Search

Purpose To characterize a novel neurodevelopmental syndrome due to loss-of-function (LoF) variants in Ankyrin 2 (ANK2), and to explore the effects on neuronal network dynamics and homeostatic plasticity in human-induced pluripotent stem cell-derived neurons. Methods We collected clinical and molecular data of 12 individuals with heterozygous de novo LoF variants in ANK2. We generated a heterozygous LoF allele of ANK2 using CRISPR/Cas9 in human-induced pluripotent stem cells (hiPSCs). HiPSCs were differentiated into excitatory neurons, and we measured their spontaneous electrophysiological responses using micro-electrode arrays (MEAs). We also characterized their somatodendritic morphology and axon initial segment (AIS) structure and plasticity. Results We found a broad neurodevelopmental disorder (NDD), comprising intellectual disability, autism spectrum disorders and early onset epilepsy. Using MEAs, we found that hiPSC-derived neurons with heterozygous LoF of ANK2 show a hyperactive and desynchronized neuronal network. ANK2-deficient neurons also showed increased somatodendritic structures and altered AIS structure of which its plasticity is impaired upon activity-dependent modulation. Conclusions Phenotypic characterization of patients with de novo ANK2 LoF variants defines a novel NDD with early onset epilepsy. Our functional in vitro data of ANK2-deficient human neurons show a specific neuronal phenotype in which reduced ANKB expression leads to hyperactive and desynchronized neuronal network activity, increased somatodendritic complexity and AIS structure and impaired activity-dependent plasticity of the AIS.

ObjectiveVariants inSCN8Aare associated with a spectrum of epilepsies and neurodevelopmental disorders. Ataxia as a predominant symptom ofSCN8Avariation has not been well studied. We set out to investigate disease mechanisms and genotype-phenotype correlations ofSCN8A-related ataxia.MethodsWe collected genetic and electro-clinical data of ten individuals from nine unrelated families carrying novelSCN8Avariants associated with chronic progressive or episodic ataxia. Electrophysiological characterizations of these variants were performed in ND7/23 cells and cultured neurons.ResultsVariants associated with chronic progressive ataxia either significantly decreased Na+current densities and shifted activation curves towards more depolarized potentials (p.Asn995Asp, p.Lys1498Glu and p.Trp1266Cys) or resulted in a premature stop codon (p.Trp937Ter), i.e. strong loss-of-function (LOF) effects. Three variants (p.Arg847Gln and biallelic p.Arg191Trp/p.Asp1525Tyr) were associated with episodic ataxia causing LOF by decreasing Na+current densities or a hyperpolarizing shift of the inactivation curve. Two additional episodic ataxia-associated variants caused mixed gain-and loss-of function effects in ND7/23 cells and were further examined in primary murine hippocampal neuronal cultures. Neuronal firing in excitatory neurons was increased by p.Arg1629His, but decreased by p.Glu1201Lys. Neuronal firing in inhibitory neurons was decreased for both variants. No functional effect was observed for p.Arg1913Trp. In four individuals, treatment with sodium channel blockers exacerbated symptoms.InterpretationWe identified episodic or chronic ataxia as new phenotypes caused by variants inSCN8A. Genotype-phenotype correlations revealed a more pronounced LOF effect for variants causing chronic ataxia. Sodium channel blockers should be avoided under these conditions.Summary for Social MediaTwitter handles@cmbosselmann, @FiladelfiaGene1, @Katrine92658231, @ElegardellaWhat is the current knowledge on the topic?Variants inSCN8A, a gene encoding the voltage-gated sodium channel NaV1.6, are associated with neurodevelopmental disorders, including epilepsy, intellectual disability, and autism spectrum disorder.What question did this study address?This study investigated whetherSCN8Avariants can cause predominant episodic or chronic ataxia, as well as the cellular and molecular mechanisms underlying these variants.What does this study add to our knowledge?Episodic or chronic ataxia as a sole or predominant symptom caused by NaV1.6 channel loss-of-function comprise new phenotypes in the broad spectrum associated withSCN8Adysfunction. Genotype-phenotype correlations help to differentiate between chronic and episodic ataxia.How might this potentially impact on the practice of neurology?Loss-of-functionSCN8Avariants may represent an underdiagnosed etiology in hereditary ataxia. Treatment with sodium channel blockers, commonly prescribed in other types of episodic ataxia, may harm these individuals, and should be avoided.

Naarmate van steeds meer ziektebeelden de genetische achtergrond bekend wordt, ontstaat de mogelijkheid om gerichte behandeling te geven, niet alleen afgestemd op de persoon, maar ook gericht op het onderliggende moleculaire proces. In deze bijdrage staan we stil bij precision medicine bij epilepsie, dat op drie niveaus kan plaatsvinden.

