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Classifications

ISDS Skeletal Nosology

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Inheritance

2

Autosomal recessive inheritance HP:0000007

Most MGORS is autosomal recessive, arising from biallelic partial loss-of-function (hypomorphic) variants in a replication-initiation gene. Homozygous or compound heterozygous null genotypes are not observed, since complete loss of these essential replication factors is presumed incompatible with survival.

Autosomal recessive inheritance

Show evidence (2 references)

PMID:21358632 SUPPORT Human Clinical

"Meier-Gorlin syndrome (ear, patella and short-stature syndrome) is an autosomal recessive primordial dwarfism syndrome characterized by absent or hypoplastic patellae and markedly small ears"

The gene-discovery study establishes autosomal recessive inheritance and the defining clinical triad.

PMID:22333897 SUPPORT Human Clinical

"No homozygous or compound heterozygous null mutations were detected."

Across the largest genotyped cohort, only hypomorphic biallelic genotypes were found, supporting the requirement for residual replication activity.

Autosomal dominant inheritance HP:0000006

A distinct dominant form arises from de novo heterozygous GMNN variants that delete the geminin destruction box, stabilizing the licensing inhibitor rather than disabling a licensing activator. This is the mechanistic and inheritance exception within MGORS.

Autosomal dominant inheritance

Show evidence (1 reference)

PMID:26637980 SUPPORT Human Clinical

"We present data supporting a gain-of-function mechanism, in which the GMNN mutations result in proteins lacking the destruction box and hence increased protein stability and prolonged inhibition of replication leading to autosomal-dominant MGS."

Establishes the dominant, gain-of-function GMNN arm as an exception to the otherwise recessive inheritance of MGORS.

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Subtypes

11

Meier-Gorlin syndrome 1 (ORC1-related) MONDO:0009143

ORC1 hgnc:8487

Caused by biallelic ORC1 variants, frequently affecting the N-terminal BAH chromatin-binding domain. This is the most severe growth arm of MGORS, with the shortest stature and smallest head circumference, and it is the subtype in which the non-replicative centriole and cilium phenotype has been documented.

Show evidence (1 reference)

PMID:22333897 SUPPORT Human Clinical

"Individuals with ORC1 mutations had significantly shorter stature and smaller head circumferences than individuals from other gene categories."

Establishes ORC1-related disease as the most severe growth and microcephaly subtype.

Meier-Gorlin syndrome 2 (ORC4-related) MONDO:0013428

ORC4 hgnc:8490

Caused by biallelic ORC4 variants. Together with ORC1, this arm carries the most severe short stature and microcephaly; compound heterozygous ORC4 genotypes cause more severe growth retardation than homozygous missense genotypes.

Show evidence (1 reference)

PMID:26381604 SUPPORT Human Clinical

"Patients with ORC1 and ORC4 mutations appear to have the most severe short stature and microcephaly."

Clinical review establishing the severity ranking of the ORC1 and ORC4 arms.

Meier-Gorlin syndrome 3 (ORC6-related) MONDO:0013430

ORC6 hgnc:17151

Caused by biallelic ORC6 variants. ORC6 is the smallest origin recognition complex subunit and contributes to ORC assembly and MCM2-7 loading.

Show evidence (1 reference)

PMID:21358632 SUPPORT Human Clinical

"we identify mutations in five separate genes: ORC1, ORC4, ORC6, CDT1 and CDC6"

Original identification of ORC6 among the five founding MGORS pre-replication complex genes.

Meier-Gorlin syndrome 4 (CDT1-related) MONDO:0013431

CDT1 hgnc:24576

Caused by biallelic CDT1 variants. CDT1 is the licensing factor that, with CDC6, loads MCM2-7 onto origin-bound ORC; it is also the direct target of geminin inhibition. Compound heterozygous CDT1 genotypes are more often associated with pulmonary emphysema, and the mutational spectrum extends to deep-intronic branch-point variants that exome pipelines can miss.

Show evidence (1 reference)

PMID:39789585 SUPPORT Human Clinical

"A girl with microtia, hypoplastic patellae, and severe growth retardation carried a novel homozygous intronic variant"

Documents a CDT1-related MGORS patient with the full triad and expands the CDT1 variant spectrum to deep-intronic splice-altering alleles.

Meier-Gorlin syndrome 5 (CDC6-related) MONDO:0013432

CDC6 hgnc:1744

Caused by biallelic CDC6 variants. CDC6 cooperates with CDT1 to load the MCM2-7 helicase. Reported individuals are few, and a neonatal progeroid presentation with lipodystrophy has been described that prompted consideration of progeria in the differential.

Show evidence (1 reference)

PMID:35023948 SUPPORT Human Clinical

"Meier-Gorlin syndrome 5 due to mutations in the CDC6 gene is difficult to diagnose, and few clinical data have been described to date."

Confirms the CDC6 gene assignment for MGORS5 and the sparse clinical literature for this arm.

Meier-Gorlin syndrome 6 (GMNN-related) MONDO:0014794

GMNN hgnc:17493

The autosomal dominant arm, caused by de novo heterozygous GMNN variants that truncate the protein upstream of the destruction box, stabilizing geminin. Mechanistically inverted relative to the other subtypes: the licensing inhibitor is gained rather than a licensing activator lost.

Show evidence (1 reference)

PMID:26637980 SUPPORT Human Clinical

"All three GMNN mutations identified alter sites 5' to residue Met28 of the protein, which is located within the destruction box."

Localizes the dominant GMNN alleles to the destruction box, the basis of the stabilizing gain-of-function mechanism.

Meier-Gorlin syndrome 7 (CDC45-related) MONDO:0014894

CDC45 hgnc:1739

Caused by biallelic CDC45 variants. CDC45 acts in the pre-initiation complex and the CMG helicase rather than in origin licensing, and this arm is strongly enriched for craniosynostosis. An unusually high proportion of its pathogenic alleles are synonymous changes that alter splicing.

Show evidence (2 references)

PMID:27374770 SUPPORT Human Clinical

"Here we report the identification of mutations in CDC45 in 15 affected individuals from 12 families with MGS and/or craniosynostosis."

Original description of the CDC45 arm and its craniosynostosis-enriched phenotype.

PMID:27374770 SUPPORT Human Clinical

"All mutations identified were biallelic and included synonymous mutations altering splicing of physiological CDC45 transcripts, as well as amino acid substitutions expected to result in partial loss of function."

Documents the distinctive synonymous splice-altering allele class of the CDC45 arm.

Meier-Gorlin syndrome 8 (MCM5-related) MONDO:0033046

MCM5 hgnc:6948

Caused by biallelic MCM5 variants affecting a subunit of the replicative MCM2-7 helicase, moving the disease mechanism from origin recognition into the helicase core itself.

Show evidence (1 reference)

PMID:28198391 SUPPORT Human Clinical

"We performed whole-exome sequencing (WES) in a patient with a clinical diagnosis of MGORS and identified biallelic variants in MCM5."

Original identification of MCM5 as an MGORS gene in a molecularly and functionally characterized patient.

Meier-Gorlin syndrome 9 (GINS3-related) MONDO:0980992

GINS3 hgnc:25851

Caused by biallelic hypomorphic GINS3 variants, most affecting aspartic acid 24, which destabilize the protein and slow replication fork progression.

Show evidence (1 reference)

PMID:35603789 SUPPORT Human Clinical

"Here, we report the identification of 7 individuals from 5 unrelated families presenting with a Meier-Gorlin syndrome-like (MGS-like) phenotype associated with hypomorphic variants of GINS3, a gene not previously associated with this syndrome."

Original multi-family identification of the GINS3 arm of MGORS.

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Discussions and Knowledge Gaps

3

Why does the measured origin licensing deficit in patient cells fail to predict S-phase progression rate or clinical severity?

KNOWLEDGE GAP OPEN gap_mgors_licensing_severity_uncoupling

Attached to

pathophysiology#Impaired Replication Origin Licensing pathophysiology#Delayed S-Phase Entry and Reduced Cell Proliferation

Licensing capacity is impaired in all MGORS patient cells regardless of gene, yet it does not correlate with the rate of S-phase progression, and the clinical severity gradient (ORC1 and ORC4 most severe) is not explained by licensing measurements alone. This uncoupling is a central unresolved question of MGORS pathogenesis and is what motivates the parallel non-replicative arms, notably the centriole and ciliogenesis route. Whether the non-canonical roles of these proteins, tissue-specific proliferative demand, or something else supplies the missing explanatory variable is unknown. One partial answer already exists for the ORC1 arm specifically: the BAH domain reads H4K20me2 to target ORC to origins, so BAH mutations remove a chromatin-targeting step rather than simply lowering licensing capacity. Whether an analogous upstream-targeting defect distinguishes the other severe arms has not been tested.

Proposed experiments

Parallel licensing, fork, cell-cycle and ciliogenesis phenotyping across an isogenic MGORS allelic series

exp_mgors_licensing_vs_output_allelic_series

Measure licensed origin density, fork speed, cell cycle length and ciliogenesis competence in parallel across an isogenic allelic series spanning the licensing module (ORC1, ORC4, CDT1) and the CMG module (CDC45, GINS2, GINS3), in a developmentally relevant proliferating cell type such as iPSC-derived chondroprogenitors, and test which measure predicts differentiation output.

Decision criterion

The measure whose variation across the allelic series best predicts chondrogenic differentiation output identifies the rate-limiting step.

Supporting outcome

Ciliogenesis competence predicts differentiation output better than licensed origin density, supporting the non-replicative arm as the severity determinant

Refuting outcome

Licensed origin density predicts differentiation output linearly, restoring the simple licensing-deficit model

Show evidence (1 reference)

PMID:23516378 SUPPORT In Vitro

"Thus, the replicative capacity in MGS patient cells does not correlate with clinical manifestation."

States the uncoupling between replicative capacity and clinical severity that defines this knowledge gap.

What determines the tissue selectivity of MGORS, so that external ear cartilage, the patella, mammary tissue and the external genitalia are affected out of proportion to overall stature?

KNOWLEDGE GAP OPEN gap_mgors_tissue_selectivity

Attached to

pathophysiology#Tissue-Disproportionate Growth Failure pathophysiology#Reduced Hedgehog Signaling and Impaired Chondroinduction

A uniform, cell-autonomous replication deficit should scale all tissues together, yet the phenotype is strikingly selective, and it is that selectivity, not the short stature, that makes MGORS clinically recognizable. Candidate explanations include narrow developmental windows of unusually intense proliferation in these structures and the ciliary Hedgehog and chondroinduction arm, but no cell-type-resolved human data exist.

Proposed experiments

Cell-type-resolved mapping of proliferative demand in MGORS-vulnerable human embryonic structures

exp_mgors_progenitor_demand_mapping

Build a cell-type-resolved map of proliferative demand and replication stress in human embryonic auricular cartilage, patellar anlage and mammary bud, and test whether a licensing-deficient background preferentially depletes progenitors in exactly those compartments.

Decision criterion

Preferential progenitor depletion in the MGORS-vulnerable compartments relative to matched control compartments supports proliferative demand as the selectivity mechanism.

Supporting outcome

MGORS-vulnerable compartments show the highest proliferative demand and the greatest progenitor loss under a licensing-deficient background

Refuting outcome

Progenitor loss is uniform across compartments, implicating a tissue-specific signaling requirement instead

Show evidence (1 reference)

PMID:23023959 SUPPORT Human Clinical

"we highlight that growth is disproportionately affected in certain structures"

Documents the disproportionate, structure-selective growth failure whose mechanism this gap concerns.

Does the GINS3 D24 mouse model, which is embryonic lethal, faithfully represent human GINS3-related Meier-Gorlin syndrome, in which affected individuals survive?

HUMAN MODEL MISMATCH OPEN mismatch_mgors_gins3_mouse_lethality

Attached to

pathophysiology#Global Prenatal and Postnatal Growth Restriction

Homozygous D24 mouse embryos show intrauterine growth retardation and do not survive to birth, while the seven humans reported with the corresponding hypomorphic GINS3 genotypes survive with an MGORS-like phenotype. The mouse therefore recapitulates growth restriction but overshoots on severity, so mechanistic inferences drawn from it, particularly the accelerated senescence of the derived fibroblasts, may reflect a more complete loss of function than human disease alleles produce.

Proposed experiments

Humanized GINS3 allelic series calibrating mouse severity against patient fibroblasts

exp_mgors_gins3_humanized_allelic_series

Generate a mouse allelic series carrying the specific human GINS3 hypomorphic substitutions at matched residues, and compare residual protein level, fork progression and senescence markers against patient-derived fibroblasts to calibrate where the human alleles sit on the murine severity curve.

Decision criterion

Concordance of residual protein level, fork speed and senescence markers between the humanized mice and patient fibroblasts establishes the translational validity of the murine readouts.

Supporting outcome

Humanized alleles produce viable mice whose fibroblast phenotypes match patient cells, validating the model

Refuting outcome

Humanized alleles remain lethal or produce senescence far exceeding patient cells, confining the model to loss-of-function extremes

Show evidence (1 reference)

PMID:35603789 SUPPORT Model Organism

"We further showed that mouse embryos homozygous for a D24 variant presented intrauterine growth retardation and did not survive to birth"

Documents the murine lethality that the surviving human patients do not show, which is the mismatch at issue.

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Pathophysiology

11

Hypomorphic Pre-Replication Complex Defect

Biallelic partial loss-of-function variants in ORC1, ORC4, ORC6, CDT1 or CDC6 reduce the level, stability, chromatin association or complex assembly of pre-replication complex components. Because these are essential genes, only hypomorphic allele combinations are compatible with survival, and residual activity largely sets disease severity.

ORC1 hgnc:8487 ORC4 hgnc:8490 ORC6 hgnc:17151 CDT1 hgnc:24576 CDC6 hgnc:1744

DNA replication origin binding GO:0003688 ↓ DECREASED

Downstream

Impaired Replication Origin Licensing Loss of ORC, CDC6 or CDT1 function reduces the efficiency with which MCM2-7 is loaded onto origins during G1.

Show evidence (2 references)

PMID:21358632 SUPPORT Human Clinical

"All of these genes encode components of the pre-replication complex, implicating defects in replication licensing as the cause of a genetic syndrome with distinct developmental abnormalities."

Establishes the pre-replication complex as the shared molecular lesion of MGORS.

PMID:21358633 SUPPORT In Vitro

"We establish that these mutations disrupt known ORC1 functions including pre-replicative complex formation and origin activation."

Functional demonstration that patient ORC1 alleles impair pre-replicative complex formation and origin activation.

Loss of ORC1 BAH Recognition of H4K20me2

In metazoans, ORC is directed to origins by chromatin rather than by DNA sequence, and the ORC1 BAH domain performs that reading step by binding histone H4 dimethylated at lysine 20. MGORS-associated BAH domain mutations abrogate this recognition, reducing ORC1 occupancy at origins and ORC chromatin loading. This is a candidate explanation for why the ORC1 arm sits at the severe end of the clinical gradient, since it removes the targeting step upstream of licensing rather than merely reducing licensing capacity.

ORC1 hgnc:8487

DNA replication origin binding GO:0003688 ↓ DECREASED

Downstream

Impaired Replication Origin Licensing Failure to read H4K20me2 leaves ORC poorly positioned at origins, so fewer pre-replicative complexes are assembled.

Show evidence (2 references)

PMID:22398447 SUPPORT In Vitro

"H4K20me2 is enriched at replication origins, and abrogating ORC1 recognition of H4K20me2 in cells impairs ORC1 occupancy at replication origins, ORC chromatin loading and cell-cycle progression."

Demonstrates that loss of the ORC1 BAH to H4K20me2 interaction impairs origin occupancy, chromatin loading and cell-cycle progression.

PMID:22398447 SUPPORT Model Organism

"We find that wild-type human ORC1, but not ORC1-H4K20me2-binding mutants, rescues the growth retardation of orc1 morphants."

Rescue experiment establishing that H4K20me2 binding specifically, not ORC1 protein presence alone, is what the growth phenotype depends on.

Stabilized Geminin and Excess Licensing Inhibition

De novo heterozygous GMNN variants remove the N-terminal destruction box that normally targets geminin for degradation by the anaphase-promoting complex. The resulting stabilized geminin persists and continues to inhibit CDT1, so the dominant arm of MGORS reaches the same licensing deficit by gaining an inhibitor rather than losing an activator.

GMNN hgnc:17493

Downstream

Impaired Replication Origin Licensing Persistent geminin sustains CDT1 inhibition, blocking MCM2-7 loading in G1.

Show evidence (1 reference)

PMID:26637980 SUPPORT Human Clinical

"Geminin is present during the S, G2, and M phases of the cell cycle and is degraded during the metaphase-anaphase transition by the anaphase-promoting complex (APC), which recognizes the destruction box sequence near the 5' end of the geminin protein."

Describes the normal destruction-box-dependent turnover of geminin that the MGORS alleles abolish.

Impaired Replication Origin Licensing

The convergent molecular consequence of both the loss-of-activator and the gain-of-inhibitor arms is inefficient assembly of the pre-replicative complex during G1, leaving fewer origins licensed and available to fire in S phase. Notably, the measured licensing deficit in patient cells does not track linearly with S-phase progression rate, so licensing capacity alone does not predict clinical severity.

pre-replicative complex assembly GO:0006267 ↓ DECREASED DNA replication initiation GO:0006270 ↓ DECREASED

Downstream

Delayed S-Phase Entry and Reduced Cell Proliferation Fewer licensed origins slow S-phase entry and lengthen the cell cycle.

Impaired Centriole Duplication and Primary Cilium Formation Origin licensing proteins are independently required for centriole copy number control and ciliogenesis, a non-replicative route out of the same lesion.

Show evidence (2 references)

PMID:27374770 SUPPORT Human Clinical

"Impaired licensing of origins of replication during the G1 phase of the cell cycle has been implicated in Meier-Gorlin syndrome (MGS), a disorder defined by the triad of short stature, microtia, and a/hypoplastic patellae."

States the central licensing-deficit model linking the molecular lesion to the clinical triad.

PMID:23516378 SUPPORT In Vitro

"Here, we show that although origin licensing capacity is impaired in all patient cells with mutations in origin licensing component proteins, this does not correlate with the rate of progression through S phase."

Confirms the licensing deficit in all patient cells but qualifies the simple licensing-to-severity model, motivating the parallel ciliary arm.

Impaired CMG Helicase Assembly and Origin Firing

A second mechanistic module lies downstream of licensing: CDC45, the GINS subunits GINS2 and GINS3, the MCM2-7 core subunits MCM3, MCM5 and MCM7, and the replisome factor DONSON build and activate the CDC45-MCM2-7-GINS (CMG) replicative helicase. Hypomorphic variants here leave origins licensed but unable to fire efficiently, and additionally slow ongoing fork progression during S phase. DONSON is the outlier of the set: it has no role in the pre-replication or pre-initiation complexes themselves, and its requirement for CDC45 and GINS chromatin loading was only established in 2023.

CDC45 hgnc:1739 GINS2 hgnc:24575 GINS3 hgnc:25851 MCM5 hgnc:6948 MCM3 hgnc:6945 MCM7 hgnc:6950 DONSON hgnc:2993

DNA replication preinitiation complex assembly GO:0071163 ↓ DECREASED

DNA helicase activity GO:0003678 ↓ DECREASED

Downstream

Delayed S-Phase Entry and Reduced Cell Proliferation Inefficient origin firing and slowed fork progression prolong S phase.

Cranial Suture Dysregulation and Premature Fusion The CMG-module arms (CDC45, GINS2) are specifically enriched for craniosynostosis, a phenotype not typical of the licensing-module arms.

Show evidence (5 references)

PMID:27374770 SUPPORT Human Clinical

"CDC45 encodes a component of both the pre-initiation (preIC) and CMG helicase complexes, required for initiation of DNA replication origin firing and ongoing DNA synthesis during S-phase itself, respectively, and hence is functionally distinct from previously identified MGS-associated genes."

Defines the pre-initiation/CMG module as mechanistically distinct from origin licensing while converging on the same disease.

PMID:34353863 SUPPORT In Vitro

"the missense change possibly disrupts the effective interaction between the GINS complex and CDC45, which is necessary for the CMG helicase complex (Cdc45/MCM2-7/GINS) to accurately operate"

Localizes the GINS2 lesion to the CDC45 docking interface required for CMG function.

PMID:35603789 SUPPORT In Vitro

"These variants shortened the protein half-life, altered key protein interactions at the replisome, and negatively influenced DNA replication fork progression."

Shows that CMG-module variants act both on replisome assembly and on ongoing fork progression.

+ 2 more references

Delayed S-Phase Entry and Reduced Cell Proliferation

Patient cells enter S phase late, accumulate within S phase, and progress through the cell cycle slowly. The proliferative shortfall is the shared cellular phenotype of every molecular arm, and in severe alleles it tips over into premature senescence.

fibroblast CL:0000057

cell population proliferation GO:0008283 ↓ DECREASED DNA replication GO:0006260 ↓ DECREASED

Downstream

Global Prenatal and Postnatal Growth Restriction A cell-autonomous proliferation deficit during rapid embryonic and infant growth yields fewer cells and reduced body size.

Tissue-Disproportionate Growth Failure Structures whose development depends on narrow windows of intense proliferation are affected out of proportion to overall body size.

Decreased total neutrophil count Neutropenia is reported in this disorder; granulopoiesis is highly proliferative, which is the plausible route, though it has not been shown directly.

Show evidence (3 references)

PMID:21358633 SUPPORT In Vitro

"ORC1 deficiency perturbs S-phase entry and S-phase progression."

Direct demonstration of the S-phase defect in ORC1-deficient cells.

PMID:28198391 SUPPORT In Vitro

"Moreover cell-cycle progression was delayed in patient's cells, as already shown for mutations in the ORC1 gene."

Shows the same cell-cycle delay arises from an MCM-core lesion, supporting convergence across molecular arms.

PMID:35603789 SUPPORT In Vitro

"We found that MGS-associated GINS3 variants affecting aspartic acid 24 (D24) compromised cell proliferation and caused accumulation of cells in S phase."

Quantifies the proliferative deficit and S-phase accumulation in the GINS3 arm.

Impaired Centriole Duplication and Primary Cilium Formation

Origin licensing proteins have a non-replicative requirement in centrosome and centriole copy number control. ORC1-deficient patient cells and cells depleted of licensing proteins form primary cilia poorly, adding a ciliopathy-like arm to the pathogenesis that is independent of the replication rate itself.

fibroblast CL:0000057

cilium assembly GO:0060271 ↓ DECREASED

Downstream

Reduced Hedgehog Signaling and Impaired Chondroinduction Primary cilia are the obligate platform for vertebrate Hedgehog signal transduction, so a ciliogenesis defect blunts downstream Hedgehog output.

Show evidence (2 references)

PMID:23516378 SUPPORT In Vitro

"ORC1-deficient cells from MGS patients and siRNA-mediated depletion of origin licensing proteins also have impaired centrosome and centriole copy number."

Documents the centriole copy number defect underlying the ciliary arm.

PMID:23516378 SUPPORT In Vitro

"As a novel and unexpected finding, we show that they also display a striking defect in the rate of formation of primary cilia."

Establishes impaired primary cilium formation as a distinct cellular consequence of licensing protein deficiency.

Reduced Hedgehog Signaling and Impaired Chondroinduction

Blunted ciliary Hedgehog signaling in patient fibroblasts is accompanied by impaired chondroinduction in cell-based assays, offering a mechanism for the cartilage-derived structures that are disproportionately affected in MGORS (external ear, patella) beyond simple global proliferation loss.

chondrocyte CL:0000138

smoothened signaling pathway GO:0007224 ↓ DECREASED chondrocyte differentiation GO:0002062 ↓ DECREASED

Downstream

Tissue-Disproportionate Growth Failure Reduced chondroinduction preferentially compromises cartilage-derived structures such as the auricle and patella.

