Deletion of exon 2 in ALS-linked Sptlc1 causes lethality in homozygous mice but not in heterozygotes.

Mutations in the human SPTLC1 gene have recently been linked to early-onset amyotrophic lateral sclerosis (ALS), characterized by global atrophy, motor impairments, and symptoms such as tongue fasciculations. All known ALS-linked SPTLC1 mutations cluster within exon 2, and a specific variant, c.58G>T, results in exon 2 skipping. However, it is unclear how the exon 2 deletion affects SPTLC1 function in vivo and contributes to ALS pathogenesis. Leveraging the high genomic sequence similarity between mouse and human SPTLC1, we created a novel knock-in mouse model with a CRISPR/Cas9-mediated deletion of exon 2 in the endogenous murine Sptlc1 locus. Although heterozygous mice did not develop motor defects or ALS-like neuropathology, homozygous mutants died prematurely. These findings provide valuable insights into SPTLC1 exon 2 biology and serve as a useful resource for future mechanistic studies.