Mitochondrial defects in the cAMP-PKA-DRP1 pathway in a Crppa deletion model of dystroglycanopathy.

Dystroglycanopathies (DGPs) are autosomal recessive muscular dystrophies caused by abnormal α-dystroglycan glycosylation. CRPPA is one causative gene, with deletion of exons 6-9 identified as a founder variant in Chinese patients. Our previous study revealed mitochondrial abnormalities in patient muscle biopsies, although the underlying mechanism(s) remained unclear. A Crppa knockout mouse (dyC/dyC) was generated based on the founder variant, displaying muscle weakness, cerebellar hypoplasia, retinal abnormalities and neonatal lethality within 24 h. Electron microscopy showed mitochondrial structural defects in skeletal muscle, consistent with patient findings. RNA sequencing revealed dysregulation of the cAMP-PKA pathway, accompanied by decreased ATP and reduced phosphorylation of PKA and DRP1 (Ser637). To verify the link between CRPPA deficiency and mitochondrial dysfunction, Crppa knockdown C2C12 cells and CRPPA-related DGP patient-derived fibroblasts were examined. Both models exhibited reduced DRP1 Ser637 phosphorylation and ATP levels. Treatment with cAMP-PKA activators restored DRP1 phosphorylation and ATP production in a time-dependent manner. Recovery of mitochondrial membrane potential was confirmed by JC-1 staining. These findings suggest that CRPPA deficiency is associated with mitochondrial dysfunction involving the cAMP-PKA-DRP1 axis, suggesting a candidate pathway warranting further investigation for DGPs.