Abstract MATR3, one of the most abundant inner nuclear matrix proteins, is implicated in amyotrophic lateral sclerosis (ALS) and distal myopathy. MATR3 has been reported to have both DNA- RNA-binding abilities. However, it not understood mechanistically how mutation leads ALS pathogenesis. To understand its loss function effects, we mutated human HAP1 cell line using CRISPR/Cas9 technology. Usi...