Analysis of Müller glia specific genes and their histone modification using Hes1-promoter driven EGFP expressing mouse

Retinal neurons and Müller glia are generated from a common population of multipotent retinal progenitor cells. We purposed to identify Müller glia-specific molecular signatures during retinal development. Using transgenic mice carrying the Hes1 promoter (pHes1) followed by EGFP, we purified EGFP-positive Müller glia and other EGFP-negative retinal cells from developing retinas and subjected them to RNA sequencing analysis. Gene expression pattern of EGFP-positive cell was similar to genes expressed in retinal progenitors, and they were downregulated in other cell lineages. Then, we examined the modification profiles of H3K27me3 and H3K4me3 by referring to chromatin immunoprecipitation-sequencing data of rods and other cells. Clustering of the H3K4me3 and H3K27me3 values followed by ontology analysis revealed a high incidence of transcription factors including Hes1 in clusters with high H3K27me3 levels. Hes1 expression level decreased dramatically, and the H3K27me3 level at the Hes1-locus was upregulated strongly during retinal development. Furthermore, the Hes1 expression level was upregulated in an Ezh2-knockout retina. These results suggest that downregulation of Müller glia-related genes in other lineage rather than upregulation of them in Müller glia contributed Müller-specific molecular features, and a role for modified H3K27me3 in suppressing Müller glia-related genes in other retinal cell lineages to avoid unfavorable expression.