Visualisation of chicken macrophages using transgenic reporter genes: insights into the development of the avian macrophage lineage.
Bottom Line: The Fms intronic regulatory element (FIRE) within CSF1R is shown to be highly conserved in amniotes and absolutely required for myeloid-restricted expression of fluorescent reporter genes.The cell lineage specificity of reporter gene expression was confirmed by demonstration of coincident expression with the endogenous CSF1R protein.In transgenic birds, expression of the reporter gene provided a defined marker for macrophage-lineage cells, identifying the earliest stages in the yolk sac, throughout embryonic development and in all adult tissues.
Affiliation: The Roslin Institute and Royal (Dick) School of Veterinary Sciences, University of Edinburgh, Easter Bush, Midlothian EH25 9RG, UK firstname.lastname@example.org email@example.com.Show MeSH
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Mentions: Vitelline vasculature macrophages imaged in HH17 MacGreen embryos were highly motile and were observed both within blood vessels and in a perivascular locations but not integrated into the blood vessel walls, as described by Al-Roubaie et al. (2012). Within blood vessels, macrophages were observed crawling on the blood vessel walls, both as isolated cells and as cell clusters (supplementary material Movie 2). This crawling behaviour is reminiscent of ‘patrolling’ behaviour reported for a subset of blood monocytes in mice that respond to microbial infection (Auffray et al., 2007). A well-established model for studying the interactions of microbes with phagocytes is the recognition and phagocytosis of microbial-derived zymosan particles (Underhill, 2003). We determined the capacity of patrolling macrophages within the vitelline blood vessels to recognise and phagocytose zymosan particles by injection of Texas Red-labelled zymosan particles into the dorsal aorta of HH17 MacGreen embryos. These particles were observed throughout the embryonic and extra-embryonic vasculature where they stuck to the blood vessel walls. Patrolling macrophages moved towards and engulfed zymosan particles, and then either continued to crawl along the vessel walls or entered the circulation (Fig. 4; supplementary material Movie 3). Cell division of patrolling embryonic macrophages associated with the vasculature was frequently observed and macrophages containing zymosan particles were also divided. This process involved the cessation of patrolling behaviour, retraction of cellular processes and rounding of cells before cell division. After cell division, both daughter cells resumed a ramified morphology and patrolling behaviour (Fig. 4; supplementary material Movie 3), indicating that mature yolk sac-derived macrophages are a self-renewing population.Fig. 4.
Affiliation: The Roslin Institute and Royal (Dick) School of Veterinary Sciences, University of Edinburgh, Easter Bush, Midlothian EH25 9RG, UK firstname.lastname@example.org email@example.com.