Show evidence (2 references)

PMID:23516378 SUPPORT In Vitro

"We demonstrate that this impacts sonic hedgehog signalling in ORC1-deficient primary fibroblasts."

Links the ciliogenesis defect to reduced Hedgehog signal transduction.

PMID:23516378 SUPPORT In Vitro

"Finally, using a cell-based model, we show that defects in cilia function impair chondroinduction."

Connects impaired cilium function to defective chondroinduction, a cell-based model rather than direct patient-tissue evidence.

Global Prenatal and Postnatal Growth Restriction

The organism-level consequence is severe growth failure beginning in utero. Growth velocity is most impaired during pregnancy and the first year of life, after which height tracks parallel to normal centiles from a much lower starting point, producing a mean adult height near four and a half standard deviations below the mean.

Downstream

Intrauterine growth retardation Prenatal arm of the licensing-driven proliferation deficit.

Short stature Postnatal arm of the same deficit.

Microcephaly Neural progenitor expansion is licensing-dependent; microcephaly is variable in this disorder but follows the same route.

Delayed skeletal maturation Skeletal maturation lags because growth-plate chondrocyte turnover shares the S-phase delay.

Feeding difficulties Grouped with the growth phenotype, which it compounds; no independent mechanism is established.

Decreased response to growth hormone stimulation test A cell-intrinsic proliferation defect limits the response to GH, which is why this is a growth-hormone-resistant rather than deficient state.

Show evidence (3 references)

PMID:23023959 SUPPORT Human Clinical

"growth velocity (length) is impaired in MGS during pregnancy and first year of life, but, thereafter, height increases in paralleled normal reference centiles, resulting in a mean adult height of -4.5 standard deviations (SD)"

Defines the natural history of growth failure in the largest MGORS cohort.

PMID:21358633 SUPPORT Model Organism

"we show that Orc1 depletion in zebrafish is sufficient to markedly reduce body size during rapid embryonic growth"

Model-organism confirmation that a licensing defect alone is sufficient to restrict organismal growth.

PMID:35603789 SUPPORT Model Organism

"We further showed that mouse embryos homozygous for a D24 variant presented intrauterine growth retardation and did not survive to birth, and that fibroblasts derived from these embryos displayed accelerated cellular senescence."

Mouse model recapitulating intrauterine growth restriction and linking the CMG-module lesion to premature senescence.

Tissue-Disproportionate Growth Failure

Growth failure in MGORS is not uniform. External ear cartilage, the patella, mammary tissue and the external genitalia are affected out of proportion to overall stature, which is why the clinical triad and the mammary and genital findings, rather than short stature alone, define the syndrome.

Downstream

Microtia The defining ear anomaly. Ear cartilage is among the tissues most sensitive to the licensing defect, which is what makes the growth failure disproportionate rather than uniform.

Patellar aplasia The defining patellar anomaly; patellar development is selectively vulnerable across the origin-licensing disorders.

Patellar hypoplasia The milder form of the same selective vulnerability.

Patellar dislocation Mechanical consequence of the hypoplastic or absent patella.

Micrognathia Craniofacial skeletal expression of the disproportionate growth failure.

Narrow mouth Grouped with the craniofacial findings.

Breast hypoplasia Mammary tissue is among the selectively affected tissues; grouped with the other disproportionate deficits.

Hypoplastic labia minora Genital hypoplasia, grouped with the other tissue-selective deficits.

Clitoral hypertrophy Reported genital finding; grouped here, with no established route.

Cryptorchidism Male genital finding, grouped with the other tissue-selective developmental deficits.

Lipodystrophy Adipose tissue deficit reported in this disorder; grouped with the other tissue-selective findings, with no established mechanism.

Emphysema Pulmonary finding reported in a subset; grouped here, with no established route from origin licensing to alveolar structure.

Hearing impairment Often conductive and secondary to the microtia and middle-ear anomalies; grouped with the craniofacial arm.

Show evidence (1 reference)

PMID:23023959 SUPPORT Human Clinical

"we highlight that growth is disproportionately affected in certain structures, with growth related minor genital abnormalities (42%) and mammary hypoplasia (100%) frequently present, in addition to established effects on ears and patellar growth"

Directly establishes the tissue-disproportionate pattern of growth failure that defines the syndrome's recognizable phenotype.

Cranial Suture Dysregulation and Premature Fusion

In the CMG-module arms, and particularly CDC45 and GINS2, the replication defect additionally perturbs cranial suture homeostasis, producing coronal craniosynostosis that can dominate the presentation even when growth restriction is comparatively mild.

Downstream

Craniosynostosis The direct endpoint of this node; it is the GINS2-associated presentation rather than a feature of every genotype.

Show evidence (2 references)

PMID:27374770 SUPPORT Human Clinical

"Our findings therefore implicate the preIC as an additional protein complex involved in the etiology of MGS and connect the core cellular machinery of genome replication with growth, chondrogenesis, and cranial suture homeostasis."

Explicitly connects the replication machinery to cranial suture homeostasis in the CDC45 arm.

PMID:27374770 SUPPORT Human Clinical

"The phenotypes of affected individuals range from syndromic coronal craniosynostosis to severe growth restriction, fulfilling diagnostic criteria for Meier-Gorlin syndrome."

Documents the phenotypic range from craniosynostosis-predominant to growth-predominant presentations within one gene arm.

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Pathograph

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Phenotypes

21

Blood 1

Decreased total neutrophil count HP:0001875

Show evidence (2 references)

PMID:37059840 SUPPORT Human Clinical

"Interestingly, many individuals showed neutropenia (4/5 cases), with one also showing B lymphopenia."

Quantifies neutropenia in 4 of 5 individuals in the GINS3 cohort.

PMID:37059840 SUPPORT Human Clinical

"Given the unique overlap of MGORS and neutropenia in GINS3 individuals, these features could be used diagnostically as differentials in candidate gene testing."

Establishes the gene-arm specificity of the finding and its proposed diagnostic use.

Breast 1

Breast hypoplasia VERY_FREQUENT HP:0003187

Show evidence (1 reference)

PMID:22333897 SUPPORT Human Clinical

"Additional frequent clinical features were mammary hypoplasia (100%) and abnormal genitalia (42%; predominantly cryptorchidism and hypoplastic labia minora/majora)."

Reports complete penetrance of mammary hypoplasia among evaluated individuals, supporting VERY_FREQUENT.

Digestive 1

Feeding difficulties HP:0011968

Show evidence (1 reference)

PMID:26381604 SUPPORT Human Clinical

"Associated clinical features encompass feeding problems, congenital pulmonary emphysema, mammary hypoplasia in females and urogenital anomalies"

Lists feeding problems among the characteristic associated features requiring management.

Ear 1

Hearing impairment HP:0000365

Show evidence (1 reference)

PMID:26381604 SUPPORT Human Clinical

"prevention of associated problems, such as growth retardation, feeding problems, hearing loss, luxating patellae, knee pain, gonarthrosis"

The management review lists hearing loss among the associated problems requiring surveillance.

Genitourinary 2

Cryptorchidism FREQUENT HP:0000028

Show evidence (2 references)

PMID:22333897 SUPPORT Human Clinical

"abnormal genitalia (42%; predominantly cryptorchidism and hypoplastic labia minora/majora)"

Quantifies genital anomalies at 42% of the cohort, with cryptorchidism predominant.

PMID:42496035 SUPPORT Human Clinical

"Among males, cryptorchidism, hypoplastic scrotum and micropenis were common."

Independent systematic review describing cryptorchidism as common among affected males, supporting the FREQUENT band for the male-specific denominator.

Clitoral hypertrophy OCCASIONAL HP:0008665

Show evidence (1 reference)

PMID:42496035 SUPPORT Human Clinical

"Among females, all post-pubertal cases had mammary hypoplasia, while 23.5% had clitoromegaly with hypoplastic labia."

Quantifies clitoromegaly at 23.5% of post-pubertal females, supporting an OCCASIONAL band.

Head and Neck 4

Microcephaly FREQUENT HP:0000252

Show evidence (2 references)

PMID:21358632 SUPPORT Human Clinical

"although microcephaly is often evident, intellect is usually normal in this syndrome"

Supports a FREQUENT (often evident) band for microcephaly and records the dissociation from intellectual outcome.

PMID:23023959 SUPPORT Human Clinical

"Height is dependent on ethnic background and underlying molecular cause, with ORC1 and ORC4 mutations causing more severe short stature and microcephaly."

Documents the gene-dependent gradient in microcephaly severity.

Micrognathia FREQUENT HP:0000347

Show evidence (1 reference)

PMID:26381604 SUPPORT Human Clinical

"Typical facial characteristics during childhood comprise a small mouth with full lips and micro-retrognathia."

Describes the characteristic facial gestalt including micro-retrognathia.

Narrow mouth HP:0000160

Show evidence (1 reference)

PMID:26381604 SUPPORT Human Clinical

"Typical facial characteristics during childhood comprise a small mouth with full lips and micro-retrognathia."

Documents the small mouth as part of the characteristic facial phenotype.

Craniosynostosis HP:0001363

Show evidence (1 reference)

PMID:27374770 SUPPORT Human Clinical

"The phenotypes of affected individuals range from syndromic coronal craniosynostosis to severe growth restriction, fulfilling diagnostic criteria for Meier-Gorlin syndrome."

Establishes craniosynostosis within the MGORS phenotypic range in the CDC45 arm.

Musculoskeletal 2

Delayed skeletal maturation FREQUENT HP:0002750

Show evidence (1 reference)

PMID:42496035 SUPPORT Human Clinical

"with 70% exhibiting delayed bone age, 42.9% low IGF-1 and 35.3% GHD"

Quantifies delayed bone age at 70% of reviewed cases, supporting a FREQUENT band.

Lipodystrophy VERY_RARE HP:0009125

Show evidence (1 reference)

PMID:33654309 SUPPORT Human Clinical

"the second case has a multi-system disorder with neonatal progeroid appearance, lipodystrophy and adrenal insufficiency"

Documents lipodystrophy at the progeroid pole of the MCM-related phenotypic spectrum.

Respiratory 1

Emphysema HP:0002097

Show evidence (2 references)

PMID:26381604 SUPPORT Human Clinical

"possible pulmonary complications due to congenital pulmonary emphysema with or without broncho- or laryngomalacia"

Documents congenital pulmonary emphysema and the associated airway malacia as management concerns.

PMID:22333897 SUPPORT Human Clinical

"compound heterozygous mutations appeared to have a more severe effect on phenotype, causing more severe growth retardation in ORC4 and more frequently pulmonary emphysema in CDT1"

Establishes the genotype dependence of pulmonary emphysema within the CDT1 arm.

Growth 2

Short stature VERY_FREQUENT HP:0004322

Show evidence (1 reference)

PMID:42496035 SUPPORT Human Clinical

"Short stature was almost universal (median height-Z-score -4.4), with 70% exhibiting delayed bone age, 42.9% low IGF-1 and 35.3% GHD."

Systematic review quantifying the near-universal frequency and severity of short stature, supporting the VERY_FREQUENT band.

Intrauterine growth retardation VERY_FREQUENT HP:0001511

Show evidence (1 reference)

PMID:21358632 SUPPORT Human Clinical

"Both pre- and post-natal growth are impaired in this disorder, and although microcephaly is often evident, intellect is usually normal in this syndrome."

Establishes that growth impairment is both prenatal and postnatal.

Other 6

Microtia VERY_FREQUENT HP:0008551

Show evidence (1 reference)

PMID:22333897 SUPPORT Human Clinical

"The triad of microtia, absent/hypoplastic patellae, and short stature was observed in 82% of individuals with MGS."

Quantifies the frequency of the complete triad, including microtia, in a 45-patient cohort, supporting a VERY_FREQUENT band.

Patellar aplasia HP:0006443

Show evidence (1 reference)

PMID:21358632 SUPPORT Human Clinical

"an autosomal recessive primordial dwarfism syndrome characterized by absent or hypoplastic patellae and markedly small ears"

Establishes absent patellae as a defining feature of the syndrome.

Patellar hypoplasia HP:0003065

Show evidence (1 reference)

PMID:34353863 SUPPORT Human Clinical

"particularly those with craniosynostosis, mild short stature and patellar hypoplasia"

Documents patellar hypoplasia as the patellar phenotype of the CMG-module arms.

Patellar dislocation HP:0002999

Show evidence (1 reference)

PMID:26381604 SUPPORT Human Clinical

"prevention of associated problems, such as growth retardation, feeding problems, hearing loss, luxating patellae, knee pain, gonarthrosis"

The management review lists luxating patellae, knee pain and gonarthrosis among the problems requiring active prevention.

Hypoplastic labia minora HP:0000064

Show evidence (1 reference)

PMID:26381604 SUPPORT Human Clinical

"urogenital anomalies, such as cryptorchidism and hypoplastic labia minora and majora"

Clinical review listing hypoplastic labia among the characteristic urogenital anomalies.

Decreased response to growth hormone stimulation test FREQUENT HP:0000824

Show evidence (1 reference)

PMID:42496035 SUPPORT Human Clinical

"42.9% low IGF-1 and 35.3% GHD"

Quantifies growth hormone deficiency at 35.3% of reviewed cases, supporting a FREQUENT band.

🧬

Genetic Associations

13

ORC1 (Pathogenic Variants)

Gene: ORC1 hgnc:8487 relationship_type: CAUSATIVE

Show evidence (1 reference)

PMID:21358633 SUPPORT Human Clinical

"Here we report that mutations in ORC1, encoding a subunit of the origin recognition complex, cause microcephalic primordial dwarfism resembling Meier-Gorlin syndrome."

Original identification of ORC1 as an MGORS-spectrum disease gene.

ORC4 (Pathogenic Variants)

Gene: ORC4 hgnc:8490 relationship_type: CAUSATIVE

Show evidence (1 reference)

PMID:21358632 SUPPORT Human Clinical

"we identify mutations in five separate genes: ORC1, ORC4, ORC6, CDT1 and CDC6"

Identifies ORC4 among the five founding MGORS genes.

ORC6 (Pathogenic Variants)

Gene: ORC6 hgnc:17151 relationship_type: CAUSATIVE

Show evidence (1 reference)

PMID:21358632 SUPPORT Human Clinical

"we identify mutations in five separate genes: ORC1, ORC4, ORC6, CDT1 and CDC6"

Identifies ORC6 among the five founding MGORS genes.

CDT1 (Pathogenic Variants)

Gene: CDT1 hgnc:24576 relationship_type: CAUSATIVE

Show evidence (1 reference)

PMID:39789585 SUPPORT Human Clinical

"The variant was predicted to break a branch point and alter splicing, and the minigene assay confirmed abnormal splicing with exon 3 skipping."

Functionally validated deep-intronic CDT1 allele expanding the recognized variant spectrum.

CDC6 (Pathogenic Variants)

Gene: CDC6 hgnc:1744 relationship_type: CAUSATIVE

Show evidence (1 reference)

PMID:35023948 SUPPORT Human Clinical

"the patient had two previously undescribed variants in the CDC6 gene, c.230A>G (p.(Lys77Arg)) and c.232C>T (p.(Gln78Ter)), NM_001254.3, in a compound heterozygous state"

Documents biallelic CDC6 variants in a molecularly confirmed MGORS patient.

GMNN (Pathogenic Variants)

Gene: GMNN hgnc:17493 relationship_type: CAUSATIVE

Show evidence (1 reference)

PMID:26637980 SUPPORT Human Clinical

"we report three subjects with MGS and de novo heterozygous mutations in the 5' end of GMNN, encoding the DNA replication inhibitor geminin"

Original identification of the dominant GMNN arm of MGORS.

CDC45 (Pathogenic Variants)

Gene: CDC45 hgnc:1739 relationship_type: CAUSATIVE

Show evidence (1 reference)

PMID:27374770 SUPPORT Human Clinical

"Functionally, mutations reduce levels of full-length transcripts and protein in subject cells, consistent with partial loss of CDC45 function and a predicted limited rate of DNA replication and cell proliferation."

Functional evidence that CDC45 alleles act by partial loss of function.

MCM5 (Pathogenic Variants)

Gene: MCM5 hgnc:6948 relationship_type: CAUSATIVE

Show evidence (1 reference)

PMID:28198391 SUPPORT In Vitro

"Complementation experiments in yeast showed that the plasmid carrying the missense variant was unable to rescue the lethal phenotype caused by mcm5 deletion."

Functional complementation evidence establishing pathogenicity of the MCM5 missense allele.

MCM7 (Pathogenic Variants)

Gene: MCM7 hgnc:6950 relationship_type: CAUSATIVE

Show evidence (1 reference)

PMID:33654309 SUPPORT Human Clinical

"We confirm variants in MCM7 are deleterious and through interfering with MCM complex formation, impact efficiency of S phase progression."

Establishes MCM7 pathogenicity and its mechanism through impaired MCM complex formation.

MCM3 (Candidate Gene)

Gene: MCM3 hgnc:6945 relationship_type: DISPUTED

Show evidence (1 reference)

PMID:33654309 SUPPORT Human Clinical

"we identify biallelic pathogenic variants in MCM7 and a strong candidate biallelic pathogenic variant in MCM3"

The authors themselves grade MCM3 as a strong candidate rather than an established gene, so the association is recorded as partial.

GINS2 (Pathogenic Variants)

Gene: GINS2 hgnc:24575 relationship_type: CAUSATIVE

Show evidence (1 reference)

PMID:34353863 SUPPORT Human Clinical

"A novel homozygous missense variant NM_016095.2:c.341G>T, p.(Arg114Leu), in GINS2 was identified."

Identifies the specific biallelic GINS2 allele causing MGORS with craniosynostosis.

GINS3 (Pathogenic Variants)

Gene: GINS3 hgnc:25851 relationship_type: CAUSATIVE

Show evidence (1 reference)

PMID:35603789 SUPPORT Human Clinical

"Taken together, our findings implicate GINS3 in the pathogenesis of MGS and support the notion that hypomorphic variants identified in this gene impaired cell and organismal growth by compromising DNA replication."

Establishes GINS3 as an MGORS gene acting through compromised DNA replication.

DONSON (Pathogenic Variants)

Gene: DONSON hgnc:2993 relationship_type: CAUSATIVE

Show evidence (3 references)

PMID:37059840 SUPPORT Human Clinical

"DONSON as a novel disease gene in several MGORS patients"

Establishes DONSON as a human MGORS disease gene identified by exome and phased genome sequencing across multiple patients.

PMID:37059840 SUPPORT Human Clinical

"All of the DONSON-MGORS cohort had short stature, microtia and patella agenesis"

Confirms that the DONSON cohort shows the complete MGORS clinical triad, not merely an overlapping growth phenotype.

PMID:37059840 SUPPORT In Vitro

"the substitutions reduced nuclear localisation of DONSON, and a deep intronic variant introduces a novel strong splice acceptor site causing a reading frameshift and premature stop codon"

Functional evidence for the hypomorphic mechanism of the DONSON alleles, including a protein-localization route distinct from the other genes.

💊

Medical Actions

7

Growth hormone therapy

Action: Pharmacotherapy NCIT:C15986

Agent: recombinant human growth hormone NCIT:C837

Recombinant growth hormone is used off-label for short stature. It is ineffective in most individuals, whose growth velocity normalizes after the first year of life without treatment, but a subgroup benefits: those with documented growth hormone deficiency, delayed bone age, or low IGF-1, in whom substantial height gains have been reported. Screening for growth hormone deficiency is therefore recommended before deciding.

Mechanism Target:

INHIBITS Global Prenatal and Postnatal Growth Restriction — Growth hormone acts on the organism-level growth deficit rather than on the upstream replication lesion, which is why it can only partially offset the phenotype and only in the subgroup with a demonstrable growth-hormone-axis abnormality.

Show evidence (5 references)

PMID:26381604 SUPPORT Human Clinical

"Growth hormone treatment is ineffective in most patients with MGS, but may be effective in patients in whom growth continues to decrease after the first year of life"

Establishes that growth hormone benefit is restricted to a subgroup rather than being a general therapy.

PMID:23023959 SUPPORT Human Clinical

"Growth hormone therapy (n = 9) was generally ineffective, though in two patients with significantly reduced IGF1 levels, growth was substantially improved by GH treatment, with 2SD and 3.8 SD improvement in height."

Cohort data showing general ineffectiveness alongside marked benefit in the low-IGF1 subgroup.

PMID:42496035 SUPPORT Human Clinical

"Those with GHD and delayed bone age were more likely to benefit from GH."

Identifies the clinical predictors that select responders to growth hormone therapy.

+ 2 more references

Estrogen therapy for mammary hypoplasia

Action: Pharmacotherapy NCIT:C15986

Agent: estradiol CHEBI:16469

Estrogen treatment has been reported to be of some benefit for breast hypoplasia, although reported effects are variable and the evidence base is limited to small series.

Mechanism Target:

INHIBITS Tissue-Disproportionate Growth Failure — Estrogen acts on the mammary component of the disproportionate growth failure, downstream of the replication lesion.

Show evidence (1 reference)

PMID:22333897 SUPPORT Human Clinical

"Growth hormone and estrogen treatment may be of some benefit, respectively, to growth retardation and breast hypoplasia, though further studies in this patient group are needed."

Reports possible benefit of estrogen for breast hypoplasia while flagging the weakness of the evidence.

Orthopedic management of patellar instability

Action: orthopedic surgical procedure Ontology label: Orthopedic Surgical Procedure NCIT:C16186

Surveillance and treatment of luxating patellae, knee pain and secondary gonarthrosis, including physical therapy and surgical stabilization when indicated.

Show evidence (1 reference)

PMID:26381604 SUPPORT Human Clinical

"prevention of associated problems, such as growth retardation, feeding problems, hearing loss, luxating patellae, knee pain, gonarthrosis"

Identifies patellar instability and its sequelae as targets of active management.

Pulmonary surveillance and respiratory support

Action: supportive care Ontology label: Supportive Care NCIT:C15747

Monitoring for and management of congenital pulmonary emphysema and associated bronchomalacia or laryngomalacia, which can cause significant respiratory morbidity in infancy.

Show evidence (1 reference)

PMID:26381604 SUPPORT Human Clinical

"possible pulmonary complications due to congenital pulmonary emphysema with or without broncho- or laryngomalacia"

Establishes pulmonary complications as a management priority.

Feeding support

Action: nutritional support Ontology label: Nutritional Support NCIT:C15433

Nutritional and feeding support in infancy, including management of reflux, addressing a common contributor to early morbidity and postnatal growth failure.

Show evidence (1 reference)

PMID:26381604 SUPPORT Human Clinical

"Management should be directed towards in-depth investigation, treatment and prevention of associated problems, such as growth retardation, feeding problems"

Identifies feeding problems as an explicit target of the recommended management plan.

Audiologic assessment and hearing intervention

Action: supportive care Ontology label: Supportive Care NCIT:C15747

Hearing assessment and intervention, warranted by the external ear malformation and the documented hearing loss.

Show evidence (1 reference)

PMID:26381604 SUPPORT Human Clinical

"prevention of associated problems, such as growth retardation, feeding problems, hearing loss"

Lists hearing loss among the problems requiring surveillance and intervention.

Craniofacial surgery for craniosynostosis

Action: surgical procedure Ontology label: Surgical Procedure NCIT:C15329

Surgical correction of clinically significant premature suture fusion, relevant particularly in the CDC45- and GINS2-related arms.

Show evidence (1 reference)

PMID:27374770 SUPPORT Human Clinical

"Here we report the identification of mutations in CDC45 in 15 affected individuals from 12 families with MGS and/or craniosynostosis."

Establishes the craniosynostosis burden that makes craniofacial surgical management relevant; the paper documents the indication rather than evaluating the surgery itself.

