Analysis of SOD1 variants in Chinese patients with familial amyotrophic lateral sclerosis.

BACKGROUND: Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease, and genetic contributors exert a significant role in the complicated pathogenesis. Identification of the genetic causes in ALS families could be valuable for early diagnosis and management. The development of potential drugs for patients with genetic defects will shed new light on ALS therapy. AIM: To identify causative variants in three Chinese families with familial ALS (FALS), reveal the pathogenic mechanism and look for the targeted drug for ALS. DESIGN AND METHODS: Whole-exome sequencing and bioinformatics were used to perform genetic analysis of the ALS families. Functional analysis was performed to study the variants' function and search for potential drug targets. RESULTS: Three heterozygous missense variants of the superoxide dismutase 1 gene (SOD1) were identified in families with FALS. The clinical manifestations of these patients include spinal onset, predominant lower motor neurons presentation and absence of cognitive involvement. Functional analysis showed that all three SOD1 variants led to increased reactive oxygen species (ROS) levels, reduced cell viability and formation of cytoplasmic aggregates. Remarkably, the decreased cell viability induced by variants was rescued after treatment with the ROS inhibitor N-acetylcysteine. CONCLUSIONS: This study identified three SOD1 variants in three families with FALS. The variant SOD1 toxicity was associated with oxidative damage and aggregation, and N-acetylcysteine could rescue the decreased cell viability induced by these variants. Our findings support a pathogenic role for ROS in SOD1 deficiencies and provide a potential drug N-acetylcysteine for ALS therapy, especially in SOD1 patients with limb onset.