PTBP1 and amyotrophic lateral sclerosis: PTBP1, a splice factor belonging to the ubiquitously expressed heterogeneous nuclear ribonucleoprotein (hnRNP) subfamily (Bampton et al., 2020), exhibited approximately 1-fold downregulation in gene expression in ALS-FUS, ALS-TARDBP, and ALS-C9orf72.