OBJECTIVE:Polymicrogyria (PMG) is one of the most common human malformations of cortical development and is often classified by its radiographic pattern of distribution. Unilateral polymicrogyria (uPMG) is a subtype of PMG affecting a portion or all of one cerebral hemisphere. As most PMGs occur bilaterally, there has been no specific investigation as to whether the genetic underpinnings of uPMG comprise a subset of or a distinct entity from bilateral PMG. In this study, our goal was to assess both the genetic etiology of uPMG and the value of diagnostic genetic testing in this setting. METHODS:We conducted a retrospective analysis of clinical data from individuals with uPMG seen in the Brain Development and Genetics Clinic and/or research participants of the Walsh Laboratory at Boston Children's Hospital. The final study cohort included 35 individuals from 30 families who were diagnosed with uPMG on brain magnetic resonance imaging (MRI) and also underwent genetic testing. RESULTS:A likely genetic cause was identified in 26.7% (8/30) of unrelated individuals with uPMG in this cohort and segregated within one family (10/35 total subjects). Recessive genetic causes included ASPM, WDR62, and TMEM216. Dominant causes included 22q deletion syndrome, DYNC1H1, SCN3A, and hereditary hemorrhagic telangiectasia (HHT) genes, ACVRL1 and ENG. This is the first report of variants in DYNC1H1, TMEM216, and ACVRL1 in association with uPMG. INTERPRETATION:The genetic causes of bilateral PMG and uPMG can overlap, but some are unique to certain distributions of the malformation. Genetic explanations for uPMG are found at comparable rates to bilateral PMG, suggesting that germline testing for this unique presentation is warranted. ANN NEUROL 2026;99:1277-1286.

CUL1 encodes a scaffolding protein of the SKP1-CUL1-F-box E3 ubiquitin ligase complex, which mediates substrate ubiquitination and proteasomal degradation. Despite CUL1’s essential roles, it has not been implicated in human disease. We identified ten unrelated individuals with a syndromic neurodevelopmental disorder, with or without movement abnormalities carrying de novo heterozygous CUL1 variants. Patient-derived iPSCs with p.Lys515Glu exhibited elevated cyclin E level, a CUL1 target. Co-transfection with CUL1 and ubiquitin demonstrated that truncating variants (p.Arg565* and p.Gly512Trpfs*51) impaired polyubiquitin chain formation on β-catenin, supporting a dominant-negative mechanism. In vivo , neural-specific knockdown of Cul1 in Drosophila reduced survival and motor function, while enhancing sensory dendrite regeneration. These phenotypes were differentially rescued by human CUL1 wild-type (WT), p.Leu671Val or truncating variants. WT CUL1 or p.Leu671Val failed to rescue the impaired social interaction in Cul1 knockdown flies, whereas the two truncating variants exacerbated the deficit. Overexpression of p.Arg565* and p.Gly512Trpfs*51 in WT flies recapitulated dendrite regeneration and social deficits, confirming their dominant-negative effects. Their overexpression also caused Akt overactivation, previously shown to be a Cul1 substrate and promote dendrite regeneration, implicating Akt as a downstream effector. These findings establish CUL1 as a novel neurodevelopmental disorder gene and suggest that dominant-negative mechanisms underlie its pathogenesis.

