Figure 7.

Absence of the transcription factor Pitx2 and of collagen formation in the corneal stroma of Tgfbr2-mutant mice. (a) At E15, Pitx2 expression, as detected by immunohistochemistry (red; arrowheads) is restricted to corneal stromal cells in control animals but is undetectable in the corresponding structures of Tgfbr2-mutant mice (open arrowheads). (b) In situ hybridization for Dct, which marks prospective melanocytes, reveals atypical expression in the corneal stroma of Tgfbr2-mutant embryos (arrows). (c) High magnification of the corneal stroma shows the typical appearance of thin keratocytes in a parallel orientation and a dense extracellular matrix in control eyes at E18. In contrast, the corneal stroma of Tgfbr2-mutant embryos lacks extracellular matrix and has cells with large nuclei and a polygonal shape. (d) Van Gieson's staining reveals normal collagen matrix in the corneal stroma of control embryos (purple) that is absent in Tgfbr2-mutant embryos.