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Inheritance

1

Autosomal recessive inheritance HP:0000007

Classic ADGRG1-related BFPP is caused by biallelic germline variants and segregates as an autosomal recessive disorder.

Autosomal recessive inheritance

Show evidence (2 references)

PMID:20929962 SUPPORT Human Clinical

"We identified homozygous GPR56 mutations in 14 patients from eight consanguineous families with typical bilateral bifrontoparietal polymicrogyria"

Homozygous variants across eight consanguineous families establish the recessive inheritance pattern.

PMID:16240336 SUPPORT Human Clinical

"We identified homozygous GPR56 mutations in all 29 patients with typical BFPP."

Molecular confirmation in 29 typical cases independently supports biallelic recessive disease.

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Discussions and Knowledge Gaps

1

Which human-relevant cis-regulatory, splice-form and gyrencephalic features determine whether ADGRG1 disruption produces classic frontoparietal, perisylvian or diffuse polymicrogyria, and how can those spatial effects be separated from the conserved pial-boundary mechanism reproduced in mice?

HUMAN MODEL MISMATCH OPEN gap_adgrg1_human_regional_patterning_model_mismatch

Attached to

pathophysiology#Regional Cortical Patterning Dependence on GPR56 Expression pathophysiology#Neuronal Overmigration and Cortical Dyslamination

Gpr56-null and Col3a1-null mice validly reproduce pial basement-membrane breach, endfoot failure and neuronal overmigration; the null mouse should not be described as a globally unpatterned model. The unresolved mismatch is narrower: a naturally lissencephalic mouse cannot model human cortical folding, and human-relevant ADGRG1 splice forms and gyrencephalic cis-regulatory architecture are not reproduced by mouse. The human 15-base-pair regulatory deletion selectively affects perisylvian cortex, while coding variants usually produce classic BFPP but can occasionally produce diffuse disease. A human model is therefore needed to test the interaction between allele class, regional identity and the corticomeningeal pial boundary.

Proposed experiments

Regionally patterned human corticomeningeal organoid experiment

isogenic regionally patterned corticomeningeal organoid experiment

exp_adgrg1_regionally_patterned_corticomeningeal_organoids

Use isogenic human iPSC-derived cortical organoids patterned toward frontal, parietal and perisylvian/lateral identities and supplied with a meningeal collagen-III compartment adjacent to a laminin/collagen-IV-rich pial-like basement membrane. Compare biallelic coding loss of function with the 15-base-pair regulatory deletion to test how allele class and regional identity interact to alter ADGRG1 expression, pial-boundary integrity, radial-glial anchorage and neuronal overmigration.

Model systems

Human iPSC-derived regionally patterned corticomeningeal organoid

Human cortical organoids patterned toward frontal, parietal or perisylvian/lateral identity, combined with a meningeal collagen-III compartment and an adjacent laminin/collagen-IV-rich pial-like basement membrane, and carrying isogenic ADGRG1 coding or regulatory alleles.

ORGANOID namo:Organoid link

human NCBITaxon:9606

cerebral cortex UBERON:0000956

cortical radial glial cell CL:0013000 migrating cortical neuron CL:0000540

Perturbations

Biallelic ADGRG1 coding loss of function

pathophysiology#Regional Cortical Patterning Dependence on GPR56 Expression

Introduce a biallelic coding loss-of-function allele into an isogenic human iPSC background.

ADGRG1 hgnc:4512

ADGRG1 15-base-pair regional regulatory-element deletion

pathophysiology#Regional Cortical Patterning Dependence on GPR56 Expression

Introduce the perisylvian-associated non-coding regulatory deletion into the same isogenic background without disrupting the coding sequence.

ADGRG1 hgnc:4512

Readouts

Regional ADGRG1 expression and splice-form abundance

pathophysiology#Regional Cortical Patterning Dependence on GPR56 Expression

cerebral cortex regionalization GO:0021796 ⚠ ABNORMAL

spatial transcriptomics assay

Direction: NEGATIVE

Pial-like basement-membrane continuity and radial-glial endfoot anchorage

pathophysiology#Pial Basement Membrane Breach

basement membrane organization GO:0071711 ⚠ ABNORMAL

immunofluorescence microscopy assay

Direction: NEGATIVE

Region-resolved neuronal overmigration across the pial boundary

pathophysiology#Neuronal Overmigration and Cortical Dyslamination

neuron migration GO:0001764 ↑ INCREASED

live-cell imaging assay

Direction: POSITIVE

Controls

Isogenic wild-type and corrected organoids

Sham-edited wild-type organoids and variant-corrected patient lines for every regional identity and corticomeningeal culture batch.

Coding rescue arm

Re-expression of physiologic ADGRG1 in coding-loss organoids to test rescue of pial-boundary integrity and overmigration.

Interface-negative technical control

Matched cortical organoids lacking the engineered meningeal/pial interface to show which readouts require a modeled pial boundary.

Decision criterion

Support regional allelic specificity only if there is a reproducible allele-by-regional-identity interaction: the regulatory deletion must preferentially reduce ADGRG1 expression and disrupt boundary or migration readouts in perisylvian/lateral organoids, while coding loss causes a broader defect whose magnitude follows baseline regional expression. Variant correction or coding rescue must reverse the corresponding abnormalities.

Would support

pathophysiology#Regional Cortical Patterning Dependence on GPR56 Expression pathophysiology#Pial Basement Membrane Breach pathophysiology#Neuronal Overmigration and Cortical Dyslamination

Would refute

pathophysiology#Regional Cortical Patterning Dependence on GPR56 Expression

Show evidence (3 references)

PMID:18509043 SUPPORT Model Organism

"This study demonstrates that loss of the mouse Gpr56 gene leads to neuronal ectopia in the cerebral cortex, a cobblestone-like cortical malformation."

The knockout supports the conserved cortical-ectopia mechanism; it does not justify describing the mouse phenotype as globally unpatterned.

PMID:21768377 SUPPORT Model Organism

"Mutations in the GPR56 gene cause a malformed cerebral cortex in both humans and mice that resembles cobblestone lissencephaly, which is characterized by overmigration of neurons beyond the pial basement membrane."

Establishes that mouse models reproduce the conserved overmigration and cobblestone arm, isolating human folding and allele-specific regional architecture as the translational gap.

PMID:24531968 SUPPORT Other

"GPR56 splice forms are highly variable between mice and humans, and the regulatory element of gyrencephalic mammals directs restricted lateral cortical expression."

Documents that the splicing and cis-regulatory architecture controlling regional GPR56 expression differ between mouse and human and motivates a human regional-patterning model.

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Pathophysiology

9

Loss of GPR56 Adhesion GPCR Function

Recessive loss-of-function mutations in ADGRG1/GPR56, an adhesion-family G protein-coupled receptor expressed in cortical radial glial progenitors and their basal endfeet, impair receptor function. Missense variants analyzed in PMID:21349848 were located in the extracellular region (ectodomain, GPS autoproteolysis site and extracellular loops) and affected different combinations of surface expression, proteolysis, shedding, ligand interaction and membrane distribution. These heterogeneous defects converge on reduced GPR56 function as the initiating molecular lesion of BFPP.

ADGRG1 hgnc:4512

G protein-coupled receptor signaling pathway GO:0007186 ↓ DECREASED

Downstream

Disrupted GPR56-Collagen III Signaling Reduced receptor availability and function diminish the independently established collagen III-GPR56 pathway that normally restrains neuronal migration.

Impaired Oligodendrocyte Precursor Proliferation and Maturation Loss of GPR56 in oligodendrocyte-lineage cells reduces active RhoA and OPC proliferation, creating a parallel white-matter disease branch.

Rostral Cerebellar Granule Cell Adhesion Failure GPR56 loss in developing rostral cerebellar granule cells impairs adhesion to pial extracellular matrix and disrupts local morphogenesis.

Hypoplasia of the Pons Biallelic ADGRG1 loss is associated with pontine hypoplasia, but the intervening brainstem developmental mechanism has not been established.

Hypotonia Hypotonia is associated with biallelic ADGRG1 disease, but the relative contributions of cortical, cerebellar, brainstem and white-matter pathology are unresolved.

Abnormality of Eye Movement Eye-movement abnormalities are associated with ADGRG1 disease, but the responsible cortical, cerebellar or brainstem circuit has not been established.

Show evidence (2 references)

PMID:15044805 SUPPORT Human Clinical

"we show that mutations in GPR56, which encodes an orphan G protein-coupled receptor (GPCR) with a large extracellular domain, cause a human brain cortical malformation called bilateral frontoparietal polymicrogyria (BFPP)"

Establishes GPR56/ADGRG1 mutations as the cause of BFPP and identifies the gene product as a GPCR with a large extracellular domain.

PMID:21349848 SUPPORT In Vitro

"individual GPR56 mutants most likely cause BFPP via different combination of multiple mechanisms. These include reduced surface receptor expression, loss of GPS proteolysis, reduced receptor shedding, inability to interact with a novel protein ligand"

Details the convergent molecular consequences of disease-associated extracellular-region mutations that impair GPR56 function.

Disrupted GPR56-Collagen III Signaling

Collagen III (COL3A1), a pial extracellular-matrix component produced in the meninges, is a ligand of GPR56 in the developing cortex. Engagement of GPR56 by collagen III couples to the Galpha-12/13 family of G proteins and activates RhoA, which restrains neuronal migration. Loss of receptor or ligand removes this brake and destabilizes cortical lamination.

cortical radial glial cell CL:0013000

ADGRG1 hgnc:4512 COL3A1 hgnc:2201

cell-matrix adhesion GO:0007160 ↓ DECREASED Rho protein signal transduction GO:0007266 ↓ DECREASED collagen fibril organization GO:0030199 ↕ DYSREGULATED

pia mater UBERON:0002361 cerebral cortex UBERON:0000956

Downstream

Pial Basement Membrane Breach Loss of collagen III-GPR56 signaling destabilizes the pial basement membrane and removes the migratory brake, permitting overmigration.

Show evidence (2 references)

PMID:21768377 SUPPORT In Vitro

"As for intracellular signaling, GPR56 couples to the Gα(12/13) family of G proteins and activates RhoA pathway upon ligand binding."

Identifies the GPR56 intracellular signaling output (Galpha-12/13 to RhoA) activated by ligand binding.

PMID:21768377 SUPPORT In Vitro

"Functional studies suggest that the interaction of collagen III with its receptor GPR56 inhibits neural migration in vitro."

Establishes that the collagen III-GPR56 interaction normally restrains neuronal migration, the brake lost in disease.

Pial Basement Membrane Breach

GPR56 signaling at cortical radial-glial basal endfeet maintains the pial basement membrane in the developing forebrain. Loss of GPR56 (or its collagen III ligand) breaches the cortical glia limitans and creates gaps through which neurons can escape the cortical plate; the rostral cerebellar context is represented in its separate disease-specific branch.

cortical radial glial cell CL:0013000

basement membrane organization GO:0071711 ⚠ ABNORMAL

pia mater UBERON:0002361 cerebral cortex marginal layer UBERON:0014935

Downstream

Radial-Glial Basal Endfoot Detachment Pial basement membrane breach destabilizes radial glial basal endfeet at the cortical surface.

Cajal-Retzius Cell Mislocalization Pial-boundary failure is accompanied by mislocalization of Cajal-Retzius cells in the marginal zone.

Show evidence (2 references)

PMID:20929962 SUPPORT Model Organism

"loss of GPR56 leads to a dysregulation of the maintenance of the pial basement membrane integrity in the forebrain and the rostral cerebellum"

Identifies pial basement membrane integrity failure as the consequence of GPR56 loss, the structural lesion enabling overmigration.

PMID:21768377 SUPPORT Model Organism

"Mutations in the GPR56 gene cause a malformed cerebral cortex in both humans and mice that resembles cobblestone lissencephaly, which is characterized by overmigration of neurons beyond the pial basement membrane."

Links GPR56 mutation to a cobblestone-like cortex defined by neuronal overmigration beyond the breached pial basement membrane.

Radial-Glial Basal Endfoot Detachment

GPR56 is enriched in radial glial endfeet, where the GPR56-COL3A1 axis helps maintain the pial basement membrane and radial-glial scaffold. Loss of this endfoot anchoring function removes the boundary constraint that normally prevents overmigration beyond the pial surface.

cortical radial glial cell CL:0013000

formation of radial glial scaffolds GO:0021943 ↓ DECREASED

Downstream

Neuronal Overmigration and Cortical Dyslamination Abnormal endfoot anchorage occurs within the same pial-boundary failure sequence as neuronal overmigration and may contribute by disrupting the radial-glial stopping scaffold, but its independent causal order has not been isolated.

Show evidence (2 references)

PMID:18509043 SUPPORT Model Organism

"We show further that GPR56 is present in abundance in radial glial endfeet."

Localizes GPR56 to radial glial endfeet, supporting this as the cellular site of the pial-boundary failure.

PMID:18509043 SUPPORT Model Organism

"There are four crucial events in the development of cobblestone cortex, namely defective pial basement membrane (BM), abnormal anchorage of radial glial endfeet, mislocalized Cajal-Retzius cells, and neuronal overmigration."

Identifies abnormal radial-glial endfoot anchorage as part of the shared GPR56/pial-boundary overmigration skeleton.

Cajal-Retzius Cell Mislocalization

Gpr56-null cortical boundary failure mislocalizes Cajal-Retzius cells within the marginal-zone lesion sequence. This can amplify cortical disorganization, although its independent contribution to neuronal overmigration has not been isolated in ADGRG1 disease.

Cajal-Retzius cell CL:0000695

cerebral cortex marginal layer UBERON:0014935

Downstream

Neuronal Overmigration and Cortical Dyslamination Cajal-Retzius-cell mislocalization accompanies neuronal overmigration and may amplify dyslamination, but a direct causal contribution has not been isolated.

Show evidence (1 reference)

PMID:18509043 SUPPORT Model Organism

"There are four crucial events in the development of cobblestone cortex, namely defective pial basement membrane (BM), abnormal anchorage of radial glial endfeet, mislocalized Cajal-Retzius cells, and neuronal overmigration."

The Gpr56-null cortical model explicitly identifies Cajal-Retzius-cell mislocalization as part of the cobblestone lesion sequence.

Neuronal Overmigration and Cortical Dyslamination

With the pial basement membrane breached and the GPR56-RhoA migratory brake lost, postmitotic neurons overmigrate beyond their normal pial stopping point, producing a disorganized, abnormally laminated cortex. The result is a frontoparietally predominant polymicrogyria that, at its severe end, forms a cobblestone-like cortex with ectopic neuronal overmigration, forming a phenotypic continuum from BFPP to cobblestone-like lissencephaly.

cerebral cortex neuron CL:0010012

neuron migration GO:0001764 ↑ INCREASED cerebral cortex radial glia-guided migration GO:0021801 ↕ DYSREGULATED layer formation in cerebral cortex GO:0021819 ⚠ ABNORMAL

Downstream

Bilateral Frontoparietal Polymicrogyria Neuronal overmigration through a breached pial boundary directly produces the frontoparietal polymicrogyria/cobblestone cortical malformation.

Intellectual Disability Cortical dyslamination is associated with lifelong cognitive impairment, but the intervening network-level mechanisms have not been resolved.

Motor Delay The cortical malformation contributes to delayed motor development through incompletely resolved corticospinal and network-level mechanisms.

Spasticity and Pyramidal Signs Disorganized cortical motor pathways plausibly contribute to the frequent pyramidal signs reported in the clinical spectrum.

Seizures Disorganized cortical lamination creates an epileptogenic cortical substrate.

Predominantly Anterior Low-Amplitude Alpha-Like EEG Bursts The malformed cortical network is associated with a characteristic EEG pattern in the 14-person cohort, although the electrophysiologic intermediates are unresolved.

Show evidence (2 references)

PMID:20929962 SUPPORT Human Clinical

"showed a cobblestone-like lissencephaly with a succession of normal, polymicrogyric and 'cobblestone-like' cortex with ectopic neuronal overmigration"

Documents ectopic neuronal overmigration and the polymicrogyria-to- cobblestone cortical continuum in a fetopathological BFPP case.

PMID:15044805 SUPPORT Human Clinical

"BFPP is characterized by disorganized cortical lamination that is most severe in frontal cortex."

Establishes disordered cortical lamination with frontal predominance as the defining cortical pathology of BFPP.

Impaired Oligodendrocyte Precursor Proliferation and Maturation

GPR56 is highly expressed in oligodendrocyte precursor cells and signals through RhoA to maintain their proliferation. Constitutive or OPC-conditional Gpr56 loss reduces active RhoA, causes premature cell-cycle exit, lowers the numbers of mature oligodendrocytes and myelinated axons, and produces early CNS hypomyelination. This is a cell-autonomous white-matter branch rather than a consequence assigned solely to cortical dyslamination.

oligodendrocyte precursor cell CL:0002453 oligodendrocyte CL:0000128

ADGRG1 hgnc:4512

Rho protein signal transduction GO:0007266 ↓ DECREASED cell population proliferation GO:0008283 ↓ DECREASED myelination GO:0042552 ↓ DECREASED

brain white matter UBERON:0003544

Downstream

White Matter Abnormalities Fewer mature oligodendrocytes and myelinated axons provide a mechanistic basis for the patchy-to-diffuse white-matter abnormalities in BFPP.

Central Nervous System Hypomyelination Reduced oligodendrocyte production and axonal myelination directly produce the early hypomyelination phenotype.

Show evidence (2 references)

PMID:25607655 SUPPORT Model Organism

"Gpr56-knockout mice manifest with decreased oligodendrocyte precursor cell (OPC) proliferation and diminished levels of active RhoA, leading to fewer mature oligodendrocytes and a reduced number of myelinated axons in the corpus callosum and optic nerves."

The constitutive knockout identifies the RhoA, proliferation, oligodendrocyte and myelinated-axon sequence.

PMID:25607655 SUPPORT Model Organism

"Conditional ablation of Gpr56 in OPCs leads to a reduced number of mature oligodendrocytes as seen in constitutive knockout of Gpr56."

Lineage-restricted deletion establishes that the oligodendrocyte defect is cell autonomous.

Rostral Cerebellar Granule Cell Adhesion Failure

In the rostral cerebellum, GPR56 is expressed in developing granule cells and supports their adhesion to pial basement-membrane extracellular matrix. Gpr56-null mice show loss of this adhesion, pial fragmentation, fusion of adjacent lobules and disrupted neuronal and glial layering. Rescue by GPR56 re-expression supports a direct, region-specific cerebellar mechanism.

cerebellar granule cell CL:0001031

ADGRG1 hgnc:4512

cell-matrix adhesion GO:0007160 ↓ DECREASED

cerebellum UBERON:0002037

Downstream

Cerebellar Dysplasia Pial fragmentation, lobule fusion and abnormal cellular layering produce rostral cerebellar dysplasia. The model does not directly establish the cystic component described on human MRI.

Ataxia and Cerebellar Signs Cerebellar structural dysplasia contributes to the frequent ataxic and cerebellar motor phenotype.

Show evidence (2 references)

PMID:19515912 SUPPORT Model Organism

"Defects involve fusion of adjacent lobules, disrupted layering of neurons and glia, and fragmentation of the pial basement membrane."

The rostral cerebellar knockout phenotype directly identifies the local adhesion, pial and morphogenetic defect.

PMID:19515912 SUPPORT Model Organism

"reexpression of GPR56 rescues the adhesion defect in knock-out granule cells."

Rescue supports a direct GPR56 requirement for granule-cell adhesion.

Regional Cortical Patterning Dependence on GPR56 Expression

GPR56 is expressed in cortical progenitor cells in a regionally restricted, promoter-controlled pattern, and its expression levels regulate progenitor proliferation. A 15-base-pair deletion in a region-specific regulatory element selectively disrupts lateral/perisylvian cortex and represents a related ADGRG1 allelic phenotype, whereas classic BFPP is usually frontoparietal or follows an anterior-posterior severity gradient. Regional control is important but not absolute: rare coding-variant cases with diffuse polymicrogyria without a clear gradient have been reported.

cortical progenitor cell CL:0000047

ADGRG1 hgnc:4512

cerebral cortex regionalization GO:0021796 ⚠ ABNORMAL

Downstream

Bilateral Frontoparietal Polymicrogyria Spatial ADGRG1 regulation can alter the anatomical distribution of cortical malformation, but the perisylvian regulatory allele does not by itself explain classic frontoparietal vulnerability; the relevant intermediates remain unresolved.

