The two origins of hemocytes inDrosophila

Abstract

As in many other organisms, the blood of Drosophila consists of several types of hemocytes, which originate from the mesoderm. By lineage analyses of transplanted cells, we specified two separate anlagen that give rise to different populations of hemocytes: embryonic hemocytes and lymph gland hemocytes. The anlage of the embryonic hemocytes is restricted to a region within the head mesoderm between 70 and 80% egg length. In contrast to all other mesodermal cells, the cells of this anlage are already determined as hemocytes at the blastoderm stage. Unexpectedly, these hemocytes do not degenerate during late larval stages, but have the capacity to persist through metamorphosis and are still detectable in the adult fly. A second anlage,which gives rise to additional hemocytes at the onset of metamorphosis, is located within the thoracic mesoderm at 50 to 53% egg length. After transplantation within this region, clones were detected in the larval lymph glands. Labeled hemocytes are released by the lymph glands not before the late third larval instar. The anlage of these lymph gland-derived hemocytes is not determined at the blastoderm stage, as indicated by the overlap of clones with other tissues. Our analyses reveal that the hemocytes of pupae and adult flies consist of a mixture of embryonic hemocytes and lymph gland-derived hemocytes,originating from two distinct anlagen that are determined at different stages of development.

Cell lineage tracing reveals the plasticity of the hemocyte lineages and of the hematopoietic compartments in Drosophila melanogaster

“…Embryonic hemocytes were marked with the crq and the Dot drivers and their descendants were followed throughout larval development and the immune response. The crq>GFP and Dot>GFP -marked hemocytes separated from each other in two, physically isolated compartments, in agreement with the findings of the cell transplantation experiments of Holz et al (2003).…”

“…In the embryo, this differentiation proceeds in two waves (Holz et al, 2003). The procephalic mesoderm anlage gives rise to embryonic macrophages -freely moving cells in the embryoand crystal cells which remain in the anterior midgut region (Lebestky et al, 2000).…”

“…The procephalic mesoderm anlage gives rise to embryonic macrophages -freely moving cells in the embryoand crystal cells which remain in the anterior midgut region (Lebestky et al, 2000). The second wave of hematopoiesis takes place just before the end of embryogenesis, when prohemocytes originating from the cardiogenic mesoderm anlage form a compact hematopoietic organ, the lymph gland (Holz et al, 2003). In the larva, the hemocytes reside in three main cellular compartments: the lymph gland, the sessile hemocyte population and the circulating blood cells.…”

A short history of hemogenic endothelium

“…These hematopoietic cells resembled the transient population of erythromyeloid progenitors also found in the yolk sac [13], indicating their transient nature. In this the cardiac endothelium bears reminiscence of the anterior hemangioblast-derived cells in zebrafish [68] and Drosophila [69].…”

Fluorescence-activated cell sorting (FACS) of Drosophila hemocytes reveals important functional similarities to mammalian leukocytes

“…No FACS analysis of hemocytes from lymph glands, the larval hematopoietic organ (6,14,22), and no cell sorting of fresh hemocytes from either the lymph glands or hemolymph have been reported. Clearly, the ability to perform single-cell analyses and sorts on freshly harvested hemocytes and to use sorted hemocyte fractions with existing molecular tools for further in vitro or in vivo studies would provide great experimental opportunities, most notably for functional genomics.…”