Fig. 6. Partial rescue of LKB1 deficiency by exogenous TGFβ. (A) Relative TGFβ1 and PAI1 mRNA levels in LKB1-siRNA transfected HUVECS with (+) or without (-) TGFβ1 treatment (1 ng/ml, 4 hours). Measurements were normalized according to GAPDH mRNA levels and the ratio (±s.d.) of LKB1-siRNA HUVECs to control HUVECs, which were normalized to one, is presented. Bars represent means of LKB1-si1 and LKB1-si2 duplicate samples compared with four controls (^*P<0.05, ^**P<0.01). The data in non-treated samples (-TGFβ1) is summarized from Fig. 5A and is shown for reference. (B-D) pSMAD2 staining of E12.5 wild-type (B), Lkb1^lox/-, Tie1-Cre (C) and TGFβ-treated Lkb1^lox/-, Tie1-Cre (D) yolk sac sections. (E) Percentage of pSMAD2-positive cells in E12.5 wild-type and Lkb1^lox/-, Tie1-Cre yolk sacs with or without exogenous TGFβ. Means±s.d. of three embryos are indicated (^*P<0.05). (F-H) SMA staining of E12.5 wild-type (F), Lkb1^lox/-, Tie1-Cre (G) and TGFβ-treated Lkb1^lox/-, Tie1-Cre (H) yolk sac sections, demonstrating loss of SMA staining in Lkb1^lox/-, Tie1-Cre embryos and partial recovery following TGFβ1 treatment. e, endoderm; EC, endothelial cell; mes, mesenchymal cell.