Taken together, data from the current study indicates that the observed variation in clinical and pathologic phenotypes of slow/β cardiac MyHC mutation is mutation-specific and that it may in part be due to the genetic background related to the existence of E3-ligase modifier genes that may reduce or enhance the impact of the mutation, as previously suggested in our study of a Laing distal myopathy model in Drosophila (Dahl-Halvarsson et al., 2018). Here, MYH6 is linked to distal myopathy.