CELF1 and myotonic dystrophy type 1: We also examined the expression of CELF1 (formerly CUGBP1) and HNRNPA1, which have been implicated in DM1 pathogenesis (22–25), and we found much greater variation in CELF1 expression among individuals than any of the other genes examined (Supplemental Figure 1D), while HNRNPA1 showed little variation both between individuals and across muscles (Supplemental Figure 1E).