GFRA1 and Hand-foot syndrome: Botchkareva et al. had postulated that GDNF-GFRA1 signaling within proximal and distal outer root sheath (ORS) and inner root sheath (IRS) cells of HFs may play a direct role in blocking premature catagen entry based on their in situ mRNA expression pattern of Gfra1 and Gdnf39.