Importance:Polymicrogyria is the most commonly diagnosed cortical malformation and is associated with neurodevelopmental sequelae including epilepsy, motor abnormalities, and cognitive deficits. Polymicrogyria frequently co-occurs with other brain malformations or as part of syndromic diseases. Past studies of polymicrogyria have defined heterogeneous genetic and nongenetic causes but have explained only a small fraction of cases.Objective:To survey germline genetic causes of polymicrogyria in a large cohort and to consider novel polymicrogyria gene associations.Design, Setting, and Participants:This genetic association study analyzed panel sequencing and exome sequencing of accrued DNA samples from a retrospective cohort of families with members with polymicrogyria. Samples were accrued over more than 20 years (1994 to 2020), and sequencing occurred in 2 stages: panel sequencing (June 2015 to January 2016) and whole-exome sequencing (September 2019 to March 2020). Individuals seen at multiple clinical sites for neurological complaints found to have polymicrogyria on neuroimaging, then referred to the research team by evaluating clinicians, were included in the study. Targeted next-generation sequencing and/or exome sequencing were performed on probands (and available parents and siblings) from 284 families with individuals who had isolated polymicrogyria or polymicrogyria as part of a clinical syndrome and no genetic diagnosis at time of referral from clinic, with sequencing from 275 families passing quality control.Main Outcomes and Measures:The number of families in whom genetic sequencing yielded a molecular diagnosis that explained the polymicrogyria in the family. Secondarily, the relative frequency of different genetic causes of polymicrogyria and whether specific genetic causes were associated with co-occurring head size changes were also analyzed.Results:In 32.7% (90 of 275) of polymicrogyria-affected families, genetic variants were identified that provided satisfactory molecular explanations. Known genes most frequently implicated by polymicrogyria-associated variants in this cohort were PIK3R2, TUBB2B, COL4A1, and SCN3A. Six candidate novel polymicrogyria genes were identified or confirmed: de novo missense variants in PANX1, QRICH1, and SCN2A and compound heterozygous variants in TMEM161B, KIF26A, and MAN2C1, each with consistent genotype-phenotype relationships in multiple families.Conclusions and Relevance:This study's findings reveal a higher than previously recognized rate of identifiable genetic causes, specifically of channelopathies, in individuals with polymicrogyria and support the utility of exome sequencing for families affected with polymicrogyria.

While the transcription factor NEUROD2 has recently been associated with epilepsy, its precise role during nervous system development remains unclear. Using a multi-scale approach, we set out to understand how Neurod2 deletion affects the development of the cerebral cortex in mice. In Neurod2 KO embryos, cortical projection neurons over-migrated, thereby altering the final size and position of layers. In juvenile and adults, spine density and turnover were dysregulated in apical but not basal compartments in layer 5 neurons. Patch-clamp recordings in layer 5 neurons of juvenile mice revealed increased intrinsic excitability. Bulk RNA sequencing showed dysregulated expression of many genes associated with neuronal excitability and synaptic function, whose human orthologs were strongly associated with autism spectrum disorders (ASD). At the behavior level, Neurod2 KO mice displayed social interaction deficits, stereotypies, hyperactivity, and occasionally spontaneous seizures. Mice heterozygous for Neurod2 had similar defects, indicating that Neurod2 is haploinsufficient. Finally, specific deletion of Neurod2 in forebrain excitatory neurons recapitulated cellular and behavioral phenotypes found in constitutive KO mice, revealing the region-specific contribution of dysfunctional Neurod2 in symptoms. Informed by these neurobehavioral features in mouse mutants, we identified eleven patients from eight families with a neurodevelopmental disorder including intellectual disability and ASD associated with NEUROD2 pathogenic mutations. Our findings demonstrate crucial roles for Neurod2 in neocortical development, whose alterations can cause neurodevelopmental disorders including intellectual disability and ASD.

Malformations of cortical development (MCDs) are neurodevelopmental disorders that result from abnormal development of the cerebral cortex in utero. MCDs place a substantial burden on affected individuals, their families and societies worldwide, as these individuals can experience lifelong drug-resistant epilepsy, cerebral palsy, feeding difficulties, intellectual disability and other neurological and behavioural anomalies. The diagnostic pathway for MCDs is complex owing to wide variations in presentation and aetiology, thereby hampering timely and adequate management. In this article, the international MCD network Neuro-MIG provides consensus recommendations to aid both expert and non-expert clinicians in the diagnostic work-up of MCDs with the aim of improving patient management worldwide. We reviewed the literature on clinical presentation, aetiology and diagnostic approaches for the main MCD subtypes and collected data on current practices and recommendations from clinicians and diagnostic laboratories within Neuro-MIG. We reached consensus by 42 professionals from 20 countries, using expert discussions and a Delphi consensus process. We present a diagnostic workflow that can be applied to any individual with MCD and a comprehensive list of MCD-related genes with their associated phenotypes. The workflow is designed to maximize the diagnostic yield and increase the number of patients receiving personalized care and counselling on prognosis and recurrence risk.

