MBNL1 and myotonic dystrophy type 1: Although there is a question of how much of the failure to fully rescue is due to the challenge of providing full activity using exogenous MBNL, our results showing partial rescues raise an intriguing possibility that exogenous MBNL efficiently rescued the pathogenic component caused by MBNL loss of function and that what was not rescued were other mechanisms for DM1 cardiac pathogenesis induced by CUGexp RNA.