OMA1 and cardiomyopathy: Using protease-inactive Oma1<sup>E324Q/E324Q</sup> knock-in mice, we show that blunting mtISR in Chchd10<sup>S55L/+</sup> mice delays cardiomyopathy onset without rescuing CHCHD10 insolubility, cristae defects or OXPHOS impairment.