PURPOSE: Germline loss-of-function variants in CTNNB1 cause neurodevelopmental disorder with spastic diplegia and visual defects (NEDSDV; OMIM 615075) and are the most frequent, recurrent monogenic cause of cerebral palsy (CP). We investigated the range of clinical phenotypes owing to disruptions of CTNNB1 to determine the association between NEDSDV and CP.METHODS: Genetic information from 404 individuals with collectively 392 pathogenic CTNNB1 variants were ascertained for the study. From these, detailed phenotypes for 52 previously unpublished individuals were collected and combined with 68 previously published individuals with comparable clinical information. The functional effects of selected CTNNB1 missense variants were assessed using TOPFlash assay.RESULTS: The phenotypes associated with pathogenic CTNNB1 variants were similar. A diagnosis of CP was not significantly associated with any set of traits that defined a specific phenotypic subgroup, indicating that CP is not additional to NEDSDV. Two CTNNB1 missense variants were dominant negative regulators of WNT signaling, highlighting the utility of the TOPFlash assay to functionally assess variants.CONCLUSION: NEDSDV is a clinically homogeneous disorder irrespective of initial clinical diagnoses, including CP, or entry points for genetic testing.

The congenital bone marrow failure syndrome Diamond-Blackfan anemia (DBA) is typically associated with variants in ribosomal protein (RP) genes impairing erythroid cell development. Here we report multiple individuals with biallelic HEATR3 variants exhibiting bone marrow failure, short stature, facial and acromelic dysmorphic features, and intellectual disability. These variants destabilize a protein whose yeast homolog is known to synchronize the nuclear import of RPs uL5 (RPL11) and uL18 (RPL5), which are both critical for producing ribosomal subunits and for stabilizing the p53 tumor suppressor when ribosome biogenesis is compromised. Expression of HEATR3 variants or repression of HEATR3 expression in primary cells, cell lines of various origins, and yeast models impairs growth, differentiation, pre-ribosomal RNA processing, and ribosomal subunit formation reminiscent of DBA models of large subunit RP gene variants. Consistent with a role of HEATR3 in RP import, HEATR3-depleted cells or patient-derived fibroblasts display reduced nuclear accumulation of uL18. Hematopoietic progenitor cells expressing HEATR3 variants or small-hairpin RNAs knocking down HEATR3 synthesis reveal abnormal acceleration of erythrocyte maturation coupled to severe proliferation defects that are independent of p53 activation. Our study uncovers a new pathophysiological mechanism leading to DBA driven by biallelic HEATR3 variants and the destabilization of a nuclear import protein important for ribosome biogenesis. ispartof: Blood vol:139 issue:21 pages:3111-3126 ispartof: location:United States status: Published online

Background and ObjectivesPathogenic variants in the neuronal sodium channel α1 subunit gene (SCN1A) are the most frequent monogenic cause of epilepsy. Phenotypes comprise a wide clinical spectrum, including severe childhood epilepsy; Dravet syndrome, characterized by drug-resistant seizures, intellectual disability, and high mortality; and the milder genetic epilepsy with febrile seizures plus (GEFS+), characterized by normal cognition. Early recognition of a child's risk for developing Dravet syndrome vs GEFS+ is key for implementing disease-modifying therapies when available before cognitive impairment emerges. Our objective was to develop and validate a prediction model using clinical and genetic biomarkers for early diagnosis of SCN1A-related epilepsies.MethodsWe performed a retrospective multicenter cohort study comprising data from patients with SCN1A-positive Dravet syndrome and patients with GEFS+ consecutively referred for genetic testing (March 2001–June 2020) including age at seizure onset and a newly developed SCN1A genetic score. A training cohort was used to develop multiple prediction models that were validated using 2 independent blinded cohorts. Primary outcome was the discriminative accuracy of the model predicting Dravet syndrome vs other GEFS+ phenotypes.ResultsA total of 1,018 participants were included. The frequency of Dravet syndrome was 616/743 (83%) in the training cohort, 147/203 (72%) in validation cohort 1, and 60/72 (83%) in validation cohort 2. A high SCN1A genetic score (133.4 [SD 78.5] vs 52.0 [SD 57.5]; p < 0.001) and young age at onset (6.0 [SD 3.0] vs 14.8 [SD 11.8] months; p < 0.001) were each associated with Dravet syndrome vs GEFS+. A combined SCN1A genetic score and seizure onset model separated Dravet syndrome from GEFS+ more effectively (area under the curve [AUC] 0.89 [95% CI 0.86–0.92]) and outperformed all other models (AUC 0.79–0.85; p < 0.001). Model performance was replicated in both validation cohorts 1 (AUC 0.94 [95% CI 0.91–0.97]) and 2 (AUC 0.92 [95% CI 0.82–1.00]).DiscussionThe prediction model allows objective estimation at disease onset whether a child will develop Dravet syndrome vs GEFS+, assisting clinicians with prognostic counseling and decisions on early institution of precision therapies (http://scn1a-prediction-model.broadinstitute.org/).Classification of EvidenceThis study provides Class II evidence that a combined SCN1A genetic score and seizure onset model distinguishes Dravet syndrome from other GEFS+ phenotypes.

