-
Nature Genetics Jun 2012Megalencephaly-capillary malformation (MCAP) and megalencephaly-polymicrogyria-polydactyly-hydrocephalus (MPPH) syndromes are sporadic overgrowth disorders associated...
Megalencephaly-capillary malformation (MCAP) and megalencephaly-polymicrogyria-polydactyly-hydrocephalus (MPPH) syndromes are sporadic overgrowth disorders associated with markedly enlarged brain size and other recognizable features. We performed exome sequencing in 3 families with MCAP or MPPH, and our initial observations were confirmed in exomes from 7 individuals with MCAP and 174 control individuals, as well as in 40 additional subjects with megalencephaly, using a combination of Sanger sequencing, restriction enzyme assays and targeted deep sequencing. We identified de novo germline or postzygotic mutations in three core components of the phosphatidylinositol 3-kinase (PI3K)-AKT pathway. These include 2 mutations in AKT3, 1 recurrent mutation in PIK3R2 in 11 unrelated families with MPPH and 15 mostly postzygotic mutations in PIK3CA in 23 individuals with MCAP and 1 with MPPH. Our data highlight the central role of PI3K-AKT signaling in vascular, limb and brain development and emphasize the power of massively parallel sequencing in a challenging context of phenotypic and genetic heterogeneity combined with postzygotic mosaicism.
Topics: Class I Phosphatidylinositol 3-Kinases; Exome; Germ-Line Mutation; Humans; Hydrocephalus; Malformations of Cortical Development; Megalencephaly; Mutation; Mutation, Missense; Phosphatidylinositol 3-Kinases; Proto-Oncogene Proteins c-akt; Syndrome
PubMed: 22729224
DOI: 10.1038/ng.2331 -
Journal of Medical Genetics Jul 2017We aimed for a comprehensive delineation of genetic, functional and phenotypic aspects of encephalopathy and explored potential prospects of personalised medicine.
BACKGROUND
We aimed for a comprehensive delineation of genetic, functional and phenotypic aspects of encephalopathy and explored potential prospects of personalised medicine.
METHODS
Data of 48 individuals with de novo variants were collected from several diagnostic and research cohorts, as well as from 43 patients from the literature. Functional consequences and response to memantine treatment were investigated in vitro and eventually translated into patient care.
RESULTS
Overall, de novo variants in 86 patients were classified as pathogenic/likely pathogenic. Patients presented with neurodevelopmental disorders and a spectrum of hypotonia, movement disorder, cortical visual impairment, cerebral volume loss and epilepsy. Six patients presented with a consistent malformation of cortical development (MCD) intermediate between tubulinopathies and polymicrogyria. Missense variants cluster in transmembrane segments and ligand-binding sites. Functional consequences of variants were diverse, revealing various potential gain-of-function and loss-of-function mechanisms and a retained sensitivity to the use-dependent blocker memantine. However, an objectifiable beneficial treatment response in the respective patients still remains to be demonstrated.
CONCLUSIONS
In addition to previously known features of intellectual disability, epilepsy and autism, we found evidence that encephalopathy is also frequently associated with movement disorder, cortical visual impairment and MCD revealing novel phenotypic consequences of channelopathies.
Topics: Brain Diseases; Heterozygote; Humans; Magnetic Resonance Imaging; Memantine; Molecular Targeted Therapy; Mutation; Neuroimaging; Phenotype; Receptors, N-Methyl-D-Aspartate
PubMed: 28377535
DOI: 10.1136/jmedgenet-2016-104509 -
Epilepsia Apr 2021We sought to identify novel genes and to establish the contribution of known genes in a large cohort of patients with nonsyndromic sporadic polymicrogyria and epilepsy.
OBJECTIVE
We sought to identify novel genes and to establish the contribution of known genes in a large cohort of patients with nonsyndromic sporadic polymicrogyria and epilepsy.
