No abstract

Juvenile amyotrophic lateral sclerosis (JALS) occurs at an age of onset below 25 years with a heterogeneous disease onset location, variable progression and survival time. To investigate whether an ALS gene profile could resolve any aspects of clinical symptom heterogeneity, we have used targeted sequencing technology in a cohort of 12 JALS patients of Chinese descent. We detected 5 likely pathogenic mutations, 2 in familial probands and 3 in sporadic patients. One was a known TARDBP mutation (p.G348V) and 4 were FUS frameshift mutations including a known p.Gln519Ilefs*9 mutation and 3 novel mutations, p.Gly515Valfs*14, p.Gly486Profs*30, and p.Arg498Alafs*32. Of the 4 FUS mutations, 2 were able to be confirmed as de novo mutations. The TARDBP mutation carrier showed a classic ALS phenotype. All patients with FUS mutations experienced limb weakness at an early age and developed bulbar symptoms during the disease course. FUS mutations have previously been associated with increased JALS disease progression, however, we found a large range 12 to 84 months in disease survival (mean 58.2 months). Our results justify future screening for variants in FUS as it remains the most frequent genetic determinant of early onset, JALS (found in 30% of our patients).

The Bruno et al. 1 criteria are commonly used to diagnose paroxysmal kinesigenic dyskinesia (PKD), listed as follows:• Identified kinesigenic trigger for the attacks • Short duration of attacks (1 minute) • No loss of consciousness or pain during attacks • Exclusion of other organic diseases and normal neurologic examination • Control of attacks with phenytoin or carbamazepine, if tried • Age at onset between 1 and 20 years, if no family history of PKD Our previous study has identified PRRT2 as a causative gene for PKD, 2 which was supported by several independent groups. 3-5 To date, many PRRT2 mutations in PKD have been reported, but the genotype-phenotype relationship of PKD has not been well-studied. Our objective was to investigate correlations of PRRT2 mutations with phenotypes of PKD and responses to carbamazepine in a cohort of patients with PKD.Classification of evidence. This study provides Class IV evidence of a correlation between phenotype and genotype in patients with PKD, the PRRT2 mutation, and response to carbamazepine. Methods.We recruited 81 patients with PKD, including 44 familial cases from 14 pedigrees and 37 possibly sporadic cases, from Huashan Hospital and First Affiliated Hospital during 2 periods, December 2005 to March 2011 (stage 1) and April 2011 to April 2012 (stage 2), prior to or after the discovery of PRRT2 mutations, respectively. All cases met Bruno et al. criteria. The study followed standard protocol approvals, registrations, and patient consents.Clinical evaluations were performed and patients were followed up. Sanger sequencing was performed to identify PRRT2 mutations. Differences in clinical characteristics between patients with PKD with and without PRRT2 mutations were tested using the 2-sample t test or the x 2 test. A generalized estimating equation (GEE) model was used to account for familial correlation. SAS version 9.2 (SAS Inc., Cary, NC) was used for statistical analyses.Results. Phenotypes of patients with PKD in this study were classified into 2 subtypes, choreoathetosis or dystonia, according to their main symptoms (detailed classifications seen in appendix e-1 on the Neurology ® Web site at www.neurology.org). Three cases had a positive history of infantile convulsions, and one had viral encephalitis before onset of PKD attacks. All others had no significant medical history. Available EEG and brain MRI showed unremarkable results.Four documented PRRT2 mutations, 2,6 including c.649dupC, c.514_517delTCTG, c.972delA, and c.649delC, were detected in 100% of familial cases and 11% of possibly sporadic cases (table e-1 and table e-2). The c.649dupC mutation was also detected in the asymptomatic parents of family 34 and 47, suggesting the incomplete penetrance of this mutation. Interestingly, we found a de novo mutation of c.649dupC in the patient with PKD of Mongolian ancestry. 7 Associations between PRRT2 mutations and the clinical presentation of PKD are shown in table 1. The mean age at onset in PRRT2 mutation carriers was significantly lower than that in non-P...

Amyotrophic lateral sclerosis (ALS) is a progressive, fatal neurodegenerative disease characterized by selective impairment of upper and lower motor neurons. We aimed to investigate the genetic spectrum and variability in Chinese patients with ALS. A total of 24 familial ALS (FALS) and 21 early-onset sporadic ALS (SALS) of Chinese ancestry were enrolled. Targeted next-generation sequencing (NGS) was performed in the probands, followed by verification by Sanger sequencing and co-segregation analysis. Clinical features of patients with pathogenic or likely pathogenic variants were present. The mutation frequency of ALS-related genes was then analyzed in Chinese population. In this cohort, 17 known mutations (9 SOD1, 5 FUS, 2 TARDBP and one SETX) were identified in 14 FALS and 6 early-onset SALS. Moreover, 7 novel variants (SOD1 c.112G>C, OPTN c.811C>T, ERBB4 c.965T>A, DCTN1 c.1915C>T, NEFH c.2602G>A, NEK1 c.3622G>A, and TAF15 c.1535G>A) were identified. In southeastern Chinese FALS, the mutation frequency of SOD1, FUS, and TARDBP was 52.9%, 8.8%, 8.8% respectively. In early-onset SALS, FUS mutations were the most common (22.6%). In Chinese ALS cases, p.H47R is most frequent SOD1 mutations, while p.R521 is most common FUS mutation and p.M337V is most common TARDBP mutation. Our results revealed that mutations in SOD1, FUS and TARDBP are the most common cause of Chinese FALS, while FUS mutations are the most common cause of early-onset SALS. The genetic spectrum is different between Chinese ALS and Caucasian ALS.

Sorbitol dehydrogenase gene (SORD) has been identified as a novel causative gene of recessive forms of hereditary neuropathy, including Charcot–Marie–Tooth disease type 2 and distal hereditary motor neuropathy (dHMN). Our findings reveal two novel variants (c.404 A > G and c.908 + 1 G > C) and one known variant (c.757delG) within SORD in four Chinese dHMN families. Ex vivo cDNA polymerase chain reaction confirmed that c.908 + 1 G > C variant was associated with impaired splicing of the SORD transcript. In vitro cell functional studies showed that c.404 A > G variant resulted in aggregate formation of SORD and low protein solubility, confirming the pathogenicity of SORD variants. We have provided more evidence to establish SORD as a causative gene for dHMN.

Charcot‐Marie‐Tooth (CMT) disease is a heterogeneous group of inherited sensorimotor neuropathies. To clarify the genetic spectrum and clinical profiles in Chinese CMT patients, we enrolled 150 unrelated CMT patients from southeast China. We performed multiplex ligation‐dependent probe amplification (MLPA) testing in all patients and next‐generation sequencing (NGS) among those patients without PMP22 rearrangements. We identified PMP22 duplications in 40 patients and deletions in 12 patients. In addition, we found 19 novel variants and 36 known mutations in 57 patients. Among these 55 variants, 45 pathogenic or likely pathogenic variants were identified in 48 cases, and 10 variants with uncertain significance were identified in 9 cases. Therefore, we obtained a genetic diagnosis in 63.8% (88/138) of CMT patients and 66.7% (100/150) of all included patients. PMP22, GJB1, and MFN2 are the most common causative genes in CMT1 (demyelinated form), intermediate CMT, and CMT2 (axonal form), respectively. In this study, we identified a higher proportion of intermediate CMT, a relatively high frequency of NDRG1 mutations and clinical features of later onset age in CMT1A patients. Our results broaden the genetic and clinical spectrum of CMT patients, which can help optimize the genetic and clinical diagnosis.

No abstract

Charcot-Marie-Tooth disease type 4D (CMT4D) is an autosomal-recessive demyelinating form of CMT characterized by a severe distal motor and sensory neuropathy. NDRG1 is the causative gene for CMT4D. To date, only four mutations in NDRG1 -c.442C>T (p.Arg148*), c.739delC (p.His247Thrfs*74), c.538-1G>A, and duplication of exons 6-8-have been described in CMT4D patients. Here, using targeted next-generation sequencing examination, we identified for the first time two homozygous missense variants in NDRG1, c.437T>C (p.Leu146Pro) and c.701G>A (p.Arg234Gln), in two Chinese CMT families with consanguineous histories. Further functional studies were performed to characterize the biological effects of these variants. Cell culture transfection studies showed that mutant NDRG1 carrying p.Leu146Pro, p.Arg148*, or p.Arg234Gln variant degraded faster than wild-type NDRG1, resulting in lower protein levels. Live cell confocal microscopy and coimmunoprecipitation analysis indicated that these variants did not disrupt the interaction between NDRG1 and Rab4a protein. However, NDRG1-knockdown cells expressing mutant NDRG1 displayed enlarged Rab4a-positive compartments. Moreover, mutant NDRG1 could not enhance the uptake of DiI-LDL or increase the fraction of low-density lipoprotein receptor on the cell surface. Taken together, our study described two missense mutations in NDRG1 and emphasized the important role of NDRG1 in intracellular protein trafficking.