Analysis of epigenetic regulation of cone opsin expression by COUP-TF nuclear receptors

在此之前，我们已经证明COUP-Tf核受体参与了视锥视蛋白在小鼠视网膜的背腹表达模式的建立。在这项研究中，我想通过关注表观遗传机制来阐明这种调控的机制。我分析了小鼠视网膜背侧区和腹侧区的DNA甲基化状态，或内源性COUP-TF被shRNA敲除的视网膜母细胞瘤细胞系的DNA甲基化和组蛋白修饰状态。然而，COUP-TF的表达与这些表观遗传状态之间的显著相关性尚未被发现。另一方面，我对人红视蛋白基因中的TRbeta2调控区域进行了鉴定，发现COUP-TF在人和小鼠基因组中对TRbeta2介导的激活表现出不同的作用。此外，我发现染色质重塑因子BRG1激活蓝视蛋白基因的表达，而COUP-TF抑制BRG1介导的这种激活。这些结果表明，COUP-TF通过这些因素的相互作用调节视锥蛋白在视网膜中的表达，从而建立了每种动物特有的视锥蛋白表达模式。

Previously we demonstrated that COUP-TF nuclear receptors contribute to the establishment of dorso-ventral expression pattern of cone opsins in mouse retina. In this study I'd like to clarify the mechanism of this regulation by focusing on epigenetic mechanism. I analyzed DNA methylation status of dorsal- and ventral-region of mouse retina, or DNA methylation and histone modification status in retinoblastoma cell line in which endogenous COUP-TFs were knocked down by shRNA. However, significant correlation between COUP-TFs expression and these epigenetic status has not been seen yet. On the other hand, I identified TRbeta2 regulating genomic region in human red opsin gene and found that COUP-TFs show the different effect on TRbeta2-mediated activation in this genomic region between human and mouse genome. Furthermore, I found that Brg1, a chromatin remodeling factor, activates blue opsin gene expression and COUP-TFs suppress this Brg1-mediated activation. These results suggest that COUP-TFs regulate cone opsin expression in retina through interaction of these factors, which establishes each animal specific cone opsin expression pattern.