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Brittany A. Riggio, Vladimir N. Simirskii, Melinda K. Duncan; ß1 Integrin Function in the Lens Epithelium. Invest. Ophthalmol. Vis. Sci. 2011;52(14):2776.
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Integrins are heterodimeric adhesion receptors important for the detection of extracellular matrix, adhesion dependent signaling and tissue structure. Prior work from our lab has shown that loss of ß1 integrin from the 12.5 dpc mouse lens (ß1MLR10) results in micropthalmia caused by EMT of the lens epithelium at 16.5 days post coitum (dpc) followed by apoptosis. However, the identity of the cell signaling pathways that ß1 integrin controls in the lens and the mechanisms causing the cellular phenotype of these mice is not known.
ß1 integrin conditional knock out mice (ß1MLR10) were obtained by mating mice harboring loxP sites around exon 3 of the ß1 integrin gene, to MLR10-cre mice which express CRE recombinase in all lens cells. mRNA levels of known genes involved in EMT were assessed by rtPCR SuperArray. Changes in protein expression and/or activation compared to C57Bl/6 controls were detected using immunofluorescence, and western blotting.
The expression of 168 genes was profiled, and 11 genes were down regulated while 12 were up regulated in 16.5 dpc ß1MLR10 lenses compared to wild type. While confirmations are ongoing, we have found that JunB expression is up regulated at both the mRNA and protein levels. Surprisingly, in light of the observed EMT phenotype of ß1MLR10 lenses, we found that pSmad3 levels were slightly down regulated at 16.5 dpc. Similarly, pSmad1/5/8 levels were also down regulated at 16.5 dpc. Further, the levels of pFAK, a known affector of ß1 integrin signaling also appears to be sharply down regulated at 16.5 dpc in ß1MLR10 mice.
These data show that loss of ß1 integrin from the lens epithelium at 12.5 dpc results in the mis-regulation of multiple pathways including Smad. Future work will investigate the mechanisms by which ß1 integrin maintains the lens epithelial phenotype.
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