Comparison of the Dorsoventral at/at Pigmentation Boundary to the Lateral Somitic Frontier
(A) Dorsoventral slices of skin from at the midtrunk region prepared such that the dorsal midline lies in the center of the slice. Sections were taken at P1.5 (a) or P4.5 (b–e) from at/at or R26R/+; Tg.Hoxb6-Cre/+ mice (the latter were stained with X-Gal), as described in Materials and Methods. For purposes of comparison, images were proportionally scaled. The boundary of X-Gal staining marks dermis derived from lateral plate versus dermis derived from mesoderm (the lateral somitic frontier) and lies more dorsal than the at/at pigmentation boundary.
(B) Quantitation of mean (± SEM) dorsal pigmentation area (n = 5) and somite-derived dermis area (n = 3) shows a significant difference (p < 0.005, t-test).
(C) RNA in situ hybridization showing that Tbx15 expression at E11.5 is complementary to En1 expression on the flank (scale bars = 200 μm). The arrow indicates the boundary between the expression domains of the two genes.