Bing Wen Soong

Mutations in KCND3 Cause Spinocerebellar Ataxia Type 22

To identify the causative gene in spinocerebellar ataxia (SCA) 22, an autosomal dominant cerebellar ataxia mapped to chromosome 1p21‐q23.

The ‘hot cross bun’ sign in the patients with spinocerebellar ataxia

Background and purpose:u2002 The ‘hot cross bun’ sign (HCBS), typically seen in the patients with multiple system atrophy, refers to a cruciform hyperintensity in the pons on T2‐weighted MRI. Little is known about its pathological basis and prevalence in other degenerative cerebellar diseases and healthy population. We investigate the frequency of HCBS in the patients with spinocerebellar ataxia (SCA) and healthy controls.

Extensive molecular genetic survey of Taiwanese patients with amyotrophic lateral sclerosis

Identification of genetic mutations has been of burgeoning importance in amyotrophic lateral sclerosis (ALS) in recent years. The aim of this study was to determine the frequency and spectrum of mutations in major ALS-causing genes in a Taiwanese ALS cohort of Han Chinese origin. Mutational analyses of the SOD1, TARDBP, FUS, OPTN, VCP, UBQLN2, SQSTM1, PFN1, HNRNPA1, and HNRNPA2B1 genes were carried out by direct sequencing in 161 unrelated patients with ALS, including 30 with familial ALS (FALS) and 131 with sporadic ALS (SALS). The CAG repeat size in ATXN2 and the GGGGCC repeat expansion in C9ORF72 of the patients were also investigated. Mutations were identified in 33 patients (20.5%, 33/161), including 22 with FALS and 11 with SALS. Mutations were identified most frequently in SOD1 (7.5%). Three mutations are novel, including SOD1 p.G10A, SOD1 p.D83N, and OPTN p.L494W. These findings broaden the spectrum of ALS-causing mutations and are indispensable for designing optimal strategies of mutational analysis and genetic counseling of ALS for patients of Chinese origin.

Transmissible spongiform encephalopathies with P102L mutation of PRNP manifesting different phenotypes: clinical, neuroimaging, and electrophysiological studies in Chinese kindred in Taiwan

A P102L point mutation in the prion protein gene (PRNP) usually causes Gerstmann–Sträussler–Scheinker disease (GSS), which is a rare hereditary transmissible spongiform encephalopathy (TSE). The clinical features include ataxia in 50s age group with subsequent dementia, spastic paraparesis and extrapyramidal signs. Many families have been reported from the Caucasian population, but only one from the Chinese. We hereby report a large Chinese family with P102L mutation of PRNP whose clinical manifestations at onset were intriguingly heterogeneous, either rapidly progressive dementia with scanty other neurological features or slowly progressive ataxia followed by cognitive impairment. The four-generation pedigree included eight patients with a mean age at onset of 36.9xa0±xa012.9 (meanxa0±xa0SD) years. Mean disease duration to death in the four patients was 5.5xa0±xa01.7 (meanxa0±xa0SD) years. Molecular analysis revealed a P102L mutation and M129 polymorphism in the PRNP gene in all affected individuals. TSE with P102L mutation of PRNP appears to have a remarkably variable phenotypic expressivity that may change with time and does not appear related to the codon 129 polymorphism.

A recurrent WARS mutation is a novel cause of autosomal dominant distal hereditary motor neuropathy

Distal hereditary motor neuropathy is a heterogeneous group of inherited neuropathies characterized by distal limb muscle weakness and atrophy. Although at least 15 genes have been implicated in distal hereditary motor neuropathy, the genetic causes remain elusive in many families. To identify an additional causal gene for distal hereditary motor neuropathy, we performed exome sequencing for two affected individuals and two unaffected members in a Taiwanese family with an autosomal dominant distal hereditary motor neuropathy in which mutations in common distal hereditary motor neuropathy-implicated genes had been excluded. The exome sequencing revealed a heterozygous mutation, c.770A > G (p.His257Arg), in the cytoplasmic tryptophanyl-tRNA synthetase (TrpRS) gene (WARS) that co-segregates with the neuropathy in the family. Further analyses of WARS in an additional 79 Taiwanese pedigrees with inherited neuropathies and 163 index cases from Australian, European, and Korean distal hereditary motor neuropathy families identified the same mutation in another Taiwanese distal hereditary motor neuropathy pedigree with different ancestries and one additional Belgian distal hereditary motor neuropathy family of Caucasian origin. Cell transfection studies demonstrated a dominant-negative effect of the p.His257Arg mutation on aminoacylation activity of TrpRS, which subsequently compromised protein synthesis and reduced cell viability. His257Arg TrpRS also inhibited neurite outgrowth and led to neurite degeneration in the neuronal cell lines and rat motor neurons. Further in vitro analyses showed that the WARS mutation could potentiate the angiostatic activities of TrpRS by enhancing its interaction with vascular endothelial-cadherin. Taken together, these findings establish WARS as a gene whose mutations may cause distal hereditary motor neuropathy and alter canonical and non-canonical functions of TrpRS.

Clinical and Molecular Characterization of BSCL2 Mutations in a Taiwanese Cohort with Hereditary Neuropathy

Background A small group of patients with inherited neuropathy that has been shown to be caused by mutations in the BSCL2 gene. However, little information is available about the role of BSCL2 mutations in inherited neuropathies in Taiwan. Methodology and Principal Findings Utilizing targeted sequencing, 76 patients with molecularly unassigned Charcot-Marie-Tooth disease type 2 (CMT2) and 8 with distal hereditary motor neuropathy (dHMN), who were selected from 348 unrelated patients with inherited neuropathies, were screened for mutations in the coding regions of BSCL2. Two heterozygous BSCL2 mutations, p.S90L and p.R96H, were identified, of which the p.R96H mutation is novel. The p.S90L was identified in a pedigree with CMT2 while the p.R96H was identified in a patient with apparently sporadic dHMN. In vitro studies demonstrated that the p.R96H mutation results in a remarkably low seipin expression and reduced cell viability. Conclusion BSCL2 mutations account for a small number of patients with inherited neuropathies in Taiwan. The p.R96H mutation is associated with dHMN. This study expands the molecular spectrum of BSCL2 mutations and also emphasizes the pathogenic role of BSCL2 mutations in molecularly unassigned hereditary neuropathies.