Show evidence (3 references)

PMID:24531968 SUPPORT Human Clinical

"we describe a 15-base pair deletion mutation in a regulatory element of GPR56 that selectively disrupts human cortex surrounding the Sylvian fissure bilaterally including "Broca's area," the primary language area, by disrupting regional GPR56 expression and blocking RFX transcription factor binding"

Shows that a non-coding regulatory mutation produces a regionally restricted (perisylvian) malformation by disrupting regional GPR56 expression, demonstrating promoter-level regional patterning.

PMID:24531968 SUPPORT Model Organism

"GPR56 encodes a heterotrimeric guanine nucleotide-binding protein (G protein)-coupled receptor required for normal cortical development and is expressed in cortical progenitor cells. GPR56 expression levels regulate progenitor proliferation."

Establishes that GPR56 is expressed in cortical progenitors and that its expression level controls progenitor proliferation and regional patterning.

PMID:34513772 SUPPORT Human Clinical

"Magnetic resonance imaging revealed diffuse polymicrogyria with relative sparing of the anterior temporal lobes, without an anterior-posterior gradient, diffuse hypomyelination and pontine and cerebellar hypoplasia."

This atypical case shows that regional patterning is not an invariant coding-variant rule.

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Pathograph

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Phenotypes

13

Eye 1

Abnormality of Eye Movement VERY_FREQUENT HP:0000496

Show evidence (2 references)

PMID:34513772 SUPPORT Human Clinical

"Oculomotor ﬁndings Present 59 (92.1)"

Oculomotor findings occurred in 59/64, approximately 92.2% (reported as 92.1%), which falls in the VERY_FREQUENT band (80-99%).

PMID:25922261 SUPPORT Human Clinical

"Affected patients present with delayed milestones, intellectual disability, epilepsy, ataxia, and eye movement abnormalities."

The four-person series independently confirms eye-movement abnormalities.

Musculoskeletal 1

Hypotonia HP:0001252

Show evidence (1 reference)

PMID:34513772 SUPPORT Human Clinical

"Clinically, BFPP presents as a pseudomyopathic pattern, with hypotonia developing in the ﬁrst year of life and occasionally being identiﬁed at birth"

The clinical review links first-year or congenital hypotonia to the pseudomyopathic BFPP presentation.

Nervous System 7

Bilateral Frontoparietal Polymicrogyria VERY_FREQUENT HP:0002126

Show evidence (1 reference)

PMID:20929962 SUPPORT Human Clinical

"Neuroimaging demonstrated a common phenotype with bilateral frontoparietally predominant polymicrogyria (13/13)"

Bilateral frontoparietally predominant polymicrogyria occurred in 13/13 = 100% of this selected imaged cohort. VERY_FREQUENT is retained rather than inferring obligate penetrance across atypical ADGRG1 disease.

White Matter Abnormalities VERY_FREQUENT Abnormal cerebral white matter morphology HP:0002500

Show evidence (1 reference)

PMID:20929962 SUPPORT Human Clinical

"patchy to diffuse myelination abnormalities (13/13)"

White-matter/myelination abnormalities occurred in 13/13 = 100% of this selected imaged cohort. VERY_FREQUENT is retained because this subset does not establish an obligate finding across all ADGRG1 disease.

Intellectual Disability VERY_FREQUENT HP:0001249

Show evidence (2 references)

PMID:34513772 SUPPORT Human Clinical

"Cognitive impairment Severe 46 (79.3) Moderate 11 (18.9) Mild 1 (1.7)"

The severity categories sum to 58/58 = 100% with cognitive impairment in the assessed published cases, while showing that severity is not uniformly severe. VERY_FREQUENT is retained because literature-case ascertainment does not establish obligate penetrance.

PMID:25922261 SUPPORT Human Clinical

"Affected patients present with delayed milestones, intellectual disability, epilepsy, ataxia, and eye movement abnormalities."

An independent four-person series confirms intellectual disability within the recurring clinical profile.

Motor Delay VERY_FREQUENT HP:0001270

Show evidence (2 references)

PMID:34513772 SUPPORT Human Clinical

"Cognitive and motor delay are universal features, although their severity is variable between cases."

Author wording "universal" would ordinarily map to OBLIGATE. VERY_FREQUENT is used conservatively because this literature aggregation comprises selected published cases and explicitly documents variable severity.

PMID:25922261 SUPPORT Human Clinical

"Affected patients present with delayed milestones, intellectual disability, epilepsy, ataxia, and eye movement abnormalities."

The four-person clinical series independently identifies delayed motor milestones as a core manifestation.

Ataxia and Cerebellar Signs VERY_FREQUENT HP:0001251

Show evidence (2 references)

PMID:34513772 SUPPORT Human Clinical

"Cerebellar signs Present 50 (92.6) Absent 4 (7.4)"

Cerebellar signs occurred in 50/54 = 92.6%, which falls in the VERY_FREQUENT band (80-99%).

PMID:25922261 SUPPORT Human Clinical

"Affected patients present with delayed milestones, intellectual disability, epilepsy, ataxia, and eye movement abnormalities."

The independent series explicitly includes ataxia in the clinical profile.

Seizures VERY_FREQUENT HP:0001250

Show evidence (3 references)

PMID:20929962 SUPPORT Human Clinical

"Generalized seizures (12/14) occurred later with onset ranging from 2.5 to 10 years with consistent electroencephalogram findings of predominantly anterior bursts of low amplitude α-like activity"

Generalized seizures occurred in 12/14 = 85.7%, which falls in the VERY_FREQUENT band (80-99%); the same evidence documents childhood onset.

PMID:34513772 SUPPORT Human Clinical

"Seizures Present 60 (88.2) Age at onset in years, median (IQR) 3.0 (3.0) Refractory 36 (60.0)"

Seizures occurred in 60/68 = 88.2%, which falls in the VERY_FREQUENT band (80-99%). Of the 60 seizure-positive cases, 36/60 = 60.0% were reported refractory, so drug resistance is not universal.

PMID:19016831 SUPPORT Human Clinical

"Epilepsy, present in all four patients, had started between ages 1 and 8 years, with infantile spasms in one patient and with de novo Lennox-Gastaut syndrome in the remaining three."

This selected series documents the Lennox-Gastaut and infantile-spasm spectrum without implying that it is universal.

Predominantly Anterior Low-Amplitude Alpha-Like EEG Bursts EEG abnormality HP:0002353

Show evidence (1 reference)

PMID:20929962 SUPPORT Human Clinical

"consistent electroencephalogram findings of predominantly anterior bursts of low amplitude α-like activity"

The cohort directly reports the characteristic EEG pattern; ictal and recording state were not specified, so those sidecar axes remain unset.

Other 4

Cerebellar Dysplasia VERY_FREQUENT HP:0007033

Show evidence (1 reference)

PMID:20929962 SUPPORT Human Clinical

"cerebellar dysplasia with cysts mainly affecting the superior vermis (11/13)"

Cerebellar dysplasia with cysts occurred in 11/13 = 84.6%, which falls in the VERY_FREQUENT band (80-99%).

Central Nervous System Hypomyelination CNS hypomyelination HP:0003429

Show evidence (1 reference)

PMID:20929962 SUPPORT Human Clinical

"the white matter abnormalities showed a peculiar evolution from severe hypomyelination at 4 months to patchy lesions later in childhood"

Directly documents severe CNS hypomyelination rather than inferring delayed myelination from a single time point.

Hypoplasia of the Pons HP:0012110

Show evidence (1 reference)

PMID:34513772 SUPPORT Human Clinical

"Pathogenic variants of the ADGRG1 gene are associated with bilateral frontoparietal polymicrogyria, defined radiologically by polymicrogyria with an anterior-posterior gradient, pontine and cerebellar hypoplasia and patchy white matter abnormalities."

The clinicoradiologic review identifies pontine hypoplasia as part of the ADGRG1-associated imaging pattern.

Spasticity and Pyramidal Signs FREQUENT Abnormal pyramidal sign HP:0007256

Show evidence (1 reference)

PMID:34513772 SUPPORT Human Clinical

"Pyramidal signs Present 44 (75.9) Absent 14 (24.1)"

Pyramidal signs occurred in 44/58 = 75.9%, which falls in the FREQUENT band (30-79%).

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Genetic Associations

1

Biallelic ADGRG1 loss-of-function variants (Biallelic loss of function causes ADGRG1-related BFPP)

Gene: ADGRG1 (GPR56) hgnc:4512 relationship_type: CAUSATIVE variant_origin: GERMLINE

Autosomal recessive inheritance

Show evidence (5 references)

PMID:15044805 SUPPORT Human Clinical

"we show that mutations in GPR56, which encodes an orphan G protein-coupled receptor (GPCR) with a large extracellular domain, cause a human brain cortical malformation called bilateral frontoparietal polymicrogyria (BFPP)"

Founding report identifying GPR56/ADGRG1 mutations as the cause of BFPP.

PMID:20929962 SUPPORT Human Clinical

"We identified homozygous GPR56 mutations in 14 patients from eight consanguineous families with typical bilateral bifrontoparietal polymicrogyria"

Confirms recessive (homozygous) GPR56 mutations in a multi-family BFPP cohort, consistent with autosomal recessive loss of function.

PMID:16240336 SUPPORT Human Clinical

"We identified homozygous GPR56 mutations in all 29 patients with typical BFPP."

A diagnostic cohort independently establishes the biallelic ADGRG1 association with typical BFPP.

+ 2 more references

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Medical Actions

1

Anti-Seizure Medication

Category: Therapeutic Action: anticonvulsant agent therapy Ontology label: Anticonvulsant Therapy NCIT:C64172

Individualized antiseizure pharmacotherapy is used for symptomatic seizure control. Published BFPP reports document multiple seizure types and frequent refractoriness but do not establish a disease-specific preferred drug or comparative regimen.

Target Phenotypes: Seizure HP:0001250

Show evidence (2 references)

PMID:34513772 SUPPORT Human Clinical

"The patient was subsequently treated with several anti-epile ptics"

A molecularly confirmed case directly documents antiseizure pharmacotherapy; a single case does not establish a preferred agent or comparative regimen.

PMID:34513772 SUPPORT Human Clinical

"Seizures Present 60 (88.2) Age at onset in years, median (IQR) 3.0 (3.0) Refractory 36 (60.0)"

The literature aggregation documents refractory epilepsy in a subset, supporting individualized symptomatic management without implying a universal response or disease-specific regimen.

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Diagnosis

2

Brain MRI pattern recognition

Brain MRI is the principal phenotypic test. Bilateral frontoparietally predominant polymicrogyria with an anterior-posterior gradient, cerebellar dysplasia or cysts, pontine hypoplasia and patchy-to-diffuse white-matter abnormalities strongly suggests ADGRG1-related BFPP, while diffuse patterns do not exclude it.

magnetic resonance imaging procedure NCIT:C16809

Results: A characteristic bilateral frontoparietal cortical malformation with pontocerebellar and white-matter involvement prioritizes ADGRG1 testing.

Show evidence (2 references)

PMID:20929962 SUPPORT Human Clinical

"Neuroimaging demonstrated a common phenotype with bilateral frontoparietally predominant polymicrogyria (13/13), cerebellar dysplasia with cysts mainly affecting the superior vermis (11/13) and patchy to diffuse myelination abnormalities (13/13)."

The cohort defines the combined cortical, white-matter and cerebellar MRI pattern.

PMID:34513772 SUPPORT Human Clinical

"Pathogenic variants of the ADGRG1 gene are associated with bilateral frontoparietal polymicrogyria, defined radiologically by polymicrogyria with an anterior-posterior gradient, pontine and cerebellar hypoplasia and patchy white matter abnormalities."

This clinicoradiologic summary directly supports the anterior-posterior gradient and pontine component included in the diagnostic pattern.

ADGRG1 molecular genetic confirmation

Diagnosis is confirmed by identifying biallelic pathogenic or likely pathogenic ADGRG1 variants in an individual with a compatible MRI and clinical phenotype. Once familial variants are known, targeted prenatal molecular diagnosis can be offered in an at-risk pregnancy.

molecular genetic testing NCIT:C19770

Results: Biallelic pathogenic ADGRG1 variants establish molecular confirmation.

Show evidence (2 references)

PMID:16240336 SUPPORT Human Clinical

"We identified homozygous GPR56 mutations in all 29 patients with typical BFPP."

Molecular testing detected biallelic variants in all 29 typical cases in this diagnostic cohort.

PMID:25922261 SUPPORT Human Clinical

"Antenatal diagnosis is possible if the index case is genetically confirmed."

The clinical series supports familial prenatal diagnosis once the causal variants are established.

🩻

Imaging Findings

5

Bilateral frontoparietal polymicrogyria on MRI VERY_FREQUENT

Brain MRI typically shows bilateral frontoparietally predominant polymicrogyria, often with an anterior-posterior severity gradient. This is the defining imaging pattern, although atypical diffuse cases occur.

Mri Diagnostic Bilateral

Bilateral frontoparietal polymicrogyria HP:0002126 cerebral cortex UBERON:0000956 Bilateral frontoparietal polymicrogyria HP:0002126

Show evidence (2 references)

PMID:20929962 SUPPORT Human Clinical

"Neuroimaging demonstrated a common phenotype with bilateral frontoparietally predominant polymicrogyria (13/13)"

The defining bilateral MRI pattern occurred in 13/13 = 100% of this selected imaged cohort. VERY_FREQUENT conservatively avoids treating that subset as proof of obligate penetrance across atypical ADGRG1 disease.

PMID:16240336 SUPPORT Human Clinical

"To define the range of abnormalities that could be caused by human GPR56 mutations and to establish diagnostic criteria for BFPP, we analyzed the GPR56 gene in a cohort of 29 patients with typical BFPP."

The 29-person genotype-phenotype study establishes the typical imaging pattern as a diagnostic entry point for molecular screening.

Cerebellar dysplasia with cysts on MRI VERY_FREQUENT

Cerebellar dysplasia with cysts, often involving the superior vermis, accompanies the cortical malformation in most imaged individuals.

Mri

Cerebellar dysplasia with cysts HP:0007033 cerebellum UBERON:0002037 Cerebellar dysplasia with cysts HP:0007033

Show evidence (1 reference)

PMID:20929962 SUPPORT Human Clinical

"cerebellar dysplasia with cysts mainly affecting the superior vermis (11/13)"

Cerebellar dysplasia with cysts occurred in 11/13 = 84.6%, which falls in the VERY_FREQUENT band (80-99%).

Patchy-to-diffuse cerebral white-matter abnormalities on MRI VERY_FREQUENT

MRI shows patchy-to-diffuse white-matter signal or myelination abnormalities, which may evolve with age.

Mri

Abnormal cerebral white matter morphology HP:0002500 brain white matter UBERON:0003544 Abnormal cerebral white matter morphology HP:0002500

Show evidence (1 reference)

PMID:20929962 SUPPORT Human Clinical

"patchy to diffuse myelination abnormalities (13/13)"

White-matter or myelination abnormalities occurred in 13/13 = 100% of this selected imaged cohort. VERY_FREQUENT is retained because this subset does not prove an obligate finding across the full ADGRG1 spectrum.

Central nervous system hypomyelination on MRI

Severe hypomyelination can be evident in infancy and may later evolve into patchier white-matter lesions.

Mri

CNS hypomyelination HP:0003429 brain white matter UBERON:0003544 CNS hypomyelination HP:0003429

Show evidence (1 reference)

PMID:20929962 SUPPORT Human Clinical

"the white matter abnormalities showed a peculiar evolution from severe hypomyelination at 4 months to patchy lesions later in childhood"

Serial MRI directly documents early hypomyelination and later evolution.

Pontine hypoplasia on MRI

Pontine hypoplasia forms part of the characteristic pontocerebellar imaging profile and is also seen in severe diffuse ADGRG1-related disease.

Mri

Hypoplasia of the pons HP:0012110 pons UBERON:0000988 Hypoplasia of the pons HP:0012110

Show evidence (1 reference)

PMID:34513772 SUPPORT Human Clinical

"Magnetic resonance imaging revealed diffuse polymicrogyria with relative sparing of the anterior temporal lobes, without an anterior-posterior gradient, diffuse hypomyelination and pontine and cerebellar hypoplasia."

A molecularly confirmed severe case directly documents pontine hypoplasia on MRI.

📈

Progression

3

Infancy and early childhood

Age: Birth through early childhood

Hypotonia or a pseudomyopathic presentation may be the first recognized feature, followed by delayed motor and cognitive development. Normal muscle evaluation helps separate this presentation from congenital muscular dystrophy-dystroglycanopathy.

Show evidence (2 references)

PMID:20929962 SUPPORT Human Clinical

"a distinctive clinical course characterized by pseudomyopathic behaviour at onset that subsequently evolved into severe mental and motor retardation"

The cohort documents the early pseudomyopathic presentation and later neurodevelopmental impairment.

PMID:25922261 SUPPORT Human Clinical

"The clinicoradiologic profile resembles congenital muscular dystrophy. However, no muscle disease or characteristic eye abnormalities of congenial muscular dystrophy are detected in these children."

This four-person series identifies the early muscular-dystrophy-like presentation while documenting the absence of muscle disease.

Childhood epilepsy and evolving neurologic disability

Age: Childhood through adulthood

Seizures commonly begin in childhood and may include generalized or focal seizures, epileptic spasms and, in a selected series, evolution to Lennox-Gastaut syndrome. Motor and cognitive outcomes vary, although substantial lifelong disability is common.

Show evidence (2 references)

PMID:20929962 SUPPORT Human Clinical

"Generalized seizures (12/14) occurred later with onset ranging from 2.5 to 10 years"

Documents childhood seizure onset in the main 14-person cohort.

PMID:19016831 SUPPORT Human Clinical

"Epilepsy, present in all four patients, had started between ages 1 and 8 years, with infantile spasms in one patient and with de novo Lennox-Gastaut syndrome in the remaining three."

A selected four-person series expands the epilepsy spectrum but does not establish Lennox-Gastaut syndrome as universal in BFPP.

Evolution of white-matter imaging abnormalities

Age: Infancy through later childhood

Severe hypomyelination may be present in infancy and evolve into patchy white-matter lesions later in childhood.

Show evidence (1 reference)

PMID:20929962 SUPPORT Human Clinical

"the white matter abnormalities showed a peculiar evolution from severe hypomyelination at 4 months to patchy lesions later in childhood"

Serial imaging documents age-dependent evolution of the white-matter phenotype.

🔀

Differential Diagnoses

3

Conditions with similar clinical presentations that must be differentiated from ADGRG1-related Bilateral Frontoparietal Polymicrogyria:

Muscular dystrophy-dystroglycanopathy spectrum MONDO:0018276

Overlapping Features Severe dystroglycanopathies share hypotonia, developmental impairment, cobblestone cortical malformation and pontocerebellar abnormalities. The pseudomyopathic ADGRG1 presentation can therefore initially resemble a congenital muscular dystrophy.

Distinguishing Features

Normal muscle evaluation and absence of characteristic structural eye disease favor ADGRG1-related BFPP.
Elevated creatine kinase, muscular dystrophy and major structural eye anomalies favor dystroglycanopathy.
Biallelic ADGRG1 variants confirm BFPP; variants in alpha-dystroglycan glycosylation genes support dystroglycanopathy.

Show evidence (1 reference)

PMID:25922261 SUPPORT Human Clinical

"The clinicoradiologic profile resembles congenital muscular dystrophy. However, no muscle disease or characteristic eye abnormalities of congenial muscular dystrophy are detected in these children."

The four-person series directly states both the overlap and the key muscle and eye distinctions.

