Fig. 3.

Smad1/5 are efficiently inactivated in thyrocyte progenitors. (A) Compared with control thyroid lobes, Smad1/5^dKO show a ∼50% reduction in Smad1 and Smad5 mRNA levels from E14.5 onwards. Expression of Smad8 is affected at E18.5 (n≥5). (B) pSmad1/5 labeling reveals Smad activation in control but not in Smad1/5^dKO thyroid lobes at E14.5 treated in parallel with 20 ng/ml Bmp4. (C) Organization of epithelial progenitor cells (E-cadherin) in monolayers surrounding a lumen (ezrin) is impaired in Smad1/5^dKO thyroid glands. Arrows indicate ezrin⁺ structures in adjacent cells. (D) The number of cells per luminal profile of well-defined Par3⁺ structures (n≥13) is decreased by about half in thyroid glands of Smad1/5^dKO as compared with control. (E) Defective apical (ezrin) and basal (pan-laminin) specification in Smad1/5^dKO, as compared with control thyroid glands. Arrows indicates ezrin⁺ structures in adjacent cells. (F) The number of cells in contact with pan-laminin and with ezrin is decreased in Smad1/5^dKO. *P<0.05, **P<0.001, ***P<0.0001, Mann–Whitney U-test. All mRNAs were normalized to Rpl27. Data are presented as mean±s.e.m. Scale bars: 10 µm. See also Fig. S1.