Fig. 1. The effect of over expressing noggin in the eye. Eyes were infected with retroviruses expressing alkaline phosphatase or noggin at HH15-18 (E2.5-3). Lenses were fixed, sectioned and stained at E4 (A,B) or E6 (C,D). Phalloidin staining (red) primarily outlines the cell boundaries and TOTO-1 (green) labels nuclei and, to a lesser degree, cytoplasmic RNA. (A) Lens at E4 from an eye infected with control retrovirus. Primary fiber formation is nearly complete and the lumen of the lens vesicle is nearly occluded. (B) Lens at E4 from an eye infected with retrovirus expressing noggin. Primary fiber cell elongation is retarded and the lumen of the lens vesicle remains open. The apparently greater thickness of the presumptive corneal epithelium in A was an artifact of sectioning. The corneal epithelium shown in B is typical of this stage of development. (C) Lens at E6 from an eye infected with retrovirus expressing alkaline phosphatase. Fiber cell elongation appears normal. (D) Lens at E6 from an eye infected with retrovirus expressing noggin. Cells in the initial stage of fiber cell elongation at the lens equator are shorter than normal, leading to the formation of a gap between the earliest fiber cells and the equatorial epithelial cells. Older fiber cells, deeper in the lens, appear to have recovered and are elongating normally. Scale bars: 50 µm.

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