HNRNPA1 and amyotrophic lateral sclerosis: C9ORF72. RNA of the mutant C9ORF72gene with an abnormal number of GGGGCC hexanucleotides in the firstintron/promoter can also initiate a pathological process associated with ALS.An increased transcriptional level of C9ORF72, as well as theformation of focal accumulations of C9ORF72 RNA, containing,among other things, hnRNPA1 and Pur-α RNA-binding proteins, was observedin motor neurons produced after the differentiation of iPSCs from patients withthe C9-ALS familial form (hexanucleotide repeat expansion in theC9ORF72 gene) [71].hnRNPA1 is known to bind to TDP-43 molecules [72].