DEPDC5 mutations in families presenting as autosomal dominant nocturnal frontal lobe epilepsy
Fabienne Picard1, Periklis Makrythanasis1, Vincent Navarro1
1From the Department of Neurology (F.P.), and Service of Genetic Medicine (S.E.A.), University Hospitals of Geneva; Department of Genetic Medicine and Development (P.M.), and iGE3, Institute of Genetics and Genomics of Geneva (S.E.A.), University of Geneva, Switzerland; Institut national de la santé et de la recherche médicale (INSERM) (V.N., S.I., C.D., I.A.-G., M.V., M.B., E.L., S.B.), U1127, ICM, Paris, F-75013 Paris; Sorbonne Universités, UPMC Univ Paris 06, UMR S 1127, F-75013 Paris (V.N., S.I., C.D., I.A.-G., M.V., M.B., E.L., S.B.), Paris; CNRS (V.N., S.I., C.D., I.A.-G., M.V., M.B., E.L., S.B.), UMR7225, Hôpital de la Pitié-Salpêtrière, Paris; Epilepsy Unit (V.N., I.A.-G., M.V., M.B.), ICM, Paris, F-75013 Paris, France (V.N., S.I., C.D., I.A.-G., M.V., M.B., E.L., S.B.), and Département de Génétique et de Cytogénétique (C.D., E.L.), AP-HP Groupe hospitalier Pitié-Salpêtrière, Paris; Epilepsy, Sleep and Pediatric Neurophysiology (J.d.B.), University Hospitals of Lyon; Hospices Civils de Lyon (D.V.), HFME, centre de référence déficiences intellectuelles de causes rares et sclérose tubéreuse de Bourneville, Bron, France; Neurogenetics Group (S.W., A.S., P.D.J.), Department of Molecular Genetics, VIB, Antwerp; Laboratory of Neurogenetics (S.W., A.S., P.D.J.), Institute Born-Bunge, University of Antwerp, Belgium; Epilepsy Centre Kempenhaeghe (S.W.), Oosterhout, the Netherlands; Algemeen Stedelijk Ziekenhuis (E.F.), Aalst; Division of Neurology (P.D.J.), Antwerp University Hospital, Antwerp University, Belgium; Centre hospitalier général de Valence (M.V.R.); Department of Medical Genetics (G.L.), Hospices Civils de Lyon; Claude Bernard Lyon I University (G.L.); CRNL (G.L.), CNRS UMR 5292, INSERM U1028, Lyon; Centre de référence épilepsies rares et Sclérose tubéreuse de Bourneville (I.A.-G., M.B.); Genotyping and Sequencing Platform, ICM (E.M.), and DNA and Cell Bank (P.C.), Hôpital Pitié-Salpêtrière, Paris, France; Department of Surge
Objective:
To study the prevalence of DEPDC5 mutations in a series of 30 small European families with a phenotype compatible with autosomal dominant nocturnal frontal lobe epilepsy (ADNFLE).
Methods:
Thirty unrelated families referred with ADNFLE were recruited in France, Italy, Germany, Belgium, and Norway. Whole-exome sequencing was performed in 10 probands and direct sequencing of the DEPDC5 coding sequence in 20 probands. Testing for nonsense-mediated messenger RNA decay (NMD) was performed in lymphoblastic cells.
Results:
Exome sequencing revealed a splice acceptor mutation (c.2355-2A>G) in DEPDC5 in the proband of a German family. In addition, 3 nonsense DEPDC5 mutations (p.Arg487*, p.Arg1087*, and p.Trp1369*) were detected in the probands of 2 French and one Belgian family. The nonsense mutations p.Arg487* and p.Arg1087* were targeted by NMD, leading to the degradation of the mutated transcripts. At the clinical level, 78% of the patients with DEPDC5 mutations were drug resistant.
Conclusions:
DEPDC5 loss-of-function mutations were found in 13% of the families with a presentation of ADNFLE. The rate of drug resistance was high in patients with DEPDC5 mutations. Small ADNFLE pedigrees with DEPDC5 mutations might actually represent a part of the broader familial focal epilepsy with variable foci phenotype.
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