Section of Ophthalmology, Department of Clinical Studies, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America.
PLoS One. 2013 Dec 19;8(12):e85408. doi: 10.1371/journal.pone.0085408. eCollection 2013.
We used quantitative real-time PCR to examine the expression of 112 genes related to retinal function and/or belonging to known pro-apoptotic, cell survival, and autophagy pathways during photoreceptor degeneration in three early-onset canine models of human photoreceptor degeneration, rod cone dysplasia 1 (rcd1), X-linked progressive retinal atrophy 2 (xlpra2), and early retinal degeneration (erd), caused respectively, by mutations in PDE6B, RPGRORF15, and STK38L. Notably, we found that expression and timing of differentially expressed (DE) genes correlated with the cell death kinetics. Gene expression profiles of rcd1 and xlpra2 were similar; however rcd1 was more severe as demonstrated by the results of the TUNEL and ONL thickness analyses, a greater number of genes that were DE, and the identification of altered expression that occurred at earlier time points. Both diseases differed from erd, where a smaller number of genes were DE. Our studies did not highlight the potential involvement of mitochondrial or autophagy pathways, but all three diseases were accompanied by the down-regulation of photoreceptor genes, and up-regulation of several genes that belong to the TNF superfamily, the extrinsic apoptotic pathway, and pro-survival pathways. These proteins were expressed by different retinal cells, including horizontal, amacrine, ON bipolar, and Müller cells, and suggest an interplay between the dying photoreceptors and inner retinal cells. Western blot and immunohistochemistry results supported the transcriptional regulation for selected proteins. This study highlights a potential role for signaling through the extrinsic apoptotic pathway in early cell death events and suggests that retinal cells other than photoreceptors might play a primary or bystander role in the degenerative process.
我们使用定量实时 PCR 检测了三种人类早期光感受器变性犬模型（由 PDE6B、RPGRORF15 和 STK38L 突变引起的视杆-圆锥营养不良 1（rcd1）、X 连锁进行性视网膜萎缩 2（xlpra2）和早期视网膜变性（erd））中与光感受器功能相关的 112 个基因和/或属于已知的促凋亡、细胞存活和自噬途径的基因的表达。值得注意的是，我们发现差异表达（DE）基因的表达和时间与细胞死亡动力学相关。rcd1 和 xlpra2 的基因表达谱相似；然而，rcd1 更为严重，这表现在 TUNEL 和 ONL 厚度分析的结果、更多的 DE 基因以及更早时间点发生的改变表达的鉴定。这两种疾病与 erd 不同，erd 中 DE 的基因数量较少。我们的研究没有强调线粒体或自噬途径的潜在参与，但所有三种疾病都伴随着光感受器基因的下调和属于 TNF 超家族、外源性凋亡途径和生存途径的几个基因的上调。这些蛋白质由不同的视网膜细胞表达，包括水平细胞、无长突细胞、ON 双极细胞和 Müller 细胞，表明垂死的光感受器和视网膜内层细胞之间存在相互作用。Western blot 和免疫组织化学结果支持了选定蛋白质的转录调控。这项研究强调了外源性凋亡途径信号传导在早期细胞死亡事件中的潜在作用，并表明除光感受器以外的视网膜细胞可能在退行性过程中发挥主要或旁观者作用。
