Fig. 1. Expression of Tbx15 at E10.5. (A) Expression of Tbx15 in wild-type forelimb bud at E10.5. (B) Expression of Tbx15 in hindlimb bud at E11.5. (C) Pax1 expression in wild-type forelimb bud at E10.5. Note that the expression of Pax1 in the shoulder-forming region is complementary with that of Tbx15. (D,E) Alx4 expression in wild-type (D) and Gli3^–/– (E) forelimb buds at E10.5. In Gli3^–/– limb buds, Alx4 expression is downregulated in the distal part of its normal expression domain. (F-I) Expression of Emx2 in wild-type (F,H), Alx4^–/–/Cart1^–/– (G) and Gli3^–/–/Tbx15^–/– (I) forelimb buds at E10.5. (J) Tbx15 in situ hybridization on a wild-type sagittal section at E10.5. Black arrow indicates expression in notochord and surrounding mesenchyme. (K,L) Tbx15 in situ hybridization on wild-type transverse sections at E10.5. (K) Black arrowhead shows expression of Tbx15 in lateral cranial mesenchyme. (L) Higher magnification of section shown in K showing expression of Tbx15 in notochord (black arrow) and surrounding mesenchyme. a, atrium; m, mandibular component; mx, maxillary component of first branchial arch; v, ventricle.