FGF, Wnt/β-catenin and RA signaling regulate Xenopus lung development in a pathway with Osr1/Osr2. (A-D) Embryos were treated from stages 25-35 with DMSO vehicle (A), 100 μM PD173074 (B), 50 μM XAV939 (C) or 10 μM BMS493 (D), and assayed at stage 35 with the indicated probes. (E). Embryos were treated between stages 28 and 35 with vehicle (DMSO), 10 μM BIO, 80 μM SU5402, a combination of 80 μM SU5402 + 10 μM BIO, 10 μg/ml cycloheximide (CHX) or CHX +10 μM BIO, and analyzed for nkx2.1 at stage 35 and sftpc at stage 40. Black arrows indicate normal expression, red arrows indicate absent expression, yellow arrows indicate reduced expression and green arrows indicate expanded or rescued expression.