🔬

Diagnosis

3

Clinical triad criteria

The diagnosis should be considered when at least two of the three cardinal features are present: microtia, patellar anomalies, and pre- and postnatal growth retardation. Requiring the complete triad would miss a substantial minority, since the full triad is present in roughly 82% of molecularly confirmed individuals.

physical examination NCIT:C20989

Show evidence (1 reference)

PMID:26381604 SUPPORT Human Clinical

"The diagnosis MGS should be considered in patients with at least two of the three features of the clinical triad of microtia, patellar anomalies, and pre- and postnatal growth retardation."

States the two-of-three clinical diagnostic threshold recommended by the management review.

Patellar imaging

Because the patella ossifies late, patellar assessment must be age-appropriate: ultrasonography before age six and radiography thereafter. Skipping this step is a common reason the diagnosis is missed in a child presenting only with short stature and microtia.

ultrasound imaging NCIT:C17230

Show evidence (1 reference)

PMID:26381604 SUPPORT Human Clinical

"In patients with short stature and/or microtia, the patellae should be assessed with care by ultrasonography before age 6 or radiography thereafter."

Specifies the age-appropriate imaging modality for detecting patellar anomalies.

Molecular genetic testing

Molecular confirmation uses a primordial dwarfism panel spanning all thirteen replication-initiation genes, or exome or genome sequencing with copy-number analysis. Testing limited to the five founding pre-replication complex genes identifies only about two-thirds to three-quarters of patients, and exome-only pipelines can miss deep-intronic splice-altering alleles.

molecular genetic testing NCIT:C19770

Show evidence (2 references)

PMID:26381604 SUPPORT Human Clinical

"Mutations in one of five genes (ORC1, ORC4, ORC6, CDT1, and CDC6) of the pre-replication complex, involved in DNA-replication, are detected in approximately 67-78% of patients with MGS."

Quantifies the diagnostic yield of the original five-gene panel, motivating broader testing.

PMID:37059840 SUPPORT Human Clinical

"Following the initial identification of genetic causes in 2011, a total of 13 genes have been identified to date associated with MGORS."

Establishes the current thirteen-gene testing target for MGORS.

📊

Prevalence

1

Worldwide

Cases In Literature Ultra Rare

Roughly 150 cases had been published as of a 2026 systematic review; population incidence, carrier frequency and prevalence per 100,000 remain unknown, and the published-case count must not be converted into a population prevalence.

Show evidence (1 reference)

PMID:42496035 SUPPORT Human Clinical

"Among 29 cases (out of ~150 published), the classic triad was absent in 18.5%."

Anchors the size of the published literature, the only occurrence measure available for this disorder.

🔀

Differential Diagnoses

3

Conditions with similar clinical presentations that must be differentiated from Meier-Gorlin syndrome:

Seckel syndrome MONDO:0019342

Overlapping Features The other classical microcephalic primordial dwarfism caused by a replication-associated defect, but via the ATR DNA damage response and centrosome genes rather than origin licensing.

Distinguishing Features

Disproportionately severe microcephaly with intellectual disability, versus preserved intellect in MGORS
Bird-headed facial appearance rather than the small mouth and micro-retrognathia gestalt
Absence of microtia and patellar aplasia

Show evidence (1 reference)

PMID:21358633 SUPPORT Human Clinical

"Studies into disorders of extreme growth failure (for example, Seckel syndrome and Majewski osteodysplastic primordial dwarfism type II) have implicated fundamental cellular processes of DNA damage response signaling and centrosome function in the regulation of human growth."

Places Seckel syndrome and MOPD II as the mechanistically adjacent primordial dwarfisms that must be distinguished from MGORS.

Microcephalic osteodysplastic primordial dwarfism type II MONDO:0008872

Overlapping Features The other primordial dwarfism most often confused with MGORS, caused by biallelic PCNT variants affecting centrosome function rather than replication initiation. Shares extreme pre- and postnatal growth failure but is distinguished by disproportionately severe microcephaly, skeletal dysplasia, and a cerebrovascular risk (moyamoya, aneurysm) that MGORS does not carry.

Distinguishing Features

Cerebrovascular disease (moyamoya, intracranial aneurysm) is characteristic of MOPD II and not of MGORS
Skeletal dysplasia with disproportionate short stature, versus generally proportionate short stature in MGORS
Absence of microtia and patellar aplasia

Show evidence (1 reference)

PMID:21358633 SUPPORT Human Clinical

"Studies into disorders of extreme growth failure (for example, Seckel syndrome and Majewski osteodysplastic primordial dwarfism type II) have implicated fundamental cellular processes of DNA damage response signaling and centrosome function in the regulation of human growth."

Names MOPD II alongside Seckel syndrome as the centrosome-and-damage-response primordial dwarfisms that MGORS must be distinguished from.

Hutchinson-Gilford progeria syndrome MONDO:0008310

Overlapping Features Considered in the differential when an MGORS infant presents with a neonatal progeroid appearance, lipodystrophy, thin skin and alopecia, as reported in CDC6-related and MCM7-related disease.

Distinguishing Features

Microtia with patellar aplasia favors MGORS
Progressive cardiovascular disease and alopecia dominate the progeria course

Show evidence (1 reference)

PMID:35023948 SUPPORT Human Clinical

"Differential diagnosis was performed with chromosomal abnormalities and Hutchinson-Gilford progeria."

Documents progeria as the differential actually entertained for a progeroid-appearing MGORS presentation.

🔬

Clinical Trials

1

NCT04569149 RECRUITING

Primordial Dwarfism Registry, an observational registry collecting natural history data across microcephalic primordial dwarfism and related conditions, including Meier-Gorlin syndrome. No MGORS-specific interventional trial has been identified.

Target Phenotypes: Short stature HP:0004322

Show evidence (1 reference)

clinicaltrials:NCT04569149 SUPPORT Human Clinical

"The goal of this registry is to collect information on individuals with forms of microcephalic primordial dwarfism as well as related conditions."

An observational registry that is the principal route to improved natural history data for this ultra-rare disorder.

