ADGRG1-related Bilateral Frontoparietal Polymicrogyria

ADGRG1-related Bilateral Frontoparietal Polymicrogyria (BFPP): Comprehensive Disease Characteristics Report

2026-06-11
Falcon MONDO:0011738 Model: Edison Scientific Literature 35 citations

ADGRG1-related Bilateral Frontoparietal Polymicrogyria (BFPP): Comprehensive Disease Characteristics Report

Target disease

Disease name: ADGRG1-related Bilateral Frontoparietal Polymicrogyria (BFPP)
Category: Mendelian (autosomal recessive)

1. Disease information

1.1 Overview (what is the disease?)

ADGRG1-related bilateral frontoparietal polymicrogyria (BFPP) is a congenital malformation of cortical development characterized by bilateral frontoparietal polymicrogyria, typically showing an anterior-to-posterior gradient of severity, and commonly accompanied by white-matter signal abnormalities plus brainstem/cerebellar hypoplasia on MRI, with neurodevelopmental disability and high rates of epilepsy and oculomotor/cerebellar signs. (piao2005genotype–phenotypeanalysisof pages 3-5, khatib2024adgrg1relatedpolymicrogyriasyndrome pages 1-3)

A core definition of polymicrogyria used in BFPP literature is: “a cortical malformation characterized by supernumerary, small gyri with abnormal cortical lamination.” (piao2005genotype–phenotypeanalysisof pages 1-2)

1.2 Key identifiers and nomenclature

Table (click to expand)
Identifier type ID Preferred name Synonyms/notes Evidence/source
OMIM 606854 Bilateral frontoparietal polymicrogyria Common abbreviation: BFPP; classic Mendelian cortical malformation linked to ADGRG1/GPR56 Piao et al. 2005 (piao2005genotype–phenotypeanalysisof pages 1-2)
MONDO MONDO_0000087 polymicrogyria Broader parent disease term used in OpenTargets disease-target association for ADGRG1 OpenTargets association (OpenTargets Search: polymicrogyria,bilateral frontoparietal polymicrogyria-ADGRG1)
MONDO MONDO_0017091 bilateral polymicrogyria Broader bilateral PMG term associated with ADGRG1 in OpenTargets OpenTargets association (OpenTargets Search: polymicrogyria,bilateral frontoparietal polymicrogyria-ADGRG1)
OpenTargets target ENSG00000205336 ADGRG1 Approved symbol ADGRG1; former symbol/name GPR56; disease-target evidence links ADGRG1 to polymicrogyria/bilateral polymicrogyria OpenTargets association (OpenTargets Search: polymicrogyria,bilateral frontoparietal polymicrogyria-ADGRG1)
Other (gene nomenclature) ADGRG1-related polymicrogyria syndrome Also described as GPR56-related polymicrogyria; ADGRG1 formerly known as GPR56 Khatib et al. 2024 (khatib2024adgrg1relatedpolymicrogyriasyndrome pages 1-3, khatib2024adgrg1relatedpolymicrogyriasyndrome pages 6-7)
Other (cytogenetic locus) 16q12.2-21 BFPP locus / ADGRG1-linked region Historical linked interval for autosomal recessive BFPP before/alongside gene definition Jansen & Andermann 2005 (jansen2005geneticsofthe pages 5-6); Piao et al. 2005 (piao2005genotype–phenotypeanalysisof pages 1-2)
Other (gene chromosomal location) 16q21 ADGRG1 Gene location reported in recent family report; complements earlier BFPP linkage interval 16q12.2-21 Khatib et al. 2024 (khatib2024adgrg1relatedpolymicrogyriasyndrome pages 1-3)

Table: This table summarizes the key nomenclature and identifier anchors for ADGRG1-related bilateral frontoparietal polymicrogyria, including OMIM and MONDO mappings plus gene naming and chromosomal locus information. It is useful for harmonizing disease knowledge base entries across clinical and genomic resources.

Notes on missing identifiers: Orphanet, ICD-10/ICD-11, and MeSH identifiers specific to BFPP were not available in the retrieved full-text evidence; therefore, they are not reported here.

1.3 Synonyms / alternative names

Common disease names in the retrieved literature include: - “Bilateral frontoparietal polymicrogyria (BFPP)” (piao2005genotype–phenotypeanalysisof pages 1-2) - “ADGRG1-related polymicrogyria syndrome” (khatib2024adgrg1relatedpolymicrogyriasyndrome pages 1-3) - “GPR56-related polymicrogyria” / “GPR56 mutations” (ADGRG1 formerly known as GPR56) (khatib2024adgrg1relatedpolymicrogyriasyndrome pages 1-3, khatib2024adgrg1relatedpolymicrogyriasyndrome pages 6-7)

1.4 Evidence provenance

Evidence in this report is derived from aggregated disease-level resources (e.g., OpenTargets) and aggregated literature evidence (case series + reviews), supplemented by individual patient/family case reports with molecular confirmation. (OpenTargets Search: polymicrogyria,bilateral frontoparietal polymicrogyria-ADGRG1, piao2005genotype–phenotypeanalysisof pages 3-5, carneiro2021casereportdiffuse pages 1-2)

2. Etiology

2.1 Disease causal factors

Primary cause: biallelic (typically homozygous) loss-of-function or deleterious variants in ADGRG1 (GPR56) causing abnormal cortical development with characteristic MRI findings and neurodevelopmental impairment. (piao2005genotype–phenotypeanalysisof pages 3-5, piao2005genotype–phenotypeanalysisof pages 1-2, chiang2011diseaseassociatedgpr56mutations pages 1-2)

Abstract quote (primary mechanistic genetics): Chiang et al. state, “Loss-of-function mutations in the gene encoding G protein-coupled receptor 56 (GPR56) lead to bilateral frontoparietal polymicrogyria (BFPP), an autosomal recessive disorder affecting brain development.” (chiang2011diseaseassociatedgpr56mutations pages 1-2)

