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Diana Mitchell, CHI SUN, Deborah L Stenkamp; Transcriptome Analysis of Zebrafish Microglia During Retinal Regeneration. Invest. Ophthalmol. Vis. Sci. 2018;59(9):1489.
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© ARVO (1962-2015); The Authors (2016-present)
Microglia (MiG) and the immune system are involved in CNS development, synaptic pruning, response to injury, and neurodegenerative disease. However, there is a paucity of information regarding MiG characteristics and functions during successful retinal regeneration, which occurs in non-mammalian vertebrates such as zebrafish. Further, markers for zebrafish MiG are limited and are not unique from those used to label macrophages (Macs). The purpose of this work is to probe putative functions of MiG in the context of successful retinal regeneration and to identify candidate markers of zebrafish retinal MiG.
We used mpeg1:GFP transgenic zebrafish in which MiG and Macs express GFP. Following a chemical lesion causing substantial neuron death in the retina, at a time point at which Müller glia are proliferative and generate neuronal progenitors, GFP+ and GFP- retinal cells were FACS sorted and analyzed using RNA-seq. Differentially expressed transcripts in GFP+ vs. GFP- populations were identified with FDR <0.01.
The GFP+ population was enriched for MiG/Mac-specific transcripts including mpeg1 (Log2 fold change 8.8, p=2.3x10-15), while GFP- included non-immune genes such as vsx2 (-11.5, 3.3x10-12 ). Transcripts enriched in GFP+ cells included chemokines [cxcl11.1 (7.7, 2.6x10-8), cxcl20 (7.6, 4.5x10-5)] and chemokine receptors [(cxcr3.3 (5.5, 7x10-5), ccr9a (7.2, 2.1x10-8)], both pro- and anti-inflammatory cytokine receptors [il10ra (9.0, 7.2x10-17), IL6r (6.9, 5.1x10-5)], members of the TNF family [tnfrsf18 (11.2, 5.2x10-12), tnfb (7.1, 2.9x10-11)], and complement components [C1qA (6.0, 1.3x10-9), C1qB (5.7, 5x10-11), C1qC (7.1, 2.6x10-8), cfp (4.5, 0.0001)]. Interestingly, transcripts for tetraspanins (exosome proteins) were identified in GFP+ cells [cd9b (7.3, 2.9x10-6), tspan36 (4.6, 2.7x10-7)] as well as several genes not yet well described in MiG/Macs [runx3 (10.6, 2.2x10-10), ptx4 (6.1, 0.008), rbbp8 (3.7, 0.003)].
This data set identified a large number of transcripts enriched in zebrafish MiG/Macs during a successful retinal regenerative response, some of which have not been identified in any organism. This provides abundant information to probe the function of microglia as well as several candidate markers. Results suggest that MiG/immune functions during retinal regeneration involve active cell-cell communication, migration, complement, and possibly the production of exosomes.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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