Biallelic COL3A1-related cobblestone-like cortical malformation

Overlapping Features Biallelic COL3A1 disease affects the ligand side of the same GPR56-collagen III axis and can closely reproduce the cortical, cerebellar and white-matter phenotype. It is not currently represented by a separate local disease entry.

Distinguishing Features

Biallelic COL3A1 rather than ADGRG1 variants establish the ligand-side disorder.
Connective-tissue abnormalities or vascular complications support COL3A1 disease, although the brain phenotype can be strikingly similar.

Show evidence (3 references)

PMID:28258187 SUPPORT Human Clinical

"Homozygous or compound heterozygous mutations in COL3A1 are associated with cobblestone-like malformation in all three families reported to date."

Human genetic evidence establishes a ligand-side disorder that closely overlaps ADGRG1-related BFPP.

PMID:28742248 SUPPORT Human Clinical

"Bilateral frontoparietal polymicrogyria of the cobblestone variant, cerebellar microcysts, and abnormalities of the white matter characterize this brain phenotype and resemble neurological manifestations in individuals with autosomal recessive mutations in GPR56"

The second report defines the overlapping imaging pattern.

PMID:28742248 SUPPORT Human Clinical

"This patient was born with bilateral clubfoot, joint laxity, and dysmorphic facial features. At the age of 2 years she developed an aneurysmal brain hemorrhage."

Case-level connective-tissue and vascular findings support their use as distinguishing clues for biallelic COL3A1 disease, while not implying that every affected person has them.

Other bilateral polymicrogyria syndromes and BFPP2

Overlapping Features Bilateral frontal, perisylvian, generalized or BFPP-like polymicrogyria can arise without ADGRG1 variants. Imaging distribution alone is therefore not a substitute for molecular confirmation.

Distinguishing Features

A typical BFPP MRI plus biallelic pathogenic ADGRG1 variants favors this disorder.
Mutation-negative BFPP-like disease or a different regional polymicrogyria pattern should prompt broader malformation-of-cortical-development testing.

Show evidence (2 references)

PMID:16240336 SUPPORT Human Clinical

"In addition, we analyzed five patients with BFPP who did not show GPR56 mutation and found that they define a clinically, radiographically, and genetically distinct syndrome that we termed BFPP2."

The study establishes a mutation-negative BFPP-like differential.

PMID:16240336 SUPPORT Human Clinical

"Finally, we studied seven patients with a variety of other polymicrogyria syndromes including bilateral frontal polymicrogyria, bilateral perisylvian polymicrogyria, and bilateral generalized polymicrogyria. No GPR56 mutation was found in these patients."

Other regional bilateral polymicrogyria syndromes lacked GPR56 variants in this cohort and require separate molecular evaluation.

🐁

Animal Models

3

Constitutive Gpr56-null mouse Mouse (Mus musculus) Knockout

Constitutive Gpr56-null mice reproduce the core pial-boundary, overmigration, rostral cerebellar and early hypomyelination mechanisms. The lissencephalic mouse does not model human gyrification, and species-specific splice or regulatory architecture limits inference about the human perisylvian regulatory allele.

Species

Mouse (Mus musculus)

Genotype

Constitutive Gpr56-null mouse

Genes

Gpr56 (Adgrg1) hgnc:4512

Show evidence (3 references)

PMID:18509043 SUPPORT Model Organism

"This study demonstrates that loss of the mouse Gpr56 gene leads to neuronal ectopia in the cerebral cortex, a cobblestone-like cortical malformation."

The knockout reproduces cortical ectopia and the cobblestone-like overmigration mechanism.

PMID:19515912 SUPPORT Model Organism

"Gpr56(-/-) mice display a severe malformation of the rostral cerebellum that develops perinatally."

The same knockout establishes the region-specific cerebellar phenotype.

PMID:25607655 SUPPORT Model Organism

"Here, we demonstrate that loss of Gpr56 leads to hypomyelination of the central nervous system in mice."

The model also reproduces the early white-matter phenotype.

Col3a1-null mouse Mouse (Mus musculus) Knockout

Col3a1-null mice phenocopy the cortical overmigration seen in Gpr56-null mice, providing ligand-side support for the GPR56-collagen III axis.

Species

Mouse (Mus musculus)

Genotype

Col3a1-null mouse

Genes

Col3a1 hgnc:2201

Show evidence (1 reference)

PMID:21768377 SUPPORT Model Organism

"Col3a1 null mutant mice exhibit overmigration of neurons beyond the pial basement membrane and a cobblestone-like cortical malformation similar to the phenotype seen in Gpr56 null mutant mice."

The ligand-null model independently recapitulates the cortical endpoint.

Oligodendrocyte-precursor-conditional Gpr56 knockout Mouse (Mus musculus) Conditional knockout

Conditional deletion in Pdgfra-positive oligodendrocyte precursors isolates the cell-autonomous white-matter mechanism from the cortical-malformation branch.

Species

Mouse (Mus musculus)

Genotype

Oligodendrocyte-precursor-conditional Gpr56 knockout

Genes

Gpr56 (Adgrg1) hgnc:4512

Show evidence (1 reference)

PMID:25607655 SUPPORT Model Organism

"Conditional ablation of Gpr56 in OPCs leads to a reduced number of mature oligodendrocytes as seen in constitutive knockout of Gpr56."

Lineage-restricted deletion establishes cell autonomy in oligodendrocyte development.