2.2 Risk factors

2.3 Protective factors

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

2.4 Gene–environment interactions

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

3. Phenotypes

3.1 Core clinical phenotype spectrum and frequencies

Table (click to expand)
Domain Phenotype (plain) Suggested HPO term(s) Frequency/quantitative data Typical onset/course Key notes Key sources (citation ids)
Neurodevelopment Global developmental delay / psychomotor delay HP:0001263 Developmental delay; HP:0001270 Motor delay Reported as universal in classic BFPP series; mental retardation and motor developmental delay in 100% of 29 typical BFPP cases Congenital/infantile onset; chronic, nonprogressive structural brain disorder with lifelong impairment Core defining clinical feature across cohorts (piao2005genotype–phenotypeanalysisof pages 3-5, piao2005genotype–phenotypeanalysisof pages 1-2, khatib2024adgrg1relatedpolymicrogyriasyndrome pages 1-3)
Cognition Intellectual disability / severe cognitive impairment HP:0001249 Intellectual disability; HP:0011342 Severe global developmental delay Severe cognitive impairment in 79.3% of reviewed cases Apparent in infancy/early childhood; persistent Often accompanied by markedly limited language acquisition (carneiro2021casereportdiffuse pages 3-5)
Epilepsy Seizures / epilepsy HP:0001250 Seizure; HP:0002373 Febrile seizures; HP:0002123 Generalized myoclonic seizure; HP:0002121 Absence seizure 95% in 29-patient classic BFPP cohort; 88.2% (60/68) in review; refractory in 60.0% (36/60) of those with seizures; 90.4% (75/83) in 2024 review with refractory seizures in 54.7% (41/75) Usually infancy to childhood onset; often chronic and can be drug-refractory Lennox-Gastaut phenotype reported in some families; seizure types include atonic, atypical absence, myoclonic, tonic, spasms (piao2005genotype–phenotypeanalysisof pages 3-5, carneiro2021casereportdiffuse pages 5-6, parrini2009bilateralfrontoparietalpolymicrogyria pages 6-8, parrini2009bilateralfrontoparietalpolymicrogyria pages 3-5, khatib2024adgrg1relatedpolymicrogyriasyndrome pages 6-7)
Cerebellar / coordination Cerebellar signs / ataxia HP:0001251 Ataxia; HP:0002070 Cerebellar atrophy (imaging adjunct) 94% in classic BFPP cohort; 92.6% in later literature review Early childhood; generally persistent/nonprogressive relative to malformation Reflects characteristic cerebellar involvement on MRI and exam (piao2005genotype–phenotypeanalysisof pages 3-5, carneiro2021casereportdiffuse pages 3-5, khatib2024adgrg1relatedpolymicrogyriasyndrome pages 1-3)
Eye movement Dysconjugate gaze / oculomotor abnormalities HP:0000608 Abnormality of the eye movement; HP:0000486 Strabismus; HP:0000511 Nystagmus Dysconjugate gaze in 88% of classic BFPP cohort; oculomotor abnormalities in 92.1% in later review; strabismus 59.5% among those with oculomotor findings Usually recognized in infancy/childhood; persistent Commonly includes strabismus and nystagmus (piao2005genotype–phenotypeanalysisof pages 3-5, carneiro2021casereportdiffuse pages 3-5, khatib2024adgrg1relatedpolymicrogyriasyndrome pages 3-4)
Motor / pyramidal Pyramidal signs / spasticity / brisk reflexes HP:0002493 Upper motor neuron dysfunction; HP:0001257 Spasticity; HP:0001347 Hyperreflexia; HP:0002509 Limb hypertonia Pyramidal signs present in 75.9% in review Infantile/childhood onset; chronic Can include spastic quadriparesis, ankle clonus, wide-based gait, hyperreflexia (carneiro2021casereportdiffuse pages 3-5, parrini2009bilateralfrontoparietalpolymicrogyria pages 3-5)
Motor function Ambulation outcome HP:0002505 Impaired ambulation; HP:0002540 Delayed walking Able to walk in 81.6% overall in 2021 review; median walking age 3.5 years; unable to walk 18.4%; 44/63 (~70%) able to walk in 2024 review Delayed acquisition in childhood; variable ultimate attainment Walking ability is variable and useful for severity stratification (carneiro2021casereportdiffuse pages 3-5, carneiro2021casereportdiffuse pages 2-3, khatib2024adgrg1relatedpolymicrogyriasyndrome pages 4-6)
Tone / early presentation Hypotonia, sometimes evolving to hypertonia HP:0001252 Hypotonia; HP:0001276 Hypertonia No pooled percentage available in cited excerpts Often first year of life or noted at birth; chronic Early pseudomyopathic presentation can mimic congenital muscular dystrophy (carneiro2021casereportdiffuse pages 2-3, khatib2024adgrg1relatedpolymicrogyriasyndrome pages 3-4)
Growth / head size Head circumference usually normal; occasional microcephaly or macrocephaly HP:0000252 Microcephaly; HP:0000256 Macrocephaly Normal head circumference 85.1% in 2021 review; 81% in 2024 review; microcephaly 12.7%, macrocephaly 6.3% in 2024 review Congenital/childhood trait; generally stable descriptor Head size is not usually markedly abnormal despite severe neurologic disease (carneiro2021casereportdiffuse pages 5-6, khatib2024adgrg1relatedpolymicrogyriasyndrome pages 6-7)
Imaging / cortex Bilateral frontoparietal polymicrogyria with anterior-posterior gradient HP:0002126 Polymicrogyria; HP:0012650 Bilateral cerebral cortical dysgenesis Hallmark MRI pattern in essentially all classic BFPP cases; all 29 classic cases had bilateral frontoparietal PMG Congenital, static malformation Symmetric bilateral PMG with decreasing anterior-to-posterior severity is the canonical radiologic signature (piao2005genotype–phenotypeanalysisof pages 3-5, khatib2024adgrg1relatedpolymicrogyriasyndrome pages 1-3, piao2005genotype–phenotypeanalysisof media 547d7d36)
Imaging / white matter Patchy white-matter signal abnormalities / hypomyelination / reduced volume HP:0002500 Abnormal cerebral white matter morphology; HP:0002188 Delayed CNS myelination Present in all 29 classic cases as hallmark MRI finding; later reports describe diffuse hypomyelination in atypical severe cases Congenital/static on serial imaging May be patchy in classic BFPP or diffuse in atypical ADGRG1-related phenotypes (piao2005genotype–phenotypeanalysisof pages 3-5, carneiro2021casereportdiffuse pages 2-3, piao2005genotype–phenotypeanalysisof media 547d7d36)
Imaging / posterior fossa Brainstem and cerebellar hypoplasia HP:0001321 Cerebellar hypoplasia; HP:0007366 Small pons Present in all 29 classic cases as hallmark MRI finding Congenital/static Strong clue favoring ADGRG1-related BFPP over some other PMG subtypes (piao2005genotype–phenotypeanalysisof pages 3-5, jansen2005geneticsofthe pages 5-6, piao2005genotype–phenotypeanalysisof media 547d7d36)
Severity / variability Intrafamilial and interfamilial phenotypic variability HP:0003812 Variable expressivity Qualitative; no single pooled percentage Lifelong, variable severity Atypical diffuse polymicrogyria, pachygyria/lissencephaly-like changes, and severe non-ambulatory phenotypes have been reported (carneiro2021casereportdiffuse pages 3-5, khatib2024adgrg1relatedpolymicrogyriasyndrome pages 4-6, khatib2024adgrg1relatedpolymicrogyriasyndrome pages 3-4, lin2021atwinscase pages 7-10)

Table: This table summarizes the core clinical and imaging phenotype spectrum reported for ADGRG1-related bilateral frontoparietal polymicrogyria, with frequencies drawn from classic and updated literature reviews. It is useful for knowledge-base curation because it aligns phenotype terms, quantitative prevalence, and suggested HPO mappings with supporting citations.

