New hyperekplexia mutations provide insight into glycine receptor assembly, trafficking, and activation mechanisms

Background: Hyperekplexia mutations have provided much information about glycine receptor structure and function. Results: Weidentified and characterized nine new mutations. Dominant mutations resulted in spontaneous activation, whereas recessive mutations precluded surface expression. Conclusion: These data provide insight into glycine receptor activation mechanisms and surface expression determinants. Significance: The results enhance our understanding of hyperekplexia pathology and glycine receptor structure-function. © 2013 by The American Society for Biochemistry and Molecular Biology, Inc. Published in the U.S.A

Early clinical predictors of intractable epilepsy in childhood

Aim: In this retrospective study, we evaluated the clinical responses to antiepileptic drug (AED) therapy in pediatric epilepsy patients treated at a single center. Materials and methods: We identified 28 children with intractable epilepsy and 213 patients with drug-responsive epilepsy. Results: Univariate analysis showed that age at onset, high (daily) initial seizure frequency, infantile spasm, history of neonatal seizures, abnormal neurodevelopmental status, neurological abnormalities, mental retardation, remote symptomatic etiology, and abnormal brain imaging results were significant risk factors for the development of intractable epilepsy (P < 0.05). Multivariate logistic regression analysis revealed that high (daily) initial seizure frequency and remote symptomatic etiology were significant and independent risk factors for intractable epilepsy (P < 0.05). Conclusion: Our study suggests that the risk of developing intractable epilepsy in childhood may be predicted, to some extent, by the early clinical course. Early identification of patients at high risk of developing intractable epilepsy will guide appropriate therapy and reduce exposure to ineffectual treatments

22q13.3 Deletion Syndrome: An Underdiagnosed Cause of Mental Retardation

Phelan-McDermid syndrome, also known as 22q13.3 deletion syndrome, is characterized by global developmental delay, absent or delayed speech, generalized hypotonia, and minor physical anomalies. The deletion typically involves the terminal band 22q13.3 and has been associated with both familial and de-novo translocations. We report the case of an 11-year-old Turkish girl with 22q13.3 deletion syndrome presenting with repeated seizures during the course of a rubella infection. We also review the clinical features of 22q13.3 deletion syndrome and emphasize the importance of considering a rare microdeletion syndrome for idiopathic mental retardation when results of a routine karyotype analysis are normal. To the best of our knowledge, this is the first reported case of a Turkish patient with isolated 22q13.3 deletion syndrome

Novel Mutations Consolidate Kctd7 As A Progressive Myoclonus Epilepsy Gene

Background The progressive myoclonus epilepsies (PMEs) comprise a group of clinically and genetically heterogeneous disorders characterised by myoclonus, epilepsy, and neurological deterioration. This study aimed to identify the underlying gene(s) in childhood onset PME patients with unknown molecular genetic background. Methods Homozygosity mapping was applied on genome-wide single nucleotide polymorphism data of 18 Turkish patients. The potassium channel tetramerisation domain-containing 7 (KCTD7) gene, previously associated with PME in a single inbred family, was screened for mutations. The spatiotemporal expression of KCTD7 was assessed in cellular cultures and mouse brain tissue. Results Overlapping homozygosity in 8/18 patients defined a 1.5 Mb segment on 7q11.21 as the major candidate locus. Screening of the positional candidate gene KCTD7 revealed homozygous missense mutations in two of the eight cases. Screening of KCTD7 in a further 132 PME patients revealed four additional mutations (two missense, one in-frame deletion, and one frameshift-causing) in five families. Eight patients presented with myoclonus and epilepsy and one with ataxia, the mean age of onset being 19 months. Within 2 years after onset, progressive loss of mental and motor skills ensued leading to severe dementia and motor handicap. KCTD7 showed cytosolic localisation and predominant neuronal expression, with widespread expression throughout the brain. None of three polypeptides carrying patient missense mutations affected the subcellular distribution of KCTD7. Discussion These data confirm the causality of KCTD7 defects in PME, and imply that KCTD7 mutation screening should be considered in PME patients with onset around 2 years of age followed by rapid mental and motor deterioration.Wo

ALG1-CDG: Clinical and Molecular Characterization of 39 Unreported Patients

Congenital disorders of glycosylation (CDG) arise from pathogenic mutations in over 100 genes leading to impaired protein or lipid glycosylation. ALG1 encodes a beta 1,4 mannosyltransferase that catalyzes the addition of the first of nine mannose moieties to form a dolichol-lipid linked oligosaccharide intermediate required for proper N-linked glycosylation. ALG1 mutations cause a rare autosomal recessive disorder termed ALG1-CDG. To date 13 mutations in 18 patients from 14 families have been described with varying degrees of clinical severity. We identified and characterized 39 previously unreported cases of ALG1-CDG from 32 families and add 26 new mutations. Pathogenicity of each mutation was confirmed based on its inability to rescue impaired growth or hypoglycosylation of a standard biomarker in an alg1-deficient yeast strain. Using this approach we could not establish a rank order comparison of biomarker glycosylation and patient phenotype, but we identified mutations with a lethal outcome in the first two years of life. The recently identified protein-linked xeno-tetrasaccharide biomarker, NeuAc-Gal-GlcNAc2, was seen in all 27 patients tested. Our study triples the number of known patients and expands the molecular and clinical correlates of this disorder. (C) 2016 Wiley Periodicals, Inc