Novel Truncating and Missense Variants in SEMA6B in Patients With Early-Onset Epilepsy.

Progressive myoclonic epilepsy (PME) is a rare neurodegenerative disease, characterized by myoclonic seizures and tonic clonic seizures, with genetical and phenotypical heterogeneity. The semaphorin 6B (SEMA6B) gene has been recently reported a causal gene of PME. Independent studies are warranted to further support these findings. Here we report that one nonsense variant in NM_032108.3 exon17 c.2056C > T (p.Gln686∗) and one missense variant in exon14 c.1483G > T (p.Gly495Trp) of SEMA6B, both occurring de novo, underlie early-onset epilepsy with variable severity and different response to treatment in two patients. In vitro analyses have demonstrated that the nonsense variant, p.Gln686∗, results in a truncated protein with remarkably increased expression compared to that of the wild type. The truncated protein presented more homogeneous and failed to locate in the plasma membrane. The missense variant p.Gly495Trp affects evolutionarily conserved amino acid and is located in the sema domain, a key functional domain of SEMA6B. It was predicted to perturb the SEMA6B function by altering the tertiary structure of mutant protein, although neither change of protein length and expression nor difference of cellular distribution was observed. Co-immunoprecipitation studies have demonstrated that both variants influence protein binding of SEMA6B and PlxnA2 with varying degrees. Our results provide further evidence to support the initial findings of SEMA6B being causal to epilepsy and indicate that mediating Semaphorin/Plexin signaling is the potential mechanism of the SEMA6B-related disease.

Mutation analysis of two pedigrees with suspected oculocutaneous albinism / 中华医学遗传学杂志

OBJECTIVE@#To analyze the clinical presentation and gene of 2 pedigrees with suspected oculocutaneous albinism(OCA), and provide basis for clinical classification, genetic counseling and prenatal diagnosis.@*METHODS@#Variants were identified using next-generation sequencing(NGS) and confirmed by Sanger sequencing in 2 pedigrees with suspected OCA. The pathogenicity of the variants was analyzed according to the American College of Medical Genetics and Genomics (ACMG) standard.@*RESULTS@#Two compound heterozygous mutations of TYR and OCA2 genes were identified respectively in 2 pedigrees with suspected OCA. The mutation of c.819+3insATATGCC in TYR and the mutation of c.1870G>C in OCA2 are first reported in this study. The pathogenicity analysis shows that two novel mutations are likely pathogenic by combination of prediction of SIFT, Polyphen-2 and Human Splicing Finder.@*CONCLUSION@#The findings of this study expand the mutational spectrum of OCA. Compound heterozygous mutations in the TYR and OCA2 gene may be responsible for clinical manifestations of 2 pedigrees with suspected OCA.

Analysis of genetic defects in the 11p15.5 region in Russell-Silver syndrome / 临床儿科杂志

Objective To explore the pathogenesis of Russell-Silver syndrome (RSS). Methods Two milliliter peripheral blood samples were collected from 6 male patients aged 6 to 8 years with suspected RSS phenotype, the parents of 2 patients and 5 healthy boys. Mononuclear cells were isolated and genomic DNA was extracted. The methylation level of the H19 imprinting control region(ICR)1 on chromosome 11p15.5 was detected by pyrosequencing.The methylation status and the copy number variation in the corresponding region of one RSS patient with positive results by pyrosequencing were analysed by methylation-specific multiplex-ligation-dependent probe amplification assay (MS-MLPA). Results Pyrosequencing analysis revealed that the methylation rates on the 6 CpG targeting sites in H19 differentially methylated region(DMR)in the 6 RSS patients were about 11%~29%, which were significantly lower than those in their parents and normal controls (44%~59%). The MS-MLPA results of one patient with positive pyrosequencing showed that the methylation rates of 4 sites in H19-DMR were about 10%,which was obviously lower than the normal level.The methylation rates of the 4 sites in KCNQ1OT1 gene were about 50%, which was in the normal range. The copy number variations from all samples detected were in the normal range. Conclusion There is methylation aberration of H19-DMR in ICR1 in children with RSS.