Een monogene oorzaak bij focale epilepsie is minder zeldzaam dan vroeger werd gedacht. De meest voorkomende groep erfelijke, focale epilepsieën worden veroorzaakt door varianten in de GATOR1 complex genen (DEPDC5, NPRL2 en NPRL3), ook wel de ‘GATORopathieën’ genoemd. Er is steeds meer bekend over de verschillende ziekte-uitingen van deze aandoeningen, en zelfs over de consequenties voor behandeling. Dit maakt genetische diagnostiek belangrijk.

De kennis over genetische oorzaken van epilepsie, de mogelijkheden van genetische diagnostiek en de implicaties van een genetische diagnose nemen steeds meer toe. Deze bijdrage geeft een overzicht van de huidige stand van zaken.

Objective The study is aimed at widening the clinical and genetic spectrum and at assessing genotype-phenotype associations in QARS encephalopathy. Methods Through diagnostic gene panel screening in an epilepsy cohort, and recruiting through GeneMatcher and our international network, we collected 10 patients with biallelic QARS variants. In addition, we collected data on 12 patients described in the literature to further delineate the associated phenotype in a total cohort of 22 patients. Computer modeling was used to assess changes on protein folding. Results Biallelic pathogenic variants in QARS cause a triad of progressive microcephaly, moderate to severe developmental delay, and early-onset epilepsy. Microcephaly was present at birth in 65%, and in all patients at follow-up. Moderate (14%) or severe (73%) developmental delay was characteristic, with no achievement of sitting (85%), walking (86%), or talking (90%). Additional features included irritability (91%), hypertonia/spasticity (75%), hypotonia (83%), stereotypic movements (75%), and short stature (56%). Seventy-nine percent had pharmacoresistant epilepsy with mainly neonatal onset. Characteristic cranial MRI findings include early-onset progressive atrophy of cerebral cortex (89%) and cerebellum (61%), enlargement of ventricles (95%), and age-dependent delayed myelination (88%). A small subset of patients displayed a less severe phenotype. Conclusions These data revealed first genotype-phenotype associations and may serve for improved interpretation of new QARS variants and well-founded genetic counseling.

Recurrent and prolonged seizures are harmful for the developing brain, emphasizing the importance of early seizure recognition and effective therapy. Amplitude-integrated electroencephalography (aEEG) has become a valuable tool to diagnose epileptic seizures, and, in parallel, genetic etiologies are increasingly being recognized, changing the paradigm of the workup and management of neonatal seizures.To report the ictal aEEG pattern in neonates with KCNQ2-related epilepsy.In this multicenter descriptive study, clinical data and aEEG findings of 9 newborns with KCNQ2 mutations are reported.Refractory seizures occurred in the early neonatal period with similar seizure type, including tonic features, apnea, and desaturation. A distinct aEEG seizure pattern, consisting of a sudden rise of the lower and upper margin of the aEEG, followed by a marked depression of the aEEG amplitude, was found in 8 of the 9 patients. Prompt recognition of this pattern led to early treatment with carbamazepine in the 2 most recent cases.Early recognition of the electroclinical phenotype by using aEEG may direct genetic testing and a precision medicine approach with sodium channel blockers in neonates with KCNQ2 mutations.

‘Hij móet wel een genetische afwijking hebben. Ik weet alleen niet wat’. Op het spreekuur zien artsen die werken met patiënten met een verstandelijke beperking en epilepsie regelmatig patiënten bij wie gedacht wordt aan een genetische afwijking. Ze hebben bijvoorbeeld een combinatie van epilepsie, dysmorfe kenmerken, snelle veroudering of neurologische achteruitgang. Uit de hier beschreven casus blijkt dat het loont om een duidelijke diagnose te stellen.

Cohen syndrome is characterised by mental retardation, postnatal microcephaly, facial dysmorphism, pigmentary retinopathy, myopia, and intermittent neutropenia. Mutations in COH1 (VPS13B) have been found in patients with Cohen syndrome from diverse ethnic origins. We have carried out mutation analysis in twelve novel patients with Cohen syndrome from nine families. In this series, we have identified 13 different mutations in COH1, twelve of these are novel including six frameshift mutations, four nonsense mutations, two splice site mutations, and a one-codon deletion. Since different transcripts of COH1 have been reported previously, we have analysed the expression patterns of COH1 splice variants. The transcript variant NM_152564 including exon 28b showed ubiquitous expression in all examined human tissues. In contrast, human brain and retina showed differential splicing of exon 28 (NM_017890). Moreover, analysis of mouse tissues revealed ubiquitous expression of Coh1 homologous to human NM_152564 in all examined tissues but no prevalent alternative splicing.