Key quantitative phenotype statistics from landmark and updated reviews include: - In a classic cohort of 29 typical BFPP cases, cerebellar signs (94%), dysconjugate gaze (88%), and seizures (95%) were highly prevalent; cognitive and motor developmental delay were universal. (piao2005genotype–phenotypeanalysisof pages 3-5) - In an updated literature synthesis (as captured in the Carneiro 2021 excerpts), seizures were reported in 88.2%, with 60.0% of those being drug-refractory; severe cognitive impairment was reported in 79.3%; oculomotor findings in 92.1%. (carneiro2021casereportdiffuse pages 5-6, carneiro2021casereportdiffuse pages 3-5) - In the Khatib 2024 review excerpt, seizures were present in 75/83 (90.4%), refractory in 41/75 (54.7%). (khatib2024adgrg1relatedpolymicrogyriasyndrome pages 6-7)

3.2 Phenotype characteristics (onset, progression, QoL impact)

3.3 Suggested HPO terms

HPO suggestions are included per-phenotype in Artifact-01.

4. Genetic / molecular information

4.1 Causal gene(s)

ADGRG1 (former name GPR56) is the established causal gene for classic BFPP, with autosomal recessive inheritance. (piao2005genotype–phenotypeanalysisof pages 3-5, khatib2024adgrg1relatedpolymicrogyriasyndrome pages 1-3)

4.2 Pathogenic variant spectrum

Table (click to expand)
Gene (HGNC symbol) Inheritance Variant class / region Example variants (HGVS / legacy protein) Notable genotype-phenotype notes Population / consanguinity / founder info Key counts / classification Evidence type Key sources
ADGRG1 (formerly GPR56) Autosomal recessive Disease-causing variants in classic BFPP are typically biallelic, often homozygous Historical protein-level examples span extracellular and 7TM regions In the landmark genotype-phenotype study, homozygous GPR56 mutations were identified in all 29 patients with typical BFPP; BFPP is therefore a canonical recessive ADGRG1-related cortical malformation (piao2005genotype–phenotypeanalysisof pages 3-5, piao2005genotype–phenotypeanalysisof pages 1-2) Consanguinity is common in reported families, but homozygous variants were also seen in some apparently nonconsanguineous pedigrees (jansen2005geneticsofthe pages 5-6, piao2005genotype–phenotypeanalysisof pages 3-5) OMIM BFPP 606854; ADGRG1 linked to BFPP/polymicrogyria across human cohorts (piao2005genotype–phenotypeanalysisof pages 1-2, OpenTargets Search: polymicrogyria,bilateral frontoparietal polymicrogyria-ADGRG1) Human clinical / human genetics (piao2005genotype–phenotypeanalysisof pages 3-5, piao2005genotype–phenotypeanalysisof pages 1-2, jansen2005geneticsofthe pages 5-6)
ADGRG1 Autosomal recessive Extracellular-region missense cluster: N-terminal ECD, GPS motif, extracellular loops of 7TM p.Arg38Gln (R38Q), p.Arg38Trp (R38W), p.Tyr88Cys (Y88C), p.Cys91Ser (C91S), p.Cys346Ser (C346S), p.Trp349Ser (W349S), p.Arg565Trp (R565W), p.Leu640Arg (L640R) BFPP-associated missense variants cluster in extracellular regions and act through multiple loss-of-function mechanisms including reduced surface expression, ER retention, defective glycosylation, impaired GPS proteolysis, altered receptor shedding, loss of ligand interaction, and altered lipid-raft distribution (chiang2011diseaseassociatedgpr56mutations pages 8-10, chiang2011diseaseassociatedgpr56mutations pages 3-5, chiang2011diseaseassociatedgpr56mutations pages 10-11, ke2008biochemicalcharacterizationof pages 1-2, chiang2011diseaseassociatedgpr56mutations pages 1-2) Families reported across Arabic-speaking Middle Eastern, Pakistani, Indian, Afghani, Canadian, Turkish, Italian, Israeli, and Hispanic American backgrounds; several alleles appear recurrent/founder-like in specific pedigrees (piao2005genotype–phenotypeanalysisof pages 3-5) Missense variants were absent from 260 control chromosomes in the 2005 cohort (piao2005genotype–phenotypeanalysisof pages 3-5) Human clinical + in vitro functional (chiang2011diseaseassociatedgpr56mutations pages 8-10, chiang2011diseaseassociatedgpr56mutations pages 3-5, chiang2011diseaseassociatedgpr56mutations pages 10-11, ke2008biochemicalcharacterizationof pages 1-2, chiang2011diseaseassociatedgpr56mutations pages 1-2, piao2005genotype–phenotypeanalysisof pages 3-5)
ADGRG1 Autosomal recessive Truncating variants (nonsense / frameshift / deletion) Historical 7-bp deletion; nonsense and frameshift alleles noted across BFPP pedigrees Truncating alleles are associated with severe disease and are common among the most motor-impaired/non-ambulatory cases; loss of function is an established disease mechanism (carneiro2021casereportdiffuse pages 2-3, carneiro2021casereportdiffuse pages 5-6, carneiro2021casereportdiffuse pages 3-5) Many truncating-variant families arise in consanguineous settings, though compound heterozygosity is also reported in the wider ADGRG1 literature (carneiro2021casereportdiffuse pages 5-6, carneiro2021casereportdiffuse pages 3-5) By 2021, 77 patients from 47 pedigrees with 34 distinct ADGRG1 variants had been reported (carneiro2021casereportdiffuse pages 3-5) Human clinical / literature review (carneiro2021casereportdiffuse pages 3-5, carneiro2021casereportdiffuse pages 2-3, carneiro2021casereportdiffuse pages 5-6)
ADGRG1 Autosomal recessive Nonsense variant in 7TM domain NM_001145771.2:c.1504C>T; NP_005673.3:p.Arg502Ter / p.Arg502*; dbSNP rs746634404 Reported in a child with diffuse polymicrogyria without the classic anterior-posterior gradient, diffuse hypomyelination, pontine/cerebellar hypoplasia, profound developmental impairment, and refractory epilepsy, expanding the ADGRG1 phenotypic spectrum beyond classic BFPP (carneiro2021casereportdiffuse pages 2-3, carneiro2021casereportdiffuse pages 1-2, carneiro2021casereportdiffuse pages 3-5) Found homozygously in a consanguineous family; both parents were heterozygous carriers (carneiro2021casereportdiffuse pages 1-2, carneiro2021casereportdiffuse pages 2-3) Very rare in gnomAD (f = 0.0000119 in cited report); classified as pathogenic with very strong ACMG evidence in the case report (carneiro2021casereportdiffuse pages 2-3) Human clinical + diagnostic genetics (carneiro2021casereportdiffuse pages 2-3, carneiro2021casereportdiffuse pages 1-2, carneiro2021casereportdiffuse pages 3-5)
ADGRG1 Autosomal recessive Novel missense variant NM_201525.4:c.308T>C; p.Leu103Pro Identified in a large Syrian consanguineous family with ADGRG1-related polymicrogyria/BFPP; affected individuals showed early developmental delay, severe cognitive/motor impairment, oculomotor findings, and often refractory seizures with intrafamilial variability (khatib2024adgrg1relatedpolymicrogyriasyndrome pages 3-4, khatib2024adgrg1relatedpolymicrogyriasyndrome pages 1-3, khatib2024adgrg1relatedpolymicrogyriasyndrome pages 4-6) Reported in a consanguineous Syrian family with five affected individuals (khatib2024adgrg1relatedpolymicrogyriasyndrome pages 1-3, khatib2024adgrg1relatedpolymicrogyriasyndrome pages 3-4) Absent from gnomAD v2.1.1 and predicted damaging; classified as pathogenic in study workflow using ACMG-based interpretation (khatib2024adgrg1relatedpolymicrogyriasyndrome pages 3-4, khatib2024adgrg1relatedpolymicrogyriasyndrome pages 1-3) Human clinical / exome sequencing (khatib2024adgrg1relatedpolymicrogyriasyndrome pages 1-3, khatib2024adgrg1relatedpolymicrogyriasyndrome pages 3-4, khatib2024adgrg1relatedpolymicrogyriasyndrome pages 4-6)
ADGRG1 Autosomal recessive Recurrent pathogenic missense variant c.1693C>T; p.Arg565Trp (legacy R565W) Seen in BFPP and in severe overlapping phenotypes; associated reports include Lennox-Gastaut syndrome / drug-refractory epilepsy in some families and extensive polymicrogyria with hindbrain abnormalities in others (parrini2009bilateralfrontoparietalpolymicrogyria pages 6-8, parrini2009bilateralfrontoparietalpolymicrogyria pages 3-5, shaath2024integratinggenomesequencing pages 2-4) Previously reported in a consanguineous Bedouin family; also detected homozygously in monozygotic twins from a consanguineous family (parrini2009bilateralfrontoparietalpolymicrogyria pages 6-8, shaath2024integratinggenomesequencing pages 4-5, shaath2024integratinggenomesequencing pages 2-4) In the 2024 twin report, ClinVar pathogenic (VCV000005831.23) with CADD 29.5 (shaath2024integratinggenomesequencing pages 4-5, shaath2024integratinggenomesequencing pages 2-4) Human clinical + curated clinical variant evidence (parrini2009bilateralfrontoparietalpolymicrogyria pages 6-8, parrini2009bilateralfrontoparietalpolymicrogyria pages 3-5, shaath2024integratinggenomesequencing pages 4-5, shaath2024integratinggenomesequencing pages 2-4)
ADGRG1 Autosomal recessive Cohort-level variant spectrum Missense, nonsense, frameshift, deletion; recurrent alleles plus private family-specific variants The recognized phenotype is broad: classic bilateral frontoparietal PMG with white-matter and hindbrain abnormalities, but also atypical diffuse PMG, pachygyria/lissencephaly-like presentations, and variable ambulation/cognitive outcomes (carneiro2021casereportdiffuse pages 3-5, khatib2024adgrg1relatedpolymicrogyriasyndrome pages 4-6, khatib2024adgrg1relatedpolymicrogyriasyndrome pages 3-4) Early literature: 8 independent mutations in 22 radiologically and clinically confirmed patients from 12 families, with 9 families showing close parental consanguinity and families of Middle Eastern and French Canadian origin; broader 2005 sampling was geographically diverse (jansen2005geneticsofthe pages 5-6, piao2005genotype–phenotypeanalysisof pages 3-5) 2005 landmark: all 29 typical BFPP cases mutation-positive; 2021 review: 77 patients / 47 pedigrees / 34 variants (piao2005genotype–phenotypeanalysisof pages 3-5, carneiro2021casereportdiffuse pages 3-5) Human clinical / literature review (piao2005genotype–phenotypeanalysisof pages 3-5, carneiro2021casereportdiffuse pages 3-5, jansen2005geneticsofthe pages 5-6)