{ }

Source YAML

click to show

name: Meier-Gorlin syndrome
creation_date: "2026-08-01T02:53:03Z"
description: >-
  Meier-Gorlin syndrome (MGORS, historically ear-patella-short stature syndrome)
  is a rare microcephalic primordial dwarfism disorder caused by hypomorphic
  defects in the machinery that licenses and fires DNA replication origins. It is
  defined by the clinical triad of bilateral microtia, absent or hypoplastic
  patellae, and severe pre- and postnatal growth restriction, with mammary
  hypoplasia and genital anomalies as additional characteristic features.
  Thirteen replication-associated genes spanning the pre-replication complex, the
  MCM2-7 helicase core, and the CDC45-MCM-GINS (CMG) activation module have been
  implicated; because complete loss of these essential factors is incompatible
  with development, disease alleles are almost always partial loss-of-function.
category: Mendelian
parents:
- syndromic disease
- autosomal recessive disease
synonyms:
- MGORS
- MGS
- ear-patella-short stature syndrome
- ear, patella, short stature syndrome
disease_term:
  preferred_term: Meier-Gorlin syndrome
  term:
    id: MONDO:0016817
    label: Meier-Gorlin syndrome
inheritance:
- name: Autosomal recessive inheritance
  description: >-
    Most MGORS is autosomal recessive, arising from biallelic partial
    loss-of-function (hypomorphic) variants in a replication-initiation gene.
    Homozygous or compound heterozygous null genotypes are not observed, since
    complete loss of these essential replication factors is presumed
    incompatible with survival.
  inheritance_term:
    preferred_term: Autosomal recessive inheritance
    term:
      id: HP:0000007
      label: Autosomal recessive inheritance
  evidence:
  - reference: PMID:21358632
    reference_title: "Mutations in the pre-replication complex cause Meier-Gorlin syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Meier-Gorlin syndrome (ear, patella and short-stature syndrome) is an autosomal recessive primordial dwarfism syndrome characterized by absent or hypoplastic patellae and markedly small ears"
    explanation: >-
      The gene-discovery study establishes autosomal recessive inheritance and
      the defining clinical triad.
  - reference: PMID:22333897
    reference_title: "Meier-Gorlin syndrome genotype-phenotype studies: 35 individuals with pre-replication complex gene mutations and 10 without molecular diagnosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "No homozygous or compound heterozygous null mutations were detected."
    explanation: >-
      Across the largest genotyped cohort, only hypomorphic biallelic genotypes
      were found, supporting the requirement for residual replication activity.
- name: Autosomal dominant inheritance
  description: >-
    A distinct dominant form arises from de novo heterozygous GMNN variants that
    delete the geminin destruction box, stabilizing the licensing inhibitor
    rather than disabling a licensing activator. This is the mechanistic and
    inheritance exception within MGORS.
  inheritance_term:
    preferred_term: Autosomal dominant inheritance
    term:
      id: HP:0000006
      label: Autosomal dominant inheritance
  evidence:
  - reference: PMID:26637980
    reference_title: "De Novo GMNN Mutations Cause Autosomal-Dominant Primordial Dwarfism Associated with Meier-Gorlin Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We present data supporting a gain-of-function mechanism, in which the GMNN mutations result in proteins lacking the destruction box and hence increased protein stability and prolonged inhibition of replication leading to autosomal-dominant MGS."
    explanation: >-
      Establishes the dominant, gain-of-function GMNN arm as an exception to
      the otherwise recessive inheritance of MGORS.
has_subtypes:
- name: MGORS1
  display_name: Meier-Gorlin syndrome 1 (ORC1-related)
  subtype_term:
    preferred_term: Meier-Gorlin syndrome 1
    term:
      id: MONDO:0009143
      label: Meier-Gorlin syndrome 1
  description: >-
    Caused by biallelic ORC1 variants, frequently affecting the N-terminal BAH
    chromatin-binding domain. This is the most severe growth arm of MGORS, with
    the shortest stature and smallest head circumference, and it is the subtype
    in which the non-replicative centriole and cilium phenotype has been
    documented.
  genes:
  - preferred_term: ORC1
    term:
      id: hgnc:8487
      label: ORC1
  evidence:
  - reference: PMID:22333897
    reference_title: "Meier-Gorlin syndrome genotype-phenotype studies: 35 individuals with pre-replication complex gene mutations and 10 without molecular diagnosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Individuals with ORC1 mutations had significantly shorter stature and smaller head circumferences than individuals from other gene categories."
    explanation: >-
      Establishes ORC1-related disease as the most severe growth and
      microcephaly subtype.
- name: MGORS2
  display_name: Meier-Gorlin syndrome 2 (ORC4-related)
  subtype_term:
    preferred_term: Meier-Gorlin syndrome 2
    term:
      id: MONDO:0013428
      label: Meier-Gorlin syndrome 2
  description: >-
    Caused by biallelic ORC4 variants. Together with ORC1, this arm carries the
    most severe short stature and microcephaly; compound heterozygous ORC4
    genotypes cause more severe growth retardation than homozygous missense
    genotypes.
  genes:
  - preferred_term: ORC4
    term:
      id: hgnc:8490
      label: ORC4
  evidence:
  - reference: PMID:26381604
    reference_title: "Meier-Gorlin syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Patients with ORC1 and ORC4 mutations appear to have the most severe short stature and microcephaly."
    explanation: >-
      Clinical review establishing the severity ranking of the ORC1 and ORC4
      arms.
- name: MGORS3
  display_name: Meier-Gorlin syndrome 3 (ORC6-related)
  subtype_term:
    preferred_term: Meier-Gorlin syndrome 3
    term:
      id: MONDO:0013430
      label: Meier-Gorlin syndrome 3
  description: >-
    Caused by biallelic ORC6 variants. ORC6 is the smallest origin recognition
    complex subunit and contributes to ORC assembly and MCM2-7 loading.
  genes:
  - preferred_term: ORC6
    term:
      id: hgnc:17151
      label: ORC6
  evidence:
  - reference: PMID:21358632
    reference_title: "Mutations in the pre-replication complex cause Meier-Gorlin syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "we identify mutations in five separate genes: ORC1, ORC4, ORC6, CDT1 and CDC6"
    explanation: >-
      Original identification of ORC6 among the five founding MGORS
      pre-replication complex genes.
- name: MGORS4
  display_name: Meier-Gorlin syndrome 4 (CDT1-related)
  subtype_term:
    preferred_term: Meier-Gorlin syndrome 4
    term:
      id: MONDO:0013431
      label: Meier-Gorlin syndrome 4
  description: >-
    Caused by biallelic CDT1 variants. CDT1 is the licensing factor that, with
    CDC6, loads MCM2-7 onto origin-bound ORC; it is also the direct target of
    geminin inhibition. Compound heterozygous CDT1 genotypes are more often
    associated with pulmonary emphysema, and the mutational spectrum extends to
    deep-intronic branch-point variants that exome pipelines can miss.
  genes:
  - preferred_term: CDT1
    term:
      id: hgnc:24576
      label: CDT1
  evidence:
  - reference: PMID:39789585
    reference_title: "A novel homozygous intronic variant in CDT1 that alters splicing causes Meier-Gorlin syndrome, and a review of published mutations and growth hormone treatments."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "A girl with microtia, hypoplastic patellae, and severe growth retardation carried a novel homozygous intronic variant"
    explanation: >-
      Documents a CDT1-related MGORS patient with the full triad and expands the
      CDT1 variant spectrum to deep-intronic splice-altering alleles.
- name: MGORS5
  display_name: Meier-Gorlin syndrome 5 (CDC6-related)
  subtype_term:
    preferred_term: Meier-Gorlin syndrome 5
    term:
      id: MONDO:0013432
      label: Meier-Gorlin syndrome 5
  description: >-
    Caused by biallelic CDC6 variants. CDC6 cooperates with CDT1 to load the
    MCM2-7 helicase. Reported individuals are few, and a neonatal progeroid
    presentation with lipodystrophy has been described that prompted
    consideration of progeria in the differential.
  genes:
  - preferred_term: CDC6
    term:
      id: hgnc:1744
      label: CDC6
  evidence:
  - reference: PMID:35023948
    reference_title: "Novel Compound Heterozygous Variants in the CDC6 Gene in a Russian Patient with Meier-Gorlin Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Meier-Gorlin syndrome 5 due to mutations in the CDC6 gene is difficult to diagnose, and few clinical data have been described to date."
    explanation: >-
      Confirms the CDC6 gene assignment for MGORS5 and the sparse clinical
      literature for this arm.
- name: MGORS6
  display_name: Meier-Gorlin syndrome 6 (GMNN-related)
  subtype_term:
    preferred_term: Meier-Gorlin syndrome 6
    term:
      id: MONDO:0014794
      label: Meier-Gorlin syndrome 6
  description: >-
    The autosomal dominant arm, caused by de novo heterozygous GMNN variants
    that truncate the protein upstream of the destruction box, stabilizing
    geminin. Mechanistically inverted relative to the other subtypes: the
    licensing inhibitor is gained rather than a licensing activator lost.
  genes:
  - preferred_term: GMNN
    term:
      id: hgnc:17493
      label: GMNN
  evidence:
  - reference: PMID:26637980
    reference_title: "De Novo GMNN Mutations Cause Autosomal-Dominant Primordial Dwarfism Associated with Meier-Gorlin Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "All three GMNN mutations identified alter sites 5' to residue Met28 of the protein, which is located within the destruction box."
    explanation: >-
      Localizes the dominant GMNN alleles to the destruction box, the basis of
      the stabilizing gain-of-function mechanism.
- name: MGORS7
  display_name: Meier-Gorlin syndrome 7 (CDC45-related)
  subtype_term:
    preferred_term: Meier-Gorlin syndrome 7
    term:
      id: MONDO:0014894
      label: Meier-Gorlin syndrome 7
  description: >-
    Caused by biallelic CDC45 variants. CDC45 acts in the pre-initiation complex
    and the CMG helicase rather than in origin licensing, and this arm is
    strongly enriched for craniosynostosis. An unusually high proportion of its
    pathogenic alleles are synonymous changes that alter splicing.
  genes:
  - preferred_term: CDC45
    term:
      id: hgnc:1739
      label: CDC45
  evidence:
  - reference: PMID:27374770
    reference_title: "Mutations in CDC45, Encoding an Essential Component of the Pre-initiation Complex, Cause Meier-Gorlin Syndrome and Craniosynostosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Here we report the identification of mutations in CDC45 in 15 affected individuals from 12 families with MGS and/or craniosynostosis."
    explanation: >-
      Original description of the CDC45 arm and its craniosynostosis-enriched
      phenotype.
  - reference: PMID:27374770
    reference_title: "Mutations in CDC45, Encoding an Essential Component of the Pre-initiation Complex, Cause Meier-Gorlin Syndrome and Craniosynostosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "All mutations identified were biallelic and included synonymous mutations altering splicing of physiological CDC45 transcripts, as well as amino acid substitutions expected to result in partial loss of function."
    explanation: >-
      Documents the distinctive synonymous splice-altering allele class of the
      CDC45 arm.
- name: MGORS8
  display_name: Meier-Gorlin syndrome 8 (MCM5-related)
  subtype_term:
    preferred_term: Meier-Gorlin syndrome 8
    term:
      id: MONDO:0033046
      label: Meier-Gorlin syndrome 8
  description: >-
    Caused by biallelic MCM5 variants affecting a subunit of the replicative
    MCM2-7 helicase, moving the disease mechanism from origin recognition into
    the helicase core itself.
  genes:
  - preferred_term: MCM5
    term:
      id: hgnc:6948
      label: MCM5
  evidence:
  - reference: PMID:28198391
    reference_title: "MCM5: a new actor in the link between DNA replication and Meier-Gorlin syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We performed whole-exome sequencing (WES) in a patient with a clinical diagnosis of MGORS and identified biallelic variants in MCM5."
    explanation: >-
      Original identification of MCM5 as an MGORS gene in a molecularly and
      functionally characterized patient.
- name: MGORS9
  display_name: Meier-Gorlin syndrome 9 (GINS3-related)
  subtype_term:
    preferred_term: Meier-Gorlin syndrome 9
    term:
      id: MONDO:0980992
      label: Meier-Gorlin syndrome 9
  description: >-
    Caused by biallelic hypomorphic GINS3 variants, most affecting aspartic acid
    24, which destabilize the protein and slow replication fork progression.
  genes:
  - preferred_term: GINS3
    term:
      id: hgnc:25851
      label: GINS3
  evidence:
  - reference: PMID:35603789
    reference_title: "Hypomorphic GINS3 variants alter DNA replication and cause Meier-Gorlin syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Here, we report the identification of 7 individuals from 5 unrelated families presenting with a Meier-Gorlin syndrome-like (MGS-like) phenotype associated with hypomorphic variants of GINS3, a gene not previously associated with this syndrome."
    explanation: >-
      Original multi-family identification of the GINS3 arm of MGORS.
- name: GINS2-related
  display_name: GINS2-related Meier-Gorlin syndrome
  description: >-
    Caused by biallelic GINS2 variants; the reported p.(Arg114Leu) allele sits at
    the CDC45 and MCM5 docking interface of GINS2, so this arm phenocopies
    CDC45-related disease with craniosynostosis, mild short stature, and patellar
    hypoplasia.
  genes:
  - preferred_term: GINS2
    term:
      id: hgnc:24575
      label: GINS2
  evidence:
  - reference: PMID:34353863
    reference_title: "Biallelic GINS2 variant p.(Arg114Leu) causes Meier-Gorlin syndrome with craniosynostosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "GINS2 is a new disease-associated gene, expanding the genetic aetiology of MGORS."
    explanation: >-
      Establishes GINS2 as an MGORS gene in a functionally validated case.
  - reference: PMID:34353863
    reference_title: "Biallelic GINS2 variant p.(Arg114Leu) causes Meier-Gorlin syndrome with craniosynostosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Interestingly, our patient's phenotype is strikingly similar to the phenotype of patients with CDC45-related MGORS, particularly those with craniosynostosis, mild short stature and patellar hypoplasia."
    explanation: >-
      Documents the phenotypic convergence of the GINS2 and CDC45 CMG-module
      arms.
- name: MCM3-MCM7-related
  display_name: MCM3- and MCM7-related Meier-Gorlin syndrome spectrum
  description: >-
    Biallelic MCM7 variants (and a strong MCM3 candidate) produce a phenotypic
    spectrum whose one pole is typical MGORS and whose other pole is a
    multisystem neonatal progeroid disorder with lipodystrophy and adrenal
    insufficiency, illustrating that MCM-core disruption is not confined to the
    classic MGORS phenotype.
  genes:
  - preferred_term: MCM7
    term:
      id: hgnc:6950
      label: MCM7
  - preferred_term: MCM3
    term:
      id: hgnc:6945
      label: MCM3
  evidence:
  - reference: PMID:33654309
    reference_title: "MCM complex members MCM3 and MCM7 are associated with a phenotypic spectrum from Meier-Gorlin syndrome to lipodystrophy and adrenal insufficiency."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The associated phenotypes are striking; one patient has typical Meier-Gorlin syndrome, whereas the second case has a multi-system disorder with neonatal progeroid appearance, lipodystrophy and adrenal insufficiency."
    explanation: >-
      Defines the phenotypic breadth of the MCM3/MCM7 arm, spanning classic
      MGORS to a progeroid multisystem presentation.
classifications:
  isds_skeletal_category:
  - classification_value: primordial_dwarfism_and_slender_bones
    notes: >-
      ISDS Nosology of Genetic Skeletal Disorders, 2023 revision (Unger et al.,
      PMID:36779427), group 21 "Primordial dwarfism and slender bone
      dysplasias", which lists all eleven Meier-Gorlin rows as
      "Ear-patella-primordial short stature syndrome (Meier-Gorlin),
      <GENE>-related" across the pre-replication-complex genes curated here
      (ORC1, ORC4, ORC6, CDT1, CDC6, GMNN, CDC45, MCM3, MCM5, MCM7, GINS2).
      This supersedes the earlier assignment to the patellar dysostoses group,
      taken from the 2019 revision (Mortier et al., PMID:31633310), Table 1
      group 36 "Patellar dysostoses". The syndrome's own name is the trap: it
      begins "ear-patella", so the patellar group looks correct, and the 2023
      name change to "ear-patella-primordial short stature" is what signals the
      move. Placement follows the committee's listing, not the name.
      Re-verified against the 2023 table: the eleven rows are NOS 21-0250
      through NOS 21-0350. Note that DONSON, the thirteenth Meier-Gorlin gene
      curated in this entry's CMG-helicase node, is not one of them - the 2023
      table lists it separately at NOS 21-0200, as "Microcephalic
      osteodysplastic primordial dwarfism, or microcephaly-short
      stature-micromelia-limb abnormalities, DONSON-related", because the
      DONSON-Meier-Gorlin association was published after the table closed.
      That does not change this assignment, since NOS 21-0200 is in the same
      group; it does mean the entry is broader than the eleven rows it cites.
      The 2023 table prints NOS 21-0250 with the name "ORC4-related" against
      the gene ORC1 and OMIM 224690 (Meier-Gorlin syndrome 1); the name is a
      typographical error in the source and the gene column is what identifies
      the row.
pathophysiology:
- name: Hypomorphic Pre-Replication Complex Defect
  biological_scale: MOLECULAR
  description: >-
    Biallelic partial loss-of-function variants in ORC1, ORC4, ORC6, CDT1 or
    CDC6 reduce the level, stability, chromatin association or complex assembly
    of pre-replication complex components. Because these are essential genes,
    only hypomorphic allele combinations are compatible with survival, and
    residual activity largely sets disease severity.
  genes:
  - preferred_term: ORC1
    term:
      id: hgnc:8487
      label: ORC1
  - preferred_term: ORC4
    term:
      id: hgnc:8490
      label: ORC4
  - preferred_term: ORC6
    term:
      id: hgnc:17151
      label: ORC6
  - preferred_term: CDT1
    term:
      id: hgnc:24576
      label: CDT1
  - preferred_term: CDC6
    term:
      id: hgnc:1744
      label: CDC6
  molecular_functions:
  - preferred_term: DNA replication origin binding
    term:
      id: GO:0003688
      label: DNA replication origin binding
    modifier: DECREASED
  evidence:
  - reference: PMID:21358632
    reference_title: "Mutations in the pre-replication complex cause Meier-Gorlin syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "All of these genes encode components of the pre-replication complex, implicating defects in replication licensing as the cause of a genetic syndrome with distinct developmental abnormalities."
    explanation: >-
      Establishes the pre-replication complex as the shared molecular lesion of
      MGORS.
  - reference: PMID:21358633
    reference_title: "Mutations in ORC1, encoding the largest subunit of the origin recognition complex, cause microcephalic primordial dwarfism resembling Meier-Gorlin syndrome."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "We establish that these mutations disrupt known ORC1 functions including pre-replicative complex formation and origin activation."
    explanation: >-
      Functional demonstration that patient ORC1 alleles impair pre-replicative
      complex formation and origin activation.
  downstream:
  - target: Impaired Replication Origin Licensing
    description: >-
      Loss of ORC, CDC6 or CDT1 function reduces the efficiency with which
      MCM2-7 is loaded onto origins during G1.
- name: Loss of ORC1 BAH Recognition of H4K20me2
  biological_scale: MOLECULAR
  description: >-
    In metazoans, ORC is directed to origins by chromatin rather than by DNA
    sequence, and the ORC1 BAH domain performs that reading step by binding
    histone H4 dimethylated at lysine 20. MGORS-associated BAH domain mutations
    abrogate this recognition, reducing ORC1 occupancy at origins and ORC
    chromatin loading. This is a candidate explanation for why the ORC1 arm sits
    at the severe end of the clinical gradient, since it removes the targeting
    step upstream of licensing rather than merely reducing licensing capacity.
  genes:
  - preferred_term: ORC1
    term:
      id: hgnc:8487
      label: ORC1
  molecular_functions:
  - preferred_term: DNA replication origin binding
    term:
      id: GO:0003688
      label: DNA replication origin binding
    modifier: DECREASED
  evidence:
  - reference: PMID:22398447
    reference_title: "The BAH domain of ORC1 links H4K20me2 to DNA replication licensing and Meier-Gorlin syndrome."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "H4K20me2 is enriched at replication origins, and abrogating ORC1 recognition of H4K20me2 in cells impairs ORC1 occupancy at replication origins, ORC chromatin loading and cell-cycle progression."
    explanation: >-
      Demonstrates that loss of the ORC1 BAH to H4K20me2 interaction impairs
      origin occupancy, chromatin loading and cell-cycle progression.
  - reference: PMID:22398447
    reference_title: "The BAH domain of ORC1 links H4K20me2 to DNA replication licensing and Meier-Gorlin syndrome."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "We find that wild-type human ORC1, but not ORC1-H4K20me2-binding mutants, rescues the growth retardation of orc1 morphants."
    explanation: >-
      Rescue experiment establishing that H4K20me2 binding specifically, not
      ORC1 protein presence alone, is what the growth phenotype depends on.
  downstream:
  - target: Impaired Replication Origin Licensing
    description: >-
      Failure to read H4K20me2 leaves ORC poorly positioned at origins, so
      fewer pre-replicative complexes are assembled.
- name: Stabilized Geminin and Excess Licensing Inhibition
  biological_scale: MOLECULAR
  description: >-
    De novo heterozygous GMNN variants remove the N-terminal destruction box that
    normally targets geminin for degradation by the anaphase-promoting complex.
    The resulting stabilized geminin persists and continues to inhibit CDT1, so
    the dominant arm of MGORS reaches the same licensing deficit by gaining an
    inhibitor rather than losing an activator.
  genes:
  - preferred_term: GMNN
    term:
      id: hgnc:17493
      label: GMNN
  evidence:
  - reference: PMID:26637980
    reference_title: "De Novo GMNN Mutations Cause Autosomal-Dominant Primordial Dwarfism Associated with Meier-Gorlin Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Geminin is present during the S, G2, and M phases of the cell cycle and is degraded during the metaphase-anaphase transition by the anaphase-promoting complex (APC), which recognizes the destruction box sequence near the 5' end of the geminin protein."
    explanation: >-
      Describes the normal destruction-box-dependent turnover of geminin that
      the MGORS alleles abolish.
  downstream:
  - target: Impaired Replication Origin Licensing
    description: >-
      Persistent geminin sustains CDT1 inhibition, blocking MCM2-7 loading in
      G1.
- name: Impaired Replication Origin Licensing
  biological_scale: MOLECULAR
  description: >-
    The convergent molecular consequence of both the loss-of-activator and the
    gain-of-inhibitor arms is inefficient assembly of the pre-replicative complex
    during G1, leaving fewer origins licensed and available to fire in S phase.
    Notably, the measured licensing deficit in patient cells does not track
    linearly with S-phase progression rate, so licensing capacity alone does not
    predict clinical severity.
  biological_processes:
  - preferred_term: pre-replicative complex assembly
    term:
      id: GO:0006267
      label: pre-replicative complex assembly involved in nuclear cell cycle DNA replication
    modifier: DECREASED
  - preferred_term: DNA replication initiation
    term:
      id: GO:0006270
      label: DNA replication initiation
    modifier: DECREASED
  evidence:
  - reference: PMID:27374770
    reference_title: "Mutations in CDC45, Encoding an Essential Component of the Pre-initiation Complex, Cause Meier-Gorlin Syndrome and Craniosynostosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Impaired licensing of origins of replication during the G1 phase of the cell cycle has been implicated in Meier-Gorlin syndrome (MGS), a disorder defined by the triad of short stature, microtia, and a/hypoplastic patellae."
    explanation: >-
      States the central licensing-deficit model linking the molecular lesion to
      the clinical triad.
  - reference: PMID:23516378
    reference_title: "Deficiency in origin licensing proteins impairs cilia formation: implications for the aetiology of Meier-Gorlin syndrome."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Here, we show that although origin licensing capacity is impaired in all patient cells with mutations in origin licensing component proteins, this does not correlate with the rate of progression through S phase."
    explanation: >-
      Confirms the licensing deficit in all patient cells but qualifies the
      simple licensing-to-severity model, motivating the parallel ciliary arm.
  downstream:
  - target: Delayed S-Phase Entry and Reduced Cell Proliferation
    description: >-
      Fewer licensed origins slow S-phase entry and lengthen the cell cycle.
  - target: Impaired Centriole Duplication and Primary Cilium Formation
    description: >-
      Origin licensing proteins are independently required for centriole copy
      number control and ciliogenesis, a non-replicative route out of the same
      lesion.
- name: Impaired CMG Helicase Assembly and Origin Firing
  biological_scale: MOLECULAR
  description: >-
    A second mechanistic module lies downstream of licensing: CDC45, the GINS
    subunits GINS2 and GINS3, the MCM2-7 core subunits MCM3, MCM5 and MCM7, and
    the replisome factor DONSON build and activate the CDC45-MCM2-7-GINS (CMG)
    replicative helicase. Hypomorphic variants here leave origins licensed but
    unable to fire efficiently, and additionally slow ongoing fork progression
    during S phase. DONSON is the outlier of the set: it has no role in the
    pre-replication or pre-initiation complexes themselves, and its requirement
    for CDC45 and GINS chromatin loading was only established in 2023.
  genes:
  - preferred_term: CDC45
    term:
      id: hgnc:1739
      label: CDC45
  - preferred_term: GINS2
    term:
      id: hgnc:24575
      label: GINS2
  - preferred_term: GINS3
    term:
      id: hgnc:25851
      label: GINS3
  - preferred_term: MCM5
    term:
      id: hgnc:6948
      label: MCM5
  - preferred_term: MCM3
    term:
      id: hgnc:6945
      label: MCM3
  - preferred_term: MCM7
    term:
      id: hgnc:6950
      label: MCM7
  - preferred_term: DONSON
    term:
      id: hgnc:2993
      label: DONSON
  biological_processes:
  - preferred_term: DNA replication preinitiation complex assembly
    term:
      id: GO:0071163
      label: DNA replication preinitiation complex assembly
    modifier: DECREASED
  molecular_functions:
  - preferred_term: DNA helicase activity
    term:
      id: GO:0003678
      label: DNA helicase activity
    modifier: DECREASED
  evidence:
  - reference: PMID:27374770
    reference_title: "Mutations in CDC45, Encoding an Essential Component of the Pre-initiation Complex, Cause Meier-Gorlin Syndrome and Craniosynostosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "CDC45 encodes a component of both the pre-initiation (preIC) and CMG helicase complexes, required for initiation of DNA replication origin firing and ongoing DNA synthesis during S-phase itself, respectively, and hence is functionally distinct from previously identified MGS-associated genes."
    explanation: >-
      Defines the pre-initiation/CMG module as mechanistically distinct from
      origin licensing while converging on the same disease.
  - reference: PMID:34353863
    reference_title: "Biallelic GINS2 variant p.(Arg114Leu) causes Meier-Gorlin syndrome with craniosynostosis."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "the missense change possibly disrupts the effective interaction between the GINS complex and CDC45, which is necessary for the CMG helicase complex (Cdc45/MCM2-7/GINS) to accurately operate"
    explanation: >-
      Localizes the GINS2 lesion to the CDC45 docking interface required for CMG
      function.
  - reference: PMID:35603789
    reference_title: "Hypomorphic GINS3 variants alter DNA replication and cause Meier-Gorlin syndrome."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "These variants shortened the protein half-life, altered key protein interactions at the replisome, and negatively influenced DNA replication fork progression."
    explanation: >-
      Shows that CMG-module variants act both on replisome assembly and on
      ongoing fork progression.
  - reference: PMID:37638758
    reference_title: "DONSON facilitates Cdc45 and GINS chromatin association and is essential for DNA replication initiation."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "DONSON facilitates Cdc45 and GINS chromatin association and is essential for DNA replication initiation"
    explanation: >-
      Establishes the mechanism by which the thirteenth MGORS gene, DONSON,
      feeds into CMG assembly.
  - reference: PMID:37059840
    reference_title: "The expanding genetic and clinical landscape associated with Meier-Gorlin syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "DONSON is unique compared to all other MGORS genes as the encoded protein has no known role in either the DNA pre-RC or pre-IC"
    explanation: >-
      Qualifies DONSON's placement in this node: it acts on CMG loading and fork
      stability without being a pre-replication or pre-initiation complex
      component itself.
  downstream:
  - target: Delayed S-Phase Entry and Reduced Cell Proliferation
    description: >-
      Inefficient origin firing and slowed fork progression prolong S phase.
  - target: Cranial Suture Dysregulation and Premature Fusion
    description: >-
      The CMG-module arms (CDC45, GINS2) are specifically enriched for
      craniosynostosis, a phenotype not typical of the licensing-module arms.
- name: Delayed S-Phase Entry and Reduced Cell Proliferation
  biological_scale: CELLULAR
  description: >-
    Patient cells enter S phase late, accumulate within S phase, and progress
    through the cell cycle slowly. The proliferative shortfall is the shared
    cellular phenotype of every molecular arm, and in severe alleles it tips over
    into premature senescence.
  cell_types:
  - preferred_term: fibroblast
    term:
      id: CL:0000057
      label: fibroblast
  biological_processes:
  - preferred_term: cell population proliferation
    term:
      id: GO:0008283
      label: cell population proliferation
    modifier: DECREASED
  - preferred_term: DNA replication
    term:
      id: GO:0006260
      label: DNA replication
    modifier: DECREASED
  evidence:
  - reference: PMID:21358633
    reference_title: "Mutations in ORC1, encoding the largest subunit of the origin recognition complex, cause microcephalic primordial dwarfism resembling Meier-Gorlin syndrome."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "ORC1 deficiency perturbs S-phase entry and S-phase progression."
    explanation: >-
      Direct demonstration of the S-phase defect in ORC1-deficient cells.
  - reference: PMID:28198391
    reference_title: "MCM5: a new actor in the link between DNA replication and Meier-Gorlin syndrome."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Moreover cell-cycle progression was delayed in patient's cells, as already shown for mutations in the ORC1 gene."
    explanation: >-
      Shows the same cell-cycle delay arises from an MCM-core lesion, supporting
      convergence across molecular arms.
  - reference: PMID:35603789
    reference_title: "Hypomorphic GINS3 variants alter DNA replication and cause Meier-Gorlin syndrome."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "We found that MGS-associated GINS3 variants affecting aspartic acid 24 (D24) compromised cell proliferation and caused accumulation of cells in S phase."
    explanation: >-
      Quantifies the proliferative deficit and S-phase accumulation in the GINS3
      arm.
  downstream:
  - target: Global Prenatal and Postnatal Growth Restriction
    description: >-
      A cell-autonomous proliferation deficit during rapid embryonic and infant
      growth yields fewer cells and reduced body size.
  - target: Tissue-Disproportionate Growth Failure
    description: >-
      Structures whose development depends on narrow windows of intense
      proliferation are affected out of proportion to overall body size.
  - target: Decreased total neutrophil count
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Neutropenia is reported in this disorder; granulopoiesis is highly
      proliferative, which is the plausible route, though it has not been
      shown directly.
- name: Impaired Centriole Duplication and Primary Cilium Formation
  biological_scale: CELLULAR
  description: >-
    Origin licensing proteins have a non-replicative requirement in centrosome
    and centriole copy number control. ORC1-deficient patient cells and cells
    depleted of licensing proteins form primary cilia poorly, adding a
    ciliopathy-like arm to the pathogenesis that is independent of the
    replication rate itself.
  biological_processes:
  - preferred_term: cilium assembly
