MYOD1 and cardiomyopathy: Intriguingly, despite the fact that MYOD1 is not expressed in the heart, mdx/Myod1−/− mutants developed progressive cardiomyopathy.99 Hearts become hypertrophic by 5 months of age, with increases in ventricular diameter as well as regions of cardiomyocyte hypertrophy predominantly in the LV.