Project description:Microglia are the tissue-resident macrophages of the retina and brain, being critically involved in organ development, tissue homeostasis, and response to cellular damage. Until now, little is known about the transcriptional profile of human retinal microglia and how they differentiate from peripheral monocytes, as well as from brain microglia. Additionally, the degree to which mice are suitable models for human retinal microglia is still not clear. The present study applies fluorescence-activated cell sorting to isolate human retinal microglia from enucleated eyes and compares their transcriptional profile with that of whole retinal tissue, as well as classical, intermediate and non-classical monocytes. In addition, human retinal microglia are compared to murine retinal microglia, isolated from at least two-years old Cx3cr1GFP/+ mice, as well as human brain microglia obtained from the literature. Several overexpressed genes were identified in retinal microglia when compared to whole retinal tissue, as well as classical, intermediate, and non-classical monocytes, among them IL1B, C2, C3, TREM2, P2RY12 and SPP1. In relation to whole retina sequencing, several risk genes, such as APOE and TGBR1, as well as PLXDC2 and ARHGAP22 associated with age-related macular degeneration (AMD) and diabetic retinopathy (DRP), were preferentially expressed in retinal microglia, indicating their potential pathophysiological involvement. The top expressed genes exhibited a strong consistency between retinal and brain microglia, among them CD74, SPP1, ACTB, FTL and C3. There was a high degree of similarity between human and murine retinal microglia, although there were several species-specific genes, revealing for which genes mice are suitable models for human retinal microglia. This study provides detailed insights into the molecular profile of human retinal microglia and indicate a high similarity to brain microglia. It advances our under-standing about their role in human retinal disease, such as AMD and DRP. The similarities and differences between human and mice will facilitate the transferability of knowledge between both species.
Project description:In order to evaluate the gene expression profile of retinal microglia cells in different age, we purified CD11b-positive microglia from the retinas of wild type C57BL/6 mice at 3, 12, 18, and 24 months age using cell sorting method with flow cytometry. Age-related genes from isolated retinal microglia were performed using 16 Affymetrix GeneChips of Mouse Exon 1.0ST Arrays. Gene expression level between consecutive age groups (i.e. between 3 and 12 months, 12 and 18 months, and 18 and 24 months) was examined to identify microglia relevant aging genes that demonstrated significant changes. We identified a total 719 genes that showed increasing or decreasing more than 1.5-fold change (p<0.05, one-way ANOVA) for at least one of the three inter age-group comparisons. These identified genes were subjected to a hierarchical cluster analysis to visualize trends in differential expression across individual biological repeats in the 4 age groups. The microglia cells were isolated from wild type C57BL/6 mice with microglia cell specific marker CD11b conjugated with FITC using flowcytometry sorting. The aging time point was designed as 4 groups: 3 moth, 12 month, 18 month and 24 month; each group includes 4 repeats. The total RNA was extracted from isolated retinal microglia cells and reverse transcripted to cDNA after amplification and labeling. The gene expression profile was detected with Affymetrix GeneChip of Mouse Exon 1.0ST Arrays
Project description:We report the use of RNAseq to identify gene changes in isolated retinal microglia after 4 weeks of STZ-induced diabetes. At this early time point in diabetes induction, single retinal cell suspensions were sorted via FACS using a Cd11b-FITC conjugate. RNA was isolated and preamplified using the SMARTSeq v4 low RNA input kit. After library preparation a 50bp single end read was performed at a depth of 19-34 million reads per sample using the Illumina HiSeq. Constructs were mapped to the rat genome and differential expression calculated between the STZ-treated and control groups.
Project description:We observe morphological changes of retinal microglia during early stages of diabetic retinopathy in STZ-treated mice. Therefore, in this experiment we assess the impact of STZ-induced diabetic retinopathy on retinal microglia transcriptome during early stages of disease.
Project description:The apolipoprotein E4 (APOE4) allele is associated with an increased risk of Alzheimer’s disease and a decreased risk of glaucoma, but the underlying mechanisms remain poorly understood. Here we find that in two mouse glaucoma models and in human glaucomatous retinas, microglia transition to a neurodegenerative (MGnD) phenotype characterized by upregulation of Apoe and Lgals3 (Galectin-3). Mice in which Apoe was targeted in microglia or carrying the human APOE4 allele were protected from retinal ganglion cell (RGC) loss despite elevated intraocular pressure (IOP). Similar to Apoe–/– retinal microglia, APOE4 microglia did not upregulate MGnD genes, including Lgals3, following IOP elevation. Genetic and pharmacologic targeting of Galectin-3 ameliorated RGC degeneration, and Galectin-3 expression was attenuated in human APOE4 glaucoma samples. These results demonstrate that impaired activation of APOE4 microglia is protective in glaucoma, and that the APOE-Galectin-3 signaling pathway can be targeted to treat this blinding disease.
Project description:Analysis of retinal ganglion cells (RGCs) by scRNA-seq is emerging as a state-of-the-art method for studying RGC biology and subtypes, as well as for studying the mechanisms of neuroprotection and axon regeneration in the central nervous system (CNS). Rbpms has been established as a pan-RGC marker, and Spp1 has been established as an αRGC type and macrophage marker. Here, we analyzed by scRNA-seq retinal microglia and macrophages, and found Rbpms+ subpopulations of retinal microglia/macrophages, which pose a potential pitfall in scRNA-seq studies involving RGCs. We performed comparative analysis of cellular identity of the presumed RGC cells isolated in recent scRNA-seq studies, and found that Rbpms+ microglia/macrophages confounded identification of RGCs. We also showed using immunohistological analysis that, Rbpms protein localizes to stress granules in a subpopulation of retinal microglia after optic nerve injury, which was further supported by bioinformatics analysis identifying stress granule-associated genes enriched in the Rbpms+ microglia/macrophages. Our findings suggest that the identification of Rbpms+ RGCs by immunostaining after optic nerve injury should exclude cells in which Rbpms signal is restricted to a subcellular granule, and include only those cells in which the Rbpms signal is labeling cell soma diffusely. Finally, we provide solutions for circumventing this potential pitfall of Rbpm-expressing microglia/macrophages in scRNA-seq studies, by including in RGC and αRGC selection criteria other pan-RGC and αRGC markers.
Project description:In many forms of retinal degenerative diseases in human, microglia relocate to and accumulate in the subretinal space. However, the roles of microglia in retinal degeneration are poorly understood. By leveraging single cell RNA-seq, we identified a distinct microglia subtype in the subretinal space. These microglia underwent transcriptional reprogramming characterized by reduced expression of homeostatic checkpoint genes and upregulation of injury-responsive genes. Importantly, this transition is associated with protection of the retinal pigment epithelium from damage caused by disease. Therefore, our data demonstrated microglial heterogeneity in retinal degeneration and may provide important implications for developing new strategies to prevent loss of vision.