Table: This table summarizes the core human genetic evidence linking ADGRG1 (GPR56) to bilateral frontoparietal polymicrogyria, including inheritance, variant classes, representative alleles, and cohort-level statistics. It is useful for quickly mapping variant-level findings to phenotypic interpretation, population context, and evidence type.

Key genetic findings: - Landmark genotype–phenotype analysis identified homozygous GPR56 mutations in all 29 patients with typical BFPP (defining ADGRG1 as a major Mendelian cause of this imaging phenotype). (piao2005genotype–phenotypeanalysisof pages 1-2) - BFPP-associated missense variants cluster in extracellular regions (ECD/GPS/extracellular loops), with additional truncating variants and occasional regulatory variants (e.g., promoter deletion affecting expression in developing neurons). (ke2008biochemicalcharacterizationof pages 1-2, murayama2020thepolymicrogyriaassociatedgpr56 pages 1-2) - By the time of the 2021 review excerpt, ADGRG1 BFPP-spectrum variants had been reported in 77 patients from 47 pedigrees with 34 distinct variants. (carneiro2021casereportdiffuse pages 3-5)

4.3 Functional consequences

Many BFPP-associated variants cause loss-of-function via impaired receptor maturation/processing/trafficking and impaired ligand interactions (see Mechanism/Pathophysiology). (chiang2011diseaseassociatedgpr56mutations pages 3-5, chiang2011diseaseassociatedgpr56mutations pages 10-11)

4.4 Modifier genes / multilocus disease

The retrieved excerpts note that broader sequencing (exome/genome) can reveal additional pathogenic variants that may modify severity in malformation syndromes; specific validated modifier genes for ADGRG1-BFPP were not established in the retrieved excerpts. (carneiro2021casereportdiffuse pages 3-5)

4.5 Epigenetics / chromosomal abnormalities

No disease-specific epigenetic signatures or recurrent chromosomal abnormalities were identified in the retrieved evidence.

