Myelopoiesis and myeloid leukaemogenesis in the zebrafish

Abstract

Over the past ten years, studies using the zebrafish model have contributed to our understanding of vertebrate haematopoiesis, myelopoiesis, and myeloid leukaemogenesis. Novel insights into the conservation of haematopoietic lineages and improvements in our capacity to identify, isolate, and culture such haematopoietic cells continue to enhance our ability to use this simple organism to address disease biology. Coupled with the strengths of the zebrafish embryo to dissect developmental myelopoiesis and the continually expanding repertoire of models of myeloid malignancies, this versatile organism has established its niche as a valuable tool to address key questions in the field of myelopoiesis and myeloid leukaemogenesis. In this paper, we address the recent advances and future directions in the field of myelopoiesis and leukaemogenesis using the zebrafish system.

Figure 1

Overview of zebrafish developmental myelopoiesis, key transgenic lines, and lineage identification tools labelling myeloid cell populations during developmental haematopoiesis. (Transgenic lines are shown in green, other specific lineage identifiers are in blue.) PM: primitive myelopoiesis; EMP: erythromyeloid progenitors; HSPCs: haematopoietic stem and progenitor cells; CMP: common myeloid progenitor; CLP: common lymphoid progenitor; MEP: megakaryocyte/erythroid progenitor; GMP: granulocyte/monocyte progenitor; PHA: peanut haemaglutinin. **Denotes lineages only demonstrated in adult zebrafish. Lineage intermediates are shown for clarity but are yet to be isolated as distinct populations in zebrafish.

Figure 2

Schematic of in vivo cell proliferation assay in xenotransplanted zebrafish embryos. Human leukemia cells are fluorescently labelled with a cell tracking dye. Approximately 25–50 fluorescently labelled cells are microinjected into the yolk sac of 48 hpf casper embryos. Embryos are screened using fluorescent microscopy for the presence of a fluorescent mass at the site of injection. Positive embryos are divided into two groups; one of which is maintained at 35C for 24 h, and the other group is maintained for until the time point of interest with or without drug exposure. At the end of each time point embryos are enzymatically dissociated to a single cell suspension and the number of fluorescent cells in the suspension is counted using a semiautomated macro in Image J (NIH, Bethesda, MD). The number of fluorescent cells present at the later time point divided by the number of fluorescent cells present at 24 h represents the fold increase in cell number. Adapted from Corkery et al. [90].