The AH subnetwork C23 is enriched for adult feeding behavior and energy balance and contains well known genes such as those encoding agouti related protein (Agrp) and neuropeptide Y (Npy), and also Ptx3, a gene recently reported to associate with obesity that is involved in immune system response and modification in feeding behavior [41,42]. The gene discussed is NPY; the disease is obesity due to melanocortin 4 receptor deficiency.