Fig. 7

Increased Fgf signaling reduces posterior forelimb expression of tbx5a. (A–F) Expression of tbx5a in heat-shocked control sibling and Tg(hsp70:ca-fgfr1)^pd3 embryos. (A,B) The expression of tbx5a in heat-shocked control sibling and Tg(hsp70:ca-fgfr1)^pd3 embryos at 8s is indistinguishable. Compare length between arrows in A,B. (C,D) By the 12s stage, in Tg(hsp70:ca-fgfr1)^pd3 embryos with increased Fgf signaling, the length of tbx5a expression is shorter (arrows). (E) By the 14s stage, the tbx5a expressing cardiac cells have begun to migrate medially, while the forelimb progenitors remain lateral and occupy a large portion of the LPM. (F) In Tg(hsp70:ca-fgfr1)^pd3 embryos at the 14s stage, the tbx5a expressing cardiac progenitors are expanded relative to controls, while the tbx5a expressing forelimb progenitors are extremely reduced. The lateral edge of tbx5a expression in the LPM is outlined with a dashed blue line in A–D. The lateral edges of the cardiac and forelimb tbx5a expression domains are outlined with red and yellow dashed lines respectively in E and F. Arrows in E and F indicate the separation point between the two tbx5a expressing domains. All views are dorso-lateral with anterior to the left.