Inactivation of TGFβ signaling in ocular NC-derived cells. (a,b) TGFβ ligand and receptor expression in the developing eye at E13.5. (a) Immunoreactive TGFβ2 (red) is predominantly expressed in the lens, whereas (b) Tgfbr2 immunostaining (brown) shows a broad expression of the receptor in the forming eye, including the periocular mesenchyme, lens, primary vitreous, and retina. (c) Strategy used for Cre/loxP-mediated deletion of exon 4 of the Tgfbr2 locus in NC stem cells (NCSC). Exon 4 (red), encoding the transmembrane domain and the intracellular phosphorylation sites of the Tgfbr2 protein, is flanked by loxP sites (triangles) and deleted in NCSCs upon breeding with Wnt1-Cre mice. (d-g) A detailed view of the forming anterior eye segment (box in b). (d) Strong expression of Tgfbr2 (brown) in the prospective chamber angle, corneal stroma and endothelium can be seen in control embryos. (f) After deletion of Tgfbr2 in NCSC, Tgfbr2 is undetectable in corresponding structures. Moreover, defective TGFβ signaling in these structures is also reflected by the absence of phosphorylated pSmad2 in (g) Tgfbr2 mutant (open arrowheads) as compared with (e) control embryos (arrowheads).
Ittner et al. Journal of Biology 2005 4:11 doi:10.1186/jbiol29