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Expression of EMAP II in the developing and adult mouse
Abstract:
Endothelial monocyte-activating polypeptide II (EMAP II) is a chemoattractant for monocytes and granulocytes. EMAP II is translated as a precursor protein, proEMAP II, and is proteolytically cleaved to become the mature, biologically active cytokine. In this study we show that the EMAP II mRNA and the EMAP II precursor protein are constitutively expressed by all cell types analyzed in vitro, whereas the mature cytokine is only present in the supernatant of apoptotic cells. During mouse embryogenesis we found widespread expression of the EMAP II mRNA with transcripts being abundant in areas of tissue remodeling, where a large number of apoptotic cells could be detected by TUNEL staining. In the adult mouse, strong expression of the EMAP II mRNA is restricted to the brain, testis and thymus. Interestingly, prominent signals for EMAP II mRNA are found in local correlation with sites of apoptosis in thymus and testis but not in the brain. We propose that during development, the generation and release of the mature EMAP II may provide a mechanism for the recruitment of phagocytic cells to sites of programmed cell death. In the adult brain, the generation of mature EMAP II may contribute to the recruitment of monocytes and the immunosurveillance of this tissue.
Insights
Mature Endothelial Monocyte-Activating Polypeptide II (EMAP II) is released by apoptotic cells, attracting immune cells. This cytokine
Area of Science:
- Immunology
- Cell Biology
- Developmental Biology
Background:
- Endothelial monocyte-activating polypeptide II (EMAP II) is a cytokine that chemoattracts monocytes and granulocytes.
- EMAP II is synthesized as a precursor protein (proEMAP II) and cleaved into its mature, active form.
- The expression and localization of mature EMAP II in relation to apoptosis are not fully understood.
Purpose of the Study:
- To investigate the expression patterns of EMAP II mRNA and protein during mouse development and in adult tissues.
- To determine the relationship between EMAP II production and apoptotic cell presence.
- To elucidate the role of EMAP II in immune cell recruitment during development and in adult tissues.
Main Methods:
- Analysis of EMAP II mRNA and precursor protein expression in various cell types in vitro.
- Detection of mature EMAP II in cell culture supernatants.
- In situ hybridization for EMAP II mRNA during mouse embryogenesis and in adult tissues.
- TUNEL staining to identify apoptotic cells.
- Correlation of EMAP II mRNA expression with sites of apoptosis.
Main Results:
- EMAP II mRNA and proEMAP II are constitutively expressed in vitro, while mature EMAP II is found in the supernatant of apoptotic cells.
- During mouse embryogenesis, EMAP II mRNA is widespread, particularly in areas of tissue remodeling with high apoptosis.
- In adult mice, EMAP II mRNA is abundant in the brain, testis, and thymus, correlating with apoptosis in the thymus and testis but not the brain.
Conclusions:
- Mature EMAP II generation and release by apoptotic cells may recruit phagocytic cells to sites of programmed cell death during development.
- In the adult brain, EMAP II may contribute to monocyte recruitment and immune surveillance.
- EMAP II plays a significant role in immune cell trafficking during both development and in specific adult tissues.