The fractalkine receptor but not CCR2 is present on microglia from embryonic development throughout adulthood
Makiko Mizutani1, Paula A Pino, Noah Saederup
1Department of Neurosciences, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, USA.
Abstract:
Microglial cells are difficult to track during development because of the lack of specific reagents for myeloid subpopulations. To further understand how myeloid lineages differentiate during development to create microglial cells, we investigated CX3CR1 and CCR2 transcription unit activation in Cx3cr1(+/GFP)CCR2(+/RFP) knockin fluorescent protein reporter mice. The principal findings include: 1) CX3CR1(+) cells localized to the aorta-gonad-mesonephros region, and visualized at embryonic day (E)9.0 in the yolk sac and neuroectoderm; 2) at E10.5, CX3CR1 single-positive microglial cells were visualized penetrating the neuroepithelium; and 3) CX3CR1 and CCR2 distinguished infiltrating macrophages from resident surveillant or activated microglia within tissue sections and by flow cytometric analyses. Our results support the contribution of the yolk sac as a source of microglial precursors. We provide a novel model to monitor chemokine receptor expression changes in microglia and myeloid cells early (E8.0-E10.5) in development and during inflammatory conditions, which have been challenging to visualize in mammalian tissues.
Insights
Researchers tracked microglial cell development using novel fluorescent reporter mice. The yolk sac emerges as a key source of microglial precursors during early embryonic development.
Area of Science:
- Developmental Biology
- Immunology
- Neuroscience
Background:
- Microglial cells are crucial for brain development and function.
- Tracking microglial cell development is challenging due to a lack of specific reagents for myeloid subpopulations.
Purpose of the Study:
- To investigate the differentiation of myeloid lineages into microglial cells during development.
- To establish a novel model for monitoring chemokine receptor expression in early developing myeloid and microglial cells.
Main Methods:
- Utilized Cx3cr1(+/GFP)CCR2(+/RFP) knockin fluorescent protein reporter mice.
- Tracked CX3CR1 and CCR2 transcription unit activation during embryonic development (E8.0-E10.5).
- Employed tissue section analysis and flow cytometry to distinguish cell populations.
Main Results:
- CX3CR1(+) cells were identified in the aorta-gonad-mesonephros region, yolk sac, and neuroectoderm by embryonic day 9.0.
- CX3CR1 single-positive microglial cells were observed penetrating the neuroepithelium at embryonic day 10.5.
- CX3CR1 and CCR2 expression successfully distinguished infiltrating macrophages from resident microglia.
Conclusions:
- The yolk sac is a significant source of microglial precursors.
- CX3CR1 and CCR2 expression patterns provide insights into myeloid cell differentiation and microglial development.
- The developed model allows for visualization of early microglial and myeloid cell dynamics and inflammatory responses.
