Maria Rita Passos‐Bueno. Targeted molecular investigation in patients within the clinical spectrum of auriculocondylar syndrome. American Journal of Medical Genetics Part A, 173:938-945, Apr 2017. URL: https://doi.org/10.1002/ajmg.a.38101, doi:10.1002/ajmg.a.38101. This article has 17 citations.
(tavares2022newlocusunderlying pages 5-6): Vanessa Luiza Romanelli Tavares, Sofia Ligia Guimarães-Ramos, Yan Zhou, Cibele Masotti, Suzana Ezquina, Danielle de Paula Moreira, Henk Buermans, Renato S Freitas, Johan T Den Dunnen, Stephen R F Twigg, and Maria Rita Passos-Bueno. New locus underlying auriculocondylar syndrome (arcnd): 430 kb duplication involving twist1 regulatory elements. Journal of Medical Genetics, 59:895-905, Nov 2022. URL: https://doi.org/10.1136/jmedgenet-2021-107825, doi:10.1136/jmedgenet-2021-107825. This article has 9 citations and is from a domain leading peer-reviewed journal.
(tavares2015novelvariantsin pages 1-2): Vanessa L Romanelli Tavares, Christopher T Gordon, Roseli M Zechi-Ceide, Nancy Mizue Kokitsu-Nakata, Norine Voisin, Tiong Y Tan, Andrew A Heggie, Siulan Vendramini-Pittoli, Evan J Propst, Blake C Papsin, Tatiana T Torres, Henk Buermans, Luciane Portas Capelo, Johan T den Dunnen, Maria L Guion-Almeida, Stanislas Lyonnet, Jeanne Amiel, and Maria Rita Passos-Bueno. Novel variants in gnai3 associated with auriculocondylar syndrome strengthen a common dominant negative effect. European Journal of Human Genetics, 23:481-485, Jul 2015. URL: https://doi.org/10.1038/ejhg.2014.132, doi:10.1038/ejhg.2014.132. This article has 36 citations and is from a domain leading peer-reviewed journal.
(tavares2022newlocusunderlying pages 4-4): Vanessa Luiza Romanelli Tavares, Sofia Ligia Guimarães-Ramos, Yan Zhou, Cibele Masotti, Suzana Ezquina, Danielle de Paula Moreira, Henk Buermans, Renato S Freitas, Johan T Den Dunnen, Stephen R F Twigg, and Maria Rita Passos-Bueno. New locus underlying auriculocondylar syndrome (arcnd): 430 kb duplication involving twist1 regulatory elements. Journal of Medical Genetics, 59:895-905, Nov 2022. URL: https://doi.org/10.1136/jmedgenet-2021-107825, doi:10.1136/jmedgenet-2021-107825. This article has 9 citations and is from a domain leading peer-reviewed journal.
(rieder2012ahumanhomeotic pages 3-5): Mark J. Rieder, Glenn E. Green, Sarah S. Park, Brendan D. Stamper, Christopher T. Gordon, Jason M. Johnson, Christopher M. Cunniff, Joshua D. Smith, Sarah B. Emery, Stanislas Lyonnet, Jeanne Amiel, Muriel Holder, Andrew A. Heggie, Michael J. Bamshad, Deborah A. Nickerson, Timothy C. Cox, Anne V. Hing, Jeremy A. Horst, and Michael L. Cunningham. A human homeotic transformation resulting from mutations in plcb4 and gnai3 causes auriculocondylar syndrome. American journal of human genetics, 90 5:907-14, May 2012. URL: https://doi.org/10.1016/j.ajhg.2012.04.002, doi:10.1016/j.ajhg.2012.04.002. This article has 114 citations and is from a highest quality peer-reviewed journal.
(tavares2016identificaçãodenovas pages 67-68): Vanessa Luiza Romanelli Tavares. Identificação de novas variantes causativas e investigação da heterogeneidade clínica da síndrome aurículo-condilar identification of novel causative variants and investigation of clinical heterogeneity of auriculocondylar syndrome. ArXiv, Mar 2016. URL: https://doi.org/10.11606/t.41.2016.tde-14072016-142513, doi:10.11606/t.41.2016.tde-14072016-142513. This article has 0 citations.
(liu2021prenataldiagnosisof pages 1-3): Xiaoliang Liu, Wei Sun, Jun Wang, Guoming Chu, Rong He, Bijun Zhang, and Yanyan Zhao. Prenatal diagnosis of auriculocondylar syndrome with a novel missense variant of gnai3: a case report. BMC Pregnancy and Childbirth, Nov 2021. URL: https://doi.org/10.1186/s12884-021-04238-x, doi:10.1186/s12884-021-04238-x. This article has 8 citations and is from a peer-reviewed journal.
