Advances in Biological Chemistry, 2015, 5, 73-82 Published Online April 2015 in SciRes. http://www.scirp.org/journal/abc http://dx.doi.org/10.4236/abc.2015.52007 How to cite this paper: Bourget, J.-M., Morcos, M., Zaniolo, K., Guérin, S.L. and Proulx, S. (2015) Influence of Cell Conflu- ency on the Expression of the α4 Integrin Subunit of Retinal Pigment Epithelial Cells. Advances in Biological Chemistry, 5, 73-82. http://dx.doi.org/10.4236/abc.2015.52007 Influence of Cell Confluency on the Expression of the α4 Integrin Subunit of Retinal Pigment Epithelial Cells Jean-Michel Bourget 1 , Mohib Morcos 2,3 , Karine Zaniolo 1 , Sylvain L. Guérin 1,4 , Stéphanie Proulx 1,4* 1 Centre de recherche du CHU de Québec and Centre de recherche en organogénèse expérimentale de l’Université Laval/LOEX, axe médecine régénératrice, Hôpital du Saint-Sacrement, Québec, Canada 2 Département d’anatomie et de cytologie pathologiques, CHU de Québec, Hôpital du Saint-Sacrement, Québec, Canada 3 Département de biologie moléculaire, biochimie médicale et pathologie, Faculté de médecine, Université Laval, Québec, Canada 4 Département d’Ophtalmologie, Faculté de médecine, Université Laval, Québec, Canada Email: * stephanie.proulx@fmed.ulaval.ca Received 26 November 2014; accepted 27 March 2015; published 30 March 2015 Copyright © 2015 by authors and Scientific Research Publishing Inc. This work is licensed under the Creative Commons Attribution International License (CC BY). http://creativecommons.org/licenses/by/4.0/ Abstract Integrins are a family of transmembrane glycoproteins that mediate cell-cell and cell-extracellular matrix interactions. The integrin α4 subunit is widely expressed by cells from the immune system and its expression by non-hematopoietic cells is scarce. In the present study, gene and protein ex- pression of this integrin subunit was characterized in proliferating and quiescent human RPE cells. Immunofluorescent studies confirm that the α4 subunit is expressed in vitro by RPE cells, a result that has been validated by immunofluorescence and FACS analyses. The accumulation of the α4 integrin at cell-cell junctions in post-confluent RPE cell cultures negatively correlated with the level of expression of the mRNA transcript. Accordingly, transient transfection analyses reveal that the α4 promoter activity is considerably reduced when RPE cells form a confluent monolayer. Moreover, transfection of recombinant constructs bearing 5’-deletions of the α4 promoter seg- ment allows the localization of strong negative regulatory elements on the −76 to −300 region of the α4 gene suggesting that its expression is intimately linked to the proliferative state of primary cultured RPE cells. Keywords Retinal Pigment Epithelium, Integrin Alpha 4 Subunit, Cell Culture, Confluency, Promoter * Corresponding author.