Mature IGF-1 precursor isoforms have varying roles in skeletal muscle myogenesis

The insulin-like growth factor 1 protein plays a critical role in growth and development of skeletal muscle. IGF-1 is unique in that it stimulates both the proliferation and differentiation of skeletal muscle. Knockout Igf1 mutant mice were found to have birth weights 60% of wild-type mice, which was partially attributed to muscle hypoplasia. Interestingly, The Igf1 gene encodes for precursor isoforms to mature IGF-1 through alternative splicing in humans and rodents. Furthermore, these splice variants show age-dependent expression and may act via independent pathways from mature IGF-1 to induce myogenesis. Understanding the differences in biochemical pathways and regulation among IGF-1 splice variants may provide insight into mechanisms for muscle aging and therapies to treat sarcopenia