METHODS
We enrolled participants with polymicrogyria and their parents through the Epilepsy Phenome/Genome Project. We performed phenotyping and whole exome sequencing (WES), trio analysis, and gene-level collapsing analysis to identify de novo or inherited variants, including germline or mosaic (postzygotic) single nucleotide variants, small insertion-deletion (indel) variants, and copy number variants present in leukocyte-derived DNA.
RESULTS
Across the cohort of 86 individuals with polymicrogyria and epilepsy, we identified seven with pathogenic or likely pathogenic variants in PIK3R2, including four germline and three mosaic variants. PIK3R2 was the only gene harboring more than expected de novo variants across the entire cohort, and likewise the only gene that passed the genome-wide threshold of significance in the gene-level rare variant collapsing analysis. Consistent with previous reports, the PIK3R2 phenotype consisted of bilateral polymicrogyria concentrated in the perisylvian region with macrocephaly. Beyond PIK3R2, we also identified one case each with likely causal de novo variants in CCND2 and DYNC1H1 and biallelic variants in WDR62, all genes previously associated with polymicrogyria. Candidate genetic explanations in this cohort included single nucleotide de novo variants in other epilepsy-associated and neurodevelopmental disease-associated genes (SCN2A in two individuals, GRIA3, CACNA1C) and a 597-kb deletion at 15q25, a neurodevelopmental disease susceptibility locus.
SIGNIFICANCE
This study confirms germline and postzygotically acquired de novo variants in PIK3R2 as an important cause of bilateral perisylvian polymicrogyria, notably with macrocephaly. In total, trio-based WES identified a genetic diagnosis in 12% and a candidate diagnosis in 6% of our polymicrogyria cohort. Our results suggest possible roles for SCN2A, GRIA3, CACNA1C, and 15q25 deletion in polymicrogyria, each already associated with epilepsy or other neurodevelopmental conditions without brain malformations. The role of these genes in polymicrogyria will be further understood as more patients with polymicrogyria undergo genetic evaluation.
Topics: Child; Child, Preschool; Cohort Studies; Epilepsy; Female; Genetic Predisposition to Disease; Genetic Variation; Humans; Male; Phosphatidylinositol 3-Kinases; Polymicrogyria
PubMed: 33818783
DOI: 10.1111/epi.16854 -
Annals of Indian Academy of Neurology 2022Polymicrogyria (PMG) is a relatively common complex malformation with cortical development, characterized by an exorbitant number of abnormally tiny gyri separated by...
Polymicrogyria (PMG) is a relatively common complex malformation with cortical development, characterized by an exorbitant number of abnormally tiny gyri separated by shallow sulci. It is a neuronal migration disorder. Familial cases of PMG and the manifestation of PMG in patients with chromosomal aberrations and mutations indicate their important role of genetics in this disorder. The highly stereotyped and well-conserved nature of the cortical folding pattern in humans is suggestive of the genetic regulation of the process. The chromosomal abnormalities observed in PMG include deletions, duplications, chromosomal rearrangements, and aneuploidies. Two of the most common deletions in PMG are 22q11.2 deletion and 1p36 deletion. Further, mutations in several genes such as , and are known to be associated with PMG. Intriguingly, these genes are responsible only for a small number of cases of PMG. The protein products of these genes are implicated in diverse molecular and cellular functions. Taken together, PMG could be the result of the disruption of several biological pathways. Different modes of Mendelian inheritance and non-Mendelian inheritance are seen in PMG. We have suggested a gene panel that can be used for the detection of malformations of cortical development.
