Fig. 1.

Localisation of the forelimb enhancer of the mouse Tbx5 gene. (A) Tbx5 transgenic constructs. Putative regulatory sequences (thin lines) were cloned into the BGZA reporter vector, which contains a chick β-globin minimal promoter (light-blue box), the lacZ gene (dark-blue box) and an SV40 polyadenylation signal (grey box). Black boxes represent exons (e1, e2) and the green box represents a conserved non-coding element (CNE) shared between amniotes. i1, intron 1; i2, intron 2. The numbers denote size in kb. To the right is shown the number of embryos showing forelimb-restricted expression out of the total number of transgenic embryos recovered. (B-F,H,I) Representative β-galactosidase staining for the m5-10 (B), m5-5 (C), ΔRV (D), m5-5#3 (E) and intron2 (F,H,I) constructs. (G) E9.5 mouse embryo showing endogenous Tbx5 expression assayed by whole-mount in situ hybridisation. (I) Transverse section at the forelimb level of an E9.5 intron2 transgenic embryo showing β-galactosidase staining in LPM-derived limb mesenchyme. Lateral views from the right side are shown for E9.5 embryos (B-G), whereas a ventral view with anterior to the left is shown for the E8.5 embryo (H). AER, apical ectodermal ridge; lm, limb mesoderm; LPM, lateral plate mesoderm; NT, neural tube; so, somites.