Fig. 4. Excess mesenchymal cells in the prenatal vitreous cavity and persistent fetal vasculature in the postnatal Fz5^-/- eye. (A,B) DAPI-stained (A) WT and (B) Fz5^-/- mouse embryonic eyes at E14.5. Arrowhead in B indicates the excess cells between the lens and retina. (C,D) Anti-smooth muscle actin (SMA) immunostaining of whole-mount retinas at P5. The hyaloid vessels and developing retinal vasculature emerge from the optic disk (green arrowheads). The cell mass that is attached to the optic disc in the Fz5^-/- retina contains smooth muscle actin (D, red arrowhead). (E-H) Intact retinas viewed from the vitreal face (E,F) and Hematoxylin and Eosin-stained sections through the retina and optic nerve (G,H) at P56. The ectopic tissue (red arrowhead in F) is attached at the optic disc of the Fz5^-/- retina (green arrowhead in F) and contains numerous pigment cells. (I-L) Semi-thin, plastic-embedded sections through the central retina showing the vascular structure and connectivity of the intra-vitreal tissue at P56. The serial sections at low magnification (I,J) show ectopic tissue attached to the optic disc (bottom) and the posterior face of the lens (top; green arrowheads). The large blood vessels in I and J are contiguous (red arrowheads). (K) High-magnification view of the boxed region in I, showing an intermingling of pigmented and unpigmented cells surrounding a large blood vessel (asterisk). (L) At the edge of the optic disc, pigmented cells associated with the initial segment of the intravitreal vasculature (asterisk) are contiguous with the pigmented cells of the choroid (arrowheads).