HSPA9 and Mitochondrial myopathy: However, the deleterious effect of the induction of UPRmt has been only identified in the model Twnkdup of mitochondrial myopathy [27,33], and the levels of two proteins involved in UPRmt, the mitochondrial proteins stress-70 protein (HSPA9 or GRP75) and ATP-dependent Clp protease proteolytic subunit (CLPP), are unaltered in other mouse model of CoQ deficiency due to a different mutation in the Coq9 gene [34].