High-Resolution Melting (HRM) Analysis of the Cu/Zn Superoxide Dismutase (SOD1) Gene in Japanese Sporadic Amyotrophic Lateral Sclerosis (SALS) Patients

Slow progression of amyotrophic lateral sclerosis in a Chinese patient carrying SOD1 p.S135T mutation

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease. Most patients die of respiratory failure within 3 years of onset. In this study, we reported a female Chinese ALS patient with SOD1 c.404G > C, p.S135T mutation. The missense mutation was identified as "Likely pathogenic" according to the ACMG/AMP 2015 guideline. The patient presented with weakness and atrophy of lower limbs with slow progression. We reviewed two other reports on patients with the same SOD1 p.S135T mutation. These patients had lower extremity onset, negative Babinski sign, slow disease progression, and prolonged survival. This report indicates that specific phenotype-genotype correlations of SOD1 p.S135T mutation in ALS.

Comprehensive targeted next-generation sequencing in Japanese familial amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is an adult-onset neurodegenerative disease characterized by loss of motor neurons. We have recently identified SOD1 and FUS mutations as the most common causes in a consecutive series of 111 familial ALS pedigrees in Japan. To reveal possible genetic causes for the remaining 51 patients with familial ALS (45 pedigrees), we performed targeted next-generation sequencing of 35 known ALS/motor neuron diseases-related genes. Known variants in ANG, OPTN, SETX, and TARDBP were identified in 6 patients. A novel likely pathogenic homozygous variant in ALS2 was identified in 1 patient. In addition, 18 patients harbored 1-3 novel variants of uncertain significance, whereas hexanucleotide repeat expansions in C9ORF72 were not detected using repeat-primed polymerase chain reaction. Collectively, in our Japanese cohort, the frequencies of SOD1, FUS, SETX, TARDBP, ANG, and OPTN variants were 32%, 11%, 2%, 2%, 1%, and 1%, respectively. These findings indicate considerable differences in the genetic variations associated with familial ALS across populations. Further genetic analyses and functional studies of novel variants are warranted.

Amyotrophic lateral sclerosis and motor neuron syndromes in Asia

While the past 2 decades have witnessed an increasing understanding of amyotrophic lateral sclerosis (ALS) arising from East Asia, particularly Japan, South Korea, Taiwan and China, knowledge of ALS throughout the whole of Asia remains limited. Asia represents >50% of the world population, making it host to the largest patient cohort of ALS. Furthermore, Asia represents a diverse population in terms of ethnic, social and cultural backgrounds. In this review, an overview is presented that covers what is currently known of ALS in Asia from basic epidemiology and genetic influences, through to disease characteristics including atypical phenotypes which manifest a predilection for Asians. With the recent establishment of the Pan-Asian Consortium for Treatment and Research in ALS to facilitate collaborations between clinicians and researchers across the region, it is anticipated that Asia and the Pacific will contribute to unravelling the uncertainties in ALS.

Next-generation sequencing of 28 ALS-related genes in a Japanese ALS cohort

We investigated the frequency and contribution of variants of the 28 known amyotrophic lateral sclerosis (ALS)-related genes in Japanese ALS patients. We designed a multiplex, polymerase chain reaction-based primer panel to amplify the coding regions of the 28 ALS-related genes and sequenced DNA samples from 257 Japanese ALS patients using an Ion Torrent PGM sequencer. We also performed exome sequencing and identified variants of the 28 genes in an additional 251 ALS patients using an Illumina HiSeq 2000 platform. We identified the known ALS pathogenic variants and predicted the functional properties of novel nonsynonymous variants in silico. These variants were confirmed by Sanger sequencing. Known pathogenic variants were identified in 19 (48.7%) of the 39 familial ALS patients and 14 (3.0%) of the 469 sporadic ALS patients. Thirty-two sporadic ALS patients (6.8%) harbored 1 or 2 novel nonsynonymous variants of ALS-related genes that might be deleterious. This study reports the first extensive genetic screening of Japanese ALS patients. These findings are useful for developing genetic screening and counseling strategies for such patients.