Essential role for Gata2 in modulating lineage output from hematopoietic stem cells in zebrafish

Abstract

The differentiation of hematopoietic stem cells (HSCs) is tightly controlled to ensure a proper balance between myeloid and lymphoid cell output. GATA2 is a pivotal hematopoietic transcription factor required for generation and maintenance of HSCs. GATA2 is expressed throughout development, but because of early embryonic lethality in mice, its role during adult hematopoiesis is incompletely understood. Zebrafish contains 2 orthologs of GATA2: Gata2a and Gata2b, which are expressed in different cell types. We show that the mammalian functions of GATA2 are split between these orthologs. Gata2b-deficient zebrafish have a reduction in embryonic definitive hematopoietic stem and progenitor cell (HSPC) numbers, but are viable. This allows us to uniquely study the role of GATA2 in adult hematopoiesis. gata2b mutants have impaired myeloid lineage differentiation. Interestingly, this defect arises not in granulocyte-monocyte progenitors, but in HSPCs. Gata2b-deficient HSPCs showed impaired progression of the myeloid transcriptional program, concomitant with increased coexpression of lymphoid genes. This resulted in a decrease in myeloid-programmed progenitors and a relative increase in lymphoid-programmed progenitors. This shift in the lineage output could function as an escape mechanism to avoid a block in lineage differentiation. Our study helps to deconstruct the functions of GATA2 during hematopoiesis and shows that lineage differentiation flows toward a lymphoid lineage in the absence of Gata2b.

Differential Requirement of Gata2a and Gata2b for Primitive and Definitive Myeloid Development in Zebrafish

“…These observations are consistent with the recovery of HSPC development reported in fish with mutations in a conserved enhancer that drives endothelial expression of Gata2a ( Dobrzycki et al, 2020 ). Other recent studies have shown that initial specification and endothelial-to-hematopoietic transition of HSC is intact in Gata2b knockout animals ( Gioacchino et al, 2021 ). In our studies we demonstrated that Gata2b u 5008/u5008 mutants have normal vascular development but have a reduction in HSPCs in the aorta from 36 hpf.…”

Notch Signaling in HSC Emergence: When, Why and How

“…As an example, the use of a blocking antibody directed against DLL4 during AGM hematopoiesis has provided great insight; blocking DLL4 during IAHC formation greatly enhances IAHC size and to a lesser extent HSC activity [38]. Finally, perhaps we will be able to decipher the molecular programs that are driven by Notch to specify HSCs by mining the vast number of single cell RNA sequencing data [29,33,37,[143][144][145][146][147][148][149]. In this case, we can circumvent modulation of Notch activity and directly induce the desired downstream signaling.…”

Gata2-regulated Gfi1b expression controls endothelial programming during endothelial-to-hematopoietic transition

“…Following injections, embryos were treated with 0.003% 1-phenyl-2-thiourea (PTU, Sigma) at 24 hpf and fixed overnight with 4 % paraformaldehyde (PFA) in phosphate-buffered saline (PBS) containing 3% sucrose at 33 hpf. In situ hybridization (ISH) for cmyb was performed as previously described (Gioacchino at al., 2021;Chocron et al, 2007). The cmyb probe was a gift from Roger Patient.…”