We identified seven families associating NEUROD2 pathogenic mutations with ASD and intellectual disability. To get insight into the pathophysiological mechanisms, we analyzed cortical development in Neurod2 KO mice. Cortical projection neurons (CPNs) over-migrated during embryogenesis, inducing abnormal thickness and laminar positioning of cortical layers. At juvenile ages, dendritic spine turnover and intrinsic excitability were increased in L5 CPNs. Differentially expressed genes in Neurod2 KO mice were enriched for voltage-gated ion channels, and the human orthologs of these genes were strongly associated with ASD. Furthermore, adult Neurod2 KO mice exhibited core ASD-like behavioral abnormalities. Finally, by generating Neurod2 conditional mutant mice we demonstrate that forebrain excitatory neuron-specific Neurod2 deletion recapitulates cellular and behavioral ASD phenotypes found in full KO mice. Our findings demonstrate crucial roles for Neurod2 in cortical development and function, whose alterations likely account for ASD and related symptoms in the newly defined NEUROD2 mutation syndrome.

Early onset cerebellar Ataxia (EOAc) comprises a large group of rare heterogeneous disorders. Determination of the underlying etiology can be difficult given the broad differential diagnosis and the complexity of the genotype-phenotype relationships. This may change the diagnostic work-up into a time-consuming, costly and not always rewarding task. In this overview, the Childhood Ataxia and Cerebellar Group of the European Pediatric Neurology Society (CACG-EPNS) presents a diagnostic algorithm for EOAc patients. In seven consecutive steps, the algorithm leads the clinician through the diagnostic process, including EOA identification, application of the Inventory of Non-Ataxic Signs (INAS), consideration of the family history, neuro-imaging, laboratory investigations, genetic testing by array CGH and Next Generation Sequencing (NGS). In children with EOAc, this algorithm is intended to contribute to the diagnostic process and to allow uniform data entry in EOAc databases.

Polymicrogyria (PMG) is a heterogeneous brain malformation that may result from prenatal vascular disruption or infection, or from numerous genetic causes that still remain difficult to identify. We identified three unrelated patients with polymicrogyria and duplications of chromosome 2p, defined the smallest region of overlap, and performed gene pathway analysis using Cytoscape. The smallest region of overlap in all three children involved 2p16.1-p16.3. All three children have bilateral perisylvian polymicrogyria (BPP), intrauterine and postnatal growth deficiency, similar dysmorphic features, and poor feeding. Two of the three children had documented intellectual disability. Gene pathway analysis suggested a number of developmentally relevant genes and gene clusters that were over-represented in the critical region. We narrowed a rare locus for polymicrogyria to a region of 2p16.1-p16.3 that contains 33-34 genes, 23 of which are expressed in cerebral cortex during human fetal development. Using pathway analysis, we showed that several of the duplicated genes contribute to neurodevelopmental pathways including morphogen, cytokine, hormonal and growth factor signaling, regulation of cell cycle progression, cell morphogenesis, axonal guidance, and neuronal migration. These findings strengthen the evidence for a novel locus associated with polymicrogyria on 2p16.1-p16.3, and comprise the first step in defining the underlying genetic etiology.

AbstractWe identified seven families associatingNEUROD2pathogenic mutations with ASD and intellectual disability. To get insight into the pathophysiological mechanisms, we analyzed cortical development inNeurod2KO mice. Cortical projection neurons (CPNs) over-migrated during embryogenesis, inducing abnormal thickness and laminar positioning of cortical layers. At juvenile ages, dendritic spine turnover and intrinsic excitability were increased in L5 CPNs. Differentially expressed genes inNeurod2KO mice were enriched for voltage-gated ion channels, and the human orthologs of these genes were strongly associated with ASD. Furthermore, adultNeurod2KO mice exhibited core ASD-like behavioral abnormalities. Finally, by generatingNeurod2conditional mutant mice we demonstrate that forebrain excitatory neuron-specificNeurod2deletion recapitulates cellular and behavioral ASD phenotypes found in full KO mice. Our findings demonstrate crucial roles forNeurod2in cortical development and function, whose alterations likely account for ASD and related symptoms in the newly definedNEUROD2mutation syndrome.