{ }

Source YAML

click to show

name: ADGRG1-related Bilateral Frontoparietal Polymicrogyria
creation_date: "2026-06-10T00:00:00Z"
category: Mendelian
synonyms:
- bilateral frontoparietal polymicrogyria
- BFPP
- GPR56-related bilateral frontoparietal polymicrogyria
disease_term:
  preferred_term: bilateral frontoparietal polymicrogyria
  term:
    id: MONDO:0011738
    label: bilateral frontoparietal polymicrogyria
inheritance:
- name: Autosomal recessive inheritance
  inheritance_term:
    preferred_term: Autosomal recessive inheritance
    term:
      id: HP:0000007
      label: Autosomal recessive inheritance
  description: >-
    Classic ADGRG1-related BFPP is caused by biallelic germline variants and
    segregates as an autosomal recessive disorder.
  evidence:
  - reference: PMID:20929962
    reference_title: "GPR56-related bilateral frontoparietal polymicrogyria: further evidence for an overlap with the cobblestone complex."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      We identified homozygous GPR56 mutations in 14 patients from eight
      consanguineous families with typical bilateral bifrontoparietal
      polymicrogyria
    explanation: >-
      Homozygous variants across eight consanguineous families establish the
      recessive inheritance pattern.
  - reference: PMID:16240336
    reference_title: Genotype-phenotype analysis of human frontoparietal polymicrogyria syndromes.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: We identified homozygous GPR56 mutations in all 29 patients with typical BFPP.
    explanation: >-
      Molecular confirmation in 29 typical cases independently supports
      biallelic recessive disease.
description: >-
  Bilateral frontoparietal polymicrogyria (BFPP) is an autosomal recessive
  malformation of cortical development caused by biallelic loss-of-function
  variants in
  ADGRG1 (formerly GPR56), which encodes an adhesion G protein-coupled receptor.
  GPR56 is expressed in cortical radial glial progenitors and their basal
  endfeet, where it binds its extracellular-matrix ligand collagen III (COL3A1)
  to maintain the integrity of the pial basement membrane and to restrain
  neuronal migration through Galpha-12/13-RhoA signaling. Loss of GPR56 function
  breaches the pial basement membrane and permits ectopic overmigration of
  neurons beyond the pial limit, producing a frontoparietally predominant
  polymicrogyria that overlaps with the cobblestone (type II lissencephaly)
  malformation spectrum. Clinical severity varies: developmental and motor
  delay, intellectual disability, seizures (refractory in a reported subset),
  cerebellar or pyramidal signs, oculomotor abnormalities, pontocerebellar
  dysplasia and white-matter abnormalities are recurrent. Mouse constitutive and
  conditional studies support a cell-autonomous GPR56 role in oligodendrocyte
  precursors, providing a parallel candidate mechanism for hypomyelination.
  Regional ADGRG1 regulation helps shape the
  classic frontoparietal pattern; a non-coding regulatory deletion produces a
  related perisylvian-predominant phenotype, while atypical diffuse disease has
  also been reported. Biallelic COL3A1 ligand-side disease is a closely related
  but genetically distinct cobblestone-like differential diagnosis.
parents:
- congenital nervous system disorder
- disorder of development or morphogenesis
- hereditary neurological disease
references:
- reference: PMID:15044805
  title: "G protein-coupled receptor-dependent development of human frontal cortex."
- reference: PMID:16240336
  title: Genotype-phenotype analysis of human frontoparietal polymicrogyria syndromes.
- reference: PMID:18509043
  title: GPR56 regulates pial basement membrane integrity and cortical lamination.
- reference: PMID:19016831
  title: "Bilateral frontoparietal polymicrogyria, Lennox-Gastaut syndrome, and GPR56 gene mutations."
- reference: PMID:19515912
  title: GPR56-regulated granule cell adhesion is essential for rostral cerebellar development.
- reference: PMID:20929962
  title: "GPR56-related bilateral frontoparietal polymicrogyria: further evidence for an overlap with the cobblestone complex."
- reference: PMID:21349848
  title: Disease-associated GPR56 mutations cause bilateral frontoparietal polymicrogyria via multiple mechanisms.
- reference: PMID:21768377
  title: "G protein-coupled receptor 56 and collagen III, a receptor-ligand pair, regulates cortical development and lamination."
- reference: PMID:24531968
  title: Evolutionarily dynamic alternative splicing of GPR56 regulates regional cerebral cortical patterning.
- reference: PMID:25607655
  title: The adhesion G protein-coupled receptor GPR56 is a cell-autonomous regulator of oligodendrocyte development.
- reference: PMID:25922261
  title: "GPR56-Related Polymicrogyria: Clinicoradiologic Profile of 4 Patients."
- reference: PMID:28258187
  title: "Bi-allelic variants in COL3A1 encoding the ligand to GPR56 are associated with cobblestone-like cortical malformation, white matter changes and cerebellar cysts."
- reference: PMID:28742248
  title: Biallelic COL3A1 mutations result in a clinical spectrum of specific structural brain anomalies and connective tissue abnormalities.
- reference: PMID:34513772
  title: "Case Report: Diffuse Polymicrogyria Associated With a Novel ADGRG1 Variant."
progression:
- phase: Infancy and early childhood
  age_range: Birth through early childhood
  notes: >-
    Hypotonia or a pseudomyopathic presentation may be the first recognized
    feature, followed by delayed motor and cognitive development. Normal muscle
    evaluation helps separate this presentation from congenital muscular
    dystrophy-dystroglycanopathy.
  evidence:
  - reference: PMID:20929962
    reference_title: "GPR56-related bilateral frontoparietal polymicrogyria: further evidence for an overlap with the cobblestone complex."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      a distinctive clinical course characterized by pseudomyopathic behaviour
      at onset that subsequently evolved into severe mental and motor
      retardation
    explanation: >-
      The cohort documents the early pseudomyopathic presentation and later
      neurodevelopmental impairment.
  - reference: PMID:25922261
    reference_title: "GPR56-Related Polymicrogyria: Clinicoradiologic Profile of 4 Patients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The clinicoradiologic profile resembles congenital muscular dystrophy.
      However, no muscle disease or characteristic eye abnormalities of
      congenial muscular dystrophy are detected in these children.
    explanation: >-
      This four-person series identifies the early muscular-dystrophy-like
      presentation while documenting the absence of muscle disease.
- phase: Childhood epilepsy and evolving neurologic disability
  age_range: Childhood through adulthood
  notes: >-
    Seizures commonly begin in childhood and may include generalized or focal
    seizures, epileptic spasms and, in a selected series, evolution to
    Lennox-Gastaut syndrome. Motor and cognitive outcomes vary, although
    substantial lifelong disability is common.
  evidence:
  - reference: PMID:20929962
    reference_title: "GPR56-related bilateral frontoparietal polymicrogyria: further evidence for an overlap with the cobblestone complex."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Generalized seizures (12/14) occurred later with onset ranging from 2.5
      to 10 years
    explanation: >-
      Documents childhood seizure onset in the main 14-person cohort.
  - reference: PMID:19016831
    reference_title: "Bilateral frontoparietal polymicrogyria, Lennox-Gastaut syndrome, and GPR56 gene mutations."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Epilepsy, present in all four patients, had started between ages 1 and 8
      years, with infantile spasms in one patient and with de novo Lennox-Gastaut
      syndrome in the remaining three.
    explanation: >-
      A selected four-person series expands the epilepsy spectrum but does not
      establish Lennox-Gastaut syndrome as universal in BFPP.
- phase: Evolution of white-matter imaging abnormalities
  age_range: Infancy through later childhood
  notes: >-
    Severe hypomyelination may be present in infancy and evolve into patchy
    white-matter lesions later in childhood.
  evidence:
  - reference: PMID:20929962
    reference_title: "GPR56-related bilateral frontoparietal polymicrogyria: further evidence for an overlap with the cobblestone complex."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      the white matter abnormalities showed a peculiar evolution from severe
      hypomyelination at 4 months to patchy lesions later in childhood
    explanation: >-
      Serial imaging documents age-dependent evolution of the white-matter
      phenotype.
pathophysiology:
- name: Loss of GPR56 Adhesion GPCR Function
  description: >-
    Recessive loss-of-function mutations in ADGRG1/GPR56, an adhesion-family G
    protein-coupled receptor expressed in cortical radial glial progenitors and
    their basal endfeet, impair receptor function. Missense variants analyzed in
    PMID:21349848 were located in the extracellular region (ectodomain, GPS
    autoproteolysis site and extracellular loops) and affected different
    combinations of surface expression, proteolysis, shedding, ligand
    interaction and membrane distribution. These heterogeneous defects converge
    on reduced GPR56 function as the initiating molecular lesion of BFPP.
  genes:
  - preferred_term: ADGRG1
    term:
      id: hgnc:4512
      label: ADGRG1
  biological_processes:
  - preferred_term: G protein-coupled receptor signaling pathway
    term:
      id: GO:0007186
      label: G protein-coupled receptor signaling pathway
    modifier: DECREASED
  evidence:
  - reference: PMID:15044805
    reference_title: "G protein-coupled receptor-dependent development of human frontal cortex."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      we show that mutations in GPR56, which encodes an orphan G
      protein-coupled receptor (GPCR) with a large extracellular domain, cause a
      human brain cortical malformation called bilateral frontoparietal
      polymicrogyria (BFPP)
    explanation: >-
      Establishes GPR56/ADGRG1 mutations as the cause of BFPP and identifies the
      gene product as a GPCR with a large extracellular domain.
  - reference: PMID:21349848
    reference_title: Disease-associated GPR56 mutations cause bilateral frontoparietal polymicrogyria via multiple mechanisms.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: >-
      individual GPR56 mutants most likely cause BFPP via different combination
      of multiple mechanisms. These include reduced surface receptor
      expression, loss of GPS proteolysis, reduced receptor shedding, inability
      to interact with a novel protein ligand
    explanation: >-
      Details the convergent molecular consequences of disease-associated
      extracellular-region mutations that impair GPR56 function.
  downstream:
  - target: Disrupted GPR56-Collagen III Signaling
    description: >-
      Reduced receptor availability and function diminish the independently
      established collagen III-GPR56 pathway that normally restrains neuronal
      migration.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:21768377
      reference_title: "G protein-coupled receptor 56 and collagen III, a receptor-ligand pair, regulates cortical development and lamination."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: >-
        Here we identify collagen, type III, alpha-1 (gene symbol Col3a1) as the
        ligand of GPR56 through an in vitro biotinylation/proteomics approach.
      explanation: >-
        Directly identifies collagen III as the GPR56 ligand; it does not depend
        on the unidentified ligand-binding assay in PMID:21349848.
    - reference: PMID:21349848
      reference_title: Disease-associated GPR56 mutations cause bilateral frontoparietal polymicrogyria via multiple mechanisms.
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: >-
        individual GPR56 mutants most likely cause BFPP via different combination
        of multiple mechanisms. These include reduced surface receptor
        expression, loss of GPS proteolysis, reduced receptor shedding, inability
        to interact with a novel protein ligand
      explanation: >-
        Variant-specific assays support reduced functional receptor availability
        but did not identify the assayed novel ligand as collagen III; this item
        therefore provides only partial support for the collagen-pathway edge.
  - target: Impaired Oligodendrocyte Precursor Proliferation and Maturation
    description: >-
      Loss of GPR56 in oligodendrocyte-lineage cells reduces active RhoA and OPC
      proliferation, creating a parallel white-matter disease branch.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:25607655
      reference_title: The adhesion G protein-coupled receptor GPR56 is a cell-autonomous regulator of oligodendrocyte development.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        Gpr56-knockout mice manifest with decreased oligodendrocyte precursor
        cell (OPC) proliferation and diminished levels of active RhoA, leading
        to fewer mature oligodendrocytes and a reduced number of myelinated axons
        in the corpus callosum and optic nerves.
      explanation: >-
        Constitutive and conditional mouse experiments establish a
        cell-autonomous oligodendrocyte-lineage branch downstream of GPR56 loss.
  - target: Rostral Cerebellar Granule Cell Adhesion Failure
    description: >-
      GPR56 loss in developing rostral cerebellar granule cells impairs adhesion
      to pial extracellular matrix and disrupts local morphogenesis.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:19515912
      reference_title: GPR56-regulated granule cell adhesion is essential for rostral cerebellar development.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        granule cells from the rostral region of perinatal Gpr56(-/-) cerebella
        show loss of adhesion to extracellular matrix molecules of the pial
        basement membrane.
      explanation: >-
        The knockout and rescue experiments directly link GPR56 loss to impaired
        rostral cerebellar granule-cell adhesion.
  - target: Hypoplasia of the Pons
    description: >-
      Biallelic ADGRG1 loss is associated with pontine hypoplasia, but the
      intervening brainstem developmental mechanism has not been established.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:34513772
      reference_title: "Case Report: Diffuse Polymicrogyria Associated With a Novel ADGRG1 Variant."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Pathogenic variants of the ADGRG1 gene are associated with bilateral
        frontoparietal polymicrogyria, defined radiologically by polymicrogyria
        with an anterior-posterior gradient, pontine and cerebellar hypoplasia and
        patchy white matter abnormalities.
      explanation: >-
        Human clinicoradiologic evidence links ADGRG1 disease to pontine
        hypoplasia while leaving the intervening mechanism unresolved.
  - target: Hypotonia
    description: >-
      Hypotonia is associated with biallelic ADGRG1 disease, but the relative
      contributions of cortical, cerebellar, brainstem and white-matter pathology
      are unresolved.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:34513772
      reference_title: "Case Report: Diffuse Polymicrogyria Associated With a Novel ADGRG1 Variant."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Clinically, BFPP presents as a pseudomyopathic pattern, with hypotonia
        developing in the ﬁrst year of life and occasionally being identiﬁed at
        birth
      explanation: >-
        Human clinical evidence links ADGRG1-related BFPP to early hypotonia but
        does not resolve the intervening neural mechanism.
  - target: Abnormality of Eye Movement
    description: >-
      Eye-movement abnormalities are associated with ADGRG1 disease, but the
      responsible cortical, cerebellar or brainstem circuit has not been
      established.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:25922261
      reference_title: "GPR56-Related Polymicrogyria: Clinicoradiologic Profile of 4 Patients."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Affected patients present with delayed milestones, intellectual
        disability, epilepsy, ataxia, and eye movement abnormalities.
      explanation: >-
        The clinical series links ADGRG1-related polymicrogyria to eye-movement
        abnormalities while leaving the causal circuit unresolved.
- name: Disrupted GPR56-Collagen III Signaling
  description: >-
    Collagen III (COL3A1), a pial extracellular-matrix component produced in the
    meninges, is a ligand of GPR56 in the developing cortex. Engagement of GPR56
    by collagen III couples to the Galpha-12/13 family of G proteins and activates
    RhoA, which restrains neuronal migration. Loss of receptor or ligand removes
    this brake and destabilizes cortical lamination.
  conforms_to: pial_basement_membrane_radial_glial_endfoot_failure#GPR56-COL3A1 Pial ECM Signaling Failure
  genes:
  - preferred_term: ADGRG1
    term:
      id: hgnc:4512
      label: ADGRG1
  - preferred_term: COL3A1
    term:
      id: hgnc:2201
      label: COL3A1
  locations:
  - preferred_term: pia mater
    term:
      id: UBERON:0002361
      label: pia mater
  - preferred_term: cerebral cortex
    term:
      id: UBERON:0000956
      label: cerebral cortex
  cell_types:
  - preferred_term: cortical radial glial cell
    term:
      id: CL:0013000
      label: forebrain radial glial cell
  biological_processes:
  - preferred_term: cell-matrix adhesion
    term:
      id: GO:0007160
      label: cell-matrix adhesion
    modifier: DECREASED
  - preferred_term: Rho protein signal transduction
    term:
      id: GO:0007266
      label: Rho protein signal transduction
    modifier: DECREASED
  - preferred_term: collagen fibril organization
    term:
      id: GO:0030199
      label: collagen fibril organization
    modifier: DYSREGULATED
  evidence:
  - reference: PMID:21768377
    reference_title: "G protein-coupled receptor 56 and collagen III, a receptor-ligand pair, regulates cortical development and lamination."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: >-
      As for intracellular signaling, GPR56 couples to the Gα(12/13) family of
      G proteins and activates RhoA pathway upon ligand binding.
    explanation: >-
      Identifies the GPR56 intracellular signaling output (Galpha-12/13 to RhoA)
      activated by ligand binding.
  - reference: PMID:21768377
    reference_title: "G protein-coupled receptor 56 and collagen III, a receptor-ligand pair, regulates cortical development and lamination."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: >-
      Functional studies suggest that the interaction of collagen III with its
      receptor GPR56 inhibits neural migration in vitro.
    explanation: >-
      Establishes that the collagen III-GPR56 interaction normally restrains
      neuronal migration, the brake lost in disease.
  downstream:
  - target: Pial Basement Membrane Breach
    description: >-
      Loss of collagen III-GPR56 signaling destabilizes the pial basement
      membrane and removes the migratory brake, permitting overmigration.
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - impaired GPR56-dependent radial-glial and pial extracellular-matrix adhesion
    evidence:
    - reference: PMID:21768377
      reference_title: "G protein-coupled receptor 56 and collagen III, a receptor-ligand pair, regulates cortical development and lamination."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        Col3a1 null mutant mice exhibit overmigration of neurons beyond the pial
        basement membrane and a cobblestone-like cortical malformation similar
        to the phenotype seen in Gpr56 null mutant mice.
      explanation: >-
        Concordant ligand- and receptor-null phenotypes connect loss of the
        signaling axis to failure at the pial boundary.
- name: Pial Basement Membrane Breach
  description: >-
    GPR56 signaling at cortical radial-glial basal endfeet maintains the pial
    basement membrane in the developing forebrain. Loss of GPR56 (or its
    collagen III ligand) breaches the cortical glia limitans and creates gaps
    through which neurons can escape the cortical plate; the rostral cerebellar
    context is represented in its separate disease-specific branch.
  conforms_to: pial_basement_membrane_radial_glial_endfoot_failure#Pial Basement Membrane Breach
  locations:
  - preferred_term: pia mater
    term:
      id: UBERON:0002361
      label: pia mater
  - preferred_term: cerebral cortex marginal layer
    term:
      id: UBERON:0014935
      label: cerebral cortex marginal layer
  cell_types:
  - preferred_term: cortical radial glial cell
    term:
      id: CL:0013000
      label: forebrain radial glial cell
  biological_processes:
  - preferred_term: basement membrane organization
    term:
      id: GO:0071711
      label: basement membrane organization
    modifier: ABNORMAL
  evidence:
  - reference: PMID:20929962
    reference_title: "GPR56-related bilateral frontoparietal polymicrogyria: further evidence for an overlap with the cobblestone complex."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      loss of GPR56 leads to a dysregulation of the maintenance of the pial
      basement membrane integrity in the forebrain and the rostral cerebellum
    explanation: >-
      Identifies pial basement membrane integrity failure as the consequence of
      GPR56 loss, the structural lesion enabling overmigration.
  - reference: PMID:21768377
    reference_title: "G protein-coupled receptor 56 and collagen III, a receptor-ligand pair, regulates cortical development and lamination."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      Mutations in the GPR56 gene cause a malformed cerebral cortex in both
      humans and mice that resembles cobblestone lissencephaly, which is
      characterized by overmigration of neurons beyond the pial basement
      membrane.
    explanation: >-
      Links GPR56 mutation to a cobblestone-like cortex defined by neuronal
      overmigration beyond the breached pial basement membrane.
  downstream:
  - target: Radial-Glial Basal Endfoot Detachment
    description: >-
      Pial basement membrane breach destabilizes radial glial basal endfeet at
      the cortical surface.
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - loss of radial-glial endfoot anchorage to the pial extracellular matrix
    evidence:
    - reference: PMID:18509043
      reference_title: GPR56 regulates pial basement membrane integrity and cortical lamination.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        There are four crucial events in the development of cobblestone cortex,
        namely defective pial basement membrane (BM), abnormal anchorage of
        radial glial endfeet, mislocalized Cajal-Retzius cells, and neuronal
        overmigration. By detailed time course analysis, we reveal that the
        leading causal events are likely the breaches in the pial BM.
      explanation: >-
        Time-course analysis places pial basement-membrane breach upstream of
        abnormal radial-glial endfoot anchorage.
  - target: Cajal-Retzius Cell Mislocalization
    description: >-
      Pial-boundary failure is accompanied by mislocalization of Cajal-Retzius
      cells in the marginal zone.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:18509043
      reference_title: GPR56 regulates pial basement membrane integrity and cortical lamination.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        There are four crucial events in the development of cobblestone cortex,
        namely defective pial basement membrane (BM), abnormal anchorage of radial
        glial endfeet, mislocalized Cajal-Retzius cells, and neuronal
        overmigration.
      explanation: >-
        The Gpr56-null cortical sequence explicitly includes Cajal-Retzius-cell
        mislocalization downstream of pial-boundary failure.
- name: Radial-Glial Basal Endfoot Detachment
  description: >-
    GPR56 is enriched in radial glial endfeet, where the GPR56-COL3A1 axis helps
    maintain the pial basement membrane and radial-glial scaffold. Loss of this
    endfoot anchoring function removes the boundary constraint that normally
    prevents overmigration beyond the pial surface.
  conforms_to: pial_basement_membrane_radial_glial_endfoot_failure#Radial-Glial Basal Endfoot Detachment
  cell_types:
  - preferred_term: cortical radial glial cell
    term:
      id: CL:0013000
      label: forebrain radial glial cell
  biological_processes:
  - preferred_term: formation of radial glial scaffolds
    term:
      id: GO:0021943
      label: formation of radial glial scaffolds
    modifier: DECREASED
  evidence:
  - reference: PMID:18509043
    reference_title: "GPR56 regulates pial basement membrane integrity and cortical lamination."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      We show further that GPR56 is present in abundance in radial glial
      endfeet.
    explanation: >-
      Localizes GPR56 to radial glial endfeet, supporting this as the cellular
      site of the pial-boundary failure.
  - reference: PMID:18509043
    reference_title: "GPR56 regulates pial basement membrane integrity and cortical lamination."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      There are four crucial events in the development of cobblestone cortex,
      namely defective pial basement membrane (BM), abnormal anchorage of radial
      glial endfeet, mislocalized Cajal-Retzius cells, and neuronal
      overmigration.
    explanation: >-
      Identifies abnormal radial-glial endfoot anchorage as part of the shared
      GPR56/pial-boundary overmigration skeleton.
  downstream:
  - target: Neuronal Overmigration and Cortical Dyslamination
    description: >-
      Abnormal endfoot anchorage occurs within the same pial-boundary failure
      sequence as neuronal overmigration and may contribute by disrupting the
      radial-glial stopping scaffold, but its independent causal order has not
      been isolated.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:18509043
      reference_title: GPR56 regulates pial basement membrane integrity and cortical lamination.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        There are four crucial events in the development of cobblestone cortex,
        namely defective pial basement membrane (BM), abnormal anchorage of
        radial glial endfeet, mislocalized Cajal-Retzius cells, and neuronal
        overmigration.
      explanation: >-
        The study places endfoot-anchorage failure and neuronal overmigration in
        the same cobblestone sequence but does not independently order the former
        as the direct cause of the latter.
- name: Cajal-Retzius Cell Mislocalization
  description: >-
    Gpr56-null cortical boundary failure mislocalizes Cajal-Retzius cells within
    the marginal-zone lesion sequence. This can amplify cortical disorganization,
    although its independent contribution to neuronal overmigration has not been
    isolated in ADGRG1 disease.
  conforms_to: pial_basement_membrane_radial_glial_endfoot_failure#Cajal-Retzius Cell Mislocalization
  locations:
  - preferred_term: cerebral cortex marginal layer
    term:
      id: UBERON:0014935
      label: cerebral cortex marginal layer
  cell_types:
  - preferred_term: Cajal-Retzius cell
    term:
      id: CL:0000695
      label: Cajal-Retzius cell
  evidence:
  - reference: PMID:18509043
    reference_title: GPR56 regulates pial basement membrane integrity and cortical lamination.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      There are four crucial events in the development of cobblestone cortex,
      namely defective pial basement membrane (BM), abnormal anchorage of radial
      glial endfeet, mislocalized Cajal-Retzius cells, and neuronal overmigration.
    explanation: >-
      The Gpr56-null cortical model explicitly identifies Cajal-Retzius-cell
      mislocalization as part of the cobblestone lesion sequence.
  downstream:
  - target: Neuronal Overmigration and Cortical Dyslamination
    description: >-
      Cajal-Retzius-cell mislocalization accompanies neuronal overmigration and
      may amplify dyslamination, but a direct causal contribution has not been
      isolated.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:18509043
      reference_title: GPR56 regulates pial basement membrane integrity and cortical lamination.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        There are four crucial events in the development of cobblestone cortex,
        namely defective pial basement membrane (BM), abnormal anchorage of radial
        glial endfeet, mislocalized Cajal-Retzius cells, and neuronal overmigration.
      explanation: >-
        The model places both events in the same lesion sequence but does not
        independently prove that mislocalized Cajal-Retzius cells cause
        overmigration.
- name: Neuronal Overmigration and Cortical Dyslamination
  description: >-
    With the pial basement membrane breached and the GPR56-RhoA migratory brake
    lost, postmitotic neurons overmigrate beyond their normal pial stopping
    point, producing a disorganized, abnormally laminated cortex. The result is
    a frontoparietally predominant polymicrogyria that, at its severe end,
    forms a cobblestone-like cortex with ectopic neuronal overmigration,
    forming a phenotypic continuum from BFPP to cobblestone-like lissencephaly.
  conforms_to: pial_basement_membrane_radial_glial_endfoot_failure#Neuronal Overmigration Across the Pial Boundary
  cell_types:
  - preferred_term: cerebral cortex neuron
    term:
      id: CL:0010012
      label: cerebral cortex neuron
  biological_processes:
  - preferred_term: neuron migration
    term:
      id: GO:0001764
      label: neuron migration
    modifier: INCREASED
  - preferred_term: cerebral cortex radial glia-guided migration
    term:
      id: GO:0021801
      label: cerebral cortex radial glia-guided migration
    modifier: DYSREGULATED
  - preferred_term: layer formation in cerebral cortex
    term:
      id: GO:0021819
      label: layer formation in cerebral cortex
    modifier: ABNORMAL
  evidence:
  - reference: PMID:20929962
    reference_title: "GPR56-related bilateral frontoparietal polymicrogyria: further evidence for an overlap with the cobblestone complex."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      showed a cobblestone-like lissencephaly with a succession of normal,
      polymicrogyric and 'cobblestone-like' cortex with ectopic neuronal
      overmigration
    explanation: >-
      Documents ectopic neuronal overmigration and the polymicrogyria-to-
      cobblestone cortical continuum in a fetopathological BFPP case.
  - reference: PMID:15044805
    reference_title: "G protein-coupled receptor-dependent development of human frontal cortex."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      BFPP is characterized by disorganized cortical lamination that is most
      severe in frontal cortex.
    explanation: >-
      Establishes disordered cortical lamination with frontal predominance as
      the defining cortical pathology of BFPP.
  downstream:
  - target: Bilateral Frontoparietal Polymicrogyria
    description: >-
      Neuronal overmigration through a breached pial boundary directly produces
      the frontoparietal polymicrogyria/cobblestone cortical malformation.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:15044805
      reference_title: "G protein-coupled receptor-dependent development of human frontal cortex."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        BFPP is characterized by disorganized cortical lamination that is most
        severe in frontal cortex.
      explanation: >-
        The human pathology directly links cortical dyslamination to the defining
        frontally predominant polymicrogyria.
  - target: Intellectual Disability
    description: >-
      Cortical dyslamination is associated with lifelong cognitive impairment,
      but the intervening network-level mechanisms have not been resolved.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:34513772
