A BAG3 Coding Variant in Mice Determines Susceptibility to Ischemic Limb Muscle Myopathy by Directing Autophagy.

Background — Critical limb ischemia(CLI) is a manifestation of peripheral artery disease (PAD) that carries significant mortality and morbidity risk in humans, although its genetic determinants remain largely unknown. We previously discovered two overlapping quantitative trait loci (QTL) in mice, Lsq-1 and Civq-1 , that affected limb muscle survival and stroke volume following femoral artery or middle cerebral artery ligation, respectively. Here we report that a Bag3variant (Ile81Met) segregates with tissue protection from hindlimbischemia (HLI). Methods —We treated mice with either adeno-associated viruses (AAV) encoding a control (GFP), or two BAG3variants, namely Met81 or Ile81, and subjected the mice to hindlimbischemia. 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 ). Treating BALB/c mice with AAV encoding the BL6 BAG3variant (Ile81) ( n =25) displayed reduced limb tissue necrosis and increased limb tissue perfusion compared to Met81- ( n =25) or GFP- ( 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 AAV-BAG3Ile81 ( n =9), but not BAG3Met81 ( n =10) or GFP ( n =5), improved ischemic limb blood flow, limb muscle histology, and restored muscle function (force production). Compared to 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.