FIGURE 2.

Conditional loss of Arf in Wnt1-expressing neural crest cells causes primary vitreous hyperplasia. A and B, shown are representative photomicrographs of hematoxylin- and eosin-stained sections through Arf^fl/fl (a), Wnt1-Cre, Arf^fl/+ (b), and Wnt1-Cre, Arf^fl/fl (c) eyes at P15 (A) and at E13.5 (B). Hyperplastic retrolental mass observed in the postnatal period (A, *) is evident as early as E13.5 (B, arrow). Arrows (A) indicate remnants of normal, regressing hyaloid vessels when functional p19^Arf is present. C and D, shown are representative photomicrographs (C) and quantification (D) of BrdU incorporation in the vitreous E13.5 mouse embryo eyes of the indicated genotypes. Note the expansion of BrdU-positive, proliferating cells (C, *) in the primary vitreous between the lens (L) and the neuroretina (NR) in Wnt1-Cre, Arf^fl/fl mice. Quantitative data are expressed as average percent of total cells in the vitreous space. Increased BrdU+ cells in Wnt1-Cre, Arf^fl/fl embryos (D, lane 3) is statistically significant. p < 0.001(*) for lane 3 versus lanes 1 or 2).