Two proteins mutated in familial cases of amyotrophic lateral sclerosis (ALS) or FTLD, the RNA-binding proteins TAR DNA-binding protein-43 (TDP-43) and fused in sarcoma (FUS), have been identified in Microprocessor complexes (Gregory et al., 2004; Kawahara and Mieda-Sato, 2012). Here, FUS is linked to amyotrophic lateral sclerosis.