Channelopathies are disorders caused by abnormal ion channel function in differentiated excitable tissues. We discovered a unique neurodevelopmental channelopathy resulting from pathogenic variants in SCN3A, a gene encoding the voltage-gated sodium channel NaV1.3. Pathogenic NaV1.3 channels showed altered biophysical properties including increased persistent current. Remarkably, affected individuals showed disrupted folding (polymicrogyria) of the perisylvian cortex of the brain but did not typically exhibit epilepsy; they presented with prominent speech and oral motor dysfunction, implicating SCN3A in prenatal development of human cortical language areas. The development of this disorder parallels SCN3A expression, which we observed to be highest early in fetal cortical development in progenitor cells of the outer subventricular zone and cortical plate neurons and decreased postnatally, when SCN1A (NaV1.1) expression increased. Disrupted cerebral cortical folding and neuronal migration were recapitulated in ferrets expressing the mutant channel, underscoring the unexpected role of SCN3A in progenitor cells and migrating neurons.

Background Despite progress in understanding the genetics of rare epilepsies, the more common epilepsies have proven less amenable to traditional gene-discovery analyses. We aimed to assess the contribution of ultra-rare genetic variation to common epilepsies.Methods We did a case-control sequencing study with exome sequence data from unrelated individuals clinically evaluated for one of the two most common epilepsy syndromes: familial genetic generalised epilepsy, or familial or sporadic non-acquired focal epilepsy. Individuals of any age were recruited between Nov 26, 2007, and Aug 2, 2013, through the multicentre Epilepsy Phenome/Genome Project and Epi4K collaborations, and samples were sequenced at the Institute for Genomic Medicine (New York, USA) between Feb 6, 2013, and Aug 18, 2015. To identify epilepsy risk signals, we tested all protein-coding genes for an excess of ultra-rare genetic variation among the cases, compared with control samples with no known epilepsy or epilepsy comorbidity sequenced through unrelated studies.Findings We separately compared the sequence data from 640 individuals with familial genetic generalised epilepsy and 525 individuals with familial non-acquired focal epilepsy to the same group of 3877 controls, and found significantly higher rates of ultra-rare deleterious variation in genes established as causative for dominant epilepsy disorders (familial genetic generalised epilepsy: odd ratio [OR] 2.3, 95% CI 1.7-3.2, p=9.1 x 10(-8); familial non acquired focal epilepsy 3.6, 2.7-4.9, p=1.1 x 10(17)). Comparison of an additional cohort of 662 individuals with sporadic non-acquired focal epilepsy to controls did not identify study-wide significant signals. For the individuals with familial non-acquired focal epilepsy, we found that five known epilepsy genes ranked as the top five genes enriched for ultra-rare deleterious variation. After accounting for the control carrier rate, we estimate that these five genes contribute to the risk of epilepsy in approximately 8% of individuals with familial non-acquired focal epilepsy. Our analyses showed that no individual gene was significantly associated with familial genetic generalised epilepsy; however, known epilepsy genes had lower p values relative to the rest of the protein-coding genes (p=5.8 x 10(-8)) that were lower than expected from a random sampling of genes.Interpretation We identified excess ultra-rare variation in known epilepsy genes, which establishes a clear connection I between the genetics of common and rare, severe epilepsies, and shows that the variants responsible for epilepsy risk are exceptionally rare in the general population. Our results suggest that the emerging paradigm of targeting of treatments to the genetic cause in rare devastating epilepsies might also extend to a proportion of common epilepsies. These findings might allow clinicians to broadly explain the cause of these syndromes to patients, and lay the foundation for possible precision treatments in the future.

