SRXN1 and cardiomyopathy: Using muscle biopsy specimens obtained from patients, molecular analysis of 10 distinct MYH7 mutations in the light-meromyosin (LMM) core of the thick filament, which result in skeletal muscle diseases rather than cardiomyopathies, found a significant decrease in the proportion of SRX myosin (Carrington et al, 2023; Buvoli et al, 2024).