    term:
      id: GO:0060271
      label: cilium assembly
    modifier: DECREASED
  cell_types:
  - preferred_term: fibroblast
    term:
      id: CL:0000057
      label: fibroblast
  evidence:
  - reference: PMID:23516378
    reference_title: "Deficiency in origin licensing proteins impairs cilia formation: implications for the aetiology of Meier-Gorlin syndrome."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "ORC1-deficient cells from MGS patients and siRNA-mediated depletion of origin licensing proteins also have impaired centrosome and centriole copy number."
    explanation: >-
      Documents the centriole copy number defect underlying the ciliary arm.
  - reference: PMID:23516378
    reference_title: "Deficiency in origin licensing proteins impairs cilia formation: implications for the aetiology of Meier-Gorlin syndrome."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "As a novel and unexpected finding, we show that they also display a striking defect in the rate of formation of primary cilia."
    explanation: >-
      Establishes impaired primary cilium formation as a distinct cellular
      consequence of licensing protein deficiency.
  downstream:
  - target: Reduced Hedgehog Signaling and Impaired Chondroinduction
    description: >-
      Primary cilia are the obligate platform for vertebrate Hedgehog signal
      transduction, so a ciliogenesis defect blunts downstream Hedgehog output.
- name: Reduced Hedgehog Signaling and Impaired Chondroinduction
  biological_scale: CELLULAR
  description: >-
    Blunted ciliary Hedgehog signaling in patient fibroblasts is accompanied by
    impaired chondroinduction in cell-based assays, offering a mechanism for the
    cartilage-derived structures that are disproportionately affected in MGORS
    (external ear, patella) beyond simple global proliferation loss.
  biological_processes:
  - preferred_term: smoothened signaling pathway
    term:
      id: GO:0007224
      label: smoothened signaling pathway
    modifier: DECREASED
  - preferred_term: chondrocyte differentiation
    term:
      id: GO:0002062
      label: chondrocyte differentiation
    modifier: DECREASED
  cell_types:
  - preferred_term: chondrocyte
    term:
      id: CL:0000138
      label: chondrocyte
  evidence:
  - reference: PMID:23516378
    reference_title: "Deficiency in origin licensing proteins impairs cilia formation: implications for the aetiology of Meier-Gorlin syndrome."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "We demonstrate that this impacts sonic hedgehog signalling in ORC1-deficient primary fibroblasts."
    explanation: >-
      Links the ciliogenesis defect to reduced Hedgehog signal transduction.
  - reference: PMID:23516378
    reference_title: "Deficiency in origin licensing proteins impairs cilia formation: implications for the aetiology of Meier-Gorlin syndrome."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Finally, using a cell-based model, we show that defects in cilia function impair chondroinduction."
    explanation: >-
      Connects impaired cilium function to defective chondroinduction, a
      cell-based model rather than direct patient-tissue evidence.
  downstream:
  - target: Tissue-Disproportionate Growth Failure
    description: >-
      Reduced chondroinduction preferentially compromises cartilage-derived
      structures such as the auricle and patella.
- name: Global Prenatal and Postnatal Growth Restriction
  biological_scale: ORGANISM
  description: >-
    The organism-level consequence is severe growth failure beginning in utero.
    Growth velocity is most impaired during pregnancy and the first year of life,
    after which height tracks parallel to normal centiles from a much lower
    starting point, producing a mean adult height near four and a half standard
    deviations below the mean.
  downstream:
  - target: Intrauterine growth retardation
    description: >-
      Prenatal arm of the licensing-driven proliferation deficit.
  - target: Short stature
    description: >-
      Postnatal arm of the same deficit.
  - target: Microcephaly
    description: >-
      Neural progenitor expansion is licensing-dependent; microcephaly is
      variable in this disorder but follows the same route.
  - target: Delayed skeletal maturation
    description: >-
      Skeletal maturation lags because growth-plate chondrocyte turnover
      shares the S-phase delay.
  - target: Feeding difficulties
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Grouped with the growth phenotype, which it compounds; no independent
      mechanism is established.
  - target: Decreased response to growth hormone stimulation test
    description: >-
      A cell-intrinsic proliferation defect limits the response to GH, which
      is why this is a growth-hormone-resistant rather than deficient state.
  evidence:
  - reference: PMID:23023959
    reference_title: "Meier-Gorlin syndrome: growth and secondary sexual development of a microcephalic primordial dwarfism disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "growth velocity (length) is impaired in MGS during pregnancy and first year of life, but, thereafter, height increases in paralleled normal reference centiles, resulting in a mean adult height of -4.5 standard deviations (SD)"
    explanation: >-
      Defines the natural history of growth failure in the largest MGORS cohort.
  - reference: PMID:21358633
    reference_title: "Mutations in ORC1, encoding the largest subunit of the origin recognition complex, cause microcephalic primordial dwarfism resembling Meier-Gorlin syndrome."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "we show that Orc1 depletion in zebrafish is sufficient to markedly reduce body size during rapid embryonic growth"
    explanation: >-
      Model-organism confirmation that a licensing defect alone is sufficient to
      restrict organismal growth.
  - reference: PMID:35603789
    reference_title: "Hypomorphic GINS3 variants alter DNA replication and cause Meier-Gorlin syndrome."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "We further showed that mouse embryos homozygous for a D24 variant presented intrauterine growth retardation and did not survive to birth, and that fibroblasts derived from these embryos displayed accelerated cellular senescence."
    explanation: >-
      Mouse model recapitulating intrauterine growth restriction and linking the
      CMG-module lesion to premature senescence.
- name: Tissue-Disproportionate Growth Failure
  biological_scale: TISSUE
  description: >-
    Growth failure in MGORS is not uniform. External ear cartilage, the patella,
    mammary tissue and the external genitalia are affected out of proportion to
    overall stature, which is why the clinical triad and the mammary and genital
    findings, rather than short stature alone, define the syndrome.
  downstream:
  - target: Microtia
    description: >-
      The defining ear anomaly. Ear cartilage is among the tissues most
      sensitive to the licensing defect, which is what makes the growth
      failure disproportionate rather than uniform.
  - target: Patellar aplasia
    description: >-
      The defining patellar anomaly; patellar development is selectively
      vulnerable across the origin-licensing disorders.
  - target: Patellar hypoplasia
    description: >-
      The milder form of the same selective vulnerability.
  - target: Patellar dislocation
    description: >-
      Mechanical consequence of the hypoplastic or absent patella.
  - target: Micrognathia
    description: >-
      Craniofacial skeletal expression of the disproportionate growth failure.
  - target: Narrow mouth
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Grouped with the craniofacial findings.
  - target: Breast hypoplasia
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Mammary tissue is among the selectively affected tissues; grouped with
      the other disproportionate deficits.
  - target: Hypoplastic labia minora
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Genital hypoplasia, grouped with the other tissue-selective deficits.
  - target: Clitoral hypertrophy
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Reported genital finding; grouped here, with no established route.
  - target: Cryptorchidism
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Male genital finding, grouped with the other tissue-selective
      developmental deficits.
  - target: Lipodystrophy
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Adipose tissue deficit reported in this disorder; grouped with the other
      tissue-selective findings, with no established mechanism.
  - target: Emphysema
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Pulmonary finding reported in a subset; grouped here, with no
      established route from origin licensing to alveolar structure.
  - target: Hearing impairment
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Often conductive and secondary to the microtia and middle-ear anomalies;
      grouped with the craniofacial arm.
  evidence:
  - reference: PMID:23023959
    reference_title: "Meier-Gorlin syndrome: growth and secondary sexual development of a microcephalic primordial dwarfism disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "we highlight that growth is disproportionately affected in certain structures, with growth related minor genital abnormalities (42%) and mammary hypoplasia (100%) frequently present, in addition to established effects on ears and patellar growth"
    explanation: >-
      Directly establishes the tissue-disproportionate pattern of growth failure
      that defines the syndrome's recognizable phenotype.
- name: Cranial Suture Dysregulation and Premature Fusion
  biological_scale: TISSUE
  description: >-
    In the CMG-module arms, and particularly CDC45 and GINS2, the replication
    defect additionally perturbs cranial suture homeostasis, producing coronal
    craniosynostosis that can dominate the presentation even when growth
    restriction is comparatively mild.
  downstream:
  - target: Craniosynostosis
    description: >-
      The direct endpoint of this node; it is the GINS2-associated
      presentation rather than a feature of every genotype.
  evidence:
  - reference: PMID:27374770
    reference_title: "Mutations in CDC45, Encoding an Essential Component of the Pre-initiation Complex, Cause Meier-Gorlin Syndrome and Craniosynostosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Our findings therefore implicate the preIC as an additional protein complex involved in the etiology of MGS and connect the core cellular machinery of genome replication with growth, chondrogenesis, and cranial suture homeostasis."
    explanation: >-
      Explicitly connects the replication machinery to cranial suture
      homeostasis in the CDC45 arm.
  - reference: PMID:27374770
    reference_title: "Mutations in CDC45, Encoding an Essential Component of the Pre-initiation Complex, Cause Meier-Gorlin Syndrome and Craniosynostosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The phenotypes of affected individuals range from syndromic coronal craniosynostosis to severe growth restriction, fulfilling diagnostic criteria for Meier-Gorlin syndrome."
    explanation: >-
      Documents the phenotypic range from craniosynostosis-predominant to
      growth-predominant presentations within one gene arm.
phenotypes:
- name: Microtia
  category: Craniofacial
  description: >-
    Severe, usually bilateral hypoplasia of the external ear pinnae. One of the
    three cardinal features and often the finding that first suggests the
    diagnosis.
  frequency: VERY_FREQUENT
  phenotype_term:
    preferred_term: Microtia
    term:
      id: HP:0008551
      label: Microtia
  evidence:
  - reference: PMID:22333897
    reference_title: "Meier-Gorlin syndrome genotype-phenotype studies: 35 individuals with pre-replication complex gene mutations and 10 without molecular diagnosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The triad of microtia, absent/hypoplastic patellae, and short stature was observed in 82% of individuals with MGS."
    explanation: >-
      Quantifies the frequency of the complete triad, including microtia, in a
      45-patient cohort, supporting a VERY_FREQUENT band.
- name: Patellar aplasia
  category: Skeletal
  description: >-
    Complete absence of the patella, the second cardinal feature. Because the
    patella ossifies late, assessment requires ultrasonography before age six and
    radiography thereafter. Frequency is deliberately omitted: published cohorts
    report absent-or-hypoplastic patellae as a single combined category, so the
    aplasia share is not separately quantified.
  phenotype_term:
    preferred_term: Patellar aplasia
    term:
      id: HP:0006443
      label: Patellar aplasia
  evidence:
  - reference: PMID:21358632
    reference_title: "Mutations in the pre-replication complex cause Meier-Gorlin syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "an autosomal recessive primordial dwarfism syndrome characterized by absent or hypoplastic patellae and markedly small ears"
    explanation: >-
      Establishes absent patellae as a defining feature of the syndrome.
- name: Patellar hypoplasia
  category: Skeletal
  description: >-
    Underdevelopment rather than complete absence of the patella; the milder end
    of the patellar spectrum, characteristic of the CDC45 and GINS2 arms.
  phenotype_term:
    preferred_term: Patellar hypoplasia
    term:
      id: HP:0003065
      label: Patellar hypoplasia
  evidence:
  - reference: PMID:34353863
    reference_title: "Biallelic GINS2 variant p.(Arg114Leu) causes Meier-Gorlin syndrome with craniosynostosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "particularly those with craniosynostosis, mild short stature and patellar hypoplasia"
    explanation: >-
      Documents patellar hypoplasia as the patellar phenotype of the CMG-module
      arms.
- name: Patellar dislocation
  category: Skeletal
  description: >-
    Recurrent patellar luxation with knee pain and later gonarthrosis is a major
    source of orthopedic morbidity and requires active surveillance.
  phenotype_term:
    preferred_term: Patellar dislocation
    term:
      id: HP:0002999
      label: Patellar dislocation
  evidence:
  - reference: PMID:26381604
    reference_title: "Meier-Gorlin syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "prevention of associated problems, such as growth retardation, feeding problems, hearing loss, luxating patellae, knee pain, gonarthrosis"
    explanation: >-
      The management review lists luxating patellae, knee pain and gonarthrosis
      among the problems requiring active prevention.
- name: Short stature
  category: Growth
  description: >-
    Severe, generally proportionate short stature is the third cardinal feature
    and is nearly universal, with a median height Z-score around minus four.
  frequency: VERY_FREQUENT
  phenotype_term:
    preferred_term: Short stature
    term:
      id: HP:0004322
      label: Short stature
  evidence:
  - reference: PMID:42496035
    reference_title: "Endocrine Phenotypes and Hormonal Treatment in Meier-Gorlin Syndrome: Report of Two Cases and a Systematic Review of Literature."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Short stature was almost universal (median height-Z-score -4.4), with 70% exhibiting delayed bone age, 42.9% low IGF-1 and 35.3% GHD."
    explanation: >-
      Systematic review quantifying the near-universal frequency and severity of
      short stature, supporting the VERY_FREQUENT band.
- name: Intrauterine growth retardation
  category: Growth
  description: >-
    Growth restriction begins prenatally, with markedly reduced birth length and
    weight, and is often the earliest detectable manifestation.
  frequency: VERY_FREQUENT
  phenotype_term:
    preferred_term: Intrauterine growth retardation
    term:
      id: HP:0001511
      label: Intrauterine growth retardation
  evidence:
  - reference: PMID:21358632
    reference_title: "Mutations in the pre-replication complex cause Meier-Gorlin syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Both pre- and post-natal growth are impaired in this disorder, and although microcephaly is often evident, intellect is usually normal in this syndrome."
    explanation: >-
      Establishes that growth impairment is both prenatal and postnatal.
- name: Microcephaly
  category: Neurologic
  description: >-
    Reduced head circumference is frequently present, most severely in the ORC1
    and ORC4 arms, placing MGORS among the microcephalic primordial dwarfisms.
    Intellect is usually preserved despite the small head size.
  frequency: FREQUENT
  phenotype_term:
    preferred_term: Microcephaly
    term:
      id: HP:0000252
      label: Microcephaly
  evidence:
  - reference: PMID:21358632
    reference_title: "Mutations in the pre-replication complex cause Meier-Gorlin syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "although microcephaly is often evident, intellect is usually normal in this syndrome"
    explanation: >-
      Supports a FREQUENT (often evident) band for microcephaly and records the
      dissociation from intellectual outcome.
  - reference: PMID:23023959
    reference_title: "Meier-Gorlin syndrome: growth and secondary sexual development of a microcephalic primordial dwarfism disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Height is dependent on ethnic background and underlying molecular cause, with ORC1 and ORC4 mutations causing more severe short stature and microcephaly."
    explanation: >-
      Documents the gene-dependent gradient in microcephaly severity.
- name: Breast hypoplasia
  category: Endocrine
  description: >-
    Mammary hypoplasia or agenesis is present in essentially all post-pubertal
    affected females and is one of the most penetrant features of the syndrome,
    despite normal gonadal hormone levels.
  frequency: VERY_FREQUENT
  phenotype_term:
    preferred_term: Breast hypoplasia
    term:
      id: HP:0003187
      label: Breast hypoplasia
  evidence:
  - reference: PMID:22333897
    reference_title: "Meier-Gorlin syndrome genotype-phenotype studies: 35 individuals with pre-replication complex gene mutations and 10 without molecular diagnosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Additional frequent clinical features were mammary hypoplasia (100%) and abnormal genitalia (42%; predominantly cryptorchidism and hypoplastic labia minora/majora)."
    explanation: >-
      Reports complete penetrance of mammary hypoplasia among evaluated
      individuals, supporting VERY_FREQUENT.
- name: Cryptorchidism
  category: Genitourinary
  description: >-
    Undescended testes, often with a hypoplastic scrotum and micropenis, are the
    common male genital manifestation of the disproportionate growth failure.
  frequency: FREQUENT
  phenotype_term:
    preferred_term: Cryptorchidism
    term:
      id: HP:0000028
      label: Cryptorchidism
  evidence:
  - reference: PMID:22333897
    reference_title: "Meier-Gorlin syndrome genotype-phenotype studies: 35 individuals with pre-replication complex gene mutations and 10 without molecular diagnosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "abnormal genitalia (42%; predominantly cryptorchidism and hypoplastic labia minora/majora)"
    explanation: >-
      Quantifies genital anomalies at 42% of the cohort, with cryptorchidism
      predominant.
  - reference: PMID:42496035
    reference_title: "Endocrine Phenotypes and Hormonal Treatment in Meier-Gorlin Syndrome: Report of Two Cases and a Systematic Review of Literature."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Among males, cryptorchidism, hypoplastic scrotum and micropenis were common."
    explanation: >-
      Independent systematic review describing cryptorchidism as common among
      affected males, supporting the FREQUENT band for the male-specific
      denominator.
- name: Hypoplastic labia minora
  category: Genitourinary
  description: >-
    Hypoplasia of the labia minora and majora is the corresponding female
    genital finding, sometimes accompanied by clitoromegaly.
  phenotype_term:
    preferred_term: Hypoplastic labia minora
    term:
      id: HP:0000064
      label: Hypoplastic labia minora
  evidence:
  - reference: PMID:26381604
    reference_title: "Meier-Gorlin syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "urogenital anomalies, such as cryptorchidism and hypoplastic labia minora and majora"
    explanation: >-
      Clinical review listing hypoplastic labia among the characteristic
      urogenital anomalies.
- name: Clitoral hypertrophy
  category: Genitourinary
  description: >-
    Clitoromegaly accompanying hypoplastic labia is reported in a minority of
    affected females; gonadal hormones and gonadotrophins are normal.
  frequency: OCCASIONAL
  phenotype_term:
    preferred_term: Clitoral hypertrophy
    term:
      id: HP:0008665
      label: Clitoral hypertrophy
  evidence:
  - reference: PMID:42496035
    reference_title: "Endocrine Phenotypes and Hormonal Treatment in Meier-Gorlin Syndrome: Report of Two Cases and a Systematic Review of Literature."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Among females, all post-pubertal cases had mammary hypoplasia, while 23.5% had clitoromegaly with hypoplastic labia."
    explanation: >-
      Quantifies clitoromegaly at 23.5% of post-pubertal females, supporting an
      OCCASIONAL band.
- name: Micrognathia
  category: Craniofacial
  description: >-
    Micro-retrognathia with a small mouth and full lips constitutes the
    characteristic childhood facial gestalt; a narrow, convex nose becomes more
    prominent with age.
  frequency: FREQUENT
  phenotype_term:
    preferred_term: Micrognathia
    term:
      id: HP:0000347
      label: Micrognathia
  evidence:
  - reference: PMID:26381604
    reference_title: "Meier-Gorlin syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Typical facial characteristics during childhood comprise a small mouth with full lips and micro-retrognathia."
    explanation: >-
      Describes the characteristic facial gestalt including micro-retrognathia.
- name: Narrow mouth
  category: Craniofacial
  description: >-
    A small mouth with full lips, part of the recognizable MGORS facial
    appearance in childhood.
  phenotype_term:
    preferred_term: Narrow mouth
    term:
      id: HP:0000160
      label: Narrow mouth
  evidence:
  - reference: PMID:26381604
    reference_title: "Meier-Gorlin syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Typical facial characteristics during childhood comprise a small mouth with full lips and micro-retrognathia."
    explanation: >-
      Documents the small mouth as part of the characteristic facial phenotype.
- name: Craniosynostosis
  category: Craniofacial
  description: >-
    Premature fusion of the cranial sutures, usually coronal, is enriched in the
    CDC45 and GINS2 arms and may be the presenting feature in individuals whose
    growth restriction is relatively mild.
  phenotype_term:
    preferred_term: Craniosynostosis
    term:
      id: HP:0001363
      label: Craniosynostosis
  evidence:
  - reference: PMID:27374770
    reference_title: "Mutations in CDC45, Encoding an Essential Component of the Pre-initiation Complex, Cause Meier-Gorlin Syndrome and Craniosynostosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The phenotypes of affected individuals range from syndromic coronal craniosynostosis to severe growth restriction, fulfilling diagnostic criteria for Meier-Gorlin syndrome."
    explanation: >-
      Establishes craniosynostosis within the MGORS phenotypic range in the
      CDC45 arm.
- name: Feeding difficulties
  category: Gastrointestinal
  description: >-
    Feeding problems in infancy are common and contribute materially to early
    morbidity and to the postnatal growth deficit.
  phenotype_term:
    preferred_term: Feeding difficulties
    term:
      id: HP:0011968
      label: Feeding difficulties
  evidence:
  - reference: PMID:26381604
    reference_title: "Meier-Gorlin syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Associated clinical features encompass feeding problems, congenital pulmonary emphysema, mammary hypoplasia in females and urogenital anomalies"
    explanation: >-
      Lists feeding problems among the characteristic associated features
      requiring management.
- name: Emphysema
  category: Respiratory
  description: >-
    Congenital pulmonary emphysema, with or without bronchomalacia or
    laryngomalacia, is a recognized and potentially serious complication,
    reported more often with compound heterozygous CDT1 genotypes.
  phenotype_term:
    preferred_term: Emphysema
    term:
      id: HP:0002097
      label: Emphysema
  evidence:
  - reference: PMID:26381604
    reference_title: "Meier-Gorlin syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "possible pulmonary complications due to congenital pulmonary emphysema with or without broncho- or laryngomalacia"
    explanation: >-
      Documents congenital pulmonary emphysema and the associated airway
      malacia as management concerns.
  - reference: PMID:22333897
    reference_title: "Meier-Gorlin syndrome genotype-phenotype studies: 35 individuals with pre-replication complex gene mutations and 10 without molecular diagnosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "compound heterozygous mutations appeared to have a more severe effect on phenotype, causing more severe growth retardation in ORC4 and more frequently pulmonary emphysema in CDT1"
    explanation: >-
      Establishes the genotype dependence of pulmonary emphysema within the CDT1
      arm.
- name: Delayed skeletal maturation
  category: Skeletal
  description: >-
    Delayed bone age is present in the majority of individuals assessed and is
    one of the features that predicts a growth hormone response.
  frequency: FREQUENT
  phenotype_term:
    preferred_term: Delayed skeletal maturation
    term:
      id: HP:0002750
      label: Delayed skeletal maturation
  evidence:
  - reference: PMID:42496035
    reference_title: "Endocrine Phenotypes and Hormonal Treatment in Meier-Gorlin Syndrome: Report of Two Cases and a Systematic Review of Literature."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "with 70% exhibiting delayed bone age, 42.9% low IGF-1 and 35.3% GHD"
    explanation: >-
      Quantifies delayed bone age at 70% of reviewed cases, supporting a
      FREQUENT band.
- name: Hearing impairment
  category: Otologic
  description: >-
    Hearing loss accompanies the external ear malformation and warrants
    audiologic assessment and intervention.
  phenotype_term:
    preferred_term: Hearing impairment
    term:
      id: HP:0000365
      label: Hearing impairment
  evidence:
  - reference: PMID:26381604
    reference_title: "Meier-Gorlin syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "prevention of associated problems, such as growth retardation, feeding problems, hearing loss, luxating patellae, knee pain, gonarthrosis"
    explanation: >-
      The management review lists hearing loss among the associated problems
      requiring surveillance.
- name: Decreased response to growth hormone stimulation test
  category: Endocrine
  description: >-
    A substantial minority of individuals meet criteria for growth hormone
    deficiency on stimulation testing, and low IGF-1 is more common still. These
    findings identify the subgroup most likely to benefit from growth hormone.
  frequency: FREQUENT
  phenotype_term:
    preferred_term: Decreased response to growth hormone stimulation test
    term:
      id: HP:0000824
      label: Decreased response to growth hormone stimulation test
  evidence:
  - reference: PMID:42496035
    reference_title: "Endocrine Phenotypes and Hormonal Treatment in Meier-Gorlin Syndrome: Report of Two Cases and a Systematic Review of Literature."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "42.9% low IGF-1 and 35.3% GHD"
    explanation: >-
      Quantifies growth hormone deficiency at 35.3% of reviewed cases,
      supporting a FREQUENT band.
- name: Decreased total neutrophil count
  category: Hematologic
  description: >-
    Neutropenia, occasionally with B lymphopenia, is reported in most
    individuals in the GINS3 cohort. It is a gene-arm-specific rather than a
    general MGORS feature, and the combination of MGORS plus neutropenia has
    been proposed as a pointer toward GINS3 in candidate gene testing.
  subtype: MGORS9
  phenotype_term:
    preferred_term: Decreased total neutrophil count
    term:
      id: HP:0001875
      label: Decreased total neutrophil count
  evidence:
  - reference: PMID:37059840
    reference_title: "The expanding genetic and clinical landscape associated with Meier-Gorlin syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Interestingly, many individuals showed neutropenia (4/5 cases), with one also showing B lymphopenia."
    explanation: >-
      Quantifies neutropenia in 4 of 5 individuals in the GINS3 cohort.
  - reference: PMID:37059840
    reference_title: "The expanding genetic and clinical landscape associated with Meier-Gorlin syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Given the unique overlap of MGORS and neutropenia in GINS3 individuals, these features could be used diagnostically as differentials in candidate gene testing."
    explanation: >-
      Establishes the gene-arm specificity of the finding and its proposed
      diagnostic use.
- name: Lipodystrophy
  category: Endocrine
  description: >-
    At the severe pole of the MCM-core spectrum, a neonatal progeroid appearance
    with lipodystrophy and adrenal insufficiency has been reported, and a
    progeroid presentation has also been described with CDC6. This is a boundary
    phenotype rather than a feature of classic MGORS.
  frequency: VERY_RARE
  phenotype_term:
    preferred_term: Lipodystrophy
    term:
      id: HP:0009125
      label: Lipodystrophy
  evidence:
  - reference: PMID:33654309
    reference_title: "MCM complex members MCM3 and MCM7 are associated with a phenotypic spectrum from Meier-Gorlin syndrome to lipodystrophy and adrenal insufficiency."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "the second case has a multi-system disorder with neonatal progeroid appearance, lipodystrophy and adrenal insufficiency"
    explanation: >-
      Documents lipodystrophy at the progeroid pole of the MCM-related
      phenotypic spectrum.
genetic:
- name: ORC1
  gene_term:
    preferred_term: ORC1
    term:
      id: hgnc:8487
      label: ORC1
  association: Pathogenic Variants
  relationship_type: CAUSATIVE
  notes: >-
    Largest subunit of the origin recognition complex; its N-terminal BAH domain
    reads H4K20me2 to position ORC on chromatin. Biallelic hypomorphic variants
    cause the most severe growth and microcephaly phenotype, and ORC1-deficient
    cells additionally show the centriole and ciliogenesis defect.
  evidence:
  - reference: PMID:21358633
    reference_title: "Mutations in ORC1, encoding the largest subunit of the origin recognition complex, cause microcephalic primordial dwarfism resembling Meier-Gorlin syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Here we report that mutations in ORC1, encoding a subunit of the origin recognition complex, cause microcephalic primordial dwarfism resembling Meier-Gorlin syndrome."
    explanation: >-
      Original identification of ORC1 as an MGORS-spectrum disease gene.
- name: ORC4
  gene_term:
    preferred_term: ORC4
    term:
      id: hgnc:8490
      label: ORC4
  association: Pathogenic Variants
  relationship_type: CAUSATIVE
  notes: >-
    Origin recognition complex subunit; with ORC1 defines the most severe
    short-stature and microcephaly arm. Compound heterozygous genotypes cause
    more severe growth retardation than homozygous missense genotypes.
  evidence:
  - reference: PMID:21358632
    reference_title: "Mutations in the pre-replication complex cause Meier-Gorlin syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "we identify mutations in five separate genes: ORC1, ORC4, ORC6, CDT1 and CDC6"
    explanation: >-
      Identifies ORC4 among the five founding MGORS genes.
- name: ORC6
  gene_term:
    preferred_term: ORC6
    term:
      id: hgnc:17151
      label: ORC6
  association: Pathogenic Variants
  relationship_type: CAUSATIVE
  notes: >-
    Smallest origin recognition complex subunit, contributing to ORC assembly and
    MCM2-7 loading.
  evidence:
  - reference: PMID:21358632
    reference_title: "Mutations in the pre-replication complex cause Meier-Gorlin syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "we identify mutations in five separate genes: ORC1, ORC4, ORC6, CDT1 and CDC6"
    explanation: >-
      Identifies ORC6 among the five founding MGORS genes.
- name: CDT1
  gene_term:
    preferred_term: CDT1
    term:
      id: hgnc:24576
      label: CDT1
  association: Pathogenic Variants
  relationship_type: CAUSATIVE
  notes: >-
    Chromatin licensing and DNA replication factor 1, the direct target of
    geminin inhibition. Compound heterozygous genotypes are associated with
    pulmonary emphysema; the variant spectrum includes deep-intronic branch-point
    alleles that exome-only pipelines can miss.
  evidence:
  - reference: PMID:39789585
    reference_title: "A novel homozygous intronic variant in CDT1 that alters splicing causes Meier-Gorlin syndrome, and a review of published mutations and growth hormone treatments."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The variant was predicted to break a branch point and alter splicing, and the minigene assay confirmed abnormal splicing with exon 3 skipping."
    explanation: >-
      Functionally validated deep-intronic CDT1 allele expanding the recognized
      variant spectrum.
- name: CDC6
  gene_term:
    preferred_term: CDC6
    term:
      id: hgnc:1744
      label: CDC6
  association: Pathogenic Variants
  relationship_type: CAUSATIVE
  notes: >-
    Cell division cycle 6, which cooperates with CDT1 to load the MCM2-7
    helicase onto origin-bound ORC. Few individuals are reported.
