Both PI3K and MEK signaling contribute to lung and liver development. (A) Western blot analysis of embryos cultured in DMSO, PI3Ki (LY294002), or MEKi (U0126) from stages NF18 to NF35 in triplicate shows a dramatic decrease in pAkt and pErk levels with PI3Ki and MEKi treatment respectively. (B) Embryos cultured in DMSO or the indicated inhibitors from NF18 to NF35 were analyzed at stage NF35 for liver (nr1h5), lung (nkx2.1), pancreas (ptf1α), liver/thyroid (hhex), and pancreatic/duodenal (pdx1) expression. Embryos cultured in DMSO or the indicated inhibitors from NF18 to NF35 were analyzed at stage NF42 for organ bud appearance with hnf4α-stained gut tubes. Yellow arrows indicate normal expression, red arrows indicate reduced or absent expression. Foregut organ buds are outlined in dashed lines (lu; lung, p; pancreas, lv; liver, s; stomach, i; intestine, th; thyroid, p/d; pancreas/duodenum). (C) Summary of the percentage of inhibited embryos with expanded, normal, weak, or severely reduced/absent foregut marker expression compared to controls with the number of embryos analyzed listed for each condition. FGFRi data is repeated from Figure 3 for comparison.