5. Environmental information

No convincing disease-specific environmental, lifestyle, or infectious etiologic triggers were identified in the retrieved evidence for ADGRG1-related BFPP as a Mendelian disorder. However, congenital infections (e.g., CMV/HSV) can mimic the MRI pattern and must be considered in differential diagnosis. (khatib2024adgrg1relatedpolymicrogyriasyndrome pages 4-6)

6. Mechanism / pathophysiology

6.1 Molecular mechanism: ADGRG1 receptor biology and BFPP loss-of-function

ADGRG1/GPR56 is an adhesion GPCR with an extracellular domain (ECD), a GPCR proteolysis site (GPS/GAIN) and a 7TM signaling domain; BFPP-associated missense variants occur in extracellular regions and can cause disease through multiple convergent loss-of-function mechanisms. (chiang2011diseaseassociatedgpr56mutations pages 1-2)

Primary functional mechanisms in BFPP variants (cellular/biochemical): - Defective processing and trafficking: BFPP mutants frequently show ER retention, EndoH-sensitive glycosylation, reduced surface expression, and likely increased degradation. (chiang2011diseaseassociatedgpr56mutations pages 3-5, chiang2011diseaseassociatedgpr56mutations pages 5-6) - Loss of GPS proteolysis: GPS-site mutants (e.g., C346S, W349S) can become uncleaved single-chain forms and fail to reach the cell surface. (chiang2011diseaseassociatedgpr56mutations pages 3-5, ke2008biochemicalcharacterizationof pages 1-2) - Impaired ligand interactions / adhesion: N-terminal variants can abolish or reduce binding to a protein ligand and impair ligand-dependent adhesion. (chiang2011diseaseassociatedgpr56mutations pages 8-10, chiang2011diseaseassociatedgpr56mutations pages 7-8) - Membrane microdomain mislocalization: Some extracellular-loop variants (e.g., R565W, L640R) alter β-subunit behavior and lipid-raft distribution, supporting pathogenic mechanisms beyond simple surface expression loss. (chiang2011diseaseassociatedgpr56mutations pages 8-10)

6.2 Signaling pathways and ligand modalities (current understanding; 2023–2024 emphasis)

ADGRG1 signaling is strongly linked to Gα12/Gα13 → RhoA pathways: - Abstract quote (2024): “GPR56 constitutively activates both G12 and G13.” (jallouli2024gproteinselectivity pages 1-2) - Abstract quote (2024): “[10C7 antibody] led to an activation that favors G13 over G12.” (jallouli2024gproteinselectivity pages 1-2)

Endogenous ligand/binding-partner biology relevant to development and myelination includes: - Collagen III (basement membrane ligand): ADGRG1 binding to collagen III in the basement membrane is linked to Gα12/13–RhoA-dependent inhibition of neuronal migration, and loss of this regulation contributes to BFPP cortical malformation. (einspahr2022pathophysiologicalimpactof pages 5-9) - Transglutaminase-2 (TG2): TG2 is an ADGRG1 ligand/binding partner in multiple contexts, including oligodendrocyte lineage signaling (microglia→OPC) and epithelial migration systems. (giera2018microglialtransglutaminase2drives pages 1-2, giera2018microglialtransglutaminase2drives pages 3-5, bauer2024mesenchymaltransglutaminase2 pages 1-2)

Recent mechanistic development (2024, epithelial context): Bauer et al. describe TG2–GPR56 as a ligand–receptor pair that activates RhoA/ROCK and ADAM17, leading to EGFR transactivation and rapid keratinocyte migration, illustrating mechanistic routes by which extracellular ligands can drive ADGRG1 signaling. (bauer2024mesenchymaltransglutaminase2 pages 1-2, bauer2024mesenchymaltransglutaminase2 pages 2-5, bauer2024mesenchymaltransglutaminase2 pages 6-9)

6.3 Causal chain from gene defect to clinical phenotype (integrated)

1) Biallelic ADGRG1 variants → impaired receptor processing/trafficking and/or impaired extracellular ligand interactions (collagen III; protein ligands), reducing effective receptor function at the cell surface. (chiang2011diseaseassociatedgpr56mutations pages 3-5, chiang2011diseaseassociatedgpr56mutations pages 10-11, chiang2011diseaseassociatedgpr56mutations pages 1-2)
2) Reduced ADGRG1 function perturbs Gα12/13–RhoA signaling that normally regulates neuronal migration, cortical lamination, and pial basement membrane integrity. (einspahr2022pathophysiologicalimpactof pages 5-9, murayama2020thepolymicrogyriaassociatedgpr56 pages 1-2)
3) Developmental disruption yields frontoparietal-predominant polymicrogyria, abnormal cortical lamination, associated white-matter abnormalities, and posterior fossa involvement (pons/vermian/cerebellar hypoplasia), producing a characteristic radiologic pattern. (piao2005genotype–phenotypeanalysisof pages 3-5, piao2005genotype–phenotypeanalysisof media 547d7d36)
4) The resulting circuit malformation and developmental perturbations manifest as global developmental delay/intellectual disability, seizures (often refractory), oculomotor abnormalities, pyramidal signs/spasticity, and cerebellar signs. (piao2005genotype–phenotypeanalysisof pages 3-5, carneiro2021casereportdiffuse pages 5-6)

6.4 Suggested ontology terms (mechanism, anatomy, cells)

GO Biological Process (suggested): - Neuronal migration (GO:0001764) (supported conceptually by Gα12/13–RhoA migration regulation and cortical malformation) (einspahr2022pathophysiologicalimpactof pages 5-9) - Cell adhesion (GO:0007155) (ligand-dependent adhesion and receptor–ligand interactions) (chiang2011diseaseassociatedgpr56mutations pages 10-11) - Myelination / glial development (GO:0042552; oligodendrocyte precursor proliferation related processes) (giera2018microglialtransglutaminase2drives pages 1-2, ackerman2018gpr56adgrg1regulatesdevelopment pages 1-2)

Cell Ontology (CL; suggested): - Radial glial cell (CL:0000243) (pial basement membrane/endfeet abnormalities in Gpr56 loss model) (murayama2020thepolymicrogyriaassociatedgpr56 pages 1-2) - Neural progenitor cell (CL:0011020) (reduced proliferation in mouse loss models; BFPP developmental mechanism) (murayama2020thepolymicrogyriaassociatedgpr56 pages 1-2) - GABAergic interneuron (CL:0000099) (e1m promoter activity in developing GABAergic neurons; epilepsy link) (murayama2020thepolymicrogyriaassociatedgpr56 pages 1-2) - Oligodendrocyte precursor cell (CL:0002453) (TG2→ADGRG1 promotes OPC proliferation and remyelination) (giera2018microglialtransglutaminase2drives pages 1-2) - Microglial cell (CL:0000129) (microglial TG2 source) (giera2018microglialtransglutaminase2drives pages 3-5) - Schwann cell (CL:0000688) (peripheral myelin roles) (ackerman2018gpr56adgrg1regulatesdevelopment pages 1-2)

UBERON (suggested): - Cerebral cortex (UBERON:0000956), frontal lobe (UBERON:0001870), parietal lobe (UBERON:0001872) (piao2005genotype–phenotypeanalysisof pages 3-5) - Pons (UBERON:0000988), cerebellar vermis (UBERON:0002124), cerebellum (UBERON:0002037) (piao2005genotype–phenotypeanalysisof pages 3-5, piao2005genotype–phenotypeanalysisof media 547d7d36) - Cerebral white matter (UBERON:0002314) (piao2005genotype–phenotypeanalysisof pages 3-5)

