Net39 protects muscle nuclei from mechanical stress during the pathogenesis of Emery-Dreifuss muscular dystrophy [snRNA-seq]

Mutations in genes encoding nuclear envelope proteins lead to diseases known as nuclear envelopathies, characterized by skeletal muscle and heart abnormalities, such as Emery-Dreifuss Muscular Dystrophy (EDMD). The tissue-specific role of the nuclear envelope in the etiology of these diseases has not been extensively explored. We previously showed that global deletion of the muscle-specific nuclear envelope protein NET39 in mice leads to neonatal lethality due to skeletal muscle dysfunction. To study the potential role of the Net39 gene in adulthood, we generated a muscle-specific conditional knockout (cKO) of Net39 in mice. cKO mice recapitulated key skeletal muscle features of EDMD, including muscle wasting, impaired muscle contractility, abnormal myonuclear morphology, and DNA damage. The loss of Net39 rendered myoblasts hypersensitive to mechanical stretch, resulting in stretch-induced DNA damage. Net39 was downregulated in a mouse model of congenital myopathy, and restoration of Net39 expression through AAV gene delivery extended lifespan and ameliorated the muscle abnormalities. These findings establish NET39 as a direct contributor to the pathogenesis of EDMD by protecting against mechanical stress and DNA damage. Comparative gene expression profiling analysis of single nucleus RNA-seq data for three biological replicates of Gastrocnemius-plantaris (GP) muscles from control and Net39 adult-inducible conditional knockout mice (cKO) at 5 months of age.