Fig. 4. Normal development of the thyroid primordia in Eya1^–/– embryos. (A-D) Transverse sections showing the thyroid primordia (ty) in wild-type (A,C) and Eya1^–/– (B,D) embryos at E10.5. The thyroid primordia were evident in Eya1^–/– embryos. (E,F) Transverse sections showing Pax8 expression in the thyroid primordia of wild-type and Eya1^–/– embryos at E10.5. (G,H) Sagittal sections showing Ttf1 expression in wild-type and Eya1^–/– thyroid primordia at E10.5. (I,J) Transverse sections showing that Eya1 expression was not detectable in the thyroid primordia at E10.5-11.5 in wild-type embryos. ph, pharynx; baa, 2nd branchial arch artery. For transverse sections, dorsal is up; for sagittal sections, cranial is up and dorsal is to the left.