BAG3 (Bcl-2–Associated Athanogene-3) Coding Variant in Mice Determines Susceptibility to Ischemic Limb Muscle Myopathy by Directing Autophagy

Background: Critical limb ischemiais a manifestation of peripheral artery disease that carries significant mortality and morbidity risk in humans, although its genetic determinants remain largely unknown. We previously discovered 2 overlapping quantitative trait loci in mice, Lsq-1 and Civq-1 , that affected limbmuscle survival and stroke volume after femoral artery or middle cerebral artery ligation, respectively. Here, we report that a Bag3variant (Ile81Met) segregates with tissue protection from hind- limbischemia. Methods: We treated mice with either adeno-associated viruses encoding a control ( green fluorescent protein) or 2 BAG3(Bcl-2–associated athanogene-3) variants, namely Met81 or Ile81, and subjected the mice to hind- limbischemia. Results: We found that the BAG3Ile81Met variant in the C57BL/6 (BL6) mouse background segregates with protection from tissue necrosis in a shorter congenic fragment of Lsq-1 (C.B6– Lsq1-3 ). BALB/c mice treated with adeno-associated virusencoding the BL6 BAG3variant (Ile81; n=25) displayed reduced limb-tissue necrosis and increased limbtissue perfusion compared with Met81- (n=25) or green fluorescent protein– (n=29) expressing animals. BAG3Ile81 , but not BAG3Met81 , improved ischemic muscle myopathy and muscle precursor cell differentiation and improved muscle regeneration in a separate, toxin-induced model of injury. Systemic injection of adeno-associated virus– BAG3Ile81 (n=9), but not BAG3Met81 (n=10) or green fluorescent protein(n=5), improved ischemic limbblood flow and limbmuscle histology and restored muscle function (force production). Compared with BAG3Met81 , BAG3Ile81 displayed improved binding to the small heat shock protein (HspB8) in ischemic skeletal muscle cells and enhanced ischemic muscle autophagic flux. Conclusions: Taken together, our data demonstrate that genetic variation in BAG3plays an important role in the prevention of ischemic tissue necrosis. These results highlight a pathway that preserves tissue survival and muscle function in the setting of ischemia.