MBNL1 and myotonic dystrophy type 1: To address why these 2 diseases present disparate muscle phenotypes despite shared sequestration of MBNL proteins, we determined the expression of DMPK, CNBP, and MBNL1 genes across healthy human muscles using a transcriptomic atlas, and we evaluated multiple muscles from Mbnl-KO mice to assess differential susceptibility, which muscles better recapitulate DM pathology, and whether mouse muscles resemble DM1, DM2, or neither following MBNL loss.