7. Anatomical structures affected

7.1 Organ/system level

Primary affected system is the central nervous system, especially: - Bilateral frontoparietal cerebral cortex (polymicrogyria) (piao2005genotype–phenotypeanalysisof pages 3-5) - White matter (patchy signal change/hypomyelination) (piao2005genotype–phenotypeanalysisof pages 3-5, carneiro2021casereportdiffuse pages 2-3) - Brainstem and cerebellum (pons/vermian/cerebellar hypoplasia) (piao2005genotype–phenotypeanalysisof pages 3-5, piao2005genotype–phenotypeanalysisof media 547d7d36)

7.2 Tissue/cell level

Evidence from mammalian models indicates involvement of neurodevelopmental and glial lineages (radial glia, neuronal progenitors, migrating neurons), and later roles in myelination involving Schwann cells and oligodendrocyte lineage cells. (murayama2020thepolymicrogyriaassociatedgpr56 pages 1-2, ackerman2018gpr56adgrg1regulatesdevelopment pages 1-2, giera2018microglialtransglutaminase2drives pages 1-2)

7.3 Subcellular level

Mutant receptor biology implicates ER retention/misprocessing (EndoH sensitivity) and altered membrane microdomain distribution (lipid rafts). (chiang2011diseaseassociatedgpr56mutations pages 3-5, chiang2011diseaseassociatedgpr56mutations pages 8-10)

8. Temporal development

9. Inheritance and population

9.1 Inheritance

BFPP is autosomal recessive, frequently observed in consanguineous pedigrees; classic cohorts show biallelic/homozygous ADGRG1 variants in typical BFPP. (jansen2005geneticsofthe pages 5-6, piao2005genotype–phenotypeanalysisof pages 1-2)

9.2 Epidemiology

True prevalence/incidence estimates specific to ADGRG1-related BFPP were not identified in the retrieved evidence.

9.3 Population and geographic distribution

Reported mutation-positive BFPP families in the landmark cohort included Arabic-speaking Middle Eastern, Pakistani, Indian, Afghani, Canadian, Turkish, Italian, Israeli, and Hispanic American backgrounds. (piao2005genotype–phenotypeanalysisof pages 3-5)

9.4 Statistics supporting clinical relevance in PMG cohorts (recent)

In a large polymicrogyria genetics study (275 families), a genetic etiology was found in 32.7% (90/275); ADGRG1/GPR56 was listed among known PMG genes detected in the cohort, though per-gene counts were not extractable from the retrieved excerpts. (akula2023exomesequencingand pages 2-3)

