Scientists have pinpointed the cells that cause hair to turn gray and to go bald in mice, according to a new study published in the journal Genes & Development.

Researchers from the University of Texas Southwestern Medical Center accidentally stumbled upon this explanation for baldness and graying hairs—at least in mouse models—while studying a rare genetic disease that causes tumors to grow on nerves, according to a press release from the center.

They found that a protein called KROX20 switches on skin cells that become a hair shaft, which then causes cells to produce another protein called stem cell factor. In mice, these two proteins turned out to be important for baldness and graying. When researchers deleted the cells that produce KROX20, mice stopped growing hair and eventually went bald; when they deleted the SCF gene, the animals’ hair turned white.