      reference_title: "Case Report: Diffuse Polymicrogyria Associated With a Novel ADGRG1 Variant."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Cognitive impairment
        Severe 46 (79.3)
        Moderate 11 (18.9)
        Mild 1 (1.7)
      explanation: >-
        Cognitive impairment co-occurs with ADGRG1 cortical malformation, but
        clinical association does not resolve mediation by dyslamination.
  - target: Motor Delay
    description: >-
      The cortical malformation contributes to delayed motor development through
      incompletely resolved corticospinal and network-level mechanisms.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:34513772
      reference_title: "Case Report: Diffuse Polymicrogyria Associated With a Novel ADGRG1 Variant."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Cognitive and motor delay are universal features, although their severity
        is variable between cases.
      explanation: >-
        Motor delay is strongly associated with ADGRG1 disease, but the source
        does not isolate the cortical contribution from other affected systems.
  - target: Spasticity and Pyramidal Signs
    description: >-
      Disorganized cortical motor pathways plausibly contribute to the frequent
      pyramidal signs reported in the clinical spectrum.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:34513772
      reference_title: "Case Report: Diffuse Polymicrogyria Associated With a Novel ADGRG1 Variant."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Pyramidal signs
        Present 44 (75.9)
        Absent 14 (24.1)
      explanation: >-
        Pyramidal signs co-occur with the malformation, but the responsible
        cortical pathways and intermediates were not tested.
  - target: Seizures
    description: Disorganized cortical lamination creates an epileptogenic cortical substrate.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:20929962
      reference_title: "GPR56-related bilateral frontoparietal polymicrogyria: further evidence for an overlap with the cobblestone complex."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Generalized seizures (12/14) occurred later with onset ranging from 2.5
        to 10 years
      explanation: >-
        Seizures are strongly associated with the cortical malformation, but the
        clinical series does not directly establish the epileptogenic pathway.
  - target: Predominantly Anterior Low-Amplitude Alpha-Like EEG Bursts
    description: >-
      The malformed cortical network is associated with a characteristic EEG
      pattern in the 14-person cohort, although the electrophysiologic
      intermediates are unresolved.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:20929962
      reference_title: "GPR56-related bilateral frontoparietal polymicrogyria: further evidence for an overlap with the cobblestone complex."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        consistent electroencephalogram findings of predominantly anterior bursts
        of low amplitude α-like activity
      explanation: >-
        The EEG pattern co-occurs with ADGRG1 cortical malformation, but its
        mechanistic derivation from dyslamination remains unresolved.
- name: Impaired Oligodendrocyte Precursor Proliferation and Maturation
  description: >-
    GPR56 is highly expressed in oligodendrocyte precursor cells and signals
    through RhoA to maintain their proliferation. Constitutive or
    OPC-conditional Gpr56 loss reduces active RhoA, causes premature cell-cycle
    exit, lowers the numbers of mature oligodendrocytes and myelinated axons, and
    produces early CNS hypomyelination. This is a cell-autonomous white-matter
    branch rather than a consequence assigned solely to cortical dyslamination.
  genes:
  - preferred_term: ADGRG1
    term:
      id: hgnc:4512
      label: ADGRG1
  cell_types:
  - preferred_term: oligodendrocyte precursor cell
    term:
      id: CL:0002453
      label: oligodendrocyte precursor cell
  - preferred_term: oligodendrocyte
    term:
      id: CL:0000128
      label: oligodendrocyte
  locations:
  - preferred_term: brain white matter
    term:
      id: UBERON:0003544
      label: brain white matter
  biological_processes:
  - preferred_term: Rho protein signal transduction
    term:
      id: GO:0007266
      label: Rho protein signal transduction
    modifier: DECREASED
  - preferred_term: cell population proliferation
    term:
      id: GO:0008283
      label: cell population proliferation
    modifier: DECREASED
  - preferred_term: myelination
    term:
      id: GO:0042552
      label: myelination
    modifier: DECREASED
  evidence:
  - reference: PMID:25607655
    reference_title: The adhesion G protein-coupled receptor GPR56 is a cell-autonomous regulator of oligodendrocyte development.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      Gpr56-knockout mice manifest with decreased oligodendrocyte precursor cell
      (OPC) proliferation and diminished levels of active RhoA, leading to fewer
      mature oligodendrocytes and a reduced number of myelinated axons in the
      corpus callosum and optic nerves.
    explanation: >-
      The constitutive knockout identifies the RhoA, proliferation,
      oligodendrocyte and myelinated-axon sequence.
  - reference: PMID:25607655
    reference_title: The adhesion G protein-coupled receptor GPR56 is a cell-autonomous regulator of oligodendrocyte development.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      Conditional ablation of Gpr56 in OPCs leads to a reduced number of mature
      oligodendrocytes as seen in constitutive knockout of Gpr56.
    explanation: >-
      Lineage-restricted deletion establishes that the oligodendrocyte defect is
      cell autonomous.
  downstream:
  - target: White Matter Abnormalities
    description: >-
      Fewer mature oligodendrocytes and myelinated axons provide a mechanistic
      basis for the patchy-to-diffuse white-matter abnormalities in BFPP.
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - reduced mature oligodendrocyte abundance
    - reduced number of myelinated axons
    evidence:
    - reference: PMID:25607655
      reference_title: The adhesion G protein-coupled receptor GPR56 is a cell-autonomous regulator of oligodendrocyte development.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        Gpr56-knockout mice manifest with decreased oligodendrocyte precursor cell
        (OPC) proliferation and diminished levels of active RhoA, leading to fewer
        mature oligodendrocytes and a reduced number of myelinated axons in the
        corpus callosum and optic nerves.
      explanation: >-
        The model supplies the stated oligodendrocyte and myelinated-axon
        intermediates for the white-matter branch.
  - target: Central Nervous System Hypomyelination
    description: >-
      Reduced oligodendrocyte production and axonal myelination directly produce
      the early hypomyelination phenotype.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:25607655
      reference_title: The adhesion G protein-coupled receptor GPR56 is a cell-autonomous regulator of oligodendrocyte development.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        Here, we demonstrate that loss of Gpr56 leads to hypomyelination of the
        central nervous system in mice.
      explanation: >-
        Directly links Gpr56 loss to CNS hypomyelination in vivo.
- name: Rostral Cerebellar Granule Cell Adhesion Failure
  description: >-
    In the rostral cerebellum, GPR56 is expressed in developing granule cells and
    supports their adhesion to pial basement-membrane extracellular matrix.
    Gpr56-null mice show loss of this adhesion, pial fragmentation, fusion of
    adjacent lobules and disrupted neuronal and glial layering. Rescue by GPR56
    re-expression supports a direct, region-specific cerebellar mechanism.
  genes:
  - preferred_term: ADGRG1
    term:
      id: hgnc:4512
      label: ADGRG1
  cell_types:
  - preferred_term: cerebellar granule cell
    term:
      id: CL:0001031
      label: cerebellar granule cell
  locations:
  - preferred_term: cerebellum
    term:
      id: UBERON:0002037
      label: cerebellum
  biological_processes:
  - preferred_term: cell-matrix adhesion
    term:
      id: GO:0007160
      label: cell-matrix adhesion
    modifier: DECREASED
  evidence:
  - reference: PMID:19515912
    reference_title: GPR56-regulated granule cell adhesion is essential for rostral cerebellar development.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      Defects involve fusion of adjacent lobules, disrupted layering of neurons
      and glia, and fragmentation of the pial basement membrane.
    explanation: >-
      The rostral cerebellar knockout phenotype directly identifies the local
      adhesion, pial and morphogenetic defect.
  - reference: PMID:19515912
    reference_title: GPR56-regulated granule cell adhesion is essential for rostral cerebellar development.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      reexpression of GPR56 rescues the adhesion defect in knock-out granule cells.
    explanation: >-
      Rescue supports a direct GPR56 requirement for granule-cell adhesion.
  downstream:
  - target: Cerebellar Dysplasia
    description: >-
      Pial fragmentation, lobule fusion and abnormal cellular layering produce
      rostral cerebellar dysplasia. The model does not directly establish the
      cystic component described on human MRI.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:19515912
      reference_title: GPR56-regulated granule cell adhesion is essential for rostral cerebellar development.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        Defects involve fusion of adjacent lobules, disrupted layering of neurons
        and glia, and fragmentation of the pial basement membrane.
      explanation: >-
        The rostral Gpr56-null cerebellum directly develops the structural
        dysplasia represented by this edge; human cysts remain a separate imaging
        association.
  - target: Ataxia and Cerebellar Signs
    description: >-
      Cerebellar structural dysplasia contributes to the frequent ataxic and
      cerebellar motor phenotype.
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - cerebellar dysplasia and abnormal cerebellar layering
    evidence:
    - reference: PMID:25922261
      reference_title: "GPR56-Related Polymicrogyria: Clinicoradiologic Profile of 4 Patients."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Affected patients present with delayed milestones, intellectual
        disability, epilepsy, ataxia, and eye movement abnormalities.
      explanation: >-
        Human disease associates ataxia with ADGRG1-related polymicrogyria, while
        the cerebellar mediation is supported indirectly by the model and imaging
        phenotype.
- name: Regional Cortical Patterning Dependence on GPR56 Expression
  description: >-
    GPR56 is expressed in cortical progenitor cells in a regionally restricted,
    promoter-controlled pattern, and its expression levels regulate progenitor
    proliferation. A 15-base-pair deletion in a region-specific regulatory
    element selectively disrupts lateral/perisylvian cortex and represents a
    related ADGRG1 allelic phenotype, whereas classic BFPP is usually
    frontoparietal or follows an anterior-posterior severity gradient. Regional
    control is important but not absolute: rare coding-variant cases with diffuse
    polymicrogyria without a clear gradient have been reported.
  genes:
  - preferred_term: ADGRG1
    term:
      id: hgnc:4512
      label: ADGRG1
  cell_types:
  - preferred_term: cortical progenitor cell
    term:
      id: CL:0000047
      label: neural stem cell
  biological_processes:
  - preferred_term: cerebral cortex regionalization
    term:
      id: GO:0021796
      label: cerebral cortex regionalization
    modifier: ABNORMAL
  evidence:
  - reference: PMID:24531968
    reference_title: Evolutionarily dynamic alternative splicing of GPR56 regulates regional cerebral cortical patterning.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      we describe a 15-base pair deletion mutation in a regulatory element of
      GPR56 that selectively disrupts human cortex surrounding the Sylvian
      fissure bilaterally including "Broca's area," the primary language area,
      by disrupting regional GPR56 expression and blocking RFX transcription
      factor binding
    explanation: >-
      Shows that a non-coding regulatory mutation produces a regionally
      restricted (perisylvian) malformation by disrupting regional GPR56
      expression, demonstrating promoter-level regional patterning.
  - reference: PMID:24531968
    reference_title: Evolutionarily dynamic alternative splicing of GPR56 regulates regional cerebral cortical patterning.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      GPR56 encodes a heterotrimeric guanine nucleotide-binding protein (G
      protein)-coupled receptor required for normal cortical development and is
      expressed in cortical progenitor cells. GPR56 expression levels regulate
      progenitor proliferation.
    explanation: >-
      Establishes that GPR56 is expressed in cortical progenitors and that its
      expression level controls progenitor proliferation and regional patterning.
  - reference: PMID:34513772
    reference_title: "Case Report: Diffuse Polymicrogyria Associated With a Novel ADGRG1 Variant."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Magnetic resonance imaging revealed diffuse polymicrogyria with relative
      sparing of the anterior temporal lobes, without an anterior-posterior
      gradient, diffuse hypomyelination and pontine and cerebellar hypoplasia.
    explanation: >-
      This atypical case shows that regional patterning is not an invariant
      coding-variant rule.
  downstream:
  - target: Bilateral Frontoparietal Polymicrogyria
    description: >-
      Spatial ADGRG1 regulation can alter the anatomical distribution of cortical
      malformation, but the perisylvian regulatory allele does not by itself
      explain classic frontoparietal vulnerability; the relevant intermediates
      remain unresolved.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:24531968
      reference_title: Evolutionarily dynamic alternative splicing of GPR56 regulates regional cerebral cortical patterning.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        we describe a 15-base pair deletion mutation in a regulatory element of
        GPR56 that selectively disrupts human cortex surrounding the Sylvian
        fissure bilaterally including "Broca's area," the primary language area,
        by disrupting regional GPR56 expression and blocking RFX transcription
        factor binding
      explanation: >-
        The regulatory allele directly links spatial ADGRG1 expression to a
        perisylvian malformation pattern, but it provides only partial evidence
        for the distinct regional distribution of classic BFPP.
phenotypes:
- name: Bilateral Frontoparietal Polymicrogyria
  description: >-
    The defining neuroradiological feature: bilateral, frontoparietally
    predominant polymicrogyria with disorganized cortical lamination, reflecting
    neuronal overmigration through the breached pial basement membrane.
  phenotype_term:
    preferred_term: Bilateral frontoparietal polymicrogyria
    term:
      id: HP:0002126
      label: Polymicrogyria
  frequency: VERY_FREQUENT
  diagnostic: true
  evidence:
  - reference: PMID:20929962
    reference_title: "GPR56-related bilateral frontoparietal polymicrogyria: further evidence for an overlap with the cobblestone complex."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Neuroimaging demonstrated a common phenotype with bilateral
      frontoparietally predominant polymicrogyria (13/13)
    explanation: >-
      Bilateral frontoparietally predominant polymicrogyria occurred in 13/13 =
      100% of this selected imaged cohort. VERY_FREQUENT is retained rather than
      inferring obligate penetrance across atypical ADGRG1 disease.
- name: Cerebellar Dysplasia
  description: >-
    Cerebellar dysplasia, frequently with cysts mainly affecting the superior
    vermis, accompanies the cortical malformation and reflects pial basement
    membrane failure in the rostral cerebellum.
  phenotype_term:
    preferred_term: Cerebellar dysplasia with cysts
    term:
      id: HP:0007033
      label: Cerebellar dysplasia
  frequency: VERY_FREQUENT
  evidence:
  - reference: PMID:20929962
    reference_title: "GPR56-related bilateral frontoparietal polymicrogyria: further evidence for an overlap with the cobblestone complex."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      cerebellar dysplasia with cysts mainly affecting the superior vermis
      (11/13)
    explanation: >-
      Cerebellar dysplasia with cysts occurred in 11/13 = 84.6%, which falls in
      the VERY_FREQUENT band (80-99%).
- name: White Matter Abnormalities
  description: >-
    Patchy to diffuse myelination abnormalities are a consistent feature,
    evolving from severe hypomyelination in infancy to patchy lesions later in
    childhood.
  phenotype_term:
    preferred_term: Abnormal cerebral white matter morphology
    term:
      id: HP:0002500
      label: Abnormal cerebral white matter morphology
  frequency: VERY_FREQUENT
  evidence:
  - reference: PMID:20929962
    reference_title: "GPR56-related bilateral frontoparietal polymicrogyria: further evidence for an overlap with the cobblestone complex."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      patchy to diffuse myelination abnormalities (13/13)
    explanation: >-
      White-matter/myelination abnormalities occurred in 13/13 = 100% of this
      selected imaged cohort. VERY_FREQUENT is retained because this subset does
      not establish an obligate finding across all ADGRG1 disease.
- name: Central Nervous System Hypomyelination
  description: >-
    White-matter abnormalities may begin as severe CNS hypomyelination in
    infancy and evolve into patchy lesions later in childhood.
  phenotype_term:
    preferred_term: CNS hypomyelination
    term:
      id: HP:0003429
      label: CNS hypomyelination
  evidence:
  - reference: PMID:20929962
    reference_title: "GPR56-related bilateral frontoparietal polymicrogyria: further evidence for an overlap with the cobblestone complex."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      the white matter abnormalities showed a peculiar evolution from severe
      hypomyelination at 4 months to patchy lesions later in childhood
    explanation: >-
      Directly documents severe CNS hypomyelination rather than inferring delayed
      myelination from a single time point.
- name: Hypoplasia of the Pons
  description: >-
    Pontine hypoplasia is part of the characteristic pontocerebellar imaging
    phenotype and can accompany both classic and diffuse ADGRG1-related
    polymicrogyria.
  phenotype_term:
    preferred_term: Hypoplasia of the pons
    term:
      id: HP:0012110
      label: Hypoplasia of the pons
  evidence:
  - reference: PMID:34513772
    reference_title: "Case Report: Diffuse Polymicrogyria Associated With a Novel ADGRG1 Variant."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Pathogenic variants of the ADGRG1 gene are associated with bilateral
      frontoparietal polymicrogyria, defined radiologically by polymicrogyria
      with an anterior-posterior gradient, pontine and cerebellar hypoplasia and
      patchy white matter abnormalities.
    explanation: >-
      The clinicoradiologic review identifies pontine hypoplasia as part of the
      ADGRG1-associated imaging pattern.
- name: Intellectual Disability
  description: >-
    Intellectual disability is a core feature but ranges from mild or moderate
    impairment to severe disability with only a few words. In a published
    aggregation, 46 of 58 assessed individuals had severe impairment, while 12
    had moderate or mild impairment.
  phenotype_term:
    preferred_term: Intellectual disability
    term:
      id: HP:0001249
      label: Intellectual disability
  frequency: VERY_FREQUENT
  evidence:
  - reference: PMID:34513772
    reference_title: "Case Report: Diffuse Polymicrogyria Associated With a Novel ADGRG1 Variant."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Cognitive impairment
      Severe 46 (79.3)
      Moderate 11 (18.9)
      Mild 1 (1.7)
    explanation: >-
      The severity categories sum to 58/58 = 100% with cognitive impairment in
      the assessed published cases, while showing that severity is not uniformly
      severe. VERY_FREQUENT is retained because literature-case ascertainment
      does not establish obligate penetrance.
  - reference: PMID:25922261
    reference_title: "GPR56-Related Polymicrogyria: Clinicoradiologic Profile of 4 Patients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Affected patients present with delayed milestones, intellectual
      disability, epilepsy, ataxia, and eye movement abnormalities.
    explanation: >-
      An independent four-person series confirms intellectual disability within
      the recurring clinical profile.
- name: Motor Delay
  description: >-
    Delayed motor milestones are nearly universal, but eventual motor ability is
    variable; many reported individuals walk late with or without support,
    whereas a minority never acquire walking.
  phenotype_term:
    preferred_term: Motor delay
    term:
      id: HP:0001270
      label: Motor delay
  frequency: VERY_FREQUENT
  evidence:
  - reference: PMID:34513772
    reference_title: "Case Report: Diffuse Polymicrogyria Associated With a Novel ADGRG1 Variant."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Cognitive and motor delay are universal features, although
      their severity is variable between cases.
    explanation: >-
      Author wording "universal" would ordinarily map to OBLIGATE. VERY_FREQUENT
      is used conservatively because this literature aggregation comprises
      selected published cases and explicitly documents variable severity.
  - reference: PMID:25922261
    reference_title: "GPR56-Related Polymicrogyria: Clinicoradiologic Profile of 4 Patients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Affected patients present with delayed milestones, intellectual
      disability, epilepsy, ataxia, and eye movement abnormalities.
    explanation: >-
      The four-person clinical series independently identifies delayed motor
      milestones as a core manifestation.
- name: Hypotonia
  description: >-
    Hypotonia, sometimes with hyporeflexia, can produce the early
    pseudomyopathic presentation and may be recognized during the first year of
    life or at birth.
  phenotype_term:
    preferred_term: Hypotonia
    term:
      id: HP:0001252
      label: Hypotonia
  evidence:
  - reference: PMID:34513772
    reference_title: "Case Report: Diffuse Polymicrogyria Associated With a Novel ADGRG1 Variant."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Clinically, BFPP presents as a pseudomyopathic pattern, with
      hypotonia developing in the ﬁrst year of life and occasionally
      being identiﬁed at birth
    explanation: >-
      The clinical review links first-year or congenital hypotonia to the
      pseudomyopathic BFPP presentation.
- name: Ataxia and Cerebellar Signs
  description: >-
    Ataxia and other cerebellar signs are common and align with the rostral
    cerebellar dysplasia; assessment may be limited in individuals with severe
    motor impairment.
  phenotype_term:
    preferred_term: Ataxia
    term:
      id: HP:0001251
      label: Ataxia
  frequency: VERY_FREQUENT
  evidence:
  - reference: PMID:34513772
    reference_title: "Case Report: Diffuse Polymicrogyria Associated With a Novel ADGRG1 Variant."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Cerebellar signs
      Present 50 (92.6)
      Absent 4 (7.4)
    explanation: >-
      Cerebellar signs occurred in 50/54 = 92.6%, which falls in the
      VERY_FREQUENT band (80-99%).
  - reference: PMID:25922261
    reference_title: "GPR56-Related Polymicrogyria: Clinicoradiologic Profile of 4 Patients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Affected patients present with delayed milestones, intellectual
      disability, epilepsy, ataxia, and eye movement abnormalities.
    explanation: >-
      The independent series explicitly includes ataxia in the clinical profile.
- name: Spasticity and Pyramidal Signs
  description: >-
    Pyramidal signs, including spasticity or hyperreflexia, occur frequently and
    indicate corticospinal-system involvement, although they are not present in
    every individual.
  phenotype_term:
    preferred_term: Abnormal pyramidal sign
    term:
      id: HP:0007256
      label: Abnormal pyramidal sign
  frequency: FREQUENT
  evidence:
  - reference: PMID:34513772
    reference_title: "Case Report: Diffuse Polymicrogyria Associated With a Novel ADGRG1 Variant."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Pyramidal signs
      Present 44 (75.9)
      Absent 14 (24.1)
    explanation: >-
      Pyramidal signs occurred in 44/58 = 75.9%, which falls in the FREQUENT band
      (30-79%).
- name: Abnormality of Eye Movement
  description: >-
    Oculomotor abnormalities are common and include strabismus, nystagmus and
    other abnormal eye movements; these differ from the characteristic
    structural eye disease of severe dystroglycanopathy.
  phenotype_term:
    preferred_term: Abnormality of eye movement
    term:
      id: HP:0000496
      label: Abnormality of eye movement
  frequency: VERY_FREQUENT
  evidence:
  - reference: PMID:34513772
    reference_title: "Case Report: Diffuse Polymicrogyria Associated With a Novel ADGRG1 Variant."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Oculomotor ﬁndings
      Present 59 (92.1)
    explanation: >-
      Oculomotor findings occurred in 59/64, approximately 92.2% (reported as
      92.1%), which falls in the VERY_FREQUENT band (80-99%).
  - reference: PMID:25922261
    reference_title: "GPR56-Related Polymicrogyria: Clinicoradiologic Profile of 4 Patients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Affected patients present with delayed milestones, intellectual
      disability, epilepsy, ataxia, and eye movement abnormalities.
    explanation: >-
      The four-person series independently confirms eye-movement abnormalities.
- name: Seizures
  description: >-
    Seizures occur in most reported individuals, with focal, generalized and
    multiple seizure types described. Refractory epilepsy occurs in a substantial
    subset but is not universal; a selected four-person series documented
    infantile spasms or Lennox-Gastaut syndrome.
  phenotype_term:
    preferred_term: Seizure
    term:
      id: HP:0001250
      label: Seizure
  frequency: VERY_FREQUENT
  evidence:
  - reference: PMID:20929962
    reference_title: "GPR56-related bilateral frontoparietal polymicrogyria: further evidence for an overlap with the cobblestone complex."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Generalized seizures (12/14) occurred later with onset ranging from 2.5
      to 10 years with consistent electroencephalogram findings of
      predominantly anterior bursts of low amplitude α-like activity
    explanation: >-
      Generalized seizures occurred in 12/14 = 85.7%, which falls in the
      VERY_FREQUENT band (80-99%); the same evidence documents childhood onset.
  - reference: PMID:34513772
    reference_title: "Case Report: Diffuse Polymicrogyria Associated With a Novel ADGRG1 Variant."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Seizures
      Present 60 (88.2)
      Age at onset in years, median (IQR) 3.0 (3.0)
      Refractory 36 (60.0)
    explanation: >-
      Seizures occurred in 60/68 = 88.2%, which falls in the VERY_FREQUENT band
      (80-99%). Of the 60 seizure-positive cases, 36/60 = 60.0% were reported
      refractory, so drug resistance is not universal.
  - reference: PMID:19016831
    reference_title: "Bilateral frontoparietal polymicrogyria, Lennox-Gastaut syndrome, and GPR56 gene mutations."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Epilepsy, present in all four patients, had started between ages 1 and 8
      years, with infantile spasms in one patient and with de novo Lennox-Gastaut
      syndrome in the remaining three.
    explanation: >-
      This selected series documents the Lennox-Gastaut and infantile-spasm
      spectrum without implying that it is universal.
- name: Predominantly Anterior Low-Amplitude Alpha-Like EEG Bursts
  description: >-
    The 14-person cohort reported predominantly anterior bursts of low-amplitude
    alpha-like activity as a consistent EEG observation. It is represented
    separately from the seizure phenotype because it is an electrophysiologic
    finding rather than a seizure type.
  phenotype_term:
    preferred_term: EEG abnormality
    term:
      id: HP:0002353
      label: EEG abnormality
  electrophysiology:
    electrophysiology_modality: EEG
  evidence:
  - reference: PMID:20929962
    reference_title: "GPR56-related bilateral frontoparietal polymicrogyria: further evidence for an overlap with the cobblestone complex."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      consistent electroencephalogram findings of predominantly anterior bursts
      of low amplitude α-like activity
    explanation: >-
      The cohort directly reports the characteristic EEG pattern; ictal and
      recording state were not specified, so those sidecar axes remain unset.
imaging_findings:
- name: Bilateral frontoparietal polymicrogyria on MRI
  modality: MRI
  imaging_finding_term:
    preferred_term: Bilateral frontoparietal polymicrogyria
    term:
      id: HP:0002126
      label: Polymicrogyria
  description: >-
    Brain MRI typically shows bilateral frontoparietally predominant
    polymicrogyria, often with an anterior-posterior severity gradient. This is
    the defining imaging pattern, although atypical diffuse cases occur.
  located_in:
    preferred_term: cerebral cortex
    term:
      id: UBERON:0000956
      label: cerebral cortex
  laterality: BILATERAL
  phenotype_term:
    preferred_term: Bilateral frontoparietal polymicrogyria
    term:
      id: HP:0002126
      label: Polymicrogyria
  diagnostic: true
  frequency: VERY_FREQUENT
  evidence:
  - reference: PMID:20929962
    reference_title: "GPR56-related bilateral frontoparietal polymicrogyria: further evidence for an overlap with the cobblestone complex."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Neuroimaging demonstrated a common phenotype with bilateral
      frontoparietally predominant polymicrogyria (13/13)
    explanation: >-
      The defining bilateral MRI pattern occurred in 13/13 = 100% of this
      selected imaged cohort. VERY_FREQUENT conservatively avoids treating that
      subset as proof of obligate penetrance across atypical ADGRG1 disease.
  - reference: PMID:16240336
    reference_title: Genotype-phenotype analysis of human frontoparietal polymicrogyria syndromes.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      To define the range of abnormalities that could be caused by human GPR56
      mutations and to establish diagnostic criteria for BFPP, we analyzed the
      GPR56 gene in a cohort of 29 patients with typical BFPP.
    explanation: >-
      The 29-person genotype-phenotype study establishes the typical imaging
      pattern as a diagnostic entry point for molecular screening.
- name: Cerebellar dysplasia with cysts on MRI
  modality: MRI
  imaging_finding_term:
    preferred_term: Cerebellar dysplasia with cysts
    term:
      id: HP:0007033
      label: Cerebellar dysplasia
  description: >-
    Cerebellar dysplasia with cysts, often involving the superior vermis,
    accompanies the cortical malformation in most imaged individuals.
  located_in:
    preferred_term: cerebellum
    term:
      id: UBERON:0002037
      label: cerebellum
  phenotype_term:
    preferred_term: Cerebellar dysplasia with cysts
    term:
      id: HP:0007033
      label: Cerebellar dysplasia
  frequency: VERY_FREQUENT
  evidence:
  - reference: PMID:20929962
    reference_title: "GPR56-related bilateral frontoparietal polymicrogyria: further evidence for an overlap with the cobblestone complex."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      cerebellar dysplasia with cysts mainly affecting the superior vermis
      (11/13)
    explanation: >-
