PT - JOURNAL ARTICLE AU - Winkelsas, Audrey AU - Apfel, Athena AU - Johnson, Brian AU - Harmison, George AU - Li, Dongjun AU - Cheung, Vivian AU - Grunseich, Christopher TI - Allele-specific silencing of a dominant <em>SETX</em> mutation in familial amyotrophic lateral sclerosis type 4 AID - 10.1101/2024.10.11.617871 DP - 2024 Jan 01 TA - bioRxiv PG - 2024.10.11.617871 4099 - http://biorxiv.org/content/early/2024/10/12/2024.10.11.617871.short 4100 - http://biorxiv.org/content/early/2024/10/12/2024.10.11.617871.full AB - Amyotrophic lateral sclerosis 4 (ALS4) is an autosomal dominant motor neuron disease that is molecularly characterized by reduced R-loop levels and caused by pathogenic variants in senataxin (SETX). SETX encodes an RNA/DNA helicase that resolves three-stranded nucleic acid structures called R-loops. Currently, there are no disease-modifying therapies available for ALS4. Given that SETX is haplosufficient, removing the product of the mutated allele presents a potential therapeutic strategy. We designed a series of siRNAs to selectively target the RNA transcript from the ALS4 allele containing the c.1166T&gt;C mutation (p.Leu389Ser). Transfection of HEK293 cells with siRNA and plasmids encoding either wild-type or mutant (Leu389Ser) epitope tagged SETX revealed that three siRNAs specifically reduced mutant SETX protein levels without affecting the wild-type SETX protein. In ALS4 primary fibroblasts, siRNA treatment silenced the endogenous mutant SETX allele, while sparing the wild-type allele, and restored R-loop levels in patient cells. Our findings demonstrate that mutant SETX, differing from wild-type by a single nucleotide, can be effectively and specifically silenced by RNA interference, highlighting the potential of allele-specific siRNA as a therapeutic approach for ALS4.Competing Interest StatementThe authors have declared no competing interest.