Gene expression profile of zebrafish kidney side population (SP) cells

Side population (SP) cells are identified based on their capacity to efflux of the fluorescent dye Hoechst 33342, and are enriched for hematopoietic stem cells (HSCs) in mammalian bone marrow. We recently demonstrated that SP cells were present in the teleost kidney, the main hematopoietic organ in teleosts, and were enriched for HSCs. In this analysis, to identify the regulated genes in teleost HSCs, gene expression analysis of zebrafish kidney SP cells were performed using the GeneChip Zebrafish Genome Array. Based on their Hoechst fluorescence intensity, lymphoid cells (FS-low, SS-low) from zebrafish kidney were subdivided into SP and MP populations (referred to as “zSP” and “zMP”). To minimize the biological variability, 20 zebrafish were used for 3 independent cell sorting experiments and lysates from these 3 experiments were pooled by cell type. Each RNA sample was split into two aliquots and used for amplification, labeling, and hybridization to independent arrays.