INS and obesity due to melanocortin 4 receptor deficiency: To identify the specific cell types mediating these effects, we deleted the miR-7 family in neurons expressing the Leptin receptor (Lepr), Pomc, Agrp and Sim1. We found that Sim1-cre;mir-7fl/fl mice exhibited severe obesity due to increased food intake and decreased energy expenditure, associated with increased linear growth and increased insulin secretion.