An international research team revealed a nuclear localization role for a conserved short stretch of a cardiac muscle regulator. Mutations within the RSRSP stretch of RBM20 cause the left ventricle to enlarge and weaken, and were shown to interrupt nuclear transport of RBM20, preventing it from controlling a giant spring-like protein of cardiac muscle cells. The findings and animal model developed will pave the way for greater understanding of dilated cardiomyopathy.