Clinical characterization and founder effect analysis in Chinese amyotrophic lateral sclerosis patients with <i>SOD1</i> common variants

In the Asian population, <i>SOD1</i> variants are the most common cause of amyotrophic lateral sclerosis (ALS). To date, more than 200 variants have been reported in <i>SOD1</i>. This study aimed to summarize the genotype–phenotype correlation and determine whether the patients carrying common variants derive from a common ancestor. A total of 103 sporadic ALS (SALS) and 11 familial ALS (FALS) probands were included and variants were screened by whole exome sequencing. Functional analyses were performed on fibroblasts derived from patients with <i>SOD1</i> p.V48A and control. Haplotype analysis was performed in the probands with p.H47R or p.V48A and their familial members. A total of 25 <i>SOD1</i> variants were identified in 44 probands, in which p.H47R, p.V48A and p.C112Y variants were the most common variants. 94.3% and 60% of patients with p.H47R or p.V48A had lower limb onset with predominant lower motor neurons (LMNs) involvement. Patients with p.H47R had a slow progression and prolonged survival time, while patients with p.V48A exhibited a duration of 2–5 years. Patients with p.C112Y variant showed remarkable phenotypic variation in age at onset and disease course. <i>SOD1^V48A</i> fibroblasts showed mutant SOD1 aggregate formation, enhanced intracellular reactive oxygen species level, and decreased mitochondrial membrane potential compared to the control fibroblast. Haplotype analysis showed that seven families had two different haplotypes. p.H47R and p.V48A variants did not originate from a common founder. Our study expanded the understanding of the genotype–phenotype correlation of ALS with <i>SOD1</i> variants and revealed that the common p.H47R or p.V48A variant did not have a founder effect. In our ALS cohort, 44 ALS probands were identified with 25 <i>SOD1</i> variants, of which p.H47R, p.V48A and p.C112Y variants were the most frequent. The genotype–phenotype relationship of patients with <i>SOD1</i> p.H47R, p.V48A and p.C112Y patients were summarized.<i>SOD1^V48A</i> fibroblasts showed mutant SOD1 aggregate formation, enhanced intracellular reactive oxygen species level, and decreased mitochondrial membrane potential compared to the control fibroblast.Our study expanded the understanding of the genotype–phenotype correlation of ALS with <i>SOD1</i> variants and showed the common variants p.H47R or p.V48A did not have a founder effect. In our ALS cohort, 44 ALS probands were identified with 25 <i>SOD1</i> variants, of which p.H47R, p.V48A and p.C112Y variants were the most frequent. The genotype–phenotype relationship of patients with <i>SOD1</i> p.H47R, p.V48A and p.C112Y patients were summarized. <i>SOD1^V48A</i> fibroblasts showed mutant SOD1 aggregate formation, enhanced intracellular reactive oxygen species level, and decreased mitochondrial membrane potential compared to the control fibroblast. Our study expanded the understanding of the genotype–phenotype correlation of ALS with <i>SOD1</i> variants and showed the common variants p.H47R or p.V48A did not have a founder effect.