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Galina Dvoriantchikova, Rajeev Seemungal, Dmitry V Ivanov; Analysis of epigenetic plasticity in adult murine RPE. Invest. Ophthalmol. Vis. Sci. 2019;60(9):1928.
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© ARVO (1962-2015); The Authors (2016-present)
The epigenetic plasticity of amphibian retinal pigment epithelium (RPE) allows members of this biological class (X. laevis, Cynops pyrrhogaster) to regenerate the entire retina and restore lost sight after injury. This ability is observed to be absent in mammals; either mammals lost this ability, or amphibians obtained it during their evolutionary path. In this study, we investigated the epigenetic plasticity of adult murine RPE to identify possible mechanisms that prevent mammalian RPE from regenerating the entire retina.
To investigate the epigenetic plasticity of adult RPE, we used microarray analysis, ChIP-seq analysis (H3K4me1, H3K4me3, H3K27me3, and H3K9me3 histone modifications) and whole-genome bisulfite sequencing. The data was analyzed using Hidden Markov Model- and change-point based methods to identify RPE chromatin and methylome states in different segments of the genome following genome annotation.
We found that, in RPE, the majority of key genes required for development and function of optic vesicle progenitors, retinal progenitor cells, Müller glia, as well as genes required for epithelium-to-mesenchyme transition and the cell cycle were in a chromatin active/open state. Promoters of these genes were mostly unmethylated or low-methylated. Our findings also indicate that the majority of non-photoreceptor retinal neuronal genes had promoters in repressed chromatin states, but these promoters were also found in unmethylated or low-methylated regions. However, the majority of promoters for cone and rod photoreceptors were not found in repressed chromatin states, but they were highly methylated.
Our data suggest that adult murine RPE are epigenetically similar to progenitor-like cell types. Our data also supports the observation of RPE’s ability to proliferate and to undergo transition from an epithelial into a mesenchymal state during some retinal diseases (a condition known as proliferative vitreoretinopathy). Our findings also point to two mechanisms that prevent adult murine RPE reprogramming and differentiation into retinal neurons: 1) repressed chromatin in the promoter region of non-photoreceptor retinal neurons, 2) highly-methylated promoters of photoreceptor-related genes. However, identified chromatin states indicate the temporary repressed state of many promoter regions for key genes, and they may be open in the presence of pioneer transcription factors.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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