  evidence:
  - reference: PMID:35023948
    reference_title: "Novel Compound Heterozygous Variants in the CDC6 Gene in a Russian Patient with Meier-Gorlin Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "the patient had two previously undescribed variants in the CDC6 gene, c.230A>G (p.(Lys77Arg)) and c.232C>T (p.(Gln78Ter)), NM_001254.3, in a compound heterozygous state"
    explanation: >-
      Documents biallelic CDC6 variants in a molecularly confirmed MGORS
      patient.
- name: GMNN
  gene_term:
    preferred_term: GMNN
    term:
      id: hgnc:17493
      label: GMNN
  association: Pathogenic Variants
  relationship_type: CAUSATIVE
  notes: >-
    Geminin, the licensing inhibitor. Unique among MGORS genes in acting through
    de novo heterozygous gain-of-function alleles that delete the destruction
    box, producing autosomal dominant disease.
  evidence:
  - reference: PMID:26637980
    reference_title: "De Novo GMNN Mutations Cause Autosomal-Dominant Primordial Dwarfism Associated with Meier-Gorlin Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "we report three subjects with MGS and de novo heterozygous mutations in the 5' end of GMNN, encoding the DNA replication inhibitor geminin"
    explanation: >-
      Original identification of the dominant GMNN arm of MGORS.
- name: CDC45
  gene_term:
    preferred_term: CDC45
    term:
      id: hgnc:1739
      label: CDC45
  association: Pathogenic Variants
  relationship_type: CAUSATIVE
  notes: >-
    Component of the pre-initiation and CMG helicase complexes. Notable for an
    unusually high proportion of synonymous splice-altering pathogenic alleles
    and for strong enrichment of craniosynostosis.
  evidence:
  - reference: PMID:27374770
    reference_title: "Mutations in CDC45, Encoding an Essential Component of the Pre-initiation Complex, Cause Meier-Gorlin Syndrome and Craniosynostosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Functionally, mutations reduce levels of full-length transcripts and protein in subject cells, consistent with partial loss of CDC45 function and a predicted limited rate of DNA replication and cell proliferation."
    explanation: >-
      Functional evidence that CDC45 alleles act by partial loss of function.
- name: MCM5
  gene_term:
    preferred_term: MCM5
    term:
      id: hgnc:6948
      label: MCM5
  association: Pathogenic Variants
  relationship_type: CAUSATIVE
  notes: >-
    Subunit of the replicative MCM2-7 helicase. Yeast complementation and
    zebrafish data support pathogenicity of the reported biallelic variants.
  evidence:
  - reference: PMID:28198391
    reference_title: "MCM5: a new actor in the link between DNA replication and Meier-Gorlin syndrome."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Complementation experiments in yeast showed that the plasmid carrying the missense variant was unable to rescue the lethal phenotype caused by mcm5 deletion."
    explanation: >-
      Functional complementation evidence establishing pathogenicity of the
      MCM5 missense allele.
- name: MCM7
  gene_term:
    preferred_term: MCM7
    term:
      id: hgnc:6950
      label: MCM7
  association: Pathogenic Variants
  relationship_type: CAUSATIVE
  notes: >-
    MCM2-7 subunit whose biallelic variants span classic MGORS through a
    progeroid, lipodystrophic multisystem disorder.
  evidence:
  - reference: PMID:33654309
    reference_title: "MCM complex members MCM3 and MCM7 are associated with a phenotypic spectrum from Meier-Gorlin syndrome to lipodystrophy and adrenal insufficiency."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We confirm variants in MCM7 are deleterious and through interfering with MCM complex formation, impact efficiency of S phase progression."
    explanation: >-
      Establishes MCM7 pathogenicity and its mechanism through impaired MCM
      complex formation.
- name: MCM3
  gene_term:
    preferred_term: MCM3
    term:
      id: hgnc:6945
      label: MCM3
  association: Candidate Gene
  relationship_type: DISPUTED
  notes: >-
    Reported as a strong candidate rather than a confirmed MGORS gene; evidence
    currently rests on a single biallelic case and has not been independently
    replicated.
  evidence:
  - reference: PMID:33654309
    reference_title: "MCM complex members MCM3 and MCM7 are associated with a phenotypic spectrum from Meier-Gorlin syndrome to lipodystrophy and adrenal insufficiency."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "we identify biallelic pathogenic variants in MCM7 and a strong candidate biallelic pathogenic variant in MCM3"
    explanation: >-
      The authors themselves grade MCM3 as a strong candidate rather than an
      established gene, so the association is recorded as partial.
- name: GINS2
  gene_term:
    preferred_term: GINS2
    term:
      id: hgnc:24575
      label: GINS2
  association: Pathogenic Variants
  relationship_type: CAUSATIVE
  notes: >-
    GINS complex subunit; the reported p.(Arg114Leu) residue sits at the CDC45
    and MCM5 docking site, and this arm phenocopies CDC45-related disease
    including craniosynostosis.
  evidence:
  - reference: PMID:34353863
    reference_title: "Biallelic GINS2 variant p.(Arg114Leu) causes Meier-Gorlin syndrome with craniosynostosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "A novel homozygous missense variant NM_016095.2:c.341G>T, p.(Arg114Leu), in GINS2 was identified."
    explanation: >-
      Identifies the specific biallelic GINS2 allele causing MGORS with
      craniosynostosis.
- name: GINS3
  gene_term:
    preferred_term: GINS3
    term:
      id: hgnc:25851
      label: GINS3
  association: Pathogenic Variants
  relationship_type: CAUSATIVE
  notes: >-
    GINS complex subunit; hypomorphic variants clustering at aspartic acid 24
    shorten protein half-life and slow replication fork progression, with
    supporting yeast and mouse models.
  evidence:
  - reference: PMID:35603789
    reference_title: "Hypomorphic GINS3 variants alter DNA replication and cause Meier-Gorlin syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Taken together, our findings implicate GINS3 in the pathogenesis of MGS and support the notion that hypomorphic variants identified in this gene impaired cell and organismal growth by compromising DNA replication."
    explanation: >-
      Establishes GINS3 as an MGORS gene acting through compromised DNA
      replication.
- name: DONSON
  gene_term:
    preferred_term: DONSON
    term:
      id: hgnc:2993
      label: DONSON
  association: Pathogenic Variants
  relationship_type: CAUSATIVE
  notes: >-
    The thirteenth and most mechanistically distinct MGORS gene: a replisome
    component and replication fork stabilizer with no role in the
    pre-replication or pre-initiation complexes, which nonetheless is required
    for CDC45 and GINS chromatin loading. Patient substitutions reduce nuclear
    localization and a deep intronic variant creates a novel splice acceptor,
    confirming hypomorphic action. Biallelic DONSON variants also underlie the
    clinically distinct MISSLA and MIMIS primordial dwarfisms, making this an
    allelic continuum rather than a single-phenotype gene.
  evidence:
  - reference: PMID:37059840
    reference_title: "The expanding genetic and clinical landscape associated with Meier-Gorlin syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "DONSON as a novel disease gene in several MGORS patients"
    explanation: >-
      Establishes DONSON as a human MGORS disease gene identified by exome and
      phased genome sequencing across multiple patients.
  - reference: PMID:37059840
    reference_title: "The expanding genetic and clinical landscape associated with Meier-Gorlin syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "All of the DONSON-MGORS cohort had short stature, microtia and patella agenesis"
    explanation: >-
      Confirms that the DONSON cohort shows the complete MGORS clinical triad,
      not merely an overlapping growth phenotype.
  - reference: PMID:37059840
    reference_title: "The expanding genetic and clinical landscape associated with Meier-Gorlin syndrome."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "the substitutions reduced nuclear localisation of DONSON, and a deep intronic variant introduces a novel strong splice acceptor site causing a reading frameshift and premature stop codon"
    explanation: >-
      Functional evidence for the hypomorphic mechanism of the DONSON alleles,
      including a protein-localization route distinct from the other genes.
prevalence:
- population: Worldwide
  measure_type: CASES_IN_LITERATURE
  prevalence_class: ULTRA_RARE
  notes: >-
    Roughly 150 cases had been published as of a 2026 systematic review;
    population incidence, carrier frequency and prevalence per 100,000 remain
    unknown, and the published-case count must not be converted into a
    population prevalence.
  evidence:
  - reference: PMID:42496035
    reference_title: "Endocrine Phenotypes and Hormonal Treatment in Meier-Gorlin Syndrome: Report of Two Cases and a Systematic Review of Literature."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Among 29 cases (out of ~150 published), the classic triad was absent in 18.5%."
    explanation: >-
      Anchors the size of the published literature, the only occurrence measure
      available for this disorder.
diagnosis:
- name: Clinical triad criteria
  description: >-
    The diagnosis should be considered when at least two of the three cardinal
    features are present: microtia, patellar anomalies, and pre- and postnatal
    growth retardation. Requiring the complete triad would miss a substantial
    minority, since the full triad is present in roughly 82% of molecularly
    confirmed individuals.
  diagnosis_term:
    preferred_term: physical examination
    term:
      id: NCIT:C20989
      label: Physical Examination
  evidence:
  - reference: PMID:26381604
    reference_title: "Meier-Gorlin syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The diagnosis MGS should be considered in patients with at least two of the three features of the clinical triad of microtia, patellar anomalies, and pre- and postnatal growth retardation."
    explanation: >-
      States the two-of-three clinical diagnostic threshold recommended by the
      management review.
- name: Patellar imaging
  description: >-
    Because the patella ossifies late, patellar assessment must be
    age-appropriate: ultrasonography before age six and radiography thereafter.
    Skipping this step is a common reason the diagnosis is missed in a child
    presenting only with short stature and microtia.
  diagnosis_term:
    preferred_term: ultrasound imaging
    term:
      id: NCIT:C17230
      label: Ultrasound Imaging
  evidence:
  - reference: PMID:26381604
    reference_title: "Meier-Gorlin syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In patients with short stature and/or microtia, the patellae should be assessed with care by ultrasonography before age 6 or radiography thereafter."
    explanation: >-
      Specifies the age-appropriate imaging modality for detecting patellar
      anomalies.
- name: Molecular genetic testing
  description: >-
    Molecular confirmation uses a primordial dwarfism panel spanning all thirteen
    replication-initiation genes, or exome or genome sequencing with copy-number
    analysis. Testing limited to the five founding pre-replication complex genes
    identifies only about two-thirds to three-quarters of patients, and
    exome-only pipelines can miss deep-intronic splice-altering alleles.
  diagnosis_term:
    preferred_term: molecular genetic testing
    term:
      id: NCIT:C19770
      label: Molecular Analysis
  evidence:
  - reference: PMID:26381604
    reference_title: "Meier-Gorlin syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Mutations in one of five genes (ORC1, ORC4, ORC6, CDT1, and CDC6) of the pre-replication complex, involved in DNA-replication, are detected in approximately 67-78% of patients with MGS."
    explanation: >-
      Quantifies the diagnostic yield of the original five-gene panel, motivating
      broader testing.
  - reference: PMID:37059840
    reference_title: "The expanding genetic and clinical landscape associated with Meier-Gorlin syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Following the initial identification of genetic causes in 2011, a total of 13 genes have been identified to date associated with MGORS."
    explanation: >-
      Establishes the current thirteen-gene testing target for MGORS.
treatments:
- name: Growth hormone therapy
  description: >-
    Recombinant growth hormone is used off-label for short stature. It is
    ineffective in most individuals, whose growth velocity normalizes after the
    first year of life without treatment, but a subgroup benefits: those with
    documented growth hormone deficiency, delayed bone age, or low IGF-1, in whom
    substantial height gains have been reported. Screening for growth hormone
    deficiency is therefore recommended before deciding.
  therapeutic_modality: PEPTIDE
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: recombinant human growth hormone
      term:
        id: NCIT:C837
        label: Somatropin
  target_mechanisms:
  - target: Global Prenatal and Postnatal Growth Restriction
    treatment_effect: INHIBITS
    description: >-
      Growth hormone acts on the organism-level growth deficit rather than on
      the upstream replication lesion, which is why it can only partially offset
      the phenotype and only in the subgroup with a demonstrable
      growth-hormone-axis abnormality.
  evidence:
  - reference: PMID:26381604
    reference_title: "Meier-Gorlin syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Growth hormone treatment is ineffective in most patients with MGS, but may be effective in patients in whom growth continues to decrease after the first year of life"
    explanation: >-
      Establishes that growth hormone benefit is restricted to a subgroup rather
      than being a general therapy.
  - reference: PMID:23023959
    reference_title: "Meier-Gorlin syndrome: growth and secondary sexual development of a microcephalic primordial dwarfism disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Growth hormone therapy (n = 9) was generally ineffective, though in two patients with significantly reduced IGF1 levels, growth was substantially improved by GH treatment, with 2SD and 3.8 SD improvement in height."
    explanation: >-
      Cohort data showing general ineffectiveness alongside marked benefit in the
      low-IGF1 subgroup.
  - reference: PMID:42496035
    reference_title: "Endocrine Phenotypes and Hormonal Treatment in Meier-Gorlin Syndrome: Report of Two Cases and a Systematic Review of Literature."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Those with GHD and delayed bone age were more likely to benefit from GH."
    explanation: >-
      Identifies the clinical predictors that select responders to growth hormone
      therapy.
  - reference: PMID:39789585
    reference_title: "A novel homozygous intronic variant in CDT1 that alters splicing causes Meier-Gorlin syndrome, and a review of published mutations and growth hormone treatments."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "the vast majority of children with MGORS treated with GH had normal insulin-like growth factor 1 (IGF-1) levels, and half of them responded positively to GH therapy"
    explanation: >-
      Quantifies the response rate at roughly half of treated children in the
      pooled literature, and notes that most treated children did not have low
      IGF-1, which tempers the IGF-1-based selection rule.
  - reference: PMID:39789585
    reference_title: "A novel homozygous intronic variant in CDT1 that alters splicing causes Meier-Gorlin syndrome, and a review of published mutations and growth hormone treatments."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The patient was treated with GH for 5 years, with an increase in growth velocity from 4.0 cm/year to an average of 6.2 cm/year."
    explanation: >-
      Provides the magnitude of growth-velocity gain in a single well-documented
      responder, an individual rather than cohort measure.
- name: Estrogen therapy for mammary hypoplasia
  description: >-
    Estrogen treatment has been reported to be of some benefit for breast
    hypoplasia, although reported effects are variable and the evidence base is
    limited to small series.
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: estradiol
      term:
        id: CHEBI:16469
        label: 17beta-estradiol
  target_mechanisms:
  - target: Tissue-Disproportionate Growth Failure
    treatment_effect: INHIBITS
    description: >-
      Estrogen acts on the mammary component of the disproportionate growth
      failure, downstream of the replication lesion.
  evidence:
  - reference: PMID:22333897
    reference_title: "Meier-Gorlin syndrome genotype-phenotype studies: 35 individuals with pre-replication complex gene mutations and 10 without molecular diagnosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Growth hormone and estrogen treatment may be of some benefit, respectively, to growth retardation and breast hypoplasia, though further studies in this patient group are needed."
    explanation: >-
      Reports possible benefit of estrogen for breast hypoplasia while flagging
      the weakness of the evidence.
- name: Orthopedic management of patellar instability
  description: >-
    Surveillance and treatment of luxating patellae, knee pain and secondary
    gonarthrosis, including physical therapy and surgical stabilization when
    indicated.
  therapeutic_modality: SURGERY
  treatment_term:
    preferred_term: orthopedic surgical procedure
    term:
      id: NCIT:C16186
      label: Orthopedic Surgical Procedure
  evidence:
  - reference: PMID:26381604
    reference_title: "Meier-Gorlin syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "prevention of associated problems, such as growth retardation, feeding problems, hearing loss, luxating patellae, knee pain, gonarthrosis"
    explanation: >-
      Identifies patellar instability and its sequelae as targets of active
      management.
- name: Pulmonary surveillance and respiratory support
  description: >-
    Monitoring for and management of congenital pulmonary emphysema and
    associated bronchomalacia or laryngomalacia, which can cause significant
    respiratory morbidity in infancy.
  treatment_term:
    preferred_term: supportive care
    term:
      id: NCIT:C15747
      label: Supportive Care
  evidence:
  - reference: PMID:26381604
    reference_title: "Meier-Gorlin syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "possible pulmonary complications due to congenital pulmonary emphysema with or without broncho- or laryngomalacia"
    explanation: >-
      Establishes pulmonary complications as a management priority.
- name: Feeding support
  description: >-
    Nutritional and feeding support in infancy, including management of reflux,
    addressing a common contributor to early morbidity and postnatal growth
    failure.
  treatment_term:
    preferred_term: nutritional support
    term:
      id: NCIT:C15433
      label: Nutritional Support
  evidence:
  - reference: PMID:26381604
    reference_title: "Meier-Gorlin syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Management should be directed towards in-depth investigation, treatment and prevention of associated problems, such as growth retardation, feeding problems"
    explanation: >-
      Identifies feeding problems as an explicit target of the recommended
      management plan.
- name: Audiologic assessment and hearing intervention
  description: >-
    Hearing assessment and intervention, warranted by the external ear
    malformation and the documented hearing loss.
  treatment_term:
    preferred_term: supportive care
    term:
      id: NCIT:C15747
      label: Supportive Care
  evidence:
  - reference: PMID:26381604
    reference_title: "Meier-Gorlin syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "prevention of associated problems, such as growth retardation, feeding problems, hearing loss"
    explanation: >-
      Lists hearing loss among the problems requiring surveillance and
      intervention.
- name: Craniofacial surgery for craniosynostosis
  description: >-
    Surgical correction of clinically significant premature suture fusion,
    relevant particularly in the CDC45- and GINS2-related arms.
  therapeutic_modality: SURGERY
  treatment_term:
    preferred_term: surgical procedure
    term:
      id: NCIT:C15329
      label: Surgical Procedure
  evidence:
  - reference: PMID:27374770
    reference_title: "Mutations in CDC45, Encoding an Essential Component of the Pre-initiation Complex, Cause Meier-Gorlin Syndrome and Craniosynostosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Here we report the identification of mutations in CDC45 in 15 affected individuals from 12 families with MGS and/or craniosynostosis."
    explanation: >-
      Establishes the craniosynostosis burden that makes craniofacial surgical
      management relevant; the paper documents the indication rather than
      evaluating the surgery itself.
clinical_trials:
- name: NCT04569149
  status: RECRUITING
  description: >-
    Primordial Dwarfism Registry, an observational registry collecting natural
    history data across microcephalic primordial dwarfism and related conditions,
    including Meier-Gorlin syndrome. No MGORS-specific interventional trial has
    been identified.
  target_phenotypes:
  - preferred_term: Short stature
    term:
      id: HP:0004322
      label: Short stature
  evidence:
  - reference: clinicaltrials:NCT04569149
    reference_title: "Primordial Dwarfism Registry at Nemours Children's Hospital, Delaware"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The goal of this registry is to collect information on individuals with forms of microcephalic primordial dwarfism as well as related conditions."
    explanation: >-
      An observational registry that is the principal route to improved natural
      history data for this ultra-rare disorder.
differential_diagnoses:
- name: Seckel syndrome
  description: >-
    The other classical microcephalic primordial dwarfism caused by a
    replication-associated defect, but via the ATR DNA damage response and
    centrosome genes rather than origin licensing.
  disease_term:
    preferred_term: Seckel syndrome
    term:
      id: MONDO:0019342
      label: Seckel syndrome
  distinguishing_features:
  - Disproportionately severe microcephaly with intellectual disability, versus preserved intellect in MGORS
  - Bird-headed facial appearance rather than the small mouth and micro-retrognathia gestalt
  - Absence of microtia and patellar aplasia
  evidence:
  - reference: PMID:21358633
    reference_title: "Mutations in ORC1, encoding the largest subunit of the origin recognition complex, cause microcephalic primordial dwarfism resembling Meier-Gorlin syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Studies into disorders of extreme growth failure (for example, Seckel syndrome and Majewski osteodysplastic primordial dwarfism type II) have implicated fundamental cellular processes of DNA damage response signaling and centrosome function in the regulation of human growth."
    explanation: >-
      Places Seckel syndrome and MOPD II as the mechanistically adjacent
      primordial dwarfisms that must be distinguished from MGORS.
- name: Microcephalic osteodysplastic primordial dwarfism type II
  description: >-
    The other primordial dwarfism most often confused with MGORS, caused by
    biallelic PCNT variants affecting centrosome function rather than
    replication initiation. Shares extreme pre- and postnatal growth failure but
    is distinguished by disproportionately severe microcephaly, skeletal
    dysplasia, and a cerebrovascular risk (moyamoya, aneurysm) that MGORS does
    not carry.
  disease_term:
    preferred_term: microcephalic osteodysplastic primordial dwarfism type II
    term:
      id: MONDO:0008872
      label: microcephalic osteodysplastic primordial dwarfism type II
  distinguishing_features:
  - Cerebrovascular disease (moyamoya, intracranial aneurysm) is characteristic of MOPD II and not of MGORS
  - Skeletal dysplasia with disproportionate short stature, versus generally proportionate short stature in MGORS
  - Absence of microtia and patellar aplasia
  evidence:
  - reference: PMID:21358633
    reference_title: "Mutations in ORC1, encoding the largest subunit of the origin recognition complex, cause microcephalic primordial dwarfism resembling Meier-Gorlin syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Studies into disorders of extreme growth failure (for example, Seckel syndrome and Majewski osteodysplastic primordial dwarfism type II) have implicated fundamental cellular processes of DNA damage response signaling and centrosome function in the regulation of human growth."
    explanation: >-
      Names MOPD II alongside Seckel syndrome as the centrosome-and-damage-response
      primordial dwarfisms that MGORS must be distinguished from.
- name: Hutchinson-Gilford progeria syndrome
  description: >-
    Considered in the differential when an MGORS infant presents with a neonatal
    progeroid appearance, lipodystrophy, thin skin and alopecia, as reported in
    CDC6-related and MCM7-related disease.
  disease_term:
    preferred_term: Hutchinson-Gilford progeria syndrome
    term:
      id: MONDO:0008310
      label: Hutchinson-Gilford progeria syndrome
  distinguishing_features:
  - Microtia with patellar aplasia favors MGORS
  - Progressive cardiovascular disease and alopecia dominate the progeria course
  evidence:
  - reference: PMID:35023948
    reference_title: "Novel Compound Heterozygous Variants in the CDC6 Gene in a Russian Patient with Meier-Gorlin Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Differential diagnosis was performed with chromosomal abnormalities and Hutchinson-Gilford progeria."
    explanation: >-
      Documents progeria as the differential actually entertained for a
      progeroid-appearing MGORS presentation.
discussions:
- discussion_id: gap_mgors_licensing_severity_uncoupling
  kind: KNOWLEDGE_GAP
  status: OPEN
  prompt: >-
    Why does the measured origin licensing deficit in patient cells fail to
    predict S-phase progression rate or clinical severity?
  attaches_to:
  - pathophysiology#Impaired Replication Origin Licensing
  - pathophysiology#Delayed S-Phase Entry and Reduced Cell Proliferation
  rationale: >-
    Licensing capacity is impaired in all MGORS patient cells regardless of gene,
    yet it does not correlate with the rate of S-phase progression, and the
    clinical severity gradient (ORC1 and ORC4 most severe) is not explained by
    licensing measurements alone. This uncoupling is a central unresolved
    question of MGORS pathogenesis and is what motivates the parallel
    non-replicative arms, notably the centriole and ciliogenesis route. Whether
    the non-canonical roles of these proteins, tissue-specific proliferative
    demand, or something else supplies the missing explanatory variable is
    unknown. One partial answer already exists for the ORC1 arm specifically:
    the BAH domain reads H4K20me2 to target ORC to origins, so BAH mutations
    remove a chromatin-targeting step rather than simply lowering licensing
    capacity. Whether an analogous upstream-targeting defect distinguishes the
    other severe arms has not been tested.
  proposed_experiments:
  - experiment_id: exp_mgors_licensing_vs_output_allelic_series
    name: Parallel licensing, fork, cell-cycle and ciliogenesis phenotyping across an isogenic MGORS allelic series
    description: >-
      Measure licensed origin density, fork speed, cell cycle length and
      ciliogenesis competence in parallel across an isogenic allelic series
      spanning the licensing module (ORC1, ORC4, CDT1) and the CMG module
      (CDC45, GINS2, GINS3), in a developmentally relevant proliferating cell
      type such as iPSC-derived chondroprogenitors, and test which measure
      predicts differentiation output.
    decision_criterion: >-
      The measure whose variation across the allelic series best predicts
      chondrogenic differentiation output identifies the rate-limiting step.
    supporting_outcome:
    - Ciliogenesis competence predicts differentiation output better than licensed origin density, supporting the non-replicative arm as the severity determinant
    refuting_outcome:
    - Licensed origin density predicts differentiation output linearly, restoring the simple licensing-deficit model
  evidence:
  - reference: PMID:23516378
    reference_title: "Deficiency in origin licensing proteins impairs cilia formation: implications for the aetiology of Meier-Gorlin syndrome."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Thus, the replicative capacity in MGS patient cells does not correlate with clinical manifestation."
    explanation: >-
      States the uncoupling between replicative capacity and clinical severity
      that defines this knowledge gap.
- discussion_id: gap_mgors_tissue_selectivity
  kind: KNOWLEDGE_GAP
  status: OPEN
  prompt: >-
    What determines the tissue selectivity of MGORS, so that external ear
    cartilage, the patella, mammary tissue and the external genitalia are
    affected out of proportion to overall stature?
  attaches_to:
  - pathophysiology#Tissue-Disproportionate Growth Failure
  - pathophysiology#Reduced Hedgehog Signaling and Impaired Chondroinduction
  rationale: >-
    A uniform, cell-autonomous replication deficit should scale all tissues
    together, yet the phenotype is strikingly selective, and it is that
    selectivity, not the short stature, that makes MGORS clinically
    recognizable. Candidate explanations include narrow developmental windows of
    unusually intense proliferation in these structures and the ciliary Hedgehog
    and chondroinduction arm, but no cell-type-resolved human data exist.
  proposed_experiments:
  - experiment_id: exp_mgors_progenitor_demand_mapping
    name: Cell-type-resolved mapping of proliferative demand in MGORS-vulnerable human embryonic structures
    description: >-
      Build a cell-type-resolved map of proliferative demand and replication
      stress in human embryonic auricular cartilage, patellar anlage and
      mammary bud, and test whether a licensing-deficient background
      preferentially depletes progenitors in exactly those compartments.
    decision_criterion: >-
      Preferential progenitor depletion in the MGORS-vulnerable compartments
      relative to matched control compartments supports proliferative demand as
      the selectivity mechanism.
    supporting_outcome:
    - MGORS-vulnerable compartments show the highest proliferative demand and the greatest progenitor loss under a licensing-deficient background
    refuting_outcome:
    - Progenitor loss is uniform across compartments, implicating a tissue-specific signaling requirement instead
  evidence:
  - reference: PMID:23023959
    reference_title: "Meier-Gorlin syndrome: growth and secondary sexual development of a microcephalic primordial dwarfism disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "we highlight that growth is disproportionately affected in certain structures"
    explanation: >-
      Documents the disproportionate, structure-selective growth failure whose
      mechanism this gap concerns.
- discussion_id: mismatch_mgors_gins3_mouse_lethality
  kind: HUMAN_MODEL_MISMATCH
  status: OPEN
  prompt: >-
    Does the GINS3 D24 mouse model, which is embryonic lethal, faithfully
    represent human GINS3-related Meier-Gorlin syndrome, in which affected
    individuals survive?
  attaches_to:
  - pathophysiology#Global Prenatal and Postnatal Growth Restriction
  rationale: >-
    Homozygous D24 mouse embryos show intrauterine growth retardation and do not
    survive to birth, while the seven humans reported with the corresponding
    hypomorphic GINS3 genotypes survive with an MGORS-like phenotype. The mouse
    therefore recapitulates growth restriction but overshoots on severity, so
    mechanistic inferences drawn from it, particularly the accelerated
    senescence of the derived fibroblasts, may reflect a more complete loss of
    function than human disease alleles produce.
  proposed_experiments:
  - experiment_id: exp_mgors_gins3_humanized_allelic_series
    name: Humanized GINS3 allelic series calibrating mouse severity against patient fibroblasts
    description: >-
      Generate a mouse allelic series carrying the specific human GINS3
      hypomorphic substitutions at matched residues, and compare residual
      protein level, fork progression and senescence markers against
      patient-derived fibroblasts to calibrate where the human alleles sit on
      the murine severity curve.
    decision_criterion: >-
      Concordance of residual protein level, fork speed and senescence markers
      between the humanized mice and patient fibroblasts establishes the
      translational validity of the murine readouts.
    supporting_outcome:
    - Humanized alleles produce viable mice whose fibroblast phenotypes match patient cells, validating the model
    refuting_outcome:
    - Humanized alleles remain lethal or produce senescence far exceeding patient cells, confining the model to loss-of-function extremes
  evidence:
  - reference: PMID:35603789
    reference_title: "Hypomorphic GINS3 variants alter DNA replication and cause Meier-Gorlin syndrome."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "We further showed that mouse embryos homozygous for a D24 variant presented intrauterine growth retardation and did not survive to birth"
    explanation: >-
      Documents the murine lethality that the surviving human patients do not
      show, which is the mismatch at issue.
references:
- reference: PMID:37059840
  title: "The expanding genetic and clinical landscape associated with Meier-Gorlin syndrome"
- reference: PMID:26381604
  title: "Meier-Gorlin syndrome"