10. Diagnostics

Table (click to expand)
Category Item Details/real-world implementation Suggested ontology term (LOINC/MAXO where applicable) Evidence/notes Key sources (citation ids)
Diagnostics Brain MRI Core radiologic pattern in classic ADGRG1-related BFPP is symmetric bilateral frontoparietal polymicrogyria with a decreasing anterior-to-posterior gradient, patchy/random white-matter abnormalities, and cerebellar/brainstem hypoplasia; atypical cases may show diffuse polymicrogyria, hypomyelination, thin corpus callosum, ventriculomegaly, or pachygyria/lissencephaly-like changes. MRI is the frontline real-world diagnostic modality. MAXO: brain MRI; LOINC-style concept: Magnetic resonance imaging of brain Hallmark imaging clue; brainstem/cerebellar involvement helps distinguish ADGRG1-related disease from some broader PMG categories. Early MRI can occasionally be normal, so repeat imaging may be needed. (piao2005genotype–phenotypeanalysisof pages 3-5, khatib2024adgrg1relatedpolymicrogyriasyndrome pages 1-3, piao2005genotype–phenotypeanalysisof media 547d7d36, khatib2024adgrg1relatedpolymicrogyriasyndrome pages 4-6, carneiro2021casereportdiffuse pages 2-3)
Diagnostics EEG EEG is used for seizure characterization and longitudinal management; reported findings include predominantly frontal spikes/spike-waves, multifocal spikes, generalized slow spike-and-wave complexes, and tonic seizures during sleep in severe epileptic encephalopathy/Lennox-Gastaut presentations. LOINC-style concept: Electroencephalogram study; MAXO: electroencephalographic monitoring Supports phenotyping of high-burden epilepsy; abnormalities are variable and reflect seizure syndrome rather than disease specificity. (carneiro2021casereportdiffuse pages 2-3, parrini2009bilateralfrontoparietalpolymicrogyria pages 3-5, carneiro2021casereportdiffuse pages 1-2)
Diagnostics Whole-exome sequencing (WES) Recommended high-yield molecular test in suspected ADGRG1-related BFPP, especially with PMG plus cerebellar/brainstem findings or consanguinity. In the 2024 family report, WES used Illumina NovaSeq paired-end sequencing, alignment with BWA-MEM2, SNV/indel calling with GATK, and annotation/classification with ACMG-based pipelines. MAXO: exome sequencing Useful early when neuroradiologic interpretation is uncertain or when imaging overlaps infection/cobblestone phenotypes. (khatib2024adgrg1relatedpolymicrogyriasyndrome pages 1-3, khatib2024adgrg1relatedpolymicrogyriasyndrome pages 4-6, khatib2024adgrg1relatedpolymicrogyriasyndrome pages 6-7)
Diagnostics Targeted NGS panel Real-world alternative/adjunct to WES: targeted next-generation sequencing panels for brain morphogenesis/malformations of cortical development can detect ADGRG1 variants, as shown in the 2021 case. MAXO: targeted gene panel sequencing Practical in clinical neurogenetics workflows where phenotype strongly suggests a malformation-of-cortical-development disorder. (carneiro2021casereportdiffuse pages 1-2, carneiro2021casereportdiffuse pages 2-3)
Diagnostics Sanger segregation testing After candidate variant detection, familial segregation by Sanger sequencing is used to confirm biallelic inheritance and carrier status in parents/siblings. MAXO: Sanger sequencing; MAXO: genetic testing of family members Important for confirming autosomal recessive inheritance and informing recurrence risk/cascade testing. (carneiro2021casereportdiffuse pages 1-2, khatib2024adgrg1relatedpolymicrogyriasyndrome pages 1-3, carneiro2021casereportdiffuse pages 2-3)
Diagnostics Variant interpretation Variant interpretation should follow ACMG/AMP principles, incorporating rarity in population databases, predicted loss-of-function mechanism, in silico tools, and segregation. Examples include p.Arg502Ter classified with very strong pathogenic evidence and p.Leu103Pro interpreted through an ACMG-based workflow. MAXO: genetic variant interpretation ADGRG1 loss of function is a recognized disease mechanism, supporting pathogenic classification of truncating alleles. (carneiro2021casereportdiffuse pages 2-3, shaath2024integratinggenomesequencing pages 4-5, khatib2024adgrg1relatedpolymicrogyriasyndrome pages 1-3)
Diagnostics CNV/SV analysis Exome-era workflows may include exome-based CNV/SV calling (e.g., CoNIFER, 3bCNV in the 2024 report) to avoid missing structural contributors when single-nucleotide testing is unrevealing. MAXO: copy number variation analysis Not a classic major mechanism for ADGRG1-BFPP based on retrieved evidence, but included in modern rare-disease diagnostic pipelines. (khatib2024adgrg1relatedpolymicrogyriasyndrome pages 1-3, khatib2024adgrg1relatedpolymicrogyriasyndrome pages 6-7)
Diagnostics Ancillary exclusion testing In complex cases, clinicians have used chromosomal testing, fragile X/imprinting studies, mtDNA testing, metabolic screening, and muscle biopsy to exclude alternative diagnoses. MAXO: metabolic testing; MAXO: muscle biopsy Particularly useful when presentation mimics congenital muscular dystrophy/cobblestone complex or metabolic disease. (carneiro2021casereportdiffuse pages 2-3)
Differential diagnosis Congenital CMV/HSV and other congenital infections BFPP MRI may mimic congenital CMV or HSV because of polymicrogyria, ventriculomegaly, and white-matter abnormalities; infectious workup and molecular testing help avoid misdiagnosis. MAXO: infectious disease differential diagnosis; MAXO: brain MRI Important diagnostic pitfall emphasized in recent literature, especially where expert neuroradiology access is limited. (khatib2024adgrg1relatedpolymicrogyriasyndrome pages 4-6, khatib2024adgrg1relatedpolymicrogyriasyndrome pages 6-7)
Differential diagnosis Dystroglycanopathies / cobblestone muscular dystrophy ADGRG1-related disease can present with early hypotonia and MRI overlap resembling cobblestone complex; normal muscle biopsy and the characteristic posterior fossa/brainstem pattern favor ADGRG1-related BFPP. MAXO: muscle biopsy; MAXO: differential diagnosis Early “pseudomyopathic” presentation is a recurring clinical trap. (carneiro2021casereportdiffuse pages 2-3)
Differential diagnosis Other PMG subtypes / BGP / pachygyria-lissencephaly spectrum Atypical ADGRG1 cases may lack the canonical gradient and instead show diffuse PMG or pachygyria/lissencephaly-like changes, requiring broad malformation-of-cortical-development differential diagnosis. MAXO: exome sequencing; MAXO: neuroradiologic review Broad genomic testing helps resolve overlap syndromes and possible multilocus disease. (carneiro2021casereportdiffuse pages 3-5, khatib2024adgrg1relatedpolymicrogyriasyndrome pages 3-4)
Differential diagnosis False reassurance from normal early MRI One reported patient had a normal MRI in infancy despite later-confirmed ADGRG1-related disease; repeat imaging should be considered if clinical suspicion remains high. MAXO: follow-up brain MRI Normal early imaging does not exclude the diagnosis. (khatib2024adgrg1relatedpolymicrogyriasyndrome pages 4-6)
Management/Treatment Antiseizure therapy Seizure treatment is symptomatic and individualized. Reported medications include valproate (initially effective in one case), vigabatrin, levetiracetam, topiramate, clonazepam, and perampanel; many patients have refractory epilepsy. MAXO: antiseizure medication therapy No disease-modifying therapy identified in retrieved literature; seizure burden is often high and drug resistance common. (carneiro2021casereportdiffuse pages 2-3, carneiro2021casereportdiffuse pages 1-2, khatib2024adgrg1relatedpolymicrogyriasyndrome pages 6-7)
Management/Treatment Developmental and supportive care Real-world care typically includes multidisciplinary neurodevelopmental support for motor, cognitive, speech/language, feeding, and visual/oculomotor impairments, although disease-specific protocols are not detailed in the retrieved ADGRG1 papers. MAXO: supportive care; MAXO: physical therapy; MAXO: speech therapy; MAXO: occupational therapy Supportive management is inferred from the severe, lifelong neurodevelopmental phenotype and standard PMG care principles. (khatib2024adgrg1relatedpolymicrogyriasyndrome pages 1-3, carneiro2021casereportdiffuse pages 3-5, khatib2024adgrg1relatedpolymicrogyriasyndrome pages 6-7)
Management/Treatment Longitudinal neurologic follow-up Ongoing follow-up is needed for epilepsy evolution, ambulation, tone/pyramidal signs, cerebellar features, and developmental progress; some patients show regression with epileptic decompensation. MAXO: neurologic follow-up Clinical course is static structurally but functionally variable, especially with refractory epilepsy. (carneiro2021casereportdiffuse pages 1-2, carneiro2021casereportdiffuse pages 3-5)
Management/Treatment Clinical research implementation Observational study NCT01488461 (“Phenotypic and Genotypic Studies in Congenital and Early Onset Ataxias”) posted 2011-12-08 and completed 2014-10 included sequencing of GPR56 in patients with suggestive congenital ataxia features. MAXO: enrollment in observational study; MAXO: genetic testing Illustrates real-world incorporation of GPR56/ADGRG1 testing into neurogenetics research/diagnostic pathways for cerebellar ataxia syndromes. (NCT01488461 chunk 1)
Prevention Genetic counseling Genetic counseling is strongly recommended for affected families, especially in consanguineous settings, to explain autosomal recessive inheritance, recurrence risk, testing options, and family planning. MAXO: genetic counseling Explicitly emphasized in the 2024 family report and supported by segregation-based diagnosis. (khatib2024adgrg1relatedpolymicrogyriasyndrome pages 1-3, khatib2024adgrg1relatedpolymicrogyriasyndrome pages 4-6, khatib2024adgrg1relatedpolymicrogyriasyndrome pages 6-7)
Prevention Carrier testing / cascade testing Once the familial ADGRG1 variant is known, targeted testing of parents, siblings, and extended relatives can identify carriers and clarify reproductive risk. MAXO: carrier screening; MAXO: cascade genetic testing Practical prevention strategy for rare recessive disease in extended families. (carneiro2021casereportdiffuse pages 1-2, khatib2024adgrg1relatedpolymicrogyriasyndrome pages 1-3, carneiro2021casereportdiffuse pages 2-3)
Prevention Prenatal diagnosis / reproductive planning Although not elaborated as formal protocols in all retrieved papers, family reports show direct reproductive utility of molecular diagnosis; one cited family used fetal testing in a subsequent pregnancy, and counseling papers explicitly frame genetic diagnosis as aiding future reproductive choices. MAXO: prenatal genetic testing; MAXO: reproductive counseling; MAXO: preimplantation genetic testing Appropriate once a familial pathogenic ADGRG1 variant is established. (khatib2024adgrg1relatedpolymicrogyriasyndrome pages 4-6, khatib2024adgrg1relatedpolymicrogyriasyndrome pages 1-3, khatib2024adgrg1relatedpolymicrogyriasyndrome pages 6-7)
Prevention Consanguinity-informed risk assessment In populations/families with consanguinity, earlier consideration of autosomal recessive BFPP and earlier exome/panel testing may shorten diagnostic delay and reduce recurrence through informed planning. MAXO: risk assessment; MAXO: exome sequencing Consanguinity is a prominent feature in many reported pedigrees. (jansen2005geneticsofthe pages 5-6, piao2005genotype–phenotypeanalysisof pages 3-5, khatib2024adgrg1relatedpolymicrogyriasyndrome pages 1-3)

