We previously reported that Ntrk2 deletion in several hypothalamic areas using the Rgs9-Cre led to obesity37; however, the obesity phenotype was not as severe as what we observed in Ntrk2 hypomorphic mice that express TrkB at ~25% of the normal amount throughout the body11,37. This evidence concerns the gene RGS9 and obesity due to melanocortin 4 receptor deficiency.