Dorsoventral Patterning of the Mouse Coat by Tbx15
Dorsoventral Mouse Pigmentation Pattern

Abstract
Many members of the animal kingdom display coat or skin color differences along their dorsoventral axis. To determine the mechanisms that control regional differences in pigmentation, we have studied how a classical mouse mutation, droopy ear (deH), affects dorsoventral skin characteristics, especially those under control of the Agouti gene. Mice carrying the Agouti allele black-and-tan (at) normally have a sharp boundary between dorsal black hair and yellow ventral hair; the deH mutation raises the pigmentation boundary, producing an apparent dorsal-to-ventral transformation. We identify a 216 kb deletion in deH that removes all but the first exon of the Tbx15 gene, whose embryonic expression in developing mesenchyme correlates with pigmentary and skeletal malformations observed in deH/deH animals. Construction of a targeted allele of Tbx15 confirmed that the deH phenotype was caused by Tbx15 loss of function. Early embryonic expression of Tbx15 in dorsal mesenchyme is complementary to Agouti expression in ventral mes