C3G, a Rap1 GEF, promotes megakaryopoiesis and platelet function. Using transgenic and knock-out mouse models targeting C3G in megakaryocytes, we investigated whether C3G also affects the niche function of megakaryocytes during bone marrow (BM) recovery after myeloablation induced by 5-fluorouracil (5-FU), or total body irradiation (TBI) followed by bone marrow transplantation. C3G promoted megakaryocyte maturation and platelet production during recovery, along with increased white and red blood cell counts and enhanced survival of female mice after repeated doses of 5-FU. Additionally, megakaryocytes favored adipocyte differentiation through a C3G-mediated mechanism, likely involving Fgf1. Changes in the number or behavior of BM megakaryocytes and adipocytes influenced the hematopoietic stem cell pool, with C3G promoting its bias towards the myeloid-megakaryocytic lineage in both 5-FU- and TBI-ablated models. Therefore, C3G could be a potential target in therapies aimed at enhancing hematopoiesis in patients undergoing chemotherapy and/or BM transplantation.
© 2025. The Author(s).

Irradiation with X-rays has been widely utilized in the clinical treatment of solid tumors and certain hematopoietic malignancies. However, this method fails to completely distinguish between malignant and normal cells. Prolonged or repeated exposure to radiation, whether due to occupational hazards or therapeutical interventions, can cause damage to normal tissues, particularly impacting the hematopoietic system. Therefore, it is important to investigate the effects of total body irradiation on the hematopoietic system of mice and to compare the inhibitory effects of various doses of irradiation on this system. In this study, we primarily employed flow cytometry to analyze mature lineage cells in the peripheral blood, as well as immature hematopoietic stem and progenitor cells (HSPCs) in the bone marrow and spleen. Additionally, we evaluated the multilineage differentiation capacity of HSPCs through colony-forming cell assays. Our results indicated that peripheral B and T cells demonstrated increased sensitivity to irradiation, with significant cell death observed 1-day post-irradiation. Common lymphoid progenitor cells exhibited greater radiotolerance compared to other progenitor cell types, enabling them to maintain a certain population even at elevated doses. Moreover, notable differences were observed between intramedullary and extramedullary hematopoietic stem cells and common lymphoid progenitor cells regarding the extent of damage and recovery rate following irradiation. The multilineage differentiation capacity of HSPCs was also compromised during radiation exposure. In conclusion, different types of mature blood cells, along with immature HSPCs, exhibited varying degrees of sensitivity and tolerance to irradiation, resulting in distinct alterations in cell percentages and numbers.
Copyright © 2024 The Authors. Published by Wolters Kluwer Health Inc., on behalf of the Chinese Medical Association (CMA) and Institute of Hematology, Chinese Academy of Medical Sciences & Peking Union Medical College (IHCAMS).

Natural killer (NK) cells function by eliminating virus-infected or tumor cells. Here we identified an NK-lineage-biased progenitor population, referred to as early NK progenitors (ENKPs), which developed into NK cells independently of common precursors for innate lymphoid cells (ILCPs). ENKP-derived NK cells (ENKP_NK cells) and ILCP-derived NK cells (ILCP_NK cells) were transcriptionally different. We devised combinations of surface markers that identified highly enriched ENKP_NK and ILCP_NK cell populations in wild-type mice. Furthermore, Ly49H+ NK cells that responded to mouse cytomegalovirus infection primarily developed from ENKPs, whereas ILCP_NK cells were better IFNγ producers after infection with Salmonella and herpes simplex virus. Human CD56dim and CD56bright NK cells were transcriptionally similar to ENKP_NK cells and ILCP_NK cells, respectively. Our findings establish the existence of two pathways of NK cell development that generate functionally distinct NK cell subsets in mice and further suggest these pathways may be conserved in humans.
© 2024. This is a U.S. Government work and not under copyright protection in the US; foreign copyright protection may apply.

T cells and innate lymphoid cells (ILCs) share expression of many key transcription factors during development and at mature stage, resulting in striking functional similarities between these lineages. Taking into account ILC contribution is thus necessary to appreciate T cell functions during immune responses. Furthermore, understanding ILC development and functions helps to understand T