Common coexpression patterns with gatekeeper genes in all three species were observed for the protamines Prm1 and Prm2 that are essential for chromatin compaction during spermatogenesis, the Lep gene which is associated with obesity, the steroidogenic Star gene and genes relevant to sexual differentiation and embryogenesis. The gene discussed is PRM2; the disease is obesity due to melanocortin 4 receptor deficiency.