PubMed: 36211152
DOI: 10.4103/aian.aian_97_22 -
Molecular Syndromology Sep 2016Malformations of cortical development (MCD) represent a major cause of developmental disabilities, severe epilepsy, and reproductive disadvantage. Genes that have been... (Review)
Review
Malformations of cortical development (MCD) represent a major cause of developmental disabilities, severe epilepsy, and reproductive disadvantage. Genes that have been associated to MCD are mainly involved in cell proliferation and specification, neuronal migration, and late cortical organization. Lissencephaly-pachygyria-severe band heterotopia are diffuse neuronal migration disorders causing severe global neurological impairment. Abnormalities of the , , , , , , , , and genes have been associated with these malformations. More recent studies have also established a relationship between lissencephaly, with or without associated microcephaly, corpus callosum dysgenesis as well as cerebellar hypoplasia, and at times, a morphological pattern consistent with polymicrogyria with mutations of several genes , , , , , and , regulating the synthesis and function of microtubule and centrosome key components and hence defined as tubulinopathies. MCD only affecting subsets of neurons, such as mild subcortical band heterotopia and periventricular heterotopia, have been associated with abnormalities of the , , and genes and cause neurological and cognitive impairment that vary from severe to mild deficits. Polymicrogyria results from abnormal late cortical organization and is inconstantly associated with abnormal neuronal migration. Localized polymicrogyria has been associated with anatomo-specific deficits, including disorders of language and higher cognition. Polymicrogyria is genetically heterogeneous, and only in a small minority of patients, a definite genetic cause has been identified. Megalencephaly with normal cortex or polymicrogyria by MRI imaging, hemimegalencephaly and focal cortical dysplasia can all result from mutations in genes of the PI3K-AKT-mTOR pathway. Postzygotic mutations have been described for most MCD and can be limited to the dysplastic tissue in the less diffuse forms.
PubMed: 27781032
DOI: 10.1159/000448639 -
AJNR. American Journal of Neuroradiology Nov 2022The presence of malformations of cortical development in patients with hereditary hemorrhagic telangiectasia has been reported on previous occasions. We evaluated a...
BACKGROUND AND PURPOSE
The presence of malformations of cortical development in patients with hereditary hemorrhagic telangiectasia has been reported on previous occasions. We evaluated a sample of adults with hereditary hemorrhagic telangiectasia for the presence of malformations of cortical development, spatial coincidence of malformations of cortical development and AVMs, and the coincidence of brain and pulmonary AVMs.
MATERIALS AND METHODS
A total of 141 patients 18 years of age or older who were referred to the Augusta University hereditary hemorrhagic telangiectasia clinic and underwent brain MR imaging between January 19, 2018, and December 3, 2020, were identified. MR imaging examinations were reviewed retrospectively by 2 experienced neuroradiologists, and the presence of malformations of cortical development and AVMs was confirmed by consensus. Demographic and clinical information was collected for each case, including age, sex, hereditary hemorrhagic telangiectasia status by the Curacao Criteria, mutation type, presence of malformations of cortical development, presence of brain AVMs, presence of pulmonary AVMs, and a history of seizures or learning disabilities.
RESULTS
Five of 141 (3.5%) patients with hereditary hemorrhagic telangiectasia had malformations of cortical development. Two of the 5 patients with polymicrogyria also had closed-lip schizencephaly. One of the patients had a porencephalic cavity partially lined with heterotopic GM. The incidence of spatially coincident polymicrogyria and brain AVMs was 40% (2/5 cases). Of the patients with hereditary hemorrhagic telangiectasia and malformations of cortical development, 4/5 (80%) had pulmonary AVMs and 2/5 (40%) had brain AVMs.
CONCLUSIONS
To our knowledge, we are the first group to report the presence of schizencephaly in patients with hereditary hemorrhagic telangiectasia. The presence of schizencephaly and porencephaly lends support to the hypothesis of regional in utero cerebral hypoxic events as the etiology of malformations of cortical development in hereditary hemorrhagic telangiectasia.
Topics: Adult; Humans; Adolescent; Telangiectasia, Hereditary Hemorrhagic; Schizencephaly; Polymicrogyria; Retrospective Studies; Arteriovenous Malformations
PubMed: 36265891
DOI: 10.3174/ajnr.A7677 -
AJNR. American Journal of Neuroradiology Nov 2018
Topics: Humans; Polymicrogyria; Pyramidal Tracts
PubMed: 30287457
DOI: 10.3174/ajnr.A5822