Table1_Targeted RNAi screen identifies transcriptional mechanisms that prevent premature degeneration of adult photoreceptors.xlsx

Aging is associated with a decline in visual function and increased prevalence of ocular disease, correlating with changes in the transcriptome and epigenome of cells in the eye. Here, we sought to identify the transcriptional mechanisms that are necessary to maintain photoreceptor viability and function during aging. To do this, we performed a targeted photoreceptor-specific RNAi screen in Drosophila to identify transcriptional regulators whose knockdown results in premature, age-dependent retinal degeneration. From an initial set of 155 RNAi lines each targeting a unique gene and spanning a diverse set of transcription factors, chromatin remodelers, and histone modifiers, we identified 18 high-confidence target genes whose decreased expression in adult photoreceptors leads to premature and progressive retinal degeneration. These 18 target genes were enriched for factors involved in the regulation of transcription initiation, pausing, and elongation, suggesting that these processes are essential for maintaining the health of aging photoreceptors. To identify the genes regulated by these factors, we profiled the photoreceptor transcriptome in a subset of lines. Strikingly, two of the 18 target genes, Spt5 and domino, show similar changes in gene expression to those observed in photoreceptors with advanced age. Together, our data suggest that dysregulation of factors involved in transcription initiation and elongation plays a key role in shaping the transcriptome of aging photoreceptors. Further, our findings indicate that the age-dependent changes in gene expression not only correlate but might also contribute to an increased risk of retinal degeneration.

衰老与视觉功能衰退及眼部疾病患病率升高密切相关，这与眼部细胞的转录组（transcriptome）和表观基因组（epigenome）改变存在关联。本研究旨在阐明衰老过程中维持光感受器细胞（photoreceptor）存活与功能所必需的转录调控机制。为此，我们在果蝇（Drosophila）中开展了靶向光感受器细胞特异性的RNA干扰（RNAi）筛选，以鉴定那些经敲低后会引发过早出现年龄依赖性视网膜变性的转录调控因子。初始筛选集合包含155个RNAi品系，每个品系靶向单一基因，覆盖转录因子、染色质重塑因子（chromatin remodelers）、组蛋白修饰因子（histone modifiers）等多个功能类别；最终我们鉴定出18个高可信度靶基因，这些基因在成年光感受器细胞中的表达下调会引发过早且进行性的视网膜变性。这18个靶基因显著富集于参与转录起始（transcription initiation）、转录暂停（transcription pausing）及转录延伸（transcription elongation）调控的因子，提示这些过程对于维持衰老光感受器细胞的健康状态至关重要。为了鉴定这些因子所调控的靶基因，我们对部分RNAi品系的光感受器细胞转录组开展了谱式表征分析。值得注意的是，18个靶基因中的两个——Spt5与domino——其基因表达变化模式与高龄光感受器细胞中的表达变化高度相似。综合来看，我们的研究数据表明，参与转录起始与延伸调控的因子失调，在塑造衰老光感受器细胞的转录组特征中发挥关键作用。此外，我们的研究结果显示，基因表达的年龄依赖性变化不仅与视网膜变性风险升高存在关联，还可能直接促进该风险的增加。