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Monoallelic and bi-allelic variants in NCDN cause neurodevelopmental delay, intellectual disability, and epilepsy.

ABSTRACT: Neurochondrin (NCDN) is a cytoplasmatic neural protein of importance for neural growth, glutamate receptor (mGluR) signaling, and synaptic plasticity. Conditional loss of Ncdn in mice neural tissue causes depressive-like behaviors, impaired spatial learning, and epileptic seizures. We report on NCDN missense variants in six affected individuals with variable degrees of developmental delay, intellectual disability (ID), and seizures. Three siblings were found homozygous for a NCDN missense variant, whereas another three unrelated individuals carried different de novo missense variants in NCDN. We assayed the missense variants for their capability to rescue impaired neurite formation in human neuroblastoma (SH-SY5Y) cells depleted of NCDN. Overexpression of wild-type NCDN rescued the neurite-phenotype in contrast to expression of NCDN containing the variants of affected individuals. Two missense variants, associated with severe neurodevelopmental features and epilepsy, were unable to restore mGluR5-induced ERK phosphorylation. Electrophysiological analysis of SH-SY5Y cells depleted of NCDN exhibited altered membrane potential and impaired action potentials at repolarization, suggesting NCDN to be required for normal biophysical properties. Using available transcriptome data from human fetal cortex, we show that NCDN is highly expressed in maturing excitatory neurons. In combination, our data provide evidence that bi-allelic and de novo variants in NCDN cause a clinically variable form of neurodevelopmental delay and epilepsy, highlighting a critical role for NCDN in human brain development.

SUBMITTER: Fatima A

PROVIDER: S-EPMC8059333 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:We aimed to define a novel autosomal recessive neurodevelopmental disorder, characterize its clinical features, and identify the underlying genetic cause for this condition. Clinical and genetic data from affected individuals with neurological disorders were matched across families from five global sites. Here, we report five recessive CSPG4 (NM_001897) missense variants [three homozygous: c.A1370G (p.Asp457Gly), c.2627G>A (p.Arg876His) and c.3247C>A (p.Gln1083Lys), and two compound heterozygote: c.A1370G and c.5156A>G (p.Asp457Gly and p.Gln1719Arg) and c.658A>G and c.1220_1221delinsTG (p.(Thr220Ala and p.Pro407Leu)] by next-generation sequencing of five unrelated families with seven affected subjects. All subjects share a novel neurodevelopmental syndrome characterized by severe intellectual disability, global developmental delay, delayed ability to walk, speech and language delay, distinctive facial features, along with varying degrees of neurological impairment, including hypotonia, cerebellar hypoplasia, and/or seizures. All CSPG4 variants were predicted to be damaging using in silico tools, and three-dimensional molecular modeling suggested significant alterations in protein stability, compromising inter- and intra-molecular interactions. The impact on neurological and craniofacial development was analyzed in CRISPR/Cas9-mediated zebrafish models. CSPG4 variants affected notochord development, neuronal function, and cerebellar structure along with a disorganized head scaffold with anomalous skeletal and cartilage components. Two individuals metabolomics and crispant transcriptomics revealed significant perturbation of metabolites, extracellular matrix (ECM) regulating pathways, and genes previously described to cause mental retardation, dwarfism, and facial anomalies in humans. Our study links novel, rare, damaging variants of the ECM gene CSPG4 to a novel recessive Mendelian neurodevelopmental disorder in humans and supports the role of CSPG4 in early development.

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Monoallelic and bi-allelic variants in NCDN cause neurodevelopmental delay, intellectual disability, and epilepsy.

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