Objective: To identify the genetic basis of a family segregating episodic ataxia, infantile seizures, and heterogeneous epilepsies and to study the phenotypic spectrum of KCNA2 mutations.
Methods: A family with 7 affected individuals over 3 generations underwent detailed phenotyping. Whole genome sequencing was performed on a mildly affected grandmother and her grandson with epileptic encephalopathy (EE). Segregating variants were filtered and prioritized based on functional annotations. The effects of the mutation on channel function were analyzed in vitro by voltage clamp assay and in silico by molecular modeling. KCNA2 was sequenced in 35 probands with heterogeneous phenotypes.
Results: The 7 family members had episodic ataxia (5), self-limited infantile seizures (5), evolving to genetic generalized epilepsy (4), focal seizures (2), and EE (1). They had a segregating novel mutation in the shaker type voltage-gated potassium channel KCNA2 (CCDS_827.1: c.765_773del; p.255_257del). A rare missense SCN2A (rs200884216) variant was also found in 2 affected siblings and their unaffected mother. The p.255_257del mutation caused dominant negative loss of channel function. Molecular modeling predicted repositioning of critical arginine residues in the voltage-sensing domain. KCNA2 sequencing revealed 1 de novo mutation (CCDS_827.1: c.890G>A; p.Arg297Gln) in a girl with EE, ataxia, and tremor.
Conclusions: A KCNA2 mutation caused dominantly inherited episodic ataxia, mild infantile-onset seizures, and later generalized and focal epilepsies in the setting of normal intellect. This observation expands the KCNA2 phenotypic spectrum from EE often associated with chronic ataxia, reflecting the marked variation in severity observed in many ion channel disorders.
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http://dx.doi.org/10.1212/WNL.0000000000003309 | DOI Listing |
Proc Natl Acad Sci U S A
January 2025
Bioelectricity Laboratory, Department of Physiology and Biophysics, School of Medicine, University of California, Irvine, CA 92697.
Loss-of-function sequence variants in , which encodes the voltage-gated potassium channel Kv1.1, cause Episodic Ataxia Type 1 (EA1) and epilepsy. Due to a paucity of drugs that directly rescue mutant Kv1.
View Article and Find Full Text PDFBrain Commun
December 2024
Dipartimento Universitario di Neuroscienze, Università Cattolica del Sacro Cuore, 00168 Roma, Italy.
Familial hemiplegic migraine type 2 results from pathogenic variants in the gene, which encodes for a catalytic subunit of sodium/potassium ATPase. This extremely rare autosomal dominant disorder manifests with a spectrum of symptoms, most commonly pure hemiplegic phenotype, epilepsy, and/or intellectual disability. In this study, we detail the clinical features and genetic analysis of nine patients from a large family spanning four generations, with all carrying a previously unreported likely pathogenic variant, p.
View Article and Find Full Text PDFJ Vet Intern Med
December 2024
Small Animal Hospital, School of Veterinary Medicine, University of Glasgow, Glasgow, United Kingdom.
Background: Episodic ataxias (EAs) are a rare group of paroxysmal movement disorders (PMD) described in human medicine with only one suspected case described in veterinary literature.
Hypothesis/objectives: This study aimed to provide clinical description of a suspected primary EA in working Cocker Spaniel (WCS) dogs.
Animals: Seven WCS dogs with suspected primary EA.
Mov Disord Clin Pract
December 2024
Service de Neuropédiatrie, CHU Montpellier, Montpellier, France.
Cell Commun Signal
November 2024
Department of Physiology, College of Medicine, National Taiwan University, Taipei, 100, Taiwan.
Loss-of-function mutations in the human gene encoding the neuron-specific Ca channel Ca2.1 are linked to the neurological disease episodic ataxia type 2 (EA2), as well as neurodevelopmental disorders such as developmental delay and developmental epileptic encephalopathy. Disease-associated Ca2.
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