In fact, several genes implicated in the leptin–melanocortin pathway (LEP, LEPR, POMC, BDNF, MC4R, PCSK1, SIM1, BDNF, TrkB, etc.)are associated with obesity and neurodegenerative and neurodevelopmental diseases. The gene discussed is SIM1; the disease is obesity due to melanocortin 4 receptor deficiency.