Loss of Tbx15 also affects regional distribution of hair color in the limbs, with areas that would normally produce black hair giving rise to yellow hair instead. However, neither normal patterns of pigment-type synthesis in the limb nor their disruption in deH/deH mice correspond to obvious developmental compartments. Furthermore, losses of function for En1 or Wnt7a, which cause a partial transformation of the distal limb from dorsum to ventrum (Loomis et al. 1996) or ventrum to dorsum (Parr and McMahon 1995), respectively, have no effect on regional patterns of Agouti expression or distribution of hair-color regions (Y. Chen, unpublished data). (Ectopic pigmentation of the ventral footpads that develops in En1 mutant mice is unrelated to pigment-type synthesis and instead likely reflects a requirement for En1, independent of Wnt7a, to repress migration or proliferation (or both) of pigment cells in ventral epidermis [Cygan et al. 1997; Loomis et al. 1998].)