The kidney is the main hematopoietic organ in teleost fish. Various stages of hematopoietic cells were observed in the interstitial tissue of the kidney. We recently demonstrated that zebrafish hematopoietic stem cells (HSCs) expressing jam1a were specifically localized along the renal collecting ducts in the adult kidney. Interestingly, most of HSCs invaded into the intracellular spaces of the epithelium in collecting ducts, suggesting that collecting ducts provide a specific microenvironment for HSCs. In order to identify niche factors in collecting ducts, we performed microarray analysis in collecting ducts isolated from the Tg(jam1a:EGFP) zebrafish kidney.