May play a role in melanocortin signaling pathways that regulate energy homeostasis. Interacts with MC4R. Highly expressed in brain, heart, lung, kidney and liver. In the central nervous system, it is highly expressed in the dentate gyrus, CA1-3 regions of the hippocampus, and the ventral taenia tecta. Mice are grossly normal with no alterations of pigmentation, central nervous system pathology or body weight. In contrast, constitutive expression of Atrnl1 in mice lacking Atrn display normal, agouti-banded hairs and significantly delayed onset of spongiform neurodegeneration, indicating that overexpression of Atrnl1 compensates for loss of Atrn.