      Cerebellar dysplasia with cysts occurred in 11/13 = 84.6%, which falls in
      the VERY_FREQUENT band (80-99%).
- name: Patchy-to-diffuse cerebral white-matter abnormalities on MRI
  modality: MRI
  imaging_finding_term:
    preferred_term: Abnormal cerebral white matter morphology
    term:
      id: HP:0002500
      label: Abnormal cerebral white matter morphology
  description: >-
    MRI shows patchy-to-diffuse white-matter signal or myelination abnormalities,
    which may evolve with age.
  located_in:
    preferred_term: brain white matter
    term:
      id: UBERON:0003544
      label: brain white matter
  phenotype_term:
    preferred_term: Abnormal cerebral white matter morphology
    term:
      id: HP:0002500
      label: Abnormal cerebral white matter morphology
  frequency: VERY_FREQUENT
  evidence:
  - reference: PMID:20929962
    reference_title: "GPR56-related bilateral frontoparietal polymicrogyria: further evidence for an overlap with the cobblestone complex."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: patchy to diffuse myelination abnormalities (13/13)
    explanation: >-
      White-matter or myelination abnormalities occurred in 13/13 = 100% of this
      selected imaged cohort. VERY_FREQUENT is retained because this subset does
      not prove an obligate finding across the full ADGRG1 spectrum.
- name: Central nervous system hypomyelination on MRI
  modality: MRI
  imaging_finding_term:
    preferred_term: CNS hypomyelination
    term:
      id: HP:0003429
      label: CNS hypomyelination
  description: >-
    Severe hypomyelination can be evident in infancy and may later evolve into
    patchier white-matter lesions.
  located_in:
    preferred_term: brain white matter
    term:
      id: UBERON:0003544
      label: brain white matter
  phenotype_term:
    preferred_term: CNS hypomyelination
    term:
      id: HP:0003429
      label: CNS hypomyelination
  evidence:
  - reference: PMID:20929962
    reference_title: "GPR56-related bilateral frontoparietal polymicrogyria: further evidence for an overlap with the cobblestone complex."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      the white matter abnormalities showed a peculiar evolution from severe
      hypomyelination at 4 months to patchy lesions later in childhood
    explanation: >-
      Serial MRI directly documents early hypomyelination and later evolution.
- name: Pontine hypoplasia on MRI
  modality: MRI
  imaging_finding_term:
    preferred_term: Hypoplasia of the pons
    term:
      id: HP:0012110
      label: Hypoplasia of the pons
  description: >-
    Pontine hypoplasia forms part of the characteristic pontocerebellar imaging
    profile and is also seen in severe diffuse ADGRG1-related disease.
  located_in:
    preferred_term: pons
    term:
      id: UBERON:0000988
      label: pons
  phenotype_term:
    preferred_term: Hypoplasia of the pons
    term:
      id: HP:0012110
      label: Hypoplasia of the pons
  evidence:
  - reference: PMID:34513772
    reference_title: "Case Report: Diffuse Polymicrogyria Associated With a Novel ADGRG1 Variant."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Magnetic resonance imaging revealed diffuse polymicrogyria with relative
      sparing of the anterior temporal lobes, without an anterior-posterior
      gradient, diffuse hypomyelination and pontine and cerebellar hypoplasia.
    explanation: >-
      A molecularly confirmed severe case directly documents pontine hypoplasia
      on MRI.
diagnosis:
- name: Brain MRI pattern recognition
  description: >-
    Brain MRI is the principal phenotypic test. Bilateral frontoparietally
    predominant polymicrogyria with an anterior-posterior gradient, cerebellar
    dysplasia or cysts, pontine hypoplasia and patchy-to-diffuse white-matter
    abnormalities strongly suggests ADGRG1-related BFPP, while diffuse patterns
    do not exclude it.
  diagnosis_term:
    preferred_term: magnetic resonance imaging procedure
    term:
      id: NCIT:C16809
      label: Magnetic Resonance Imaging
  results: >-
    A characteristic bilateral frontoparietal cortical malformation with
    pontocerebellar and white-matter involvement prioritizes ADGRG1 testing.
  evidence:
  - reference: PMID:20929962
    reference_title: "GPR56-related bilateral frontoparietal polymicrogyria: further evidence for an overlap with the cobblestone complex."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Neuroimaging demonstrated a common phenotype with bilateral
      frontoparietally predominant polymicrogyria (13/13), cerebellar dysplasia
      with cysts mainly affecting the superior vermis (11/13) and patchy to
      diffuse myelination abnormalities (13/13).
    explanation: >-
      The cohort defines the combined cortical, white-matter and
      cerebellar MRI pattern.
  - reference: PMID:34513772
    reference_title: "Case Report: Diffuse Polymicrogyria Associated With a Novel ADGRG1 Variant."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Pathogenic variants of the ADGRG1 gene are associated with bilateral
      frontoparietal polymicrogyria, defined radiologically by polymicrogyria
      with an anterior-posterior gradient, pontine and cerebellar hypoplasia and
      patchy white matter abnormalities.
    explanation: >-
      This clinicoradiologic summary directly supports the anterior-posterior
      gradient and pontine component included in the diagnostic pattern.
- name: ADGRG1 molecular genetic confirmation
  description: >-
    Diagnosis is confirmed by identifying biallelic pathogenic or likely
    pathogenic ADGRG1 variants in an individual with a compatible MRI and
    clinical phenotype. Once familial variants are known, targeted prenatal
    molecular diagnosis can be offered in an at-risk pregnancy.
  diagnosis_term:
    preferred_term: molecular genetic testing
    term:
      id: NCIT:C19770
      label: Molecular Analysis
    qualifiers:
    - predicate:
        preferred_term: has participant
        term:
          id: RO:0000057
          label: has participant
      value:
        preferred_term: ADGRG1
        term:
          id: hgnc:4512
          label: ADGRG1
  results: Biallelic pathogenic ADGRG1 variants establish molecular confirmation.
  evidence:
  - reference: PMID:16240336
    reference_title: Genotype-phenotype analysis of human frontoparietal polymicrogyria syndromes.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: We identified homozygous GPR56 mutations in all 29 patients with typical BFPP.
    explanation: >-
      Molecular testing detected biallelic variants in all 29 typical cases in
      this diagnostic cohort.
  - reference: PMID:25922261
    reference_title: "GPR56-Related Polymicrogyria: Clinicoradiologic Profile of 4 Patients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Antenatal diagnosis is possible if the index case is genetically confirmed.
    explanation: >-
      The clinical series supports familial prenatal diagnosis once the causal
      variants are established.
differential_diagnoses:
- name: Muscular dystrophy-dystroglycanopathy spectrum
  disease_term:
    preferred_term: dystroglycanopathy
    term:
      id: MONDO:0018276
      label: muscular dystrophy-dystroglycanopathy
  description: >-
    Severe dystroglycanopathies share hypotonia, developmental impairment,
    cobblestone cortical malformation and pontocerebellar abnormalities. The
    pseudomyopathic ADGRG1 presentation can therefore initially resemble a
    congenital muscular dystrophy.
  distinguishing_features:
  - Normal muscle evaluation and absence of characteristic structural eye disease favor ADGRG1-related BFPP.
  - Elevated creatine kinase, muscular dystrophy and major structural eye anomalies favor dystroglycanopathy.
  - Biallelic ADGRG1 variants confirm BFPP; variants in alpha-dystroglycan glycosylation genes support dystroglycanopathy.
  evidence:
  - reference: PMID:25922261
    reference_title: "GPR56-Related Polymicrogyria: Clinicoradiologic Profile of 4 Patients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The clinicoradiologic profile resembles congenital muscular dystrophy.
      However, no muscle disease or characteristic eye abnormalities of
      congenial muscular dystrophy are detected in these children.
    explanation: >-
      The four-person series directly states both the overlap and the key muscle
      and eye distinctions.
- name: Biallelic COL3A1-related cobblestone-like cortical malformation
  disease_term:
    preferred_term: biallelic COL3A1-related cobblestone-like cortical malformation
  description: >-
    Biallelic COL3A1 disease affects the ligand side of the same GPR56-collagen
    III axis and can closely reproduce the cortical, cerebellar and white-matter
    phenotype. It is not currently represented by a separate local disease entry.
  distinguishing_features:
  - Biallelic COL3A1 rather than ADGRG1 variants establish the ligand-side disorder.
  - Connective-tissue abnormalities or vascular complications support COL3A1 disease, although the brain phenotype can be strikingly similar.
  evidence:
  - reference: PMID:28258187
    reference_title: "Bi-allelic variants in COL3A1 encoding the ligand to GPR56 are associated with cobblestone-like cortical malformation, white matter changes and cerebellar cysts."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Homozygous or compound heterozygous mutations in COL3A1 are associated with
      cobblestone-like malformation in all three families reported to date.
    explanation: >-
      Human genetic evidence establishes a ligand-side disorder that closely
      overlaps ADGRG1-related BFPP.
  - reference: PMID:28742248
    reference_title: Biallelic COL3A1 mutations result in a clinical spectrum of specific structural brain anomalies and connective tissue abnormalities.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Bilateral frontoparietal polymicrogyria of the cobblestone variant,
      cerebellar microcysts, and abnormalities of the white matter characterize
      this brain phenotype and resemble neurological manifestations in
      individuals with autosomal recessive mutations in GPR56
    explanation: >-
      The second report defines the overlapping imaging pattern.
  - reference: PMID:28742248
    reference_title: Biallelic COL3A1 mutations result in a clinical spectrum of specific structural brain anomalies and connective tissue abnormalities.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      This patient was born with bilateral clubfoot, joint laxity, and dysmorphic
      facial features. At the age of 2 years she developed an aneurysmal brain
      hemorrhage.
    explanation: >-
      Case-level connective-tissue and vascular findings support their use as
      distinguishing clues for biallelic COL3A1 disease, while not implying that
      every affected person has them.
- name: Other bilateral polymicrogyria syndromes and BFPP2
  disease_term:
    preferred_term: other bilateral polymicrogyria syndromes and BFPP2
  description: >-
    Bilateral frontal, perisylvian, generalized or BFPP-like polymicrogyria can
    arise without ADGRG1 variants. Imaging distribution alone is therefore not a
    substitute for molecular confirmation.
  distinguishing_features:
  - A typical BFPP MRI plus biallelic pathogenic ADGRG1 variants favors this disorder.
  - Mutation-negative BFPP-like disease or a different regional polymicrogyria pattern should prompt broader malformation-of-cortical-development testing.
  evidence:
  - reference: PMID:16240336
    reference_title: Genotype-phenotype analysis of human frontoparietal polymicrogyria syndromes.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      In addition, we analyzed five patients with BFPP who did not show GPR56
      mutation and found that they define a clinically, radiographically, and
      genetically distinct syndrome that we termed BFPP2.
    explanation: >-
      The study establishes a mutation-negative BFPP-like differential.
  - reference: PMID:16240336
    reference_title: Genotype-phenotype analysis of human frontoparietal polymicrogyria syndromes.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Finally, we studied seven patients with a variety of other polymicrogyria
      syndromes including bilateral frontal polymicrogyria, bilateral
      perisylvian polymicrogyria, and bilateral generalized polymicrogyria. No
      GPR56 mutation was found in these patients.
    explanation: >-
      Other regional bilateral polymicrogyria syndromes lacked GPR56 variants in
      this cohort and require separate molecular evaluation.
animal_models:
- species: Mouse (Mus musculus)
  genotype: Constitutive Gpr56-null mouse
  category: Knockout
  genes:
  - preferred_term: Gpr56 (Adgrg1)
    term:
      id: hgnc:4512
      label: ADGRG1
  associated_phenotypes:
  - Pial basement-membrane breach
  - Radial-glial endfoot detachment
  - Neuronal overmigration and cobblestone-like cortical ectopia
  - Rostral cerebellar dysplasia
  - Central nervous system hypomyelination
  description: >-
    Constitutive Gpr56-null mice reproduce the core pial-boundary,
    overmigration, rostral cerebellar and early hypomyelination mechanisms. The
    lissencephalic mouse does not model human gyrification, and species-specific
    splice or regulatory architecture limits inference about the human
    perisylvian regulatory allele.
  evidence:
  - reference: PMID:18509043
    reference_title: GPR56 regulates pial basement membrane integrity and cortical lamination.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      This study demonstrates that loss of the mouse Gpr56 gene leads to neuronal
      ectopia in the cerebral cortex, a cobblestone-like cortical malformation.
    explanation: >-
      The knockout reproduces cortical ectopia and the cobblestone-like
      overmigration mechanism.
  - reference: PMID:19515912
    reference_title: GPR56-regulated granule cell adhesion is essential for rostral cerebellar development.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      Gpr56(-/-) mice display a severe malformation of the rostral cerebellum
      that develops perinatally.
    explanation: >-
      The same knockout establishes the region-specific cerebellar phenotype.
  - reference: PMID:25607655
    reference_title: The adhesion G protein-coupled receptor GPR56 is a cell-autonomous regulator of oligodendrocyte development.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      Here, we demonstrate that loss of Gpr56 leads to hypomyelination of the
      central nervous system in mice.
    explanation: >-
      The model also reproduces the early white-matter phenotype.
- species: Mouse (Mus musculus)
  genotype: Col3a1-null mouse
  category: Knockout
  genes:
  - preferred_term: Col3a1
    term:
      id: hgnc:2201
      label: COL3A1
  associated_phenotypes:
  - Neuronal overmigration beyond the pial basement membrane
  - Cobblestone-like cortical malformation
  description: >-
    Col3a1-null mice phenocopy the cortical overmigration seen in Gpr56-null
    mice, providing ligand-side support for the GPR56-collagen III axis.
  evidence:
  - reference: PMID:21768377
    reference_title: "G protein-coupled receptor 56 and collagen III, a receptor-ligand pair, regulates cortical development and lamination."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      Col3a1 null mutant mice exhibit overmigration of neurons beyond the pial
      basement membrane and a cobblestone-like cortical malformation similar to
      the phenotype seen in Gpr56 null mutant mice.
    explanation: >-
      The ligand-null model independently recapitulates the cortical endpoint.
- species: Mouse (Mus musculus)
  genotype: Oligodendrocyte-precursor-conditional Gpr56 knockout
  category: Conditional knockout
  genes:
  - preferred_term: Gpr56 (Adgrg1)
    term:
      id: hgnc:4512
      label: ADGRG1
  associated_phenotypes:
  - Reduced mature oligodendrocyte number
  - Impaired oligodendrocyte development
  description: >-
    Conditional deletion in Pdgfra-positive oligodendrocyte precursors isolates
    the cell-autonomous white-matter mechanism from the cortical-malformation
    branch.
  evidence:
  - reference: PMID:25607655
    reference_title: The adhesion G protein-coupled receptor GPR56 is a cell-autonomous regulator of oligodendrocyte development.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      Conditional ablation of Gpr56 in OPCs leads to a reduced number of mature
      oligodendrocytes as seen in constitutive knockout of Gpr56.
    explanation: >-
      Lineage-restricted deletion establishes cell autonomy in oligodendrocyte
      development.
genetic:
- name: Biallelic ADGRG1 loss-of-function variants
  association: Biallelic loss of function causes ADGRG1-related BFPP
  relationship_type: CAUSATIVE
  variant_origin: GERMLINE
  gene_term:
    preferred_term: ADGRG1 (GPR56)
    term:
      id: hgnc:4512
      label: ADGRG1
  inheritance:
  - name: Autosomal recessive inheritance
    inheritance_term:
      preferred_term: Autosomal recessive inheritance
      term:
        id: HP:0000007
        label: Autosomal recessive inheritance
    description: >-
      Biallelic germline ADGRG1 variants segregate as an autosomal recessive
      disorder.
    evidence:
    - reference: PMID:16240336
      reference_title: Genotype-phenotype analysis of human frontoparietal polymicrogyria syndromes.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: We identified homozygous GPR56 mutations in all 29 patients with typical BFPP.
      explanation: >-
        Homozygous disease-associated variants in the diagnostic cohort support
        autosomal recessive inheritance.
  features: >-
    Homozygous coding variants have been identified across multiple populations
    and families. Disease-associated variants converge on reduced receptor
    function through heterogeneous effects on trafficking, proteolysis,
    shedding, ligand interaction and membrane distribution. A 15-base-pair
    regulatory-element deletion causes a related perisylvian-predominant ADGRG1
    phenotype by disrupting regional expression and should not be treated as
    identical to classic BFPP.
  evidence:
  - reference: PMID:15044805
    reference_title: "G protein-coupled receptor-dependent development of human frontal cortex."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      we show that mutations in GPR56, which encodes an orphan G
      protein-coupled receptor (GPCR) with a large extracellular domain, cause a
      human brain cortical malformation called bilateral frontoparietal
      polymicrogyria (BFPP)
    explanation: >-
      Founding report identifying GPR56/ADGRG1 mutations as the cause of BFPP.
  - reference: PMID:20929962
    reference_title: "GPR56-related bilateral frontoparietal polymicrogyria: further evidence for an overlap with the cobblestone complex."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      We identified homozygous GPR56 mutations in 14 patients from eight
      consanguineous families with typical bilateral bifrontoparietal
      polymicrogyria
    explanation: >-
      Confirms recessive (homozygous) GPR56 mutations in a multi-family BFPP
      cohort, consistent with autosomal recessive loss of function.
  - reference: PMID:16240336
    reference_title: Genotype-phenotype analysis of human frontoparietal polymicrogyria syndromes.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: We identified homozygous GPR56 mutations in all 29 patients with typical BFPP.
    explanation: >-
      A diagnostic cohort independently establishes the biallelic ADGRG1
      association with typical BFPP.
  - reference: PMID:21349848
    reference_title: Disease-associated GPR56 mutations cause bilateral frontoparietal polymicrogyria via multiple mechanisms.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: >-
      individual GPR56 mutants most likely cause BFPP via different combination
      of multiple mechanisms. These include reduced surface receptor expression,
      loss of GPS proteolysis, reduced receptor shedding, inability to interact
      with a novel protein ligand, and differential distribution of the 7TM
      moiety in lipid rafts.
    explanation: >-
      Functional assays define multiple variant-level routes that converge on
      loss of receptor function.
  - reference: PMID:24531968
    reference_title: Evolutionarily dynamic alternative splicing of GPR56 regulates regional cerebral cortical patterning.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      we describe a 15-base pair deletion mutation in a regulatory element of
      GPR56 that selectively disrupts human cortex surrounding the Sylvian
      fissure bilaterally including "Broca's area," the primary language area,
      by disrupting regional GPR56 expression and blocking RFX transcription
      factor binding
    explanation: >-
      This regulatory allele establishes a distinct region-specific ADGRG1
      phenotype and clarifies its boundary relative to classic BFPP.
treatments:
- name: Anti-Seizure Medication
  description: >-
    Individualized antiseizure pharmacotherapy is used for symptomatic seizure
    control. Published BFPP reports document multiple seizure types and frequent
    refractoriness but do not establish a disease-specific preferred drug or
    comparative regimen.
  action_category: THERAPEUTIC
  treatment_term:
    preferred_term: anticonvulsant agent therapy
    term:
      id: NCIT:C64172
      label: Anticonvulsant Therapy
  therapeutic_modality: SMALL_MOLECULE
  target_phenotypes:
  - preferred_term: Seizure
    term:
      id: HP:0001250
      label: Seizure
  evidence:
  - reference: PMID:34513772
    reference_title: "Case Report: Diffuse Polymicrogyria Associated With a Novel ADGRG1 Variant."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The patient was subsequently treated with several anti-epile ptics
    explanation: >-
      A molecularly confirmed case directly documents antiseizure pharmacotherapy;
      a single case does not establish a preferred agent or comparative regimen.
  - reference: PMID:34513772
    reference_title: "Case Report: Diffuse Polymicrogyria Associated With a Novel ADGRG1 Variant."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Seizures
      Present 60 (88.2)
      Age at onset in years, median (IQR) 3.0 (3.0)
      Refractory 36 (60.0)
    explanation: >-
      The literature aggregation documents refractory epilepsy in a subset,
      supporting individualized symptomatic management without implying a
      universal response or disease-specific regimen.
discussions:
- discussion_id: gap_adgrg1_human_regional_patterning_model_mismatch
  prompt: >-
    Which human-relevant cis-regulatory, splice-form and gyrencephalic features
    determine whether ADGRG1 disruption produces classic frontoparietal,
    perisylvian or diffuse polymicrogyria, and how can those spatial effects be
    separated from the conserved pial-boundary mechanism reproduced in mice?
  kind: HUMAN_MODEL_MISMATCH
  status: OPEN
  attaches_to:
  - pathophysiology#Regional Cortical Patterning Dependence on GPR56 Expression
  - pathophysiology#Neuronal Overmigration and Cortical Dyslamination
  rationale: >-
    Gpr56-null and Col3a1-null mice validly reproduce pial basement-membrane
    breach, endfoot failure and neuronal overmigration; the null mouse should not
    be described as a globally unpatterned model. The unresolved mismatch is
    narrower: a naturally lissencephalic mouse cannot model human cortical
    folding, and human-relevant ADGRG1 splice forms and gyrencephalic
    cis-regulatory architecture are not reproduced by mouse. The human
    15-base-pair regulatory deletion
    selectively affects perisylvian cortex, while coding variants usually produce
    classic BFPP but can occasionally produce diffuse disease. A human model is
    therefore needed to test the interaction between allele class, regional
    identity and the corticomeningeal pial boundary.
  evidence:
  - reference: PMID:18509043
    reference_title: GPR56 regulates pial basement membrane integrity and cortical lamination.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      This study demonstrates that loss of the mouse Gpr56 gene leads to neuronal
      ectopia in the cerebral cortex, a cobblestone-like cortical malformation.
    explanation: >-
      The knockout supports the conserved cortical-ectopia mechanism; it does not
      justify describing the mouse phenotype as globally unpatterned.
  - reference: PMID:21768377
    reference_title: "G protein-coupled receptor 56 and collagen III, a receptor-ligand pair, regulates cortical development and lamination."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      Mutations in the GPR56 gene cause a malformed cerebral cortex in both humans
      and mice that resembles cobblestone lissencephaly, which is characterized by
      overmigration of neurons beyond the pial basement membrane.
    explanation: >-
      Establishes that mouse models reproduce the conserved overmigration and
      cobblestone arm, isolating human folding and allele-specific regional
      architecture as the translational gap.
  - reference: PMID:24531968
    reference_title: Evolutionarily dynamic alternative splicing of GPR56 regulates regional cerebral cortical patterning.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      GPR56 splice forms are highly variable between mice and humans, and the
      regulatory element of gyrencephalic mammals directs restricted lateral
      cortical expression.
    explanation: >-
      Documents that the splicing and cis-regulatory architecture controlling
      regional GPR56 expression differ between mouse and human and motivates a
      human regional-patterning model.
  proposed_experiments:
  - experiment_id: exp_adgrg1_regionally_patterned_corticomeningeal_organoids
    name: Regionally patterned human corticomeningeal organoid experiment
    description: >-
      Use isogenic human iPSC-derived cortical organoids patterned toward frontal,
      parietal and perisylvian/lateral identities and supplied with a
      meningeal collagen-III compartment adjacent to a laminin/collagen-IV-rich
      pial-like basement membrane. Compare biallelic coding loss of function with
      the 15-base-pair regulatory deletion to test how allele class and regional
      identity interact to alter ADGRG1 expression, pial-boundary integrity,
      radial-glial anchorage and neuronal overmigration.
    experiment_type:
      preferred_term: isogenic regionally patterned corticomeningeal organoid experiment
    model_systems:
    - name: Human iPSC-derived regionally patterned corticomeningeal organoid
      description: >-
        Human cortical organoids patterned toward frontal, parietal or
        perisylvian/lateral identity, combined with a meningeal collagen-III
        compartment and an adjacent laminin/collagen-IV-rich pial-like basement
        membrane, and carrying isogenic ADGRG1 coding or regulatory alleles.
      experimental_model_type: ORGANOID
      namo_type: namo:Organoid
      organism:
        preferred_term: human
        term:
          id: NCBITaxon:9606
          label: Homo sapiens
      tissue_term:
        preferred_term: cerebral cortex
        term:
          id: UBERON:0000956
          label: cerebral cortex
      cell_types:
      - preferred_term: cortical radial glial cell
        term:
          id: CL:0013000
          label: forebrain radial glial cell
      - preferred_term: migrating cortical neuron
        term:
          id: CL:0000540
          label: neuron
      conditions:
      - ADGRG1-related bilateral frontoparietal polymicrogyria
      cell_source: Patient-derived or CRISPR-engineered human induced pluripotent stem cells
      culture_system: >-
        Regionally patterned three-dimensional cortical organoids with a
        meningeal collagen-III compartment adjacent to a laminin/collagen-IV-rich
        pial-like basement membrane for live-imaging migration and
        boundary-integrity assays
    perturbations:
    - name: Biallelic ADGRG1 coding loss of function
      target: pathophysiology#Regional Cortical Patterning Dependence on GPR56 Expression
      genes:
      - preferred_term: ADGRG1
        term:
          id: hgnc:4512
          label: ADGRG1
      description: >-
        Introduce a biallelic coding loss-of-function allele into an isogenic
        human iPSC background.
    - name: ADGRG1 15-base-pair regional regulatory-element deletion
      target: pathophysiology#Regional Cortical Patterning Dependence on GPR56 Expression
      genes:
      - preferred_term: ADGRG1
        term:
          id: hgnc:4512
          label: ADGRG1
      description: >-
        Introduce the perisylvian-associated non-coding regulatory deletion into
        the same isogenic background without disrupting the coding sequence.
    readouts:
    - name: Regional ADGRG1 expression and splice-form abundance
      target: pathophysiology#Regional Cortical Patterning Dependence on GPR56 Expression
      biological_processes:
      - preferred_term: cerebral cortex regionalization
        term:
          id: GO:0021796
          label: cerebral cortex regionalization
        modifier: ABNORMAL
      assays:
      - preferred_term: spatial transcriptomics assay
      direction: NEGATIVE
    - name: Pial-like basement-membrane continuity and radial-glial endfoot anchorage
      target: pathophysiology#Pial Basement Membrane Breach
      biological_processes:
      - preferred_term: basement membrane organization
        term:
          id: GO:0071711
          label: basement membrane organization
        modifier: ABNORMAL
      assays:
      - preferred_term: immunofluorescence microscopy assay
      direction: NEGATIVE
    - name: Region-resolved neuronal overmigration across the pial boundary
      target: pathophysiology#Neuronal Overmigration and Cortical Dyslamination
      biological_processes:
      - preferred_term: neuron migration
        term:
          id: GO:0001764
          label: neuron migration
        modifier: INCREASED
      assays:
      - preferred_term: live-cell imaging assay
      direction: POSITIVE
    controls:
    - name: Isogenic wild-type and corrected organoids
      description: >-
        Sham-edited wild-type organoids and variant-corrected patient lines for
        every regional identity and corticomeningeal culture batch.
    - name: Coding rescue arm
      description: >-
        Re-expression of physiologic ADGRG1 in coding-loss organoids to test
        rescue of pial-boundary integrity and overmigration.
    - name: Interface-negative technical control
      description: >-
        Matched cortical organoids lacking the engineered meningeal/pial interface
        to show which readouts require a modeled pial boundary.
    decision_criterion: >-
      Support regional allelic specificity only if there is a reproducible
      allele-by-regional-identity interaction: the regulatory deletion must
      preferentially reduce ADGRG1 expression and disrupt boundary or migration
      readouts in perisylvian/lateral organoids, while coding loss causes a broader
      defect whose magnitude follows baseline regional expression. Variant
      correction or coding rescue must reverse the corresponding abnormalities.
    would_support:
    - pathophysiology#Regional Cortical Patterning Dependence on GPR56 Expression
    - pathophysiology#Pial Basement Membrane Breach
    - pathophysiology#Neuronal Overmigration and Cortical Dyslamination
    would_refute:
    - pathophysiology#Regional Cortical Patterning Dependence on GPR56 Expression
notes: >-
  Entry created from cortical-malformation epic 4098 (issue 4087), seeded from
  Romero, Bahi-Buisson & Francis 2018 (Sem Cell Dev Biol 76:33-75). Modeled as a
  coherent ADGRG1/GPR56 pial basement-membrane / radial glial endfoot
  pathomechanism rather than lumped under generic polymicrogyria. Biallelic
  COL3A1 ligand-side disease (PMID:28258187, PMID:28742248) is represented here
  as a differential diagnosis and shared-axis context; a separate local COL3A1
  brain-malformation entry has not yet been curated. The GPR56-COL3A1, pial
  basement-membrane breach, radial-glial endfoot detachment and neuronal
  overmigration nodes conform to the pial basement membrane / radial glial
  endfoot failure module. The independent oligodendrocyte-lineage and rostral
  cerebellar branches are disease-specific additions.