Table: This table summarizes practical diagnostic workflows, common differential-diagnosis pitfalls, symptomatic management, and prevention/counseling strategies for ADGRG1-related bilateral frontoparietal polymicrogyria. It is useful for translating case-report and cohort evidence into a knowledge-base-ready clinical implementation view.

Key diagnostic principles: - Diagnosis is typically suspected from MRI pattern and confirmed by molecular testing (panel or WES) with segregation and ACMG-based interpretation. (khatib2024adgrg1relatedpolymicrogyriasyndrome pages 1-3, carneiro2021casereportdiffuse pages 2-3) - Important diagnostic pitfalls include mimicry of congenital CMV/HSV and cobblestone/dystroglycanopathy-like presentations. (khatib2024adgrg1relatedpolymicrogyriasyndrome pages 4-6, carneiro2021casereportdiffuse pages 2-3)

11. Outcome / prognosis

12. Treatment

12.1 Pharmacotherapy (symptomatic)

No disease-modifying pharmacotherapy specific to ADGRG1-BFPP was identified in the retrieved evidence. Current treatment is symptomatic, primarily targeting seizures.

Antiseizure medications (ASMs): - Valproate was “initially responsive” in one ADGRG1 case report; other reported ASMs used across severe cases include vigabatrin, levetiracetam, topiramate, clonazepam, and perampanel, with many patients remaining refractory. (carneiro2021casereportdiffuse pages 2-3, carneiro2021casereportdiffuse pages 1-2) - A separate ADGRG1 regulatory-variant–associated polymicrogyria phenotype (perisylvian-restricted) is reported to have vigabatrin efficacy in GPR56-mutated patients (reported in model-focused review context). (murayama2020thepolymicrogyriaassociatedgpr56 pages 1-2)

Suggested MAXO terms (treatment): - MAXO: antiseizure medication therapy (carneiro2021casereportdiffuse pages 1-2) - MAXO: supportive care / multidisciplinary rehabilitation (inferred standard of care; disease-specific trials absent) (khatib2024adgrg1relatedpolymicrogyriasyndrome pages 1-3)

12.2 Surgical/interventional

No ADGRG1-specific epilepsy surgery outcomes were identified in the retrieved evidence excerpts.

12.3 Experimental therapeutics

No interventional clinical trials targeting ADGRG1-BFPP were identified. An observational study in congenital/early-onset ataxias included sequencing GPR56 in participants with suggestive features (NCT01488461; first posted 2011-12-08, completion 2014-10). (NCT01488461 chunk 1)

13. Prevention

Primary prevention of the genetic disorder is not possible without reproductive interventions; prevention focuses on recurrence reduction through genetic counseling and family testing. - Genetic counseling and carrier/cascade testing are recommended and emphasized, especially in consanguineous families. (khatib2024adgrg1relatedpolymicrogyriasyndrome pages 1-3, khatib2024adgrg1relatedpolymicrogyriasyndrome pages 6-7) - Prenatal testing / reproductive planning is enabled once a familial pathogenic ADGRG1 variant is established; family reports highlight reproductive utility of molecular diagnosis. (khatib2024adgrg1relatedpolymicrogyriasyndrome pages 4-6, khatib2024adgrg1relatedpolymicrogyriasyndrome pages 6-7)

Suggested MAXO terms (prevention): - MAXO: genetic counseling; MAXO: carrier screening; MAXO: prenatal genetic testing (khatib2024adgrg1relatedpolymicrogyriasyndrome pages 6-7, khatib2024adgrg1relatedpolymicrogyriasyndrome pages 1-3)

14. Other species / natural disease

No naturally occurring veterinary disease analogs explicitly tied to ADGRG1 variants were identified in the retrieved evidence.

15. Model organisms

15.1 Model systems and key phenotypes

15.2 Model applications and limitations

These models support mechanistic interrogation of (i) cortical lamination and migration, (ii) ECM ligand interactions and Gα12/13–RhoA signaling, and (iii) myelination/glia–glia signaling (microglia→OPC; Schwann cells). However, no model fully recapitulates the complete human BFPP MRI signature (frontoparietal gradient plus hindbrain hypoplasia) in the retrieved excerpts, and species differences in ligand interactions (e.g., TG2 binding specificity in some systems) have been reported in mechanistic studies. (chiang2011diseaseassociatedgpr56mutations pages 7-8, ackerman2018gpr56adgrg1regulatesdevelopment pages 1-2)


Recent developments (2023–2024 prioritized highlights)


Expert synthesis / interpretation (authoritative-source-driven)

Taken together, the human genetics literature establishes ADGRG1 as a high-confidence Mendelian cause of BFPP with a recognizable radiogenomic signature and high burden of epilepsy and developmental disability (piao2005genotype–phenotypeanalysisof pages 3-5, piao2005genotype–phenotypeanalysisof pages 1-2). Functional biochemical studies support that many disease alleles are “processing/trafficking” loss-of-function variants in an adhesion GPCR requiring precise proteolytic maturation and extracellular interactions; this molecular fragility plausibly explains why both extracellular missense and truncating variants can converge on a similar neurodevelopmental outcome (chiang2011diseaseassociatedgpr56mutations pages 3-5, ke2008biochemicalcharacterizationof pages 1-2, chiang2011diseaseassociatedgpr56mutations pages 1-2). Recent signaling studies (2024) deepen mechanistic resolution of how distinct ADGRG1 activation modalities (antibody vs small molecule vs constitutive) can yield biased G-protein engagement while preserving Rho-pathway output, suggesting that future therapeutic exploration would likely need to consider ligand modality, receptor cleavage state, and cell-type-specific signaling context (jallouli2024gproteinselectivity pages 1-2, jallouli2024gproteinselectivity pages 7-9). At present, however, clinical management remains supportive and seizure-focused, and prevention is primarily via genetic counseling and reproductive planning in affected families. (khatib2024adgrg1relatedpolymicrogyriasyndrome pages 6-7, carneiro2021casereportdiffuse pages 1-2)

References

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