In vertebrates, conserved genetic pathways tightly regulate the production and function of myeloid cells, such as granulocytes, macrophages, monocytes, and dendritic cells. Myeloid cells perform key functions in the immune response including clearance of pathogens and antigen presentation. Although myeloid cell regulation and function in vertebrates is best understood in mammals, the zebrafish presents a new model to better understand myeloid cell biology due to embryonic transparency, which allows direct observation of cell populations using transgenic reporter lines and gene expression patterns using whole-mount in situ hybridization (WISH). Because the genetic regulation of the hematopoietic hierarchy and blood cell function in zebrafish is well conserved with mammals, the insights obtained studying zebrafish myeloid cell function can be applied to our overall understanding of vertebrate myeloid cell biology. In this study, we took advantage of the optical transparency and rapid development of zebrafish embryos to identify new genes involved in myeloid cell function. We generated a cDNA library from adult kidney myelomonocytes isolated by flow cytometry to identify novel genes. We performed WISH to identify genes expressed in known sites of embryonic myelopoiesis and identified a novel gene, clone 2B4. Using quantitative PCR, we found high levels of expression of clone 2B4 in other purified myeloid cell populations. Bioinformatics analysis revealed that clone 2B4 belongs to the PLAC8 family. Here, we present the initial characterization of the novel myeloid gene, clone 2B
