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V. Govindarajan, P.A. Overbeek; Lens and Corneal Epithelial Cells Are Sensitive to GAL4VP16 Expression . Invest. Ophthalmol. Vis. Sci. 2005;46(13):1886.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: The purpose of this study was to generate a GAL4VP16 binary transactivation system to activate transgene expression in the lens and cornea. Methods: We have generated transgenic mice that express the GAL4VP16 transactivator linked to a modified Pax6 promoter that is active in lens and corneal epithelial cells. Wild type and transgenic mice were analyzed by histological, in situ and Southern hybridization techniques. Results: Six families (OVE1931, 1932, 1934, 1935, 1936 and 1937) that carry the Pax6–GAL4VP16 transgene were generated. Unexpectedly, cataracts were seen in the mice of family OVE1936 at the time of eyelid opening. In families OVE1934 and 1935, cataracts were seen in mice that were homozygous for the transgene while heterozygous mice appeared normal. Transgenic mice in families OVE1931 and 1937 appeared normal. Histological analysis of ocular sections of OVE1934 and 1935 homozygous transgenic mice showed persistence of the lens stalk in addition to defects in anterior segment development. The corneal stromal cells were disorganized and there was no distinctive corneal endothelial layer. In addition, stratification of the lens epithelium was observed. No dramatic changes in retinal development were seen in either transgenic family. Southern hybridization results showed the presence of 28 copies of the transgene in the OVE1931 family, 4 copies each in OVE1934 and 1935 mice, and 1 copy in the OVE1937 family. In situ hybridizations showed robust expression of the GALVP16 transgene in the lens and corneal epithelial cells of the OVE1934, 1935 and 1936, but not OVE1931 families. Conclusions: GAL4VP16 expression alters lens and corneal development. Altered differentiation of these tissues is apparently not due to squelching of the endogenous Pax6 promoter by the Pax6–GAL4VP16 transgene. Instead, altered differentiation of the lens and cornea correlates with robust transgene expression in these tissues. These results suggest that: 1) either GAL4 or VP16 can induce changes in endogenous gene expression in lens and corneal cells, 2) that developmentally important genes are affected, and 3) that bigenic phenotypes will need to be interpreted with caution.
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