LEPR and obesity due to melanocortin 4 receptor deficiency: Mice with neuronal deletion of STAT5 using nestin-cre develop severe obesity, but specific STAT5 deletion in LepRb-expressing neurons does not result in the obese phenotype [25,26], suggesting that the LepR-STAT5 pathway does not play an essential role in body weight regulation, and that STAT5 may mediate other cytokine signals for regulation of energy balance.