📚

References & Deep Research

References

14

PMID:15044805

G protein-coupled receptor-dependent development of human frontal cortex.

No top-level findings curated for this source.

PMID:16240336

Genotype-phenotype analysis of human frontoparietal polymicrogyria syndromes.

No top-level findings curated for this source.

PMID:18509043

GPR56 regulates pial basement membrane integrity and cortical lamination.

No top-level findings curated for this source.

PMID:19016831

Bilateral frontoparietal polymicrogyria, Lennox-Gastaut syndrome, and GPR56 gene mutations.

No top-level findings curated for this source.

PMID:19515912

GPR56-regulated granule cell adhesion is essential for rostral cerebellar development.

No top-level findings curated for this source.

PMID:20929962

GPR56-related bilateral frontoparietal polymicrogyria: further evidence for an overlap with the cobblestone complex.

No top-level findings curated for this source.

PMID:21349848

Disease-associated GPR56 mutations cause bilateral frontoparietal polymicrogyria via multiple mechanisms.

No top-level findings curated for this source.

PMID:21768377

G protein-coupled receptor 56 and collagen III, a receptor-ligand pair, regulates cortical development and lamination.

No top-level findings curated for this source.

PMID:24531968

Evolutionarily dynamic alternative splicing of GPR56 regulates regional cerebral cortical patterning.

No top-level findings curated for this source.

PMID:25607655

The adhesion G protein-coupled receptor GPR56 is a cell-autonomous regulator of oligodendrocyte development.

No top-level findings curated for this source.

PMID:25922261

GPR56-Related Polymicrogyria: Clinicoradiologic Profile of 4 Patients.

No top-level findings curated for this source.

PMID:28258187

Bi-allelic variants in COL3A1 encoding the ligand to GPR56 are associated with cobblestone-like cortical malformation, white matter changes and cerebellar cysts.

No top-level findings curated for this source.

PMID:28742248

Biallelic COL3A1 mutations result in a clinical spectrum of specific structural brain anomalies and connective tissue abnormalities.

No top-level findings curated for this source.

PMID:34513772

Case Report: Diffuse Polymicrogyria Associated With a Novel ADGRG1 Variant.

No top-level findings curated for this source.

Deep Research

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

Edison Scientific Literature 35 citations 2026-06-11T18:54:55.671110

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

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

Consanguinity is a major familial/contextual risk factor for recessive BFPP and is common among reported pedigrees. (jansen2005geneticsofthe pages 5-6, khatib2024adgrg1relatedpolymicrogyriasyndrome pages 1-3)
Family history of BFPP / known familial ADGRG1 variant increases recurrence risk consistent with autosomal recessive inheritance. (carneiro2021casereportdiffuse pages 1-2, carneiro2021casereportdiffuse pages 2-3)

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

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)

Onset: Congenital/infantile, with developmental delay/hypotonia often evident within the first year; seizures typically begin in infancy or childhood. (carneiro2021casereportdiffuse pages 2-3, parrini2009bilateralfrontoparietalpolymicrogyria pages 3-5)
Course: The malformation is structural and nonprogressive, but functional outcomes vary; epilepsy can be refractory and can contribute to developmental decompensation (epileptic encephalopathy-like course). (carneiro2021casereportdiffuse pages 3-5, parrini2009bilateralfrontoparietalpolymicrogyria pages 6-8)
Quality-of-life impact: Severe intellectual disability, refractory epilepsy, impaired ambulation, and oculomotor dysfunction can markedly limit independence and communication; quantitative QoL metrics (e.g., EQ-5D/SF-36) were not identified in the retrieved literature.

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

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

Typical onset: congenital/infancy with early psychomotor delay; seizures often begin in infancy or early childhood. (carneiro2021casereportdiffuse pages 2-3, parrini2009bilateralfrontoparietalpolymicrogyria pages 3-5)
Progression: structural malformation is static; clinical trajectory is variable and can be complicated by refractory epilepsy and developmental plateau/regression. (carneiro2021casereportdiffuse pages 3-5, carneiro2021casereportdiffuse pages 1-2)

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

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

Many individuals have severe intellectual disability and motor impairment; however, ambulation is achieved in a majority in aggregated series (e.g., 81.6% in one literature synthesis; 44/63 ~70% in another), indicating variable functional outcomes. (carneiro2021casereportdiffuse pages 3-5, khatib2024adgrg1relatedpolymicrogyriasyndrome pages 4-6)
Epilepsy is common and frequently refractory (e.g., 54.7–60% refractory among seizure-affected individuals in aggregated datasets), which is a major driver of morbidity. (carneiro2021casereportdiffuse pages 5-6, khatib2024adgrg1relatedpolymicrogyriasyndrome pages 6-7)
Disease-specific mortality rates for BFPP were not identified in the retrieved evidence; one severe multi-system twin presentation with ADGRG1 p.Arg565Trp (plus an additional variant) died before age 2, illustrating potential severity in complex/overlapping cases rather than typical BFPP prognosis. (shaath2024integratinggenomesequencing pages 2-4, shaath2024integratinggenomesequencing pages 5-7)

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

Mouse (Gpr56 loss): reported to cause reduced progenitor proliferation, radial glial endfeet/pial basement membrane abnormalities, neuron overmigration, disorganized lamination, and a “cobblestone-like malformation.” (murayama2020thepolymicrogyriaassociatedgpr56 pages 1-2)
Zebrafish/rodent glial models: ADGRG1/GPR56 is implicated as a conserved regulator of myelination and glial development; in PNS Schwann cells, GPR56-dependent RhoA signaling supports radial sorting and myelin thickness/organization, and mutants show progressive neuropathy-like phenotypes. (ackerman2018gpr56adgrg1regulatesdevelopment pages 1-2, ackerman2018gpr56adgrg1regulatesdevelopment pages 10-11)
Microglia–OPC axis (mouse): microglia-derived TG2 signals to ADGRG1 on OPCs (with laminin) promoting OPC proliferation and improving remyelination in murine demyelination models. (giera2018microglialtransglutaminase2drives pages 1-2, giera2018microglialtransglutaminase2drives pages 3-5)
Common marmoset (transgenic promoter model): a polymicrogyria-associated GPR56 promoter element preferentially drives expression in developing GABAergic neurons, supporting interneuron involvement in epilepsy linked to GPR56 regulatory variants. (murayama2020thepolymicrogyriaassociatedgpr56 pages 1-2)

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)

2024 (family + review): identification of a novel homozygous ADGRG1 variant (p.Leu103Pro) in a large consanguineous family; detailed modern WES pipeline and emphasis on genetic counseling and diagnostic pitfalls (MRI mimicry of infections; occasional normal infancy MRI). (khatib2024adgrg1relatedpolymicrogyriasyndrome pages 1-3, khatib2024adgrg1relatedpolymicrogyriasyndrome pages 4-6)
2024 (multi-omics rare disease): integrated WGS + untargeted metabolomics in twins with homozygous ADGRG1 p.Arg565Trp and complex overlapping phenotype; metabolomics flagged 180 clinically relevant biochemicals with substantial lipid (48%) and amino-acid pathway (29%) perturbations, and evidence for oxidative stress/glutathione depletion markers and urea-cycle/arginine–proline metabolism involvement. (shaath2024integratinggenomesequencing pages 5-7, shaath2024integratinggenomesequencing pages 7-8, shaath2024integratinggenomesequencing pages 4-5)
2024 (signaling pharmacology): GPR56 ligand modalities show biased G-protein selectivity (G13 vs G12) while converging on Rho pathway activation, providing tools and conceptual frameworks potentially relevant to future targeted modulation strategies (not yet applied clinically to BFPP). (jallouli2024gproteinselectivity pages 1-2, jallouli2024gproteinselectivity pages 11-13)
2023 (cohort genetics): large polymicrogyria cohort study demonstrated 32.7% genetic diagnostic yield and highlighted convergent mechanistic categories including ion-conducting proteins; ADGRG1 remains a canonical known PMG gene within such cohorts. (akula2023exomesequencingand pages 2-3)

