Search

Mutations in STXBP1 have been identified in a subset of patients with early onset epileptic encephalopathy (EE), but the full phenotypic spectrum remains to be delineated. Therefore, we screened a cohort of 160 patients with an unexplained EE, including patients with early myoclonic encephalopathy (EME), Ohtahara syndrome, West syndrome, nonsyndromic EE with onset in the first year, and Lennox-Gastaut syndrome (LGS). We found six de novo mutations in six patients presenting as Ohtahara syndrome (2/6, 33%), West syndrome (1/65, 2%), and nonsyndromic early onset EE (3/64, 5%). No mutations were found in LGS or EME. Only two of four mutation carriers with neonatal seizures had Ohtahara syndrome. Epileptic spasms were present in five of six patients. One patient with normal magnetic resonance imaging (MRI) but focal seizures underwent epilepsy surgery and seizure frequency dropped drastically. Neuropathology showed a focal cortical dysplasia type 1a. There is a need for additional neuropathologic studies to explore whether STXBP1 mutations can lead to structural brain abnormalities., (Wiley Periodicals, Inc. © 2013 International League Against Epilepsy.)

Purpose: Neurexins are neuronal adhesion molecules located in the presynaptic terminal, where they interact with postsynaptic neuroligins to form a transsynaptic complex required for efficient neurotransmission in the brain. Recently, deletions and point mutations of the neurexin 1 (NRXN1) gene have been associated with a broad spectrum of neuropsychiatric disorders. This study aimed to investigate if NRXN1 deletions also increase the risk of idiopathic generalized epilepsies (IGEs)., Methods: We screened for deletions involving the NRXN1 gene in 1,569 patients with IGE and 6,201 controls using high-density oligonucleotide microarrays., Key Findings: We identified exon-disrupting deletions of NRXN1 in 5 of 1,569 patients with IGE and 2 of 6,201 control individuals (p = 0.0049; odds ratio (OR) 9.91, 95% confidence interval (CI) 1.92-51.12). A complex familial segregation pattern in the IGE families was observed, suggesting that heterozygous NRXN1 deletions are susceptibility variants. Intriguingly, we identified a second large copy number variant in three of five index patients, supporting an involvement of heterogeneous susceptibility alleles in the etiology of IGE., Significance: We conclude that exon-disrupting deletions of NRXN1 represent a genetic risk factor in the genetically complex predisposition of common IGE syndromes., (Wiley Periodicals, Inc. © 2012 International League Against Epilepsy.)

Epilepsy with myoclonic absences (EMA) is a rare form of generalized epilepsy occurring in childhood and is often difficult to treat. The underlying etiology of EMA is unknown in the majority of patients. Herein, we describe a patient with EMA and intellectual disability who carries a de novo balanced translocation: t(6;22)(p21.32;q11.21). We mapped the translocation breakpoints by fluorescence in situ hybridization (FISH), and the breakpoint at 6p21.32 was found to truncate the N-methyl-d-aspartate (NMDA)-receptor associated gene SYNGAP1. The breakpoint at 22q11.21 was within a highly variable region without known protein-coding genes. Mutations of SYNGAP1 are associated with nonsyndromal intellectual disability (NSID). Two-thirds of the patients described so far also have generalized epilepsy. This finding, together with our report, suggests that dysfunction of SYNGAP1 contributes to the development of generalized epilepsy, including EMA., (Wiley Periodicals, Inc. © 2011 International League Against Epilepsy.)