Overall, these results strongly suggest that the observed muscle phenotypes are associated with purine deficiency, regardless of the mode of biosynthesis of these purines since disruption of the de novo pathway (ppat.L/ppat.S MO), the recycling pathway (hprt1.L MO) or both (adsl.L MO) results in similar alterations in myogenesis. The gene discussed is HPRT1; the disease is hyperinsulinemic hypoglycemia, familial, 4.