Table 1.

Summary of skeletal muscle and cardiac phenotypes of double knockout mice

Skeletal muscle
	Protein aggregate myopathy
	Submembraneous accumulations localized inside myofibres containing MyHC and parts of sarcomeres
	Protein accumulations are not fibre type restricted
	Fibre type shift in soleus and EDL (increased slow‐, decreased fast‐twitch fibres)
	Centralized nuclei
	Decreased maximal force development of soleus and EDL
	Increased Myh3 and Myh7 expression
	Mass spectrometry:
	Increase in degradation associated proteins
	Increase in MAPKAPK3
	Decrease in mitochondrial proteins

Heart
	Increased LVESD, decreased wall thickness
	Decreased LVEF and cardiac output
	Reduced left ventricular systolic and developing pressure
	Decreased cardiac contraction and relaxation velocity
	Reduced cardiomyocyte contractility and relaxation velocity
	Reduced calcium influx and export velocities
	Increased Myh7 expression

EDL, extensor digitorum longus; LVESD, left ventricular ejection fraction; LVEF, left ventricular end‐systolic dimension; MAPKAPK, mitogen‐activated protein kinase‐activated protein kinase; Myh, myosin heavy chain.