📚

References & Deep Research

References

2

PMID:37059840

The expanding genetic and clinical landscape associated with Meier-Gorlin syndrome

No top-level findings curated for this source.

PMID:26381604

Meier-Gorlin syndrome

No top-level findings curated for this source.

Deep Research

1

Falcon ▸

Disease Characteristics Research Template

Edison Scientific Literature 29 citations 2026-07-31T23:06:34.982736

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: Meier-Gorlin syndrome
MONDO ID: (if available)
Category: Mendelian

Research Objectives

Please provide a comprehensive research report on Meier-Gorlin 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 NCIT (NCI Thesaurus) clinical-intervention 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, NCIT, 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 (NCIT terms) - Evidence items with PMIDs and exact abstract quotes - Epidemiology, prognosis, diagnostic, and prevention information - Animal model descriptions with phenotype recapitulation details

Meier–Gorlin syndrome: comprehensive disease-characteristics report

Executive summary

Meier–Gorlin syndrome (MGORS) is an extremely rare, predominantly autosomal-recessive microcephalic primordial-dwarfism disorder caused by hypomorphic defects in DNA-replication licensing or replicative-helicase assembly. Its classic triad is prenatal/postnatal growth restriction, microtia, and absent or hypoplastic patellae; genital anomalies and post-pubertal mammary hypoplasia are also characteristic. At least two elements of the classic triad occur in approximately 97% of reported patients, but molecularly confirmed cases increasingly demonstrate a broader phenotype. Fewer than 100 affected individuals had been reported by the 2023 review, so frequencies and treatment estimates remain vulnerable to ascertainment and publication bias. (nielsendandoroff2023theexpandinggenetic pages 1-2, mcquaid2022hypomorphicgins3variants pages 1-2)

The current genetic spectrum comprises 13 replication-associated genes: ORC1, ORC4, ORC6, CDT1, CDC6, GMNN, MCM3, MCM5, MCM7, CDC45, GINS2, GINS3, and DONSON. Most disease is caused by biallelic hypomorphic alleles; heterozygous/de-novo GMNN disease is the important inheritance exception. The upstream defect is insufficient origin licensing or CMG-helicase assembly, followed by impaired S-phase progression, reduced proliferation and sometimes senescence/apoptosis in rapidly growing embryonic tissues. (nielsendandoroff2023theexpandinggenetic pages 1-2, mcquaid2022hypomorphicgins3variants pages 19-20, nielsendandoroff2023theexpandinggenetic pages 2-2)

The following structured summary highlights the most reusable evidence.

domain	key finding	ontology-ready terms/IDs where confidently known	evidence type	key source/date/DOI
Disease definition / core triad	Meier-Gorlin syndrome (MGORS), previously called ear-patella-short stature syndrome, is a rare microcephalic primordial dwarfism classically defined by short stature, microtia, and patella hypo/aplasia; many patients also have genital anomalies and post-pubertal female mammary hypoplasia	Candidate disease ontology term: MONDO not confirmed here; phenotype terms confidently usable: short stature HP:0004322; microtia HP:0008551; patellar aplasia/hypoplasia candidate HPO term(s), exact ID not confirmed here; primordial dwarfism candidate term not confirmed here	Human disease review / cohort synthesis	Nielsen-Dandoroff et al., 2023, Eur J Hum Genet, published Apr 2023, https://doi.org/10.1038/s41431-023-01359-z (nielsendandoroff2023theexpandinggenetic pages 1-2)
Inheritance	Usually autosomal recessive; most disease genes act through biallelic hypomorphic variants; GMNN is an exception reported with autosomal dominant inheritance in the literature summarized by the review evidence	Autosomal recessive; autosomal dominant (GMNN exception)	Human genetics review	Nielsen-Dandoroff et al., 2023, https://doi.org/10.1038/s41431-023-01359-z; McQuaid et al., 2022, https://doi.org/10.1172/jci.insight.155648 (nielsendandoroff2023theexpandinggenetic pages 1-2, mcquaid2022hypomorphicgins3variants pages 19-20)
Causal gene set	13 genes associated with MGORS/relevant MGORS spectrum: ORC1, ORC4, ORC6, CDT1, CDC6, GMNN, CDC45, DONSON, MCM3, MCM5, MCM7, GINS2, GINS3	HGNC gene symbols listed; pre-RC / CMG-associated genes	Human review integrating primary studies	Nielsen-Dandoroff et al., 2023, https://doi.org/10.1038/s41431-023-01359-z (nielsendandoroff2023theexpandinggenetic pages 1-2, nielsendandoroff2023theexpandinggenetic pages 2-2)
Molecular mechanism	Core mechanism is defective DNA replication initiation/licensing and/or CMG helicase assembly, reducing loading of early replication machinery onto replication origins and impairing cellular proliferation during development	GO candidate terms: DNA replication initiation; DNA replication; replication origin licensing; CMG helicase complex assembly (exact GO IDs not confirmed here)	Human review + functional studies	Nielsen-Dandoroff et al., 2023, https://doi.org/10.1038/s41431-023-01359-z; Kingsley et al., 2023, https://doi.org/10.1093/nar/gkad694; Evrin et al., 2023, https://doi.org/10.15252/embr.202357677 (nielsendandoroff2023theexpandinggenetic pages 1-2, kingsley2023donsonfacilitatescdc45 pages 1-1)
Representative variant: GINS2	Homozygous GINS2 NM_016095.2:c.341G>T, p.(Arg114Leu) causes MGORS with craniosynostosis; missense change affects a conserved residue at the CDC45/MCM5 docking site, likely disrupting CMG function	GINS2; missense variant; craniosynostosis phenotype term candidate, exact HPO ID not confirmed here	Human case + yeast functional modeling	Sá et al., 2022, J Med Genet, published Aug 2022, https://doi.org/10.1136/jmedgenet-2020-107572 (sa2022biallelicgins2variant pages 1-1, sa2022biallelicgins2variant pages 1-2)
Representative variant: GINS3	Hypomorphic GINS3 variants affecting Asp24 cause an MGORS-like phenotype in 7 individuals from 5 families; effects include impaired proliferation, S-phase accumulation, reduced protein half-life, altered replisome interactions, and slower fork progression	GINS3; hypomorphic missense spectrum affecting Asp24	Human genetics + in vitro + yeast + mouse	McQuaid et al., 2022, JCI Insight, published May 2022, https://doi.org/10.1172/jci.insight.155648 (mcquaid2022hypomorphicgins3variants pages 1-2)
Representative variant: CDT1	Novel homozygous intronic CDT1 variant c.352-30A>C disrupts a branch point, causes exon 3 skipping on minigene assay, and expands the mutational spectrum to noncanonical splice/branch-point defects	CDT1; intronic/splicing variant; likely pathogenic by ACMG in study	Human case + minigene functional assay	Li et al., 2024, Orphanet J Rare Dis, published Dec 2024, https://doi.org/10.1186/s13023-024-03430-4 (li2024anovelhomozygous pages 9-10)
DONSON	DONSON is now established within the MGORS spectrum; 2023 studies show it is required for Cdc45 and GINS chromatin association and for CMG helicase assembly during S phase, explaining how DONSON variants cause disease	DONSON; CMG helicase assembly; replication initiation	Human review + Xenopus extract + mammalian cell studies	Kingsley et al., 2023, https://doi.org/10.1093/nar/gkad694; Evrin et al., 2023, https://doi.org/10.15252/embr.202357677; Nielsen-Dandoroff et al., 2023, https://doi.org/10.1038/s41431-023-01359-z (kingsley2023donsonfacilitatescdc45 pages 12-13, kingsley2023donsonfacilitatescdc45 pages 1-1, nielsendandoroff2023theexpandinggenetic pages 5-6)
Growth / phenotype statistics	Fewer than 100 cases were noted in the 2023 review; severe prenatal/postnatal growth failure is typical. In the 2024 review of molecularly defined cases, mean birth length was -3.9 SDS, birth weight -3.4 SDS, and adult height averaged -4.5 SDS; reported mean adult heights were 137.7 cm in females and 147.0 cm in males	short stature HP:0004322; intrauterine growth restriction candidate term not confirmed here; microcephaly candidate term not confirmed here	Human review / literature summary	Nielsen-Dandoroff et al., 2023, https://doi.org/10.1038/s41431-023-01359-z; Li et al., 2024, https://doi.org/10.1186/s13023-024-03430-4 (nielsendandoroff2023theexpandinggenetic pages 1-2, li2024anovelhomozygous pages 10-12)
Diagnostic phenotype threshold	At least two of the three core features are present in 97% of patients summarized in the GINS3 paper’s background review, supporting phenotype-driven suspicion even when the full triad is incomplete	short stature HP:0004322; microtia HP:0008551; patella aplasia/hypoplasia candidate HPO term(s)	Human literature synthesis	McQuaid et al., 2022, https://doi.org/10.1172/jci.insight.155648 (mcquaid2022hypomorphicgins3variants pages 1-2)
Growth hormone response	Evidence remains limited and off-label, but GH may benefit a subset: literature review of 12 treated patients found 58% (7/12) positive response; response was 100% in those with low IGF-1 and 50% in those with normal IGF-1 in the 2024 review dataset; no adverse reactions were reported in that review	Growth hormone treatment candidate NCIT term not confirmed here; IGF-1 biomarker candidate not mapped here	Human case + literature review	Li et al., 2024, https://doi.org/10.1186/s13023-024-03430-4 (li2024anovelhomozygous pages 10-12, li2024anovelhomozygous pages 9-10)
Model systems	Disease mechanism has been studied in zebrafish (ORC1 depletion causing MGS-like growth phenotype; H4K20me2 depletion reducing body size), mouse embryos/fibroblasts (GINS3 Asp24 models with growth retardation, lethality, senescence), budding yeast (GINS2/GINS3 ortholog assays), Xenopus egg extracts (DONSON-dependent CMG assembly), and Drosophila/other systems summarized in reviews	Cell/tissue candidates not fully resolved here; zebrafish NCBI Taxon candidate 7955; mouse 10090; Xenopus laevis 8355; budding yeast Saccharomyces cerevisiae 4932	Model organism + in vitro + cell-free functional evidence	Kuo et al., 2012, https://doi.org/10.1038/nature10956; McQuaid et al., 2022, https://doi.org/10.1172/jci.insight.155648; Kingsley et al., 2023, https://doi.org/10.1093/nar/gkad694; Nielsen-Dandoroff et al., 2023, https://doi.org/10.1038/s41431-023-01359-z (mcquaid2022hypomorphicgins3variants pages 1-2, kingsley2023donsonfacilitatescdc45 pages 1-1, nielsendandoroff2023theexpandinggenetic pages 8-9)
Epigenetic link	ORC1 BAH domain recognizes H4K20me2, linking histone methylation to replication licensing; loss of this interaction impairs origin occupancy/chromatin loading and can produce an MGS-like growth phenotype in zebrafish	H4K20me2 as histone mark; ORC1 BAH domain	Structural biology + cell biology + zebrafish	Kuo et al., 2012, Nature, published Mar 2012, https://doi.org/10.1038/nature10956 (nielsendandoroff2023theexpandinggenetic pages 1-2)
Clinical-trial status	No disease-specific interventional MGORS trial was identified in the retrieved evidence; one broader observational registry is recruiting: Primordial Dwarfism Registry (NCT04569149), observational, target enrollment 200	ClinicalTrials.gov: NCT04569149	Registry / observational study	ClinicalTrials.gov entry NCT04569149, recruiting at retrieval time (trial search evidence)

Table: This table summarizes high-yield knowledge-base facts for Meier-Gorlin syndrome, including core definition, gene set, mechanism, representative variants, growth data, treatment signals, models, and trial status. It is designed for rapid curation and ontology-aware annotation while avoiding uncertain IDs.

1. Disease information

Definition and identifiers

MGORS was historically called ear–patella–short stature syndrome, microtia–absent patellae–micrognathia syndrome, and Meier–Gorlin primordial dwarfism. It is a congenital, lifelong Mendelian developmental disorder rather than an acquired endocrine growth disorder. (nielsendandoroff2023theexpandinggenetic pages 1-2, mcquaid2022hypomorphicgins3variants pages 1-2)

Recommended identifiers for curation are:

OMIM phenotype: 224690, Meier-Gorlin syndrome 1; OMIM also assigns gene-specific MGORS subtypes.
Orphanet: ORPHA:2554.
MONDO: commonly mapped to MONDO:0012826; this identifier should be checked against the release used by the target knowledge base.
ICD-10/ICD-11: no uniquely specific MGORS code was identified; coding generally falls under congenital malformation or short-stature categories.
MeSH: no dedicated disease descriptor was identified in the retrieved evidence; “Dwarfism” and “Microcephaly” are broader indexing concepts.

The evidence summarized here is aggregated disease-level evidence from published cohorts, case reports, reviews, and functional studies—not individual EHR data. The 2023 review is the most current broad synthesis; the December 2024 report adds a functionally validated CDT1 splice variant and treatment review. (nielsendandoroff2023theexpandinggenetic pages 1-2, li2024anovelhomozygous pages 9-10)

2. Etiology, risk, protection, and gene–environment interaction

Causal factors

MGORS is genetic. Pathogenic variants impair proteins that license replication origins or assemble/activate the CDC45–MCM2-7–GINS (CMG) helicase. The disorder is therefore best understood as a developmental “replication-initiation disorder.” (nielsendandoroff2023theexpandinggenetic pages 2-2, nielsendandoroff2023theexpandinggenetic pages 1-2)

Most alleles are missense, splice-altering, or otherwise hypomorphic. Complete loss of an essential replication factor is frequently presumed incompatible with embryonic survival; accordingly, disease severity often reflects residual activity. A hypomorphic/hypomorphic combination tends to be less severe than a hypomorphic/null combination, although gene-specific exceptions and small sample sizes limit prediction. Approximately 20% of clinically diagnosed cases remained molecularly unresolved in one recent analysis. (sa2022biallelicgins2variant pages 1-1)

Risk factors

Genetic: biallelic pathogenic or likely pathogenic variants in the listed genes; parental consanguinity increases the probability of homozygosity but is not required.
Family history: affected siblings and carrier parents are expected under recessive inheritance; recurrence risk is ordinarily 25% for each pregnancy when both parents carry the same autosomal-recessive condition.
Environmental, lifestyle, infectious, occupational, age, and sex-dependent acquisition risks: none established. Sex changes the visibility of genital and mammary phenotypes, not the underlying genetic risk.

Protective factors and gene–environment interactions

No validated protective variant, diet, lifestyle measure, toxin avoidance strategy, or infectious prophylaxis prevents MGORS after conception. No reproducible human gene–environment interaction has been demonstrated. Nicotinamide sensitivity in a GINS2 yeast assay is a functional replication-stress readout, not evidence that dietary nicotinamide causes or modifies human MGORS. (sa2022biallelicgins2variant pages 1-1)

3. Phenotypes

Core and associated phenotype set

Phenotype	Type, onset, course	Frequency/severity evidence	Suggested HPO annotation
Prenatal growth restriction	Fetal sign; congenital; persistent into postnatal life	Mean birth length −3.9 SDS and weight −3.4 SDS in the 2024 synthesis	Intrauterine growth retardation; low birth weight
Short stature/primordial dwarfism	Physical sign; congenital/childhood; chronic, generally proportionate	Mean adult height approximately −4.5 SDS; reported means 137.7 cm in females and 147.0 cm in males	HP:0004322 Short stature, proportionate short stature
Microtia, often bilateral	Congenital structural sign; stable	One of the classic triad; severity variable	HP:0008551 Microtia
Patellar aplasia/hypoplasia	Congenital skeletal sign, sometimes recognized only when ossification permits imaging	Classic triad; can be incomplete or delayed diagnostically	Absent patella; patellar hypoplasia
Microcephaly	Congenital/developmental sign; generally proportionate to body size but can be marked	Variable by gene; MGORS is classified among microcephalic primordial dwarfisms	HP:0000252 Microcephaly
Mammary hypoplasia/agenesis	Pubertal physical manifestation	Reported as completely penetrant among evaluated post-pubertal females in the 2023 synthesis	Breast hypoplasia/aplasia
Genital anomalies	Congenital physical sign	Variable; may include cryptorchidism or hypoplastic external genitalia	Abnormality of genital system; cryptorchidism where applicable
Characteristic face	Congenital/evolving physical signs	Downslanting palpebral fissures, full lower lip, micrognathia; nasal prominence may increase with age	Downslanting palpebral fissures; full lower lip; micrognathia
Feeding/GI or respiratory difficulty	Symptom/complication, usually infancy	Variable; may materially affect early morbidity	Feeding difficulties; gastroesophageal reflux; respiratory distress as applicable
Developmental delay/intellectual disability	Neurodevelopmental phenotype	Variable and not obligatory; severe neurological involvement should prompt gene-specific interpretation or differential diagnosis	Global developmental delay; intellectual disability
Craniosynostosis	Congenital cranial sign	Enriched particularly in CDC45- and GINS2-related disease	Craniosynostosis; coronal craniosynostosis
Cardiac malformation	Congenital structural sign	Uncommon/variable; atrial septal defect documented in a GINS2 case	Congenital heart defect; atrial septal defect

Growth figures are from aggregated molecularly characterized cases and must not be treated as population norms. (li2024anovelhomozygous pages 10-12, nielsendandoroff2023theexpandinggenetic pages 1-2, sa2022biallelicgins2variant pages 1-2)

Functional and quality-of-life effects

Likely burdens include reduced mobility or knee instability from patellar defects, repeated orthopedic assessment, feeding support during infancy, surgeries for craniosynostosis or congenital anomalies, psychosocial effects of extreme short stature, and reproductive/body-image effects of genital or mammary hypoplasia. No validated MGORS-specific EQ-5D, SF-36, PROMIS, or quality-of-life cohort was found; quantitative claims would therefore be inappropriate.

4. Genetic and molecular information

Causal genes and pathway position

Origin recognition/licensing: ORC1, ORC4, ORC6, CDC6, CDT1, GMNN.
MCM helicase core: MCM3, MCM5, MCM7.
CMG activation/assembly: CDC45, GINS2, GINS3, DONSON.

The 2023 review counted 13 causal genes and emphasized that all converge on early DNA replication, although DONSON’s initiation role was only clarified in 2023. (nielsendandoroff2023theexpandinggenetic pages 1-2, kingsley2023donsonfacilitatescdc45 pages 1-1)

Representative pathogenic variants

GINS2 NM_016095.2:c.341G>T, p.(Arg114Leu): homozygous missense allele affecting a conserved CDC45/MCM5 docking interface. Yeast modeling showed increased sensitivity to replication interference; the human phenotype included coronal craniosynostosis, mild short stature, and patellar hypoplasia. (sa2022biallelicgins2variant pages 1-1, sa2022biallelicgins2variant pages 1-2)
GINS3 Asp24 variants: hypomorphic variants were found in seven individuals from five families. They shorten protein half-life, alter replisome interactions, slow fork progression, reduce proliferation, and produce S-phase accumulation. (mcquaid2022hypomorphicgins3variants pages 1-2)
CDT1 NM_030928.4:c.352-30A>C: homozygous deep-intronic/branch-point variant classified likely pathogenic by the authors (PS3, PM2, PP4); a minigene assay confirmed exon 3 skipping. (li2024anovelhomozygous pages 9-10)
ORC1: pathogenic substitutions often affect the N-terminal BAH chromatin-binding domain; splice, frameshift, and deletion alleles can lower protein abundance. (nielsendandoroff2023theexpandinggenetic pages 2-2)
CDC45: missense, splice, and an unusually prominent group of synonymous splice-altering variants occur; reduced protein abundance and craniosynostosis are recurrent observations. (nielsendandoroff2023theexpandinggenetic pages 5-6, nielsendandoroff2023theexpandinggenetic pages 1-2)
DONSON: biallelic hypomorphic missense, splice, and deep-intronic variants can reduce nuclear localization or protein function. More severe biallelic DONSON disease overlaps microcephaly–micromelia syndrome/MISSLA, illustrating an allelic continuum. (nielsendandoroff2023theexpandinggenetic pages 5-6)

Variants are constitutional germline changes, not somatic drivers. Pathogenic alleles should generally be absent or extremely rare in population databases, but variant-specific gnomAD frequencies must be obtained from the relevant genome build and transcript rather than inferred from syndrome frequency.

Modifiers, epigenetics, and chromosome abnormalities

No validated human modifier gene or MGORS-specific DNA-methylation episignature is established. The strongest epigenetic mechanistic link is that the ORC1 BAH domain recognizes H4K20me2; disruption decreases ORC1 origin occupancy, ORC chromatin loading, and cell-cycle progression. This is chromatin-mediated replication regulation, not evidence of an acquired epigenetic cause. No recurrent aneuploidy, translocation, inversion, or pathogenic copy-number syndrome defines MGORS, although deletions involving a causal gene can act as one allele.

5. Environmental information

No toxin, radiation exposure, pollutant, occupation, diet, smoking, alcohol use, exercise pattern, or infectious agent is known to cause or trigger MGORS. Environmental and infectious-agent sections are therefore not applicable as primary etiology. Standard nutrition, vaccination, and avoidance of tobacco/alcohol remain general health measures but are not disease prevention.

6. Mechanism and pathophysiology

Causal chain

Upstream germline defect: a hypomorphic replication-factor allele reduces protein level, stability, localization, chromatin interaction, or complex binding.
Origin licensing/activation defect: ORC–CDC6–CDT1 loading of MCM2-7, or subsequent CDC45/GINS recruitment, becomes inefficient.
CMG and S-phase dysfunction: fewer origins fire, replication forks progress abnormally, and cells accumulate in S phase or experience replication stress.
Cellular outcome: reduced proliferation, prolonged cell cycle, senescence and, in severe contexts, apoptosis or embryonic lethality.
Developmental outcome: rapidly expanding embryonic progenitor populations generate fewer cells, producing global growth restriction and tissue-selective malformations of ear, patella, skull, genitalia, and mammary tissue. (mcquaid2022hypomorphicgins3variants pages 1-2, nielsendandoroff2023theexpandinggenetic pages 1-2)

The 2023 DONSON work filled an important mechanistic gap: DONSON is dispensable for MCM loading in G1 but required in S phase for CDC45/GINS association and active CMG assembly. Xenopus egg extracts and mammalian-cell experiments independently support this conclusion. (kingsley2023donsonfacilitatescdc45 pages 12-13, kingsley2023donsonfacilitatescdc45 pages 1-1)

Suggested ontology annotations

GO biological process: DNA replication initiation; DNA replication origin licensing; DNA unwinding involved in DNA replication; cell-cycle S phase; regulation of mitotic cell cycle; cellular response to DNA replication stress; cellular senescence.
GO cellular component: nucleus; chromatin; replication fork; origin recognition complex; MCM complex; CMG complex/replisome.
Candidate cell types (CL): embryonic fibroblast; chondrocyte and chondrocyte progenitor; osteoblast; cranial neural-crest-derived mesenchymal cell; mammary epithelial progenitor; neural progenitor. These are biologically plausible developmental targets, but direct cell-type-resolved human evidence is limited.

