In an unexpected discovery, researchers have found that a gene previously known to control human metabolism also controls the equilibrium of bone and fat in bone marrow as well as how an adult stem cell expresses its final cell type. The findings could lead to a better understanding of the disruption of bone-to-fat ratio in bone marrow as well as its health consequences, and also point to the gene as a promising therapeutic target in the treatment of osteoporosis and skeletal aging.