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Yichen Wang, Anne Terrell, Melinda K Duncan; EGR1 deletion partially rescues the abnormalities of β1-integrin null lenses. Invest. Ophthalmol. Vis. Sci. 2014;55(13):725.
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© ARVO (1962-2015); The Authors (2016-present)
β1-integrin is the major β-integrin subunit expressed in both lens epithelial and fiber cells. Previous research has shown that β1-integrin is essential for the maintenance of lens epithelial integrity and survival in late embryonic lens development. Lack of β1-integrin in the lens will lead to severe micropthalmia and lack of lens in adult mice. RNAseq revealed that early growth response 1 (EGR1), a major regulator of fibrosis and apoptosis, was upregulated upon the conditional deletion of β1-integrin in the lens. This work investigates the possible role of EGR1 in the abnormalities found in the β1-MLR10 lens.
Mice homozygous for the β1-integrin floxed allele and carrying the MLR10 Cre gene (which can express Cre recombinase in all lens cells from lens vesicle stage, β1-MLR10) were bred to EGR1 null mice (EGR1 -/-). Mice heterozygous for the β1-integrin floxed allele, MLR10 Cre, and the EGR1 null allele (β1 F/+ MLR10 EGR1+/-) were further crossed to generate mice homozygous for the β1-integrin floxed allele and EGR1 null allele, carrying MLR10 Cre (β1-MLR10 EGR1 -/-). PCR and immunostaining were performed to confirm the loss of both β1-integrin and EGR1. General morphology was assessed by darkfield microscopy. Expression of molecular markers in the lens was studied by immunofluorescence staining.
Conditional deletion of β1-integrin from the lens led to a more than 10 fold upregulation of EGR1 mRNA at 15.5 dpc. Mice that lack both the β1-integrin and EGR1 genes from the lenses were created and loss of β1-integrin was confirmed via immunofluorescence staining. As previously reported, β1-MLR10 mice were extremely microphthalmic and lacked lenses as adults. In contrast, β1-MLR10 EGR1 -/- mice showed larger eyes as adults, with identifiable lens tissue, although it was irregular-shaped and cloudy. Analysis of β1-MLR10 EGR1 -/- lenses at 16.5 dpc revealed differences in the expression pattern of Pax6, cMaf and αSMA, compared to that of β1-MLR10 lenses. These data suggested that EGR1 deletion modified the β1-MLR10 lens phenotype.
Mice lacking both the β1-integrin and EGR1 genes from the lens exhibited a different phenotype than β1-MLR10 mice which lack β1-integrin but upregulate EGR1 expression. These data indicated that β1-integrin cross talks with the EGR1 pathway to regulate lens epithelial phenotype during development.
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