This is a preprint, a preliminary version of a manuscript that has not completed peer review at a journal. Research Square does not conduct peer review prior to posting preprints. The posting of a preprint on this server should not be interpreted as an endorsement of its validity or suitability for dissemination as established information or for guiding clinical practice.
Research
Sumiko Watanabe
Institute of Medical Science, University of Tokyo
Corresponding Author
ORCiD: https://orcid.org/0000-0003-4497-5750
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Background Microglial activation is commonly observed in neurodegenerative diseases. However, its role in the complex inflammatory network remains unclear. In this study, we generated a microglial activation mouse model by inducing the expression of a constitutively active form of Ras in microglia.
Methods The double transgenic lines CAG-LSL-RasV12-IRES-EGFP; Cx3cr1CreER (Cx3cr1-RasV12 mice) and CAG-LSL-EGFP;Cx3cr1CreER (control mice) were generated. The expression of RasV12 was induced in microglia by tamoxifen administration. Effects of the expression of RasV12 in the retina were examined by immunohistochemistry of frozen sections, RT-qPCR, and live imaging.
Results RasV12 expression in retinal microglial cells promoted cell proliferation, cytokine expression, and phagocytosis. RasV12-expressing microglia migrated towards the apical and basal regions of the retina. Examination of GFAP expression revealed activation of Müller glia in the retina. We also observed loss of the photoreceptors in the outer nuclear layer (ONL) in close proximity to microglial cells. However, no neurodegeneration was observed in the inner nuclear layer (INL) or ganglion cell layer (GCL). Furthermore, we found that RasV12-expressing microglia in the ONL were smaller in size and engulfed photoreceptors. In contrast, the morphology of RasV12-expressing microglia in the GCL and INL resembled resting microglia. In conclusion, RasV12-induced microglial activation impaired rod photoreceptor survival in the ONL, but not in other regions of the retina.
Conclusion The expression of RasV12 is sufficient to activate microglia, and our results suggested that microenvironment cues may modulate the microglial phenotypic features and effects of microglial activation.
Keywords
microglia, retina, RasV12, transgenic mice, cytokines, phagocytosis
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This is a preprint, a preliminary version of a manuscript that has not completed peer review at a journal. Research Square does not conduct peer review prior to posting preprints. The posting of a preprint on this server should not be interpreted as an endorsement of its validity or suitability for dissemination as established information or for guiding clinical practice.
Research
Sumiko Watanabe
Institute of Medical Science, University of Tokyo
Corresponding Author
ORCiD: https://orcid.org/0000-0003-4497-5750
Badges
Prescreen
This manuscript passed our Prescreen assessment
Complete author information
Appropriate declaration statements
Potential risks to human health
Prescreen
History
CURRENT STATUS: Posted
Version 1
Posted 27 May, 2020
No community comments so far
Metrics
Comments: 0
PDF Downloads: ...
HTML Views: ...
Subject Areas
Neurobiology of Disease
License:
This work is licensed under a CC BY 4.0 License. Read Full License
Background Microglial activation is commonly observed in neurodegenerative diseases. However, its role in the complex inflammatory network remains unclear. In this study, we generated a microglial activation mouse model by inducing the expression of a constitutively active form of Ras in microglia.
Methods The double transgenic lines CAG-LSL-RasV12-IRES-EGFP; Cx3cr1CreER (Cx3cr1-RasV12 mice) and CAG-LSL-EGFP;Cx3cr1CreER (control mice) were generated. The expression of RasV12 was induced in microglia by tamoxifen administration. Effects of the expression of RasV12 in the retina were examined by immunohistochemistry of frozen sections, RT-qPCR, and live imaging.
Results RasV12 expression in retinal microglial cells promoted cell proliferation, cytokine expression, and phagocytosis. RasV12-expressing microglia migrated towards the apical and basal regions of the retina. Examination of GFAP expression revealed activation of Müller glia in the retina. We also observed loss of the photoreceptors in the outer nuclear layer (ONL) in close proximity to microglial cells. However, no neurodegeneration was observed in the inner nuclear layer (INL) or ganglion cell layer (GCL). Furthermore, we found that RasV12-expressing microglia in the ONL were smaller in size and engulfed photoreceptors. In contrast, the morphology of RasV12-expressing microglia in the GCL and INL resembled resting microglia. In conclusion, RasV12-induced microglial activation impaired rod photoreceptor survival in the ONL, but not in other regions of the retina.
Conclusion The expression of RasV12 is sufficient to activate microglia, and our results suggested that microenvironment cues may modulate the microglial phenotypic features and effects of microglial activation.
Figure 1
Figure 2
Figure 3
Figure 4
Figure 5
This is a list of supplementary files associated with this preprint. Click to download.
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