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K. Lazo, I. Nasonkin, D. Hambright, M. Brooks, A. Swaroop; Developmental Expression of DNA Methyltransferases in the Mammalian Retina. Invest. Ophthalmol. Vis. Sci. 2010;51(13):722.
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We hypothesize that DNA methyltransferases - Dnmt1, Dnmt3a, and Dnmt3b - participate in the establishment of competence states and/or gene expression patterns during retinal development. Dnmt-1 acts as a maintenance methyltransferase, while Dnmt 3a and 3b are responsible for global de novo methylation (Jaenisch and Bird 2003). This study is designed to examine the expression of Dnmts in embryonic and adult mammalian retina.
Eyes and/or retinas were harvested from wild type C57BL6/J mice at several time-points from embryonic stage E11.5 to adulthood. Retinas were processed for quantitative RT-PCR (qRT-PCR) and immunoblot analysis. Eyes were processed to generate frozen sections for immunohistochemistry (IHC) using antibodies for the three DNA methyltransferases and cell type-specific retinal markers.
Dnmt1 and Dnmt3b are expressed at all stages of developing and adult mouse retina. In late embryonic stages, Dnmt1 was co-localized to post-mitotic cells in the inner-neuroblastic layer (INBL), and not to proliferating cells. In the postnatal and adult mouse retina, a strong presence of nuclear Dnmt1 is detected in all cells except Müller glia, which expressed very little nuclear Dnmt1, and in rod photoreceptors, which demonstrate a weak signal of Dnmt1 in the perinuclear area (by IHC). Dnmt 3a and Dnmt3b show a similar pattern of expression to Dnmt1 in early postnatal and adult mouse retina with the exception of bipolar cells.
Our data provide the first evidence of spatial and temporal expression of DNA methyltransferases during retinal development. Our findings suggest that the activity of DNA methyltransferases is needed during early stages of retinal development, when ganglion, horizontal, cone photoreceptor, and amacrine cells are being generated.
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