(gordon2013heterogeneityofmutational pages 11-12): Christopher T Gordon, Alice Vuillot, Sandrine Marlin, Erica Gerkes, Alex Henderson, Adila AlKindy, Muriel Holder-Espinasse, Sarah S Park, Asma Omarjee, Mateo Sanchis-Borja, Eya Ben Bdira, Myriam Oufadem, Birgit Sikkema-Raddatz, Alison Stewart, Rodger Palmer, Ruth McGowan, Florence Petit, Bruno Delobel, Michael R Speicher, Paul Aurora, David Kilner, Philippe Pellerin, Marie Simon, Jean-Paul Bonnefont, Edward S Tobias, Sixto García-Miñaúr, Maria Bitner-Glindzicz, Pernille Lindholm, Brigitte A Meijer, Véronique Abadie, Françoise Denoyelle, Marie-Paule Vazquez, Christa Rotky-Fast, Vincent Couloigner, Sébastien Pierrot, Yves Manach, Sylvain Breton, Yvonne M C Hendriks, Arnold Munnich, Linda Jakobsen, Peter Kroisel, Angela Lin, Leonard B Kaban, Lina Basel-Vanagaite, Louise Wilson, Michael L Cunningham, Stanislas Lyonnet, and Jeanne Amiel. Heterogeneity of mutational mechanisms and modes of inheritance in auriculocondylar syndrome. Journal of Medical Genetics, 50:174-186, Jan 2013. URL: https://doi.org/10.1136/jmedgenet-2012-101331, doi:10.1136/jmedgenet-2012-101331. This article has 58 citations and is from a domain leading peer-reviewed journal.
(zhang2024auriculocondylarsyndrome2 pages 2-5): Yongli Zhang, Yuwei Zhao, Liying Dai, Yu Liu, and Zifeng Shi. Auriculocondylar syndrome 2 caused by a novel plcb4 variant in a male chinese neonate: a case report and review of the literature. Molecular Genetics & Genomic Medicine, Apr 2024. URL: https://doi.org/10.1002/mgg3.2441, doi:10.1002/mgg3.2441. This article has 3 citations and is from a peer-reviewed journal.
(tavares2016identificaçãodenovas pages 68-72): Vanessa Luiza Romanelli Tavares. Identificação de novas variantes causativas e investigação da heterogeneidade clínica da síndrome aurículo-condilar identification of novel causative variants and investigation of clinical heterogeneity of auriculocondylar syndrome. ArXiv, Mar 2016. URL: https://doi.org/10.11606/t.41.2016.tde-14072016-142513, doi:10.11606/t.41.2016.tde-14072016-142513. This article has 0 citations.
(tavares2022newlocusunderlying pages 1-1): Vanessa Luiza Romanelli Tavares, Sofia Ligia Guimarães-Ramos, Yan Zhou, Cibele Masotti, Suzana Ezquina, Danielle de Paula Moreira, Henk Buermans, Renato S Freitas, Johan T Den Dunnen, Stephen R F Twigg, and Maria Rita Passos-Bueno. New locus underlying auriculocondylar syndrome (arcnd): 430 kb duplication involving twist1 regulatory elements. Journal of Medical Genetics, 59:895-905, Nov 2022. URL: https://doi.org/10.1136/jmedgenet-2021-107825, doi:10.1136/jmedgenet-2021-107825. This article has 9 citations and is from a domain leading peer-reviewed journal.
(tavares2022newlocusunderlying pages 6-7): Vanessa Luiza Romanelli Tavares, Sofia Ligia Guimarães-Ramos, Yan Zhou, Cibele Masotti, Suzana Ezquina, Danielle de Paula Moreira, Henk Buermans, Renato S Freitas, Johan T Den Dunnen, Stephen R F Twigg, and Maria Rita Passos-Bueno. New locus underlying auriculocondylar syndrome (arcnd): 430 kb duplication involving twist1 regulatory elements. Journal of Medical Genetics, 59:895-905, Nov 2022. URL: https://doi.org/10.1136/jmedgenet-2021-107825, doi:10.1136/jmedgenet-2021-107825. This article has 9 citations and is from a domain leading peer-reviewed journal.
(shi2024novelgnai3mutation media 1e0f905a): Yulin Shi, Liang Rong, Siying Liu, Yiwen Liu, Chunlin Zong, Jinbiao Lu, Hongtao Shang, Yang Xue, and Lei Tian. Novel gnai3 mutation in a chinese family with auriculocondylar syndrome and treatment of severe dentofacial deformities: a 5-year follow-up case report. BMC Oral Health, Jul 2024. URL: https://doi.org/10.1186/s12903-024-04575-1, doi:10.1186/s12903-024-04575-1. This article has 2 citations and is from a peer-reviewed journal.
(shi2024novelgnai3mutation media 063b200e): Yulin Shi, Liang Rong, Siying Liu, Yiwen Liu, Chunlin Zong, Jinbiao Lu, Hongtao Shang, Yang Xue, and Lei Tian. Novel gnai3 mutation in a chinese family with auriculocondylar syndrome and treatment of severe dentofacial deformities: a 5-year follow-up case report. BMC Oral Health, Jul 2024. URL: https://doi.org/10.1186/s12903-024-04575-1, doi:10.1186/s12903-024-04575-1. This article has 2 citations and is from a peer-reviewed journal.

