Fig. 6. Inhibition of FGF signaling partially rescues the development of somites in Bmpr-MORE embryos. (A-D) Control and Bmpr-MORE embryos at E6.5-6.75 grown in culture for 20-24 hours were examined for Lefty2 expression. Control embryos cultured with DMSO normally expressed Lefty2 (A, arrowheads). Mutant embryos cultured with DMSO showed a proximal shift and decreased expression of Lefty2 (3/3) (B, arrowheads). Control embryos cultured with 20 µM SU5402 showed normal expression of Lefty2 (C, arrowheads). Exposure to SU5402 normalized the expression of Lefty2 in Bmpr-MORE embryos (2/2) (D, arrowheads). (E-H) Control and Bmpr-MORE embryos at E6.5-6.75 were cultured for around 48 hours and examined for the expression of Uncx4.1. (E) Control embryos cultured with DMSO normally expressed Uncx4.1 (arrowheads). (F) Mutant embryos cultured with DMSO showed a significant expansion of somites to the lateral edge of the embryos (arrows) (n=9). (G) Control embryos were cultured with 20 µM SU5402 for 12-15 hours, extensively washed and then cultured with DMSO for around 48 hours in total. In this condition, somites developed normally (arrowheads). (H) Mutant embryos were cultured with 20 µM SU5402 for 12-15 hours, extensively washed and then with DMSO for around 48 hours in total. In six mutant embryos out of 10 tested, partial rescue of somite development was observed (arrowheads). Scale bars: 85 µm for A,B; 100 µm for C,D; 600 µm for E-H.