The Caudal Hematopoietic Tissue is Differentially Required for Erythrocytes and Neutrophils from Definitive Hematopoiesis in Zebrafish
Neutrophils and erythrocytes are vital to the immune system and oxygen transport, respectively. However, the mechanisms by which hematopoietic niches support their development remain incompletely understood. In hematopoiesis research, zebrafish larvae are a common model for studying the development of definitive neutrophils and erythrocytes in the caudal hematopoietic tissue. In this study, we showed that erythrocytes predominantly reside inside the blood vessels of the CHT, while neutrophils stay outside. Ectopic vascular endothelium, induced by Bone Morphogenetic Protein 2b(Bmp2b) overexpression, attracts both cell types, with erythrocytes inside and neutrophils outside. CHT removal has minimal impact on definitive neutrophils from the ventral wall of the dorsal aorta (VDA) but severely affects definitive erythrocytes from the same source. Bulk RNA-sequencing identified epoa as a vital factor for erythrocyte generation within CHT endothelium. Overexpression of epoa through the lyve1b promoter, which is specifically expressed in vein, lymphatic vessels and CHT vein endothelial cells, rescued the erythrocyte reduction in epoa mutants. Our study reveals that the caudal hematopoietic tissue is differentially required for definitive erythrocytes and neutrophils. Overall design: We then performed gene expression profiling analysis using data obtained from BULK RNA-seq of 5dpf vein endothelium cells and endothelium cells.