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Expanding the genetic and phenotypic relevance of KCNB1 variants in developmental and epileptic encephalopathies: 27 new patients and overview of the literature

2019; Wiley; Volume: 41; Issue: 1 Linguagem: Inglês

10.1002/humu.23915

1098-1004

Claire Bar, Giulia Barcia, Mélanie Jennesson, Gwenaël Le Guyader, Amy L. Schneider, Cyril Mignot, Gaëtan Lesca, Delphine Breuillard, Martino Montomoli, Boris Keren, Diane Doummar, Thierry Billette de Villemeur, Alexandra Afenjar, Isabelle Marey, Marion Gérard, Hervé Isnard, Alice Poisson, S. Dupont, Patrick Berquin, Pierre Meyer, David Geneviève, Anne de Saint Martin, Salima El Chehadeh, Jamel Chelly, Agnès Guët, Emmanuel Scalais, Nathalie Dorison, Candace T. Myers, Heather C. Mefford, Katherine B. Howell, Carla Marini, Jeremy L. Freeman, Anca Nica, Gaetano Terrone, Tayeb Sékhara, Anne-Sophie Lèbre, Sylvie Odent, Lynette G. Sadleir, Arnold Munnich, Renzo Guerrini, Ingrid E. Scheffer, Edor Kabashi, Rima Nabbout,

Genomics and Rare Diseases

Developmental and epileptic encephalopathies (DEE) refer to a heterogeneous group of devastating neurodevelopmental disorders. Variants in KCNB1 have been recently reported in patients with early-onset DEE. KCNB1 encodes the α subunit of the delayed rectifier voltage-dependent potassium channel Kv 2.1. We review the 37 previously reported patients carrying 29 distinct KCNB1 variants and significantly expand the mutational spectrum describing 18 novel variants from 27 unreported patients. Most variants occur de novo and mainly consist of missense variants located on the voltage sensor and the pore domain of Kv 2.1. We also report the first inherited variant (p.Arg583*). KCNB1-related encephalopathies encompass a wide spectrum of neurodevelopmental disorders with predominant language difficulties and behavioral impairment. Eighty-five percent of patients developed epilepsies with variable syndromes and prognosis. Truncating variants in the C-terminal domain are associated with a less-severe epileptic phenotype. Overall, this report provides an up-to-date review of the mutational and clinical spectrum of KCNB1, strengthening its place as a causal gene in DEEs and emphasizing the need for further functional studies to unravel the underlying mechanisms.