RT Journal Article SR Electronic T1 A Nonsense Mutation of the Sodium Channel Gene SCN2A in a Patient with Intractable Epilepsy and Mental Decline JF The Journal of Neuroscience JO J. Neurosci. FD Society for Neuroscience SP 2690 OP 2698 DO 10.1523/JNEUROSCI.3089-03.2004 VO 24 IS 11 A1 Kazusaku Kamiya A1 Makoto Kaneda A1 Takashi Sugawara A1 Emi Mazaki A1 Nami Okamura A1 Mauricio Montal A1 Naomasa Makita A1 Masaki Tanaka A1 Katsuyuki Fukushima A1 Tateki Fujiwara A1 Yushi Inoue A1 Kazuhiro Yamakawa YR 2004 UL http://www.jneurosci.org/content/24/11/2690.abstract AB Mutations, exclusively missense, of voltage-gated sodium channel α subunit type 1 (SCN1A) and type 2 (SCN2A) genes were reported in patients with idiopathic epilepsy: generalized epilepsy with febrile seizures plus. Nonsense and frameshift mutations of SCN1A, by contrast, were identified in intractable epilepsy: severe myoclonic epilepsy in infancy (SMEI). Here we describe a first nonsense mutation of SCN2A in a patient with intractable epilepsy and severe mental decline. The phenotype is similar to SMEI but distinct because of partial epilepsy, delayed onset (1 year 7 months), and absence of temperature sensitivity. A mutational analysis revealed that the patient had a heterozygous de novo nonsense mutation R102X of SCN2A. Patch-clamp analysis of Nav1.2 wild-type channels and the R102X mutant protein coexpressed in human embryonic kidney 293 cells showed that the truncated mutant protein shifted the voltage dependence of inactivation of wild-type channels in the hyperpolarizing direction. Analysis of the subcellular localization of R102X truncated protein suggested that its dominant negative effect could arise from direct or indirect cytoskeletal interactions of the mutant protein. Haploinsufficiency of Nav1.2 protein is one plausible explanation for the pathology of this patient; however, our biophysical findings suggest that the R102X truncated protein exerts a dominant negative effect leading to the patient's intractable epilepsy.