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Anna Korol, AFTAB TAIYAB, Judith A West-Mays; Inhibition of MRTF-A/SRF-regulated gene transcription prevents TGFβ-mediated EMT in lens explants. Invest. Ophthalmol. Vis. Sci. 2016;57(12):2016.
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© 2017 Association for Research in Vision and Ophthalmology.
TGFβ-induced epithelial-mesenchymal transition (EMT) leads to the formation of ocular fibrotic pathologies, such as anterior subcapsular cataract and posterior capsule opacification. In lens epithelial cell explants, we have previously demonstrated that RhoA/ROCK signaling leads to and is required for nuclear translocation of an actin-binding protein, myocardin-related transcription factor (MRTF)-A. Here, using lens explants, we directly assess the involvement of MRTF-A downstream of RhoA/ROCK signaling in TGFβ-induced EMT using a novel inhibitor of MRTF-A/SRF-regulated transcription, CCG-203971.
Rat lens epithelial explants, with epithelia attached to their native lens capsule, were isolated and maintained in culture. Confluent lens explants were treated with TGFβ (4ng/ml) for 48 and 72 hours in the presence or absence of CCG-203971 (10μM). Western blot and immunofluorescence analyses were carried out to quantify and visualize E-cadherin, β-catenin and α-SMA.
In the presence of CCG-203971, TGFβ was still able to induce actin polymerization as determined by the presence of F-actin-containing stress fibres in our lens explants. Importantly, CCG-203971 prevented TGFβ-induced αSMA expression. Further, the presence of CCG-203971 prevented TGFβ-induced E-cadherin delocalization, with E-cadherin localized to the membrane. β-catenin also retained marginal staining as compared to the cytoplasmic/nuclear localization when stimulated with TGFβ only.
The current work indicates that MRTF-A/SRF-regulated gene transcription is required for TGFβ-induced EMT in lens explants. Further, MRTF-A nuclear translocation and activation of target genes acts downstream of RhoA-induced actin polymerization. Overall, these studies demonstrate a central role for MRTF-A/SRF-driven signaling in the pathogenesis of primary and secondary cataract formation making this an attractive therapeutic target.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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