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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(jansen2005geneticsofthe pages 5-6): An C. Jansen and E. Andermann. Genetics of the polymicrogyria syndromes. Journal of Medical Genetics, 42:369-378, May 2005. URL: https://doi.org/10.1136/jmg.2004.023952, doi:10.1136/jmg.2004.023952. This article has 205 citations and is from a domain leading peer-reviewed journal.
(carneiro2021casereportdiffuse pages 1-2): Fábio Carneiro, Júlia Duarte, Francisco Laranjeira, Sofia Barbosa-Gouveia, María-Luz Couce, and Maria José Fonseca. Case report: diffuse polymicrogyria associated with a novel adgrg1 variant. Frontiers in Pediatrics, Aug 2021. URL: https://doi.org/10.3389/fped.2021.728077, doi:10.3389/fped.2021.728077. This article has 7 citations.
(chiang2011diseaseassociatedgpr56mutations pages 1-2): Nien-Yi Chiang, Cheng-Chih Hsiao, Yi-Shu Huang, Hsin-Yi Chen, I-Ju Hsieh, Gin-Wen Chang, and Hsi-Hsien Lin. Disease-associated gpr56 mutations cause bilateral frontoparietal polymicrogyria via multiple mechanisms. Journal of Biological Chemistry, 286:14215-14225, Apr 2011. URL: https://doi.org/10.1074/jbc.m110.183830, doi:10.1074/jbc.m110.183830. This article has 103 citations and is from a domain leading peer-reviewed journal.
(carneiro2021casereportdiffuse pages 2-3): Fábio Carneiro, Júlia Duarte, Francisco Laranjeira, Sofia Barbosa-Gouveia, María-Luz Couce, and Maria José Fonseca. Case report: diffuse polymicrogyria associated with a novel adgrg1 variant. Frontiers in Pediatrics, Aug 2021. URL: https://doi.org/10.3389/fped.2021.728077, doi:10.3389/fped.2021.728077. This article has 7 citations.
(carneiro2021casereportdiffuse pages 3-5): Fábio Carneiro, Júlia Duarte, Francisco Laranjeira, Sofia Barbosa-Gouveia, María-Luz Couce, and Maria José Fonseca. Case report: diffuse polymicrogyria associated with a novel adgrg1 variant. Frontiers in Pediatrics, Aug 2021. URL: https://doi.org/10.3389/fped.2021.728077, doi:10.3389/fped.2021.728077. This article has 7 citations.
(carneiro2021casereportdiffuse pages 5-6): Fábio Carneiro, Júlia Duarte, Francisco Laranjeira, Sofia Barbosa-Gouveia, María-Luz Couce, and Maria José Fonseca. Case report: diffuse polymicrogyria associated with a novel adgrg1 variant. Frontiers in Pediatrics, Aug 2021. URL: https://doi.org/10.3389/fped.2021.728077, doi:10.3389/fped.2021.728077. This article has 7 citations.
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(chiang2011diseaseassociatedgpr56mutations pages 8-10): Nien-Yi Chiang, Cheng-Chih Hsiao, Yi-Shu Huang, Hsin-Yi Chen, I-Ju Hsieh, Gin-Wen Chang, and Hsi-Hsien Lin. Disease-associated gpr56 mutations cause bilateral frontoparietal polymicrogyria via multiple mechanisms. Journal of Biological Chemistry, 286:14215-14225, Apr 2011. URL: https://doi.org/10.1074/jbc.m110.183830, doi:10.1074/jbc.m110.183830. This article has 103 citations and is from a domain leading peer-reviewed journal.
(chiang2011diseaseassociatedgpr56mutations pages 3-5): Nien-Yi Chiang, Cheng-Chih Hsiao, Yi-Shu Huang, Hsin-Yi Chen, I-Ju Hsieh, Gin-Wen Chang, and Hsi-Hsien Lin. Disease-associated gpr56 mutations cause bilateral frontoparietal polymicrogyria via multiple mechanisms. Journal of Biological Chemistry, 286:14215-14225, Apr 2011. URL: https://doi.org/10.1074/jbc.m110.183830, doi:10.1074/jbc.m110.183830. This article has 103 citations and is from a domain leading peer-reviewed journal.
(chiang2011diseaseassociatedgpr56mutations pages 10-11): Nien-Yi Chiang, Cheng-Chih Hsiao, Yi-Shu Huang, Hsin-Yi Chen, I-Ju Hsieh, Gin-Wen Chang, and Hsi-Hsien Lin. Disease-associated gpr56 mutations cause bilateral frontoparietal polymicrogyria via multiple mechanisms. Journal of Biological Chemistry, 286:14215-14225, Apr 2011. URL: https://doi.org/10.1074/jbc.m110.183830, doi:10.1074/jbc.m110.183830. This article has 103 citations and is from a domain leading peer-reviewed journal.
(ke2008biochemicalcharacterizationof pages 1-2): Ning Ke, Hongwen Ma, Gundo Diedrich, John Chionis, Guohong Liu, De-Hua Yu, Flossie Wong-Staal, and Qi-Xiang Li. Biochemical characterization of genetic mutations of gpr56 in patients with bilateral frontoparietal polymicrogyria (bfpp). Biochemical and biophysical research communications, 366 2:314-20, Feb 2008. URL: https://doi.org/10.1016/j.bbrc.2007.11.071, doi:10.1016/j.bbrc.2007.11.071. This article has 35 citations and is from a peer-reviewed journal.
(shaath2024integratinggenomesequencing pages 2-4): Rulan Shaath, Aljazi Al-Maraghi, Haytham Ali, Jehan AlRayahi, Adam D. Kennedy, Karen L. DeBalsi, Sura Hussein, Najwa Elbashir, Sujitha S. Padmajeya, Sasirekha Palaniswamy, Sarah H. Elsea, Ammira A. Akil, Noha A. Yousri, and Khalid A. Fakhro. Integrating genome sequencing and untargeted metabolomics in monozygotic twins with a rare complex neurological disorder. Metabolites, 14:152, Mar 2024. URL: https://doi.org/10.3390/metabo14030152, doi:10.3390/metabo14030152. This article has 5 citations.
(shaath2024integratinggenomesequencing pages 4-5): Rulan Shaath, Aljazi Al-Maraghi, Haytham Ali, Jehan AlRayahi, Adam D. Kennedy, Karen L. DeBalsi, Sura Hussein, Najwa Elbashir, Sujitha S. Padmajeya, Sasirekha Palaniswamy, Sarah H. Elsea, Ammira A. Akil, Noha A. Yousri, and Khalid A. Fakhro. Integrating genome sequencing and untargeted metabolomics in monozygotic twins with a rare complex neurological disorder. Metabolites, 14:152, Mar 2024. URL: https://doi.org/10.3390/metabo14030152, doi:10.3390/metabo14030152. This article has 5 citations.
(murayama2020thepolymicrogyriaassociatedgpr56 pages 1-2): Ayako Y. Murayama, Ken-ichiro Kuwako, Junko Okahara, Byoung-Il Bae, Misako Okuno, Hiromi Mashiko, Tomomi Shimogori, Christopher A. Walsh, Erika Sasaki, and Hideyuki Okano. The polymicrogyria-associated gpr56 promoter preferentially drives gene expression in developing gabaergic neurons in common marmosets. Scientific Reports, Dec 2020. URL: https://doi.org/10.1038/s41598-020-78608-4, doi:10.1038/s41598-020-78608-4. This article has 17 citations and is from a peer-reviewed journal.
(chiang2011diseaseassociatedgpr56mutations pages 5-6): Nien-Yi Chiang, Cheng-Chih Hsiao, Yi-Shu Huang, Hsin-Yi Chen, I-Ju Hsieh, Gin-Wen Chang, and Hsi-Hsien Lin. Disease-associated gpr56 mutations cause bilateral frontoparietal polymicrogyria via multiple mechanisms. Journal of Biological Chemistry, 286:14215-14225, Apr 2011. URL: https://doi.org/10.1074/jbc.m110.183830, doi:10.1074/jbc.m110.183830. This article has 103 citations and is from a domain leading peer-reviewed journal.
(chiang2011diseaseassociatedgpr56mutations pages 7-8): Nien-Yi Chiang, Cheng-Chih Hsiao, Yi-Shu Huang, Hsin-Yi Chen, I-Ju Hsieh, Gin-Wen Chang, and Hsi-Hsien Lin. Disease-associated gpr56 mutations cause bilateral frontoparietal polymicrogyria via multiple mechanisms. Journal of Biological Chemistry, 286:14215-14225, Apr 2011. URL: https://doi.org/10.1074/jbc.m110.183830, doi:10.1074/jbc.m110.183830. This article has 103 citations and is from a domain leading peer-reviewed journal.
(jallouli2024gproteinselectivity pages 1-2): Raida Jallouli, Ana L. Moreno-Salinas, Andréanne Laniel, Brian Holleran, Charlotte Avet, Joan Jacob, Trang Hoang, Christine Lavoie, Kendra S. Carmon, Michel Bouvier, and Richard Leduc. G protein selectivity profile of gpr56/adgrg1 and its effect on downstream effectors. Cellular and Molecular Life Sciences: CMLS, Sep 2024. URL: https://doi.org/10.1007/s00018-024-05416-8, doi:10.1007/s00018-024-05416-8. This article has 10 citations.
(einspahr2022pathophysiologicalimpactof pages 5-9): Jeanette M. Einspahr and Douglas G. Tilley. Pathophysiological impact of the adhesion g protein-coupled receptor family. Aug 2022. URL: https://doi.org/10.1152/ajpcell.00445.2021, doi:10.1152/ajpcell.00445.2021. This article has 31 citations.
(giera2018microglialtransglutaminase2drives pages 1-2): Stefanie Giera, Rong Luo, Yanqin Ying, Sarah D Ackerman, Sung-Jin Jeong, Hannah M Stoveken, Christopher J Folts, Christina A Welsh, Gregory G Tall, Beth Stevens, Kelly R Monk, and Xianhua Piao. Microglial transglutaminase-2 drives myelination and myelin repair via gpr56/adgrg1 in oligodendrocyte precursor cells. eLife, May 2018. URL: https://doi.org/10.7554/elife.33385, doi:10.7554/elife.33385. This article has 164 citations and is from a domain leading peer-reviewed journal.
(giera2018microglialtransglutaminase2drives pages 3-5): Stefanie Giera, Rong Luo, Yanqin Ying, Sarah D Ackerman, Sung-Jin Jeong, Hannah M Stoveken, Christopher J Folts, Christina A Welsh, Gregory G Tall, Beth Stevens, Kelly R Monk, and Xianhua Piao. Microglial transglutaminase-2 drives myelination and myelin repair via gpr56/adgrg1 in oligodendrocyte precursor cells. eLife, May 2018. URL: https://doi.org/10.7554/elife.33385, doi:10.7554/elife.33385. This article has 164 citations and is from a domain leading peer-reviewed journal.
(bauer2024mesenchymaltransglutaminase2 pages 1-2): Lea Bauer, Jessica Edwards, Andreas Heil, Sharon Dewitt, Heike Biebermann, Daniel Aeschlimann, and Vera Knäuper. Mesenchymal transglutaminase 2 activates epithelial adam17: link to g-protein-coupled receptor 56 (adgrg1) signalling. International Journal of Molecular Sciences, 25:2329, Feb 2024. URL: https://doi.org/10.3390/ijms25042329, doi:10.3390/ijms25042329. This article has 5 citations.
(bauer2024mesenchymaltransglutaminase2 pages 2-5): Lea Bauer, Jessica Edwards, Andreas Heil, Sharon Dewitt, Heike Biebermann, Daniel Aeschlimann, and Vera Knäuper. Mesenchymal transglutaminase 2 activates epithelial adam17: link to g-protein-coupled receptor 56 (adgrg1) signalling. International Journal of Molecular Sciences, 25:2329, Feb 2024. URL: https://doi.org/10.3390/ijms25042329, doi:10.3390/ijms25042329. This article has 5 citations.
(bauer2024mesenchymaltransglutaminase2 pages 6-9): Lea Bauer, Jessica Edwards, Andreas Heil, Sharon Dewitt, Heike Biebermann, Daniel Aeschlimann, and Vera Knäuper. Mesenchymal transglutaminase 2 activates epithelial adam17: link to g-protein-coupled receptor 56 (adgrg1) signalling. International Journal of Molecular Sciences, 25:2329, Feb 2024. URL: https://doi.org/10.3390/ijms25042329, doi:10.3390/ijms25042329. This article has 5 citations.
(ackerman2018gpr56adgrg1regulatesdevelopment pages 1-2): Sarah D. Ackerman, Rong Luo, Yannick Poitelon, Amit Mogha, Breanne L. Harty, Mitchell D’Rozario, Nicholas E. Sanchez, Asvin K.K. Lakkaraju, Paul Gamble, Jun Li, Jun Qu, Matthew R. MacEwan, Wilson Zachary Ray, Adriano Aguzzi, M. Laura Feltri, Xianhua Piao, and Kelly R. Monk. Gpr56/adgrg1 regulates development and maintenance of peripheral myelin. The Journal of Experimental Medicine, 215:941-961, Mar 2018. URL: https://doi.org/10.1084/jem.20161714, doi:10.1084/jem.20161714. This article has 73 citations.
(akula2023exomesequencingand pages 2-3): Shyam K. Akula, Allen Y. Chen, Jennifer E. Neil, Diane D. Shao, Alisa Mo, Norma K. Hylton, Stephanie DiTroia, Vijay S. Ganesh, Richard S. Smith, Katherine O’Kane, Rebecca C. Yeh, Jack H. Marciano, Samantha Kirkham, Connor J. Kenny, Janet H. T. Song, Muna Al Saffar, Francisca Millan, David J. Harris, Andrea V. Murphy, Kara C. Klemp, Stephen R. Braddock, Harrison Brand, Isaac Wong, Michael E. Talkowski, Anne O’Donnell-Luria, Abbe Lai, Robert Sean Hill, Ganeshwaran H. Mochida, Ryan N. Doan, A. James Barkovich, Edward Yang, Dina Amrom, Eva Andermann, Annapurna Poduri, Christopher A. Walsh, Bassam Abu-Libdeh, Lihadh Al-Gazali, Muna Al Saffar, Edith Alva Moncayo, Dina Amrom, Eva Anderman, Anna-Kaisa Anttonen, Saunder Barnes, Sara Barnett, Todd Barron, Brenda J. Barry, Lina Basel-Vanagaite, Laila Bastaki, Luis Bello-Espinosa, Tawfeg Ben-Omran, Matthew Bernard, Carsten G. Bonneman, Blaise Bourgeois, Stephen Brown, Roberto H. Caraballo, Gergory Cascino, Michael Clarke, Monika Cohen, Yanick Crow, Bernard Dan, Kira A. Dies, William B. Dobyns, François Dubeau, Christelle El Achkar, Gregory M. Enns, Laurence Faivre, Laura Flores-Sarnat, John Gaitanis, Kuchukhidze Giorgi, Andrew Green, Alan Guberman, Renzo Guerrini, Micheil Innes, Richard Jacobsen, Sebastian Jacquemont, Samir Khalil, Joerg Klepper, Dimitri Kranic, Kalpathy Krishnamoorthy, Anna-Elina Lehesjoki, Dorit Lev, Richard J. Leventer, Emily Lisi, Valerie Loik Ramey, Sally Ann Lynch, Laila Mahmoud, David Manchester, David Mandelbaum, Daphna Marom, Deborah Marsden, Mayra Martinez Ojeda, Amira Masri, Livija Medne, Denis Melanson, David T. Miller, Anna Minster, Edward Neilan, Dang Khoa Nguyen, Heather E. Olson, Ignacio Pascual-Castroviejo, Philip L. Pearl, Daniela Pilz, Nada Quercia, Salmo Raskin, Miriam Regev, Lance Rodan, Cynthia Rooney, Michael Rutlin, Mustafa Sahin, Mustafa A. Salih, Pierre Sarda, Harvey B. Sarnat, Ingrid Scheffer, Joseph Shieh, Sharon E. Smith, Janet S. Soul, Siddharth Srivastava, Laszlo Sztriha, Donatella Tampieri, John Tolmie, Meral Topçu, Eugen Trinka, John Tsai, Jack Tsao, Sheila Unger, Iris Unterberger, Goekhan Uyanik, Kette Valente, Thomas Voit, Louise Wilson, and Grace Yoon. Exome sequencing and the identification of new genes and shared mechanisms in polymicrogyria. JAMA Neurology, 80:980, Sep 2023. URL: https://doi.org/10.1001/jamaneurol.2023.2363, doi:10.1001/jamaneurol.2023.2363. This article has 39 citations and is from a highest quality peer-reviewed journal.
(NCT01488461 chunk 1): Phenotypic and Genotypic Studies in Congenital and Early Onset Ataxias. Assistance Publique - Hôpitaux de Paris. 2012. ClinicalTrials.gov Identifier: NCT01488461
(shaath2024integratinggenomesequencing pages 5-7): Rulan Shaath, Aljazi Al-Maraghi, Haytham Ali, Jehan AlRayahi, Adam D. Kennedy, Karen L. DeBalsi, Sura Hussein, Najwa Elbashir, Sujitha S. Padmajeya, Sasirekha Palaniswamy, Sarah H. Elsea, Ammira A. Akil, Noha A. Yousri, and Khalid A. Fakhro. Integrating genome sequencing and untargeted metabolomics in monozygotic twins with a rare complex neurological disorder. Metabolites, 14:152, Mar 2024. URL: https://doi.org/10.3390/metabo14030152, doi:10.3390/metabo14030152. This article has 5 citations.
(ackerman2018gpr56adgrg1regulatesdevelopment pages 10-11): Sarah D. Ackerman, Rong Luo, Yannick Poitelon, Amit Mogha, Breanne L. Harty, Mitchell D’Rozario, Nicholas E. Sanchez, Asvin K.K. Lakkaraju, Paul Gamble, Jun Li, Jun Qu, Matthew R. MacEwan, Wilson Zachary Ray, Adriano Aguzzi, M. Laura Feltri, Xianhua Piao, and Kelly R. Monk. Gpr56/adgrg1 regulates development and maintenance of peripheral myelin. The Journal of Experimental Medicine, 215:941-961, Mar 2018. URL: https://doi.org/10.1084/jem.20161714, doi:10.1084/jem.20161714. This article has 73 citations.
(shaath2024integratinggenomesequencing pages 7-8): Rulan Shaath, Aljazi Al-Maraghi, Haytham Ali, Jehan AlRayahi, Adam D. Kennedy, Karen L. DeBalsi, Sura Hussein, Najwa Elbashir, Sujitha S. Padmajeya, Sasirekha Palaniswamy, Sarah H. Elsea, Ammira A. Akil, Noha A. Yousri, and Khalid A. Fakhro. Integrating genome sequencing and untargeted metabolomics in monozygotic twins with a rare complex neurological disorder. Metabolites, 14:152, Mar 2024. URL: https://doi.org/10.3390/metabo14030152, doi:10.3390/metabo14030152. This article has 5 citations.
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(jallouli2024gproteinselectivity pages 7-9): Raida Jallouli, Ana L. Moreno-Salinas, Andréanne Laniel, Brian Holleran, Charlotte Avet, Joan Jacob, Trang Hoang, Christine Lavoie, Kendra S. Carmon, Michel Bouvier, and Richard Leduc. G protein selectivity profile of gpr56/adgrg1 and its effect on downstream effectors. Cellular and Molecular Life Sciences: CMLS, Sep 2024. URL: https://doi.org/10.1007/s00018-024-05416-8, doi:10.1007/s00018-024-05416-8. This article has 10 citations.

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Inheritance

Discussions and Knowledge Gaps

Pathophysiology

Pathograph

Phenotypes

Genetic Associations

Medical Actions

Diagnosis

Imaging Findings

Progression

Differential Diagnoses

Animal Models

Source YAML

References & Deep Research

References

Deep Research

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

Target disease

1. Disease information

1.1 Overview (what is the disease?)

1.2 Key identifiers and nomenclature

1.3 Synonyms / alternative names

1.4 Evidence provenance

2. Etiology

2.1 Disease causal factors

2.2 Risk factors

2.3 Protective factors

2.4 Gene–environment interactions

3. Phenotypes

3.1 Core clinical phenotype spectrum and frequencies

3.2 Phenotype characteristics (onset, progression, QoL impact)

3.3 Suggested HPO terms

4. Genetic / molecular information

4.1 Causal gene(s)

4.2 Pathogenic variant spectrum

4.3 Functional consequences

4.4 Modifier genes / multilocus disease

4.5 Epigenetics / chromosomal abnormalities

5. Environmental information

6. Mechanism / pathophysiology

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

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

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

6.4 Suggested ontology terms (mechanism, anatomy, cells)

7. Anatomical structures affected

7.1 Organ/system level

7.2 Tissue/cell level

7.3 Subcellular level

8. Temporal development

9. Inheritance and population

9.1 Inheritance

9.2 Epidemiology

9.3 Population and geographic distribution

9.4 Statistics supporting clinical relevance in PMG cohorts (recent)

10. Diagnostics

11. Outcome / prognosis

12. Treatment

12.1 Pharmacotherapy (symptomatic)

12.2 Surgical/interventional

12.3 Experimental therapeutics

13. Prevention

14. Other species / natural disease

15. Model organisms

15.1 Model systems and key phenotypes

15.2 Model applications and limitations

Recent developments (2023–2024 prioritized highlights)

Expert synthesis / interpretation (authoritative-source-driven)

Artifacts