Omics and advanced technologies

Patient-cell protein abundance, interaction, cell-cycle, and replication-fork assays provide the strongest molecular profiles. No validated diagnostic metabolomic, lipidomic, bulk-transcriptomic, single-cell, spatial-transcriptomic, or integrated multi-omic signature was identified. A 2024 computational “progeria phenome” study clustered MGORS with progeroid disorders, but this is hypothesis-generating rather than proof that MGORS is clinically a premature-aging syndrome. (worm2024definingtheprogeria pages 10-11)

7. Anatomical structures affected

Primary structures include the whole-body skeleton/growth plate, external ear, patella/knee, skull sutures, brain/head, external genitalia, testes, and mammary gland. Secondary or variably involved systems include gastrointestinal, respiratory, cardiac, and neurodevelopmental systems. Most structural abnormalities are bilateral or generalized; microtia and patellar changes may nevertheless be asymmetric.

Suggested mappings include UBERON:0001690 ear, patella, knee, skull suture, mammary gland, external genitalia, testis, brain, and growth plate. At the subcellular level, the principal sites are nucleus, chromatin, replication origin, replication fork, and replisome, not mitochondria, lysosomes, or extracellular matrix.

8. Temporal development and natural history

Onset is prenatal and insidious, with fetal growth restriction often detectable by ultrasound. Microtia and genital anomalies are apparent at birth; patellar hypoplasia may not be radiographically obvious until later childhood because of normal ossification timing. Growth failure persists throughout childhood, while mammary hypoplasia becomes assessable only at puberty. Facial nasal prominence may become more evident with age. (nielsendandoroff2023theexpandinggenetic pages 1-2)

MGORS is chronic and lifelong, not episodic or relapsing-remitting. There are no standardized stages or spontaneous remission. Critical windows include prenatal development, infancy for feeding/respiratory support, childhood for growth and orthopedic surveillance, and puberty for sexual development and mammary assessment. Severe combinations can cause prenatal or neonatal lethality, but lethality is unusual in classic surviving MGORS. (nielsendandoroff2023theexpandinggenetic pages 2-2)

9. Inheritance and population characteristics

The usual inheritance pattern is autosomal recessive with variable expressivity. Penetrance for a molecularly severe biallelic genotype appears high, but gene- and feature-specific penetrance cannot be estimated reliably from fewer than 100 published cases. Mammary hypoplasia was completely penetrant among evaluated post-pubertal females in the available synthesis. (nielsendandoroff2023theexpandinggenetic pages 1-2)

No anticipation is known. Parental germline mosaicism is theoretically relevant to apparently de-novo cases but is not a defining feature. Founder variants may occur in individual consanguineous or geographically restricted families, but no universal founder population was identified. Carrier frequency, incidence, sex ratio, and prevalence per 100,000 are unknown; the published-case count must not be converted into population prevalence. Both sexes and multiple ancestries are affected. Consanguinity increases case ascertainment for recessive forms but non-consanguineous families are well documented, including the GINS2 family. (sa2022biallelicgins2variant pages 1-1)

10. Diagnostics

Clinical evaluation

Diagnostic suspicion should arise with severe prenatal/postnatal proportionate short stature plus microtia and/or absent/hypoplastic patellae. Recommended evaluation includes serial length/height, weight and head circumference; detailed dysmorphology; knee examination and age-appropriate radiographs; hearing assessment; feeding/respiratory review; genital examination; pubertal and endocrine assessment; and targeted cardiac, renal, gastrointestinal, or cranial imaging when indicated.

No enzyme assay, circulating protein, metabolite, liquid biopsy, EEG, EMG, or biopsy is diagnostic. IGF-1 and growth-hormone-axis testing can evaluate coincident endocrine abnormalities and treatment candidacy but do not establish MGORS.

Molecular testing algorithm

Use a primordial dwarfism/short-stature panel containing all 13 genes, or exome/genome sequencing with copy-number analysis.
Confirm likely causal variants and phase them in parents.
Analyze splice effects, including synonymous and noncanonical intronic variants; RNA studies or minigene assays may be necessary.
If exome/panel testing is negative, prefer genome sequencing or targeted deep-intronic/CNV analysis. The CDT1 branch-point case demonstrates why exome-centered pipelines may miss causal intronic variants. (li2024anovelhomozygous pages 9-10)

CMA can detect a deletion involving a causal gene but is not a first-line standalone diagnostic test. Karyotyping, FISH, mitochondrial-DNA testing, and repeat-expansion testing have no routine role unless another diagnosis is suspected.

Differential diagnosis

Important alternatives include Seckel syndrome, microcephalic osteodysplastic primordial dwarfism types I/III and II, Silver–Russell syndrome, 3-M syndrome, SHORT syndrome, mandibulofacial dysostosis with microcephaly, and other replication disorders. Microtia plus absent/hypoplastic patellae strongly favors MGORS; cerebrovascular disease is more characteristic of PCNT-related MOPD II, and Silver–Russell syndrome more often shows relative macrocephaly and body asymmetry.

Screening

MGORS is not included in population newborn screening. Cascade carrier testing, prenatal diagnosis by chorionic-villus sampling/amniocentesis, and preimplantation genetic testing are possible after familial variants are identified.

11. Outcome and prognosis

No robust 5-year survival, mortality rate, or life-expectancy estimate exists. Many classically affected individuals survive into adulthood; lethality is rare in typical MGORS but can occur with severe allelic combinations. Major morbidity arises from extreme short stature, feeding or respiratory problems, orthopedic dysfunction, craniosynostosis, genital anomalies, and variable developmental involvement. (nielsendandoroff2023theexpandinggenetic pages 2-2)

Potential prognostic factors include causal gene, residual protein function, null-versus-hypomorphic allele combination, severity of prenatal growth restriction, microcephaly, respiratory compromise, and major congenital anomalies. CDC45/GINS2 variants raise concern for craniosynostosis; broader GINS/MCM disorders can overlap immunodeficiency, although this is not universal MGORS. No validated molecular prognostic biomarker or risk calculator exists. (sa2022biallelicgins2variant pages 4-5, sa2022biallelicgins2variant pages 1-1)

12. Treatment and current applications

There is no approved disease-modifying drug, gene therapy, RNA therapy, cell therapy, or replication-targeted therapy. Management is individualized and multidisciplinary:

nutritional and feeding support, including reflux management;
respiratory care when required;
audiology and hearing intervention;
physical/occupational therapy and orthopedic management of patellar/knee dysfunction;
craniofacial/neurosurgical treatment of clinically significant craniosynostosis;
endocrine monitoring, pubertal support, and management of genital anomalies;
developmental assessment and educational intervention;
cardiac or other organ-specific treatment.

Suggested NCIT intervention concepts include Genetic Counseling, Physical Therapy, Occupational Therapy, Nutritional Support, Hearing Aid, Surgical Procedure, and Growth Hormone Therapy; exact NCIT codes should be resolved against the implementation release.

Growth hormone

GH is off-label and evidence is limited to case reports/series. In a 2024 review of 12 treated children, mean treatment-start age was 3.7±1.2 years, baseline height −5.9±1.2 SDS, and treatment duration 4.8±2.9 years. Seven of 12 (58%) were considered responders; five gained a mean 2.2±0.9 height SDS and two had accelerated growth velocity. The index CDT1 patient’s velocity increased from 4.0 to an average 6.2 cm/year over five years. No adverse reactions were reported in that small literature set, but long-term safety and final-height efficacy remain uncertain. (li2024anovelhomozygous pages 10-12, li2024anovelhomozygous pages 9-10)

No MGORS-specific interventional trial was identified. NCT04569149, the recruiting Primordial Dwarfism Registry, is observational with planned enrollment of 200 and may improve natural-history knowledge.

13. Prevention

Primary prevention by lifestyle modification or vaccination is impossible because MGORS is inherited. Meaningful prevention consists of reproductive genetics: carrier/cascade testing, counseling about recurrence, prenatal molecular diagnosis, donor gametes, or preimplantation genetic testing.

Secondary prevention means early recognition of fetal growth restriction and the microtia–patella phenotype, followed by molecular diagnosis and surveillance. Tertiary prevention includes early nutrition and respiratory support, monitoring cranial sutures and hearing, orthopedic therapy, developmental services, and endocrine/puberty follow-up. Routine immunization remains appropriate but is not MGORS-specific prophylaxis.

14. Other species and natural disease

No well-established naturally occurring veterinary counterpart, breed predisposition, zoonotic transmission, or cross-species infectious susceptibility was found. MGORS is noncommunicable and has no zoonotic potential. Orthologs of the causal replication genes are deeply conserved across eukaryotes, enabling comparative functional modeling rather than veterinary case surveillance.

Relevant taxa include Homo sapiens (NCBI Taxon 9606), Mus musculus (10090), Danio rerio (7955), Drosophila melanogaster (7227), Xenopus laevis (8355), and Saccharomyces cerevisiae (4932).

15. Model organisms and experimental systems

Zebrafish: ORC1 depletion causes an MGORS-like small-body phenotype; wild-type human ORC1, but not H4K20me2-binding-defective ORC1, rescues growth. H4K20me2 depletion also reduces body size, connecting chromatin recognition to organismal growth.
Mouse: embryos homozygous for GINS3 Asp24-associated alleles show intrauterine growth retardation and fail to survive to birth; embryonic fibroblasts undergo accelerated senescence. This recapitulates growth failure but is more severe than many surviving humans. (mcquaid2022hypomorphicgins3variants pages 1-2, nielsendandoroff2023theexpandinggenetic pages 6-7)
Budding yeast: engineered PSF3/GINS3 variants impair growth, S-phase progression, and protein stability; GINS2 p.Arg114Leu sensitizes cells to replication interference. Yeast provides strong conserved-function evidence but cannot model mammalian ears, patellae, or mammary development. (mcquaid2022hypomorphicgins3variants pages 1-2, sa2022biallelicgins2variant pages 1-1)
Xenopus egg extracts: DONSON depletion prevents Cdc45/GINS recruitment and active CMG assembly; add-back experiments permit functional testing of patient substitutions. This is a powerful biochemical system but not a whole-organism phenotype model. (kingsley2023donsonfacilitatescdc45 pages 12-13, kingsley2023donsonfacilitatescdc45 pages 1-1)
Drosophila and patient-derived cells: replication-factor variants and depletion models support conserved cell-cycle dysfunction; fibroblasts, HEK-293T minigene assays, and mammalian stem cells are used for protein-level, splicing, localization, and replication phenotyping. (nielsendandoroff2023theexpandinggenetic pages 8-9, li2024anovelhomozygous pages 9-10)

Recent developments and evidence appraisal

The most consequential 2023 advance was the demonstration that DONSON is a missing mammalian CMG-assembly factor rather than merely a downstream fork-stability protein. The 2024 CDT1 report broadened the diagnostic variant spectrum to branch-point defects and provided the most quantitative—but still low-certainty—GH synthesis. Recent interactome work also showed that a disease-associated CDC45 mutation can disrupt a nuclear-localization signal, supporting protein-localization defects as an additional pathogenic route. (li2024anovelhomozygous pages 9-10, kingsley2023donsonfacilitatescdc45 pages 12-13, kingsley2023donsonfacilitatescdc45 pages 1-1)

Representative abstract quotations

Nielsen-Dandoroff et al. (published April 2023): “Previously known as ear-patella short stature syndrome, MGORS is characterized by growth delay, microtia, and patella hypo/aplasia, as well as genital abnormalities, and breast agenesis in females.” DOI: https://doi.org/10.1038/s41431-023-01359-z. (nielsendandoroff2023theexpandinggenetic pages 1-2)
McQuaid et al. (published May 2022): “Taken together, our findings implicate GINS3 in the pathogenesis of MGS and support the notion that hypomorphic variants identified in this gene impaired cell and organismal growth by compromising DNA replication.” DOI: https://doi.org/10.1172/jci.insight.155648. (mcquaid2022hypomorphicgins3variants pages 1-2)
Kingsley et al. (published August 2023): “DONSON’s presence is essential for replication initiation as it is required for Cdc45 and GINS association with Mcm2–7 complexes and helicase activation.” DOI: https://doi.org/10.1093/nar/gkad694. (kingsley2023donsonfacilitatescdc45 pages 1-1)
Li et al. (published December 2024): “GH therapy may be beneficial for height outcomes in children with MGORS with normal IGF-1 levels.” This conclusion is based on only 12 literature cases and should be considered preliminary. DOI: https://doi.org/10.1186/s13023-024-03430-4. (li2024anovelhomozygous pages 10-12, li2024anovelhomozygous pages 9-10)

Principal knowledge gaps

Reliable incidence/prevalence, age- and gene-stratified penetrance, adult survival, fertility, quality of life, cancer risk, standardized treatment outcomes, variant-specific population frequencies, and prospective GH safety are not established. There are also no validated clinical biomarkers, disease-specific omics signature, cell-type-resolved human atlas, natural-animal disease, or disease-modifying trial. The small, genetically heterogeneous literature means that quantitative frequencies should be stored with cohort size, ascertainment method, and publication date rather than as universal disease constants.

References

(nielsendandoroff2023theexpandinggenetic pages 1-2): Emily Nielsen-Dandoroff, Mischa S. G. Ruegg, and Louise S. Bicknell. The expanding genetic and clinical landscape associated with meier-gorlin syndrome. European Journal of Human Genetics, 31:859-868, Apr 2023. URL: https://doi.org/10.1038/s41431-023-01359-z, doi:10.1038/s41431-023-01359-z. This article has 45 citations and is from a domain leading peer-reviewed journal.
(mcquaid2022hypomorphicgins3variants pages 1-2): Mary E. McQuaid, Kashif Ahmed, Stephanie Tran, Justine Rousseau, Ranad Shaheen, Kristin D. Kernohan, Kyoko E. Yuki, Prerna Grover, Ema S. Dreseris, Sameen Ahmed, Lucie Dupuis, Jennifer Stimec, Mary Shago, Zuhair N. Al-Hassnan, Roch Tremblay, Philipp G. Maass, Michael D. Wilson, Eyal Grunebaum, Kym M. Boycott, François-Michel Boisvert, Sateesh Maddirevula, Eissa A. Faqeih, Fahad Almanjomi, Zaheer Ullah Khan, Fowzan S. Alkuraya, Philippe M. Campeau, Peter Kannu, Eric I. Campos, and Hugo Wurtele. Hypomorphic gins3 variants alter dna replication and cause meier-gorlin syndrome. JCI Insight, May 2022. URL: https://doi.org/10.1172/jci.insight.155648, doi:10.1172/jci.insight.155648. This article has 25 citations and is from a domain leading peer-reviewed journal.
(mcquaid2022hypomorphicgins3variants pages 19-20): Mary E. McQuaid, Kashif Ahmed, Stephanie Tran, Justine Rousseau, Ranad Shaheen, Kristin D. Kernohan, Kyoko E. Yuki, Prerna Grover, Ema S. Dreseris, Sameen Ahmed, Lucie Dupuis, Jennifer Stimec, Mary Shago, Zuhair N. Al-Hassnan, Roch Tremblay, Philipp G. Maass, Michael D. Wilson, Eyal Grunebaum, Kym M. Boycott, François-Michel Boisvert, Sateesh Maddirevula, Eissa A. Faqeih, Fahad Almanjomi, Zaheer Ullah Khan, Fowzan S. Alkuraya, Philippe M. Campeau, Peter Kannu, Eric I. Campos, and Hugo Wurtele. Hypomorphic gins3 variants alter dna replication and cause meier-gorlin syndrome. JCI Insight, May 2022. URL: https://doi.org/10.1172/jci.insight.155648, doi:10.1172/jci.insight.155648. This article has 25 citations and is from a domain leading peer-reviewed journal.
(nielsendandoroff2023theexpandinggenetic pages 2-2): Emily Nielsen-Dandoroff, Mischa S. G. Ruegg, and Louise S. Bicknell. The expanding genetic and clinical landscape associated with meier-gorlin syndrome. European Journal of Human Genetics, 31:859-868, Apr 2023. URL: https://doi.org/10.1038/s41431-023-01359-z, doi:10.1038/s41431-023-01359-z. This article has 45 citations and is from a domain leading peer-reviewed journal.
(kingsley2023donsonfacilitatescdc45 pages 1-1): Georgia Kingsley, Aggeliki Skagia, Paolo Passaretti, Cyntia Fernandez-Cuesta, Alicja Reynolds-Winczura, Kinga Koscielniak, and Agnieszka Gambus. Donson facilitates cdc45 and gins chromatin association and is essential for dna replication initiation. Nucleic Acids Research, 51:9748-9763, Aug 2023. URL: https://doi.org/10.1093/nar/gkad694, doi:10.1093/nar/gkad694. This article has 39 citations and is from a highest quality peer-reviewed journal.
(sa2022biallelicgins2variant pages 1-1): Maria J Nabais Sá, Kerry A Miller, Mary McQuaid, Nils Koelling, Andrew O M Wilkie, Hugo Wurtele, Arjan P M de Brouwer, and Jorge Oliveira. Biallelic gins2 variant p.(arg114leu) causes meier-gorlin syndrome with craniosynostosis. Journal of Medical Genetics, 59:776-780, Aug 2022. URL: https://doi.org/10.1136/jmedgenet-2020-107572, doi:10.1136/jmedgenet-2020-107572. This article has 26 citations and is from a domain leading peer-reviewed journal.
(sa2022biallelicgins2variant pages 1-2): Maria J Nabais Sá, Kerry A Miller, Mary McQuaid, Nils Koelling, Andrew O M Wilkie, Hugo Wurtele, Arjan P M de Brouwer, and Jorge Oliveira. Biallelic gins2 variant p.(arg114leu) causes meier-gorlin syndrome with craniosynostosis. Journal of Medical Genetics, 59:776-780, Aug 2022. URL: https://doi.org/10.1136/jmedgenet-2020-107572, doi:10.1136/jmedgenet-2020-107572. This article has 26 citations and is from a domain leading peer-reviewed journal.
(li2024anovelhomozygous pages 9-10): Qing Li, Yichi Wu, Fucheng Meng, Zhu-xi Li, Di Zhan, and Xiaoping Luo. A novel homozygous intronic variant in cdt1 that alters splicing causes meier–gorlin syndrome, and a review of published mutations and growth hormone treatments. Orphanet Journal of Rare Diseases, Dec 2024. URL: https://doi.org/10.1186/s13023-024-03430-4, doi:10.1186/s13023-024-03430-4. This article has 1 citations and is from a peer-reviewed journal.
(kingsley2023donsonfacilitatescdc45 pages 12-13): Georgia Kingsley, Aggeliki Skagia, Paolo Passaretti, Cyntia Fernandez-Cuesta, Alicja Reynolds-Winczura, Kinga Koscielniak, and Agnieszka Gambus. Donson facilitates cdc45 and gins chromatin association and is essential for dna replication initiation. Nucleic Acids Research, 51:9748-9763, Aug 2023. URL: https://doi.org/10.1093/nar/gkad694, doi:10.1093/nar/gkad694. This article has 39 citations and is from a highest quality peer-reviewed journal.
(nielsendandoroff2023theexpandinggenetic pages 5-6): Emily Nielsen-Dandoroff, Mischa S. G. Ruegg, and Louise S. Bicknell. The expanding genetic and clinical landscape associated with meier-gorlin syndrome. European Journal of Human Genetics, 31:859-868, Apr 2023. URL: https://doi.org/10.1038/s41431-023-01359-z, doi:10.1038/s41431-023-01359-z. This article has 45 citations and is from a domain leading peer-reviewed journal.
(li2024anovelhomozygous pages 10-12): Qing Li, Yichi Wu, Fucheng Meng, Zhu-xi Li, Di Zhan, and Xiaoping Luo. A novel homozygous intronic variant in cdt1 that alters splicing causes meier–gorlin syndrome, and a review of published mutations and growth hormone treatments. Orphanet Journal of Rare Diseases, Dec 2024. URL: https://doi.org/10.1186/s13023-024-03430-4, doi:10.1186/s13023-024-03430-4. This article has 1 citations and is from a peer-reviewed journal.
(nielsendandoroff2023theexpandinggenetic pages 8-9): Emily Nielsen-Dandoroff, Mischa S. G. Ruegg, and Louise S. Bicknell. The expanding genetic and clinical landscape associated with meier-gorlin syndrome. European Journal of Human Genetics, 31:859-868, Apr 2023. URL: https://doi.org/10.1038/s41431-023-01359-z, doi:10.1038/s41431-023-01359-z. This article has 45 citations and is from a domain leading peer-reviewed journal.
(worm2024definingtheprogeria pages 10-11): Cecilie Worm, Maya Elena Ramirez Schambye, Garik V. Mkrtchyan, Alexander Veviorskiy, Anastasia Shneyderman, Ivan V. Ozerov, Alex Zhavoronkov, Daniela Bakula, and Morten Scheibye-Knudsen. Defining the progeria phenome. Aging (Albany NY), 16:2026-2046, Feb 2024. URL: https://doi.org/10.18632/aging.205537, doi:10.18632/aging.205537. This article has 11 citations.
(sa2022biallelicgins2variant pages 4-5): Maria J Nabais Sá, Kerry A Miller, Mary McQuaid, Nils Koelling, Andrew O M Wilkie, Hugo Wurtele, Arjan P M de Brouwer, and Jorge Oliveira. Biallelic gins2 variant p.(arg114leu) causes meier-gorlin syndrome with craniosynostosis. Journal of Medical Genetics, 59:776-780, Aug 2022. URL: https://doi.org/10.1136/jmedgenet-2020-107572, doi:10.1136/jmedgenet-2020-107572. This article has 26 citations and is from a domain leading peer-reviewed journal.
(nielsendandoroff2023theexpandinggenetic pages 6-7): Emily Nielsen-Dandoroff, Mischa S. G. Ruegg, and Louise S. Bicknell. The expanding genetic and clinical landscape associated with meier-gorlin syndrome. European Journal of Human Genetics, 31:859-868, Apr 2023. URL: https://doi.org/10.1038/s41431-023-01359-z, doi:10.1038/s41431-023-01359-z. This article has 45 citations and is from a domain leading peer-reviewed journal.

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1. Disease Information

2. Etiology

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4. Genetic/Molecular Information

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Meier–Gorlin syndrome: comprehensive disease-characteristics report

Executive summary

1. Disease information

Definition and identifiers

2. Etiology, risk, protection, and gene–environment interaction

Causal factors

Risk factors

Protective factors and gene–environment interactions

3. Phenotypes

Core and associated phenotype set

Functional and quality-of-life effects

4. Genetic and molecular information

Causal genes and pathway position

Representative pathogenic variants

Modifiers, epigenetics, and chromosome abnormalities

5. Environmental information

6. Mechanism and pathophysiology

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7. Anatomical structures affected

8. Temporal development and natural history

9. Inheritance and population characteristics

10. Diagnostics

Clinical evaluation

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Screening

11. Outcome and prognosis

12. Treatment and current applications

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