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Melinda K Duncan, Yichen Wang, Priyha Mahesh, Yan Wang; Canonical Wnt activity is dynamic in the developing lens and upregulates dramatically in fibrotic lens cells. Invest. Ophthalmol. Vis. Sci. 2017;58(8):3195.
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© ARVO (1962-2015); The Authors (2016-present)
Canonical Wnt signaling plays both positive and negative roles in regulating eye development. Prior work utilizing mice harboring reporters of canonical Wnt signaling has suggested that this pathway is inactive in the lens after its initial specification, however, the design of the previously used Wnt reporter strains make it difficult to assess low level or mosaic patterns of pathway activation. Here we use an improved Wnt reporter strain to both reevaluate the extent of canonical (TCF/Lef mediated) Wnt signaling in the developing lens, and to test the hypothesis that this pathway is strongly activated during the formation of posterior capsular opacification.
Mice harboring a canonical Wnt reporter gene consisting of six copies of the T cell factor (TCF)/lef binding site upstream of a hsp68 minimal promoter driving the expression of a histone 2b/green fluorescent protein (GFP) fusion protein were obtained from the Jackson laboratory. Embryos and postnatal mice heterozygous for this reporter were obtained from timed matings and were analyzed for reporter expression by confocal immunofluorescence. Anterior subcapsular cataract (ASC) was induced by subjecting reporter mice to full thickness corneal wounds. Posterior capsular opacification was modeled by removing lens fiber cells from adult mice.
In the lens, no TCF activity was detected in either the lens placode or lens pit as previously reported. However, at E11.5, a few cells of the anterior lens vesicle are GFP positive. By E12.5, many cells of the newly formed lens epithelium exhibit TCF activity, and by E14.5, most cells of the lens epithelium are GFP positive. At later times in development, the GFP signal decreases, and in the normal adult lens, only occasional lens epithelial cells are GFP positive. However, TCF activity is highly upregulated in the α-Smooth muscle actin positive fibrotic plaques that form in both injury induced ASC and after lens fiber cell removal in a PCO model.
The extent of canonical Wnt signaling is very dynamic in the developing lens and upregulates dramatically upon surgically induced fibrosis. As canonical Wnt signaling mediated by TCF transcription factors can collaborate with TGFβ signaling to drive fibrotic responses in other systems, these data suggest that canonical Wnt may synergize with TGFβ signaling to drive fibrotic PCO.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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