Figure 2
Foxn1ex9lacZand Foxn1ex9creexpression from E10.5 to newborn. Cre expression was assayed using the R26R reporter allele. Panels C, F, I, L show Cre negative control embryos with no expression. Black arrows in (A-I) point to the third pharyngeal pouch. White arrows in (J-L) indicate the Foxn1-negative parathyroid region of the primordium. For sagittal sections, ventral is left and anterior is up. For transverse sections, dorsal is up. A, B, Lateral views of E10.5 Foxn1+/ex9lacZ(A) and Foxn1+/ex9cre;R26R+/- (B) whole embryos, and D, E, coronal sections through E10.5 Foxn1+/ex9lacZ(D) and Foxn1+/ex9cre;R26R+/- (E) embryos showing no expression in the third pharyngeal pouch. G, H, Lateral views of E11.5 Foxn1+/ex9lacZ(G) and Foxn1+/ex9cre;R26R+/- (H) embryos showing expression only in the developing thymus primordium. J, K, Sagittal sections through E11.5 Foxn1+/ex9lacZembryo (J) and E11.5 Foxn1+/ex9cre;R26R+/- embryo (K) showing expression restricted to the ventral thymus domain of the 3rd pouch-derived organ primordium. M, Sagittal section through E12.5 Foxn1+/IRESlacZthymus primordium. N, Transverse section through E12.5 Foxn1+/ex9cre;R26R+/- thymus primordium. O, Transverse section through E12.5 thymus showing in situ hybridization for Foxn1 mRNA. P, Section through E16.5 Foxn1+/ex9lacZthymus. Q, R, Sections through E16.5 (Q) and newborn (R) Foxn1+/ex9cre;R26R+/- thymi showing more intense staining in the prospective medullary regions. c = cortex, m = medulla.