NF1 and obesity due to melanocortin 4 receptor deficiency: Recently, we demonstrated that mice harboring germline mutations in a single Nf1 allele (Nf1+/−) recapitulate many of the metabolic features observed in persons with NF1.8Nf1+/− mice rapidly metabolize glucose and are protected from diet-induced hyperglycemia and obesity when compared with littermate wild-type (WT) mice; however, the response to insulin and glucagon did not differ between genotypes, suggesting that neurofibromin, the protein product of NF1, controls basal glucose uptake and/or glycolysis.