Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disorder affecting upper motor neurons in the brain and lower motor neurons in the brain stem and spinal cord, resulting in fatal paralysis. It has been found to be associated with frontotemporal lobar degeneration (FTLD). In the present study, we have described homozygosity mapping and gene sequencing in a consanguineous autosomal recessive Pakistani family showing non-juvenile ALS without signs of FTLD. Gene mapping was carried out in all recruited family members using microsatellite markers, and linkage was established with sigma non-opioid intracellular receptor 1 (SIGMAR1) gene at chromosome 9p13.2. Gene sequencing of SIGMAR1 revealed a novel 3'-UTR nucleotide variation c.672*31A>G (rs4879809) segregating with disease in this family. The C9ORF72 repeat region in intron 1, previously implicated in a related phenotype, was excluded through linkage, and further confirmation of exclusion was obtained by amplifying intron 1 of C9ORF72 with multiple primers in affected individuals and controls. In silico analysis was carried out to explore the possible role of 3'-UTR variant of SIGMAR1 in ALS. The Regulatory RNA motif and Element Finder program revealed disturbance in miRNA (hsa-miR-1205) binding site due to this variation. ESEFinder analysis showed new SRSF1 and SRSF1-IgM-BRCA1 binding sites with significant scores due to this variation. Our results indicate that the 3'-UTR SIGMAR1 variant c.672*31A>G may have a role in the pathogenesis of ALS in this family.
Keywords: 3′-UTR; ALS; Pakistan; SIGMAR1.