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OpenScientist Report

Classifications

Inheritance

Subtypes

Discussions and Knowledge Gaps

Pathophysiology

Pathograph

Phenotypes

Genetic Associations

Medical Actions

Diagnosis

Progression

Prevalence

Differential Diagnoses

Related Datasets

Experimental Models

Animal Models

Source YAML

References & Deep Research

References

Deep Research

Disease Characteristics Research Template

Target Disease

Research Objectives

1. Disease Information

2. Etiology

3. Phenotypes

4. Genetic/Molecular Information

5. Environmental Information

6. Mechanism / Pathophysiology

7. Anatomical Structures Affected

8. Temporal Development

9. Inheritance and Population

10. Diagnostics

11. Outcome/Prognosis

12. Treatment

13. Prevention

14. Other Species / Natural Disease

15. Model Organisms

Citation Requirements

Output Format

Auriculocondylar Syndrome (ARCND/ACS): Comprehensive Disease Characteristics Report

Executive summary

1. Disease information

1.1 Definition and current understanding

1.2 Key identifiers (available in retrieved evidence)

1.3 Synonyms and alternative names

1.4 Evidence sources (individual vs aggregated)

2. Etiology

2.1 Disease causal factors (primary causes)

2.2 Risk factors

Genetic risk factors (causal variants)

Environmental risk factors

2.3 Protective factors

2.4 Gene–environment interactions

3. Phenotypes

3.1 Core phenotype (triad)

3.2 Additional phenotypes and frequencies/statistics

3.3 Age of onset, severity, progression

3.4 Quality-of-life impact

3.5 Suggested HPO terms (non-exhaustive)

4. Genetic / molecular information

4.1 Causal genes and loci

4.2 Pathogenic variants: types and functional consequences

4.3 Allele frequencies

4.4 Modifier genes / epigenetics / chromosomal abnormalities

5. Environmental information

6. Mechanism / pathophysiology

6.1 Molecular pathway: EDN1–EDNRA–(GNAI3/PLCB4)–DLX5/6 craniofacial patterning

6.2 Regulatory mechanism: TWIST1 dosage and neural crest migration (ARCND4)

6.3 Suggested GO biological process terms (examples)

6.4 Suggested cell types (Cell Ontology; examples)

7. Anatomical structures affected

7.1 Organ/tissue level (with UBERON suggestions)

8. Temporal development (natural history)

9. Inheritance and population

9.1 Inheritance

9.2 Epidemiology

10. Diagnostics