(The American Journal of Human Genetics 95, 360–370; October 2, 2014) In the list of consortium members for the Epilepsy Phenome/Genome Project, member Dina Amrom’s name was misspelled as Amron. The authors regret the error. De Novo Mutations in Synaptic Transmission Genes Including DNM1 Cause Epileptic EncephalopathiesAppenzeller et al.The American Journal of Human GeneticsSeptember 25, 2014In BriefEmerging evidence indicates that epileptic encephalopathies are genetically highly heterogeneous, underscoring the need for large cohorts of well-characterized individuals to further define the genetic landscape. Through a collaboration between two consortia (EuroEPINOMICS and Epi4K/EPGP), we analyzed exome-sequencing data of 356 trios with the “classical” epileptic encephalopathies, infantile spasms and Lennox Gastaut syndrome, including 264 trios previously analyzed by the Epi4K/EPGP consortium. Full-Text PDF Open Archive

Infantile spasms (IS) and Lennox–Gastaut syndrome (LGS) are epileptic encephalopathies characterized by early onset, intractable seizures, and poor developmental outcomes. De novo sequence mutations and copy number variants (CNVs) are causative in a subset of cases. We used exome sequence data in 349 trios with IS or LGS to identify putative de novo CNVs. We confirm 18 de novo CNVs in 17 patients (4.8%), 10 of which are likely pathogenic, giving a firm genetic diagnosis for 2.9% of patients. Confirmation of exome‐predicted CNVs by array‐based methods is still required due to false‐positive rates of prediction algorithms. Our exome‐based results are consistent with recent array‐based studies in similar cohorts and highlight novel candidate genes for IS and LGS. Ann Neurol 2015;78:323–328

OBJECTIVE: To analyse novel DCX and LIS1 mutations employing phenotypic, molecular and functional/structural techniques. BACKGROUND: Most patients with (SBH/LIS) spectrum have either DCX or LIS1 mutations, associated with predominantly anterior or posterior distribution of the malformation, respectively. DESIGN/METHODS: Detailed review of the phenotype of two patients with SBH/LIS spectrum caused by novel mutations in DCX and LIS1 ; functional analysis of DCX mutation using in vitro fluorescence-based assays with dynamic microtubules; bioinformatic analysis of the LIS1 mutation and mapping on to a structural model of the mutated LIS 1 protein. RESULTS: Patient 1 (Pt1) is a 46-year-old woman of French-Canadian ancestry; Patient 2 (Pt2) is a 28-year-old man of British ancestry. Both patients presented with developmental delay and refractory epilepsy, at 3 and 6 months respectively. Brain MRI in Pt1: double cortex predominating in the frontal regions; in Pt2: predominantly posterior lissencephaly associated with partial callosal agenesis, cavum septum pellucidum, and diffuse cerebellar atrophy. Parents declined genetic testing. DCX sequencing in Pt1 showed a c.578delA variant. LIS1 sequencing in Pt2 revealed duplication of five nucleotides in exon 8 (c.728_732dupATCAA). The recombinant mutated DCX protein was found to be defective in promoting microtubule nucleation and polymerization, and showed impaired cooperative binding to microtubules. The change in the mutated LIS1 protein introduces a five residue stretch of altered sequence followed by a premature stop codon at residue 250, early in the 4th WD repeat of the LIS1 beta propeller. CONCLUSIONS: We report two novel pathogenic variants causing severe phenotypes of the SBH/LIS spectrum. Our functional analyses show that the DCX variant disrupts microtubule binding as well as the cooperative interaction between DCX molecules. Our structural interpretation of the LIS1 variant suggests that the LIS1 protein does not fold properly, is unable to bind dynein, and is likely targeted for degradation in cells. Disclosure: Dr. Amrom has nothing to disclose. Dr. Brouhard has nothing to disclose. Dr. Bechstedt has nothing to disclose. Dr. Toropova has nothing to disclose. Dr. Dubeau has nothing to disclose. Dr. Andermann has nothing to disclose. Dr. Melancon has nothing to disclose. Dr. Tampieri has nothing to disclose. Dr. Reck-Peterson has nothing to disclose. Dr. Andermann has nothing to disclose.

