Abstract
Purpose :
The ability of organisms to repair damaged tissue declines with age, in part owing to a decreased ability to activate remedial gene programs. One example is the retinal pigment epithelium (RPE) of the embryonic chicken, which prior to embryonic day 5 (E5) responds to injury signals and FGF2 by reprogramming to regenerate damaged retina. Here, we employ high-throughput sequencing to explore the coordination of gene expression and genomic accessibility in producing regenerative versus non-regenerative outcomes during development.
Methods :
RPE was isolated from E4 (regeneration-competent) and E5 (non-regenerative) chickens, and changes in gene expression and chromatin accessibility were assessed using RNA-seq and ATAC-seq. Similarly, E4 or E5 RPE was injured via surgical retina removal and collected 6 hours later in the presence or absence of FGF2. Differential genomic accessibility between injury-only and FGF2-treated samples was identified and integrated with gene expression data to construct a gene regulatory network, as well as identify putative enhancer regions and transcription factor activity promoting RPE-to-retina reprogramming.
Results :
428 differentially expressed genes were identified between E4 and E5 RPE with functions relating to retina development, including transcription factors ATOH7, VSX1, and SIX6. Moreover, E4 RPE exhibits increased genomic accessibility proximal to key retina development genes, reflective of its ability to mount a regenerative response. Comparison of RPE E4 and E5 response to FGF2 revealed decreased activation of MAPK and PI3K signaling targets at E5, as well as failure to activate cell migration and neurogenesis-related genes necessary for regeneration. Central to these differences we identified 5 factors, including 3 neurogenic transcription factors, limiting the E5 RPE response to FGF2.
Conclusions :
E4 RPE exhibits coordinated changes in gene expression in response to injury and FGF2 that facilitate retina regeneration. Conversely, the E5 RPE fails to activate necessary genetic programs for regeneration, largely as a result of altered genomic accessibility and transcription factor activity.
This is a 2020 ARVO Annual Meeting abstract.