Figure 3.

BACs 199 and 178 drive expression of lacZ at sites predicted from effects of regulatory mutations on endogenous Bmp5 expression. (A) BACs 199 and 178 extend proximal of the se^30DThWb and distal of the se^4CHLd breakpoint, respectively. Previous expression studies suggest that control elements for the indicated sites also should be located proximal or distal of these breakpoints. (B) BAC 199 drives expression in three sites predicted by previous studies: the ribs (top arrow), the finger tips (middle arrow), and the intestines (bottom arrow). A frontal view (C) shows that the ribs, but not the sternum, display robust reporter expression, consistent with normal rib expression (arrowhead) and reduced sternum expression (arrow) of Bmp5 in se^30DThWb embryos (E and F). In contrast, BAC 178 (L) drives strong expression in the sternal bands as well as some expression in the ribs (K). This is consistent with regulatory mutant data that place the sternal enhancer 3′ of the se^30DThWb breakpoint and BAC 551 data that place it further 3′ as shown in A. The intestinal mesenchyme enhancer activity in BAC 199 (B and D) matches Bmp5 expression at the same site (G) and is consistent with normal Bmp5 expression in se^30DThWb embryos (H). The BAC 178-driven reporter expression in the base of the ear (arrowheads in L and M) coincides with one part of the endogenous Bmp5 ear expression domain (arrowhead in I). The position of this enhancer in the 3′ BAC 178 is consistent with the effects of se^4CHLd on Bmp5 expression at that site (arrowhead in J).