NOP2 and amyotrophic lateral sclerosis: Quantification of NSUN1 levels in ALS/FTD with confirmed TDP-43 pathology showed that NSUN1 isoforms 1/2 were significantly reduced (Fig 8D–G), whereas isoform 3—the NSUN1 isoform that preferentially interacts with TDP-43 (Fig 6)—and isoform 4 were unaffected (Fig 8D–G).