PPP1CB and myotonic dystrophy type 1: When Mp expression is attenuated via RNAi in Hand > Bru3 DM1 context (Hand > Bru3;Mp RNAi), diastolic and systolic diameters are reduced in comparison to DM1 flies (Hand > UPRT; Bru3) (Fig 6D, E, G, H, and I), and the cardiac contractility defect is ameliorated and becomes similar to that of aged control flies (UAS‐UPRT; Bru3) (Fig 6F).