OBJECTIVE: We present a family with 5 individuals in three generations where the clinical pattern consisted largely of nocturnal generalized tonic-clonic seizures (GTCS), but who were then shown to have an LGI1 mutation. BACKGROUND: It is well known that patients with temporal lobe epilepsy may present with nocturnal GTCS; the temporal localization depends on further investigation. DESIGN/METHODS: We discuss the clinical and EEG findings in this family, and compare these with reported families with autosomal dominant partial epilepsy with auditory features (ADPEAF). LGI1 sequencing was performed in the proband. RESULTS: The proband is a 46-year-old female who had four GTCS during sleep, beginning at age 19 years. She has been seizure free since adequate compliance with carbamazepine. An EEG at 22 years showed spikes and slow sharp waves alternating over both temporal regions. During intermittent photic stimulation, a photomyoclonic response appeared. Her 40-year-old sister had her first GTCS at 12 years. Before the only seizure that occurred while awake, she felt numbness of her whole body and heard a whooshing sound. Her 52-year-old sister had her first GTCS at 19 years. A year prior to this, she had transient symptoms of a tingling sensation associated with a whooshing noise. She later had other GTCS preceded by this aura. A diagnosis of lateral temporal epilepsy, possibly ADPEAF, was suggested. Although the proband had only nocturnal GTCS, LGI1 sequencing was performed on the basis of the family history. A c.611delC mutation leading to a frameshift and premature termination of the protein was identified. CONCLUSIONS: Nocturnal and diurnal GTCS as the predominant seizure type in a family with ADPEAF is unusual. They may represent secondarily or primary generalized seizures or both. Photosensitivity is unusual as well. This family illustrates that patients with ADPEAF may present with GTCS, and have marked intrafamilial phenotypic variability. Intensive monitoring and attention to auras with auditory features should lead to accurate diagnosis of this genetically determined epileptic syndrome.

It is well known that patients with temporal lobe epilepsy may present with generalized seizures, and the temporal localization depends on further investigation. We present a family with five individuals in three generations where the clinical pattern consisted largely of generalized seizures, but who were then shown to have epilepsy due to an LGI1 mutation. We wish to discuss the clinical and EEG findings in these patients, and to compare these with families with autosomal dominant partial epilepsy with auditory features (ADPEAF) or familial lateral temporal lobe epilepsy (FLTLE) reported in the literature. The proband is a 46-year-old female college graduate who had normal development and no history of head trauma, central nervous system infection or febrile seizures. She had four nocturnal generalized tonic-clonic seizures (GTCS), all occurred around 5–6 am, the first one at age 19 years. Diphenylhydantoin was prescribed and later replaced by carbamazepine CR. She has been seizure free since adequate compliance with treatment. Her first EEG performed at 19 years showed an excess of slow waves at 2–4 Hz over both posterior head regions without epileptic activity. Her second EEG at 22 years showed spikes and slow spike waves alternating over both temporal regions, mostly during drowsiness, and increased during hyperventilation. During intermittent photic stimulation, a photomyoclonic response appeared. Her 40-year-old sister had her first GTCS at 12 years which was generalized from the onset. All but one of her subsequent attacks occurred during sleep. Before the only seizure that occurred while awake, she felt numbness of her whole body and heard a whooshing sound suggestive of neocortical temporal lobe involvement. The third sister is 52 years old; she had her first GTCS at 19 years. A year prior to this, she had transient symptoms of a tingling sensation associated with a whooshing noise. She later had other generalized attacks preceded by this aura. A diagnosis of neocortical or lateral temporal lobe epilepsy, possibly ADPEAF or FLTLE, was suggested. Although the proband only had nocturnal GTCS, LGI1 sequencing was performed on the basis of the family history. A c.611delC mutation leading to a frameshift and premature termination of the protein was identified. Generalized nocturnal and diurnal seizures associated with interictal generalized spike-wave activity occurring in a family with ADPEAF is unusual. They may represent secondarily generalized seizures or primary generalized seizures or both. In addition, photosensitivity in the proband is unusual as well. Among the reported patients with LGI1 mutation, there are several who have had GTCS and interictal generalized spike-wave and/or polyspike-wave discharges [Ottman et al., 2004]. This family further illustrates that patients with ADPEAF or FLTLE may present with generalized seizures and generalized spike and wave epileptic discharges. Intensive monitoring and attention to aura with auditory features should lead to accurate diagnosis of this genetically determined epileptic syndrome. This report points to the importance of detailed family history to help orient the diagnosis by genetic testing.