Ribosome biogenesis is a significant process in cells. Dysfunction in this process will result in the defects of protein synthesis and consequently cause the development of specific diseases called ribosomopathies. Mutations in ribosome biogenesis protein Rps19, Rpl5, or Rpl11 can lead to hematopoietic defects in human, thus triggering the disease Diamond Blackfan anemia. However, the regulatory mechanisms of ribosome biogenesis in hematopoiesis remain incompletely understood. In this study, we describe a zebrafish mutant cq42, which carries a nonsense mutation in the gene that encodes ribosome biogenesis 2 homolog (Urb2). Urb2 is strongly expressed in the caudal hematopoietic tissue (CHT) during hematopoietic stem cells (HSCs) expanding. Molecular characterization of urb2(cq42) larvae suggest that urb2 deficiency notably decrease the population of HSCs in CHT and early T cells in thymus. Further analysis shows that compromised cell proliferation and superfluous apoptosis are observed in the CHT of urb2(cq42) mutant. P53 pathway is upregulated in the urb2(cq42) larvae and loss-of-function of P53 can fully rescue the hematopoietic defects in urb2(cq42) mutant. These data demonstrate that urb2 is essential for HSCs development through the regulation of P53 pathway. (C) 2018 Elsevier Inc. All rights reserved.