[C9orf72 in Japanese amyotrophic lateral sclerosis (ALS)]

A novel mutation of VAPB in one Chinese familial amyotrophic lateral sclerosis pedigree and its clinical characteristics

The mutation of vesicle-associated membrane protein-associated protein B (VAPB) was proved to cause family amyotrophic lateral sclerosis (FALS). Only two mutations of VAPB associated with ALS have been reported (p.Pro56Ser and p.Thr46Ile). Here we reported a Chinese Han FALS family caused by a novel VAPB point mutation. The clinical materials of one Chinese Han FALS family were collected. The genetic analysis was carried out by target sequencing and further verified by Sanger sequencing. One novel mutation of c.167C>A (p.Pro56His) on VAPB was found in the proband. The age at onset of the proband was 48 with the onset symptoms of weakness in the right arm, followed by progressive limb and trunk weakness with decreased deep-tendon reflexes, muscular cramps and fasciculation. But the disease duration was more than 15 years. He was under the tracheotomy for 1 year at last visit. Electromyography showed widespread acute and chronic neurogenic damages. His mother presented weakness in her limbs in 50 s and died 15 years later. One of his younger sisters diagnosed as ALS for 6 years also carried the same mutation. She presented the similar symptoms on 41. No dominant upper motor neuron sign was showed. The clinical features were similar to the patients carrying the known mutation of p.Pro56Ser. A novel mutation of VAPB was found in one Chinese Han FALS pedigree. The affected patients presented a much slower progression and the lesions were limited in lower motor neurons.

Genetic epidemiology of amyotrophic lateral sclerosis: a systematic review and meta-analysis

BACKGROUND

Genetic studies have shown that C9orf72, SOD1, TARDBP and FUS are the most common mutated genes in amyotrophic lateral sclerosis (ALS). Here, we performed a meta-analysis to determine the mutation frequencies of these major ALS-related genes in patients with ALS.

METHODS

We performed an extensive literature research to identify all original articles reporting frequencies of C9orf72, SOD1, TARDBP and FUS mutations in ALS. The mutation frequency and effect size of each study were combined. Possible sources of heterogeneity across studies were determined by meta-regression, sensitivity analysis and subgroup analysis.

RESULTS

111 studies were included in the meta-analysis. The overall pooled mutation frequencies of these major ALS-related genes were 47.7% in familial amyotrophic lateral sclerosis (FALS) and 5.2% in sporadic ALS (SALS). A significant difference was identified regarding the frequencies of mutations in major ALS genes between European and Asian patients. In European populations, the most common mutations were the C9orf72 repeat expansions (FALS 33.7%, SALS 5.1%), followed by SOD1 (FALS 14.8%, SALS 1.2%), TARDBP (FALS 4.2%, SALS 0.8%) and FUS mutations (FALS 2.8%, SALS 0.3%), while in Asian populations the most common mutations were SOD1 mutations (FALS 30.0%, SALS 1.5%), followed by FUS (FALS 6.4%, SALS 0.9%), C9orf72 (FALS 2.3%, SALS 0.3%) and TARDBP (FALS 1.5%, SALS 0.2%) mutations.

CONCLUSIONS

These findings demonstrated that the genetic architecture of ALS in Asian populations is distinct from that in European populations, which need to be given appropriate consideration when performing genetic testing of patients with ALS.