Identification of co-segregating RUBCN and KANK1 mutations in a UK ALS kindred

Bioinformatic analysis of next-generation sequencing data from a 3-generation UK amyotrophic lateral sclerosis (ALS) kindred identified co-segregating novel variants in RUBCN (p.Cys517Phe) and KANK1 (p.Pro1332Ala) genes. We tested the association of these variants segregating in this family with ALS using the EMMAX test, incorporating related individuals from the kindred and unrelated UK controls. Both variants were associated with ALS (p < 1 × 10^-8). We then applied sequence kernel association tests to these deleterious ultra-rare variants in ALS cohorts versus controls, which showed exome-wide significance with ALS (SKAT-O; p < 1 × 10^-9). Functional investigation of lymphoblastoid cell lines (LCL) derived from the variant carriers exhibited a significant increase in apoptosis (p < 0.05). In addition, the transcript levels of markers for endocytosis, LC3-associated phagocytosis, ER stress and cytoskeletal organisation were significantly dysregulated in these variant carriers, suggesting that these pathways were impaired. In ALS spinal cord cases, transcript analysis of RUBCN and KANK1 expression revealed a significant upregulation of RUBCN (2.85-fold) and a significant downregulation of KANK1 (0.40-fold) (p < 0.05), indicating their involvement in the broader context of sporadic ALS. Based on these findings, we conclude that RUBCN and KANK1 have a putative role in ALS pathogenesis.