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

我们已经证实，COUP-TF核受体参与了小鼠视网膜视锥蛋白背-腹侧表达模式的建立。在本研究中，我想从表观遗传机制的角度来阐明这一调控的机制。我分析了小鼠视网膜背侧和腹侧区域的DNA甲基化状态，或内源性coup - tf被shRNA敲低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发现。另一方面，我鉴定了人红视蛋白基因中TRbeta2调控的基因组区域，发现在人和小鼠基因组中，coup - tf对TRbeta2介导的该基因组区域激活的影响是不同的。此外，我发现Brg1，一种染色质重塑因子，激活蓝色视蛋白基因表达，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网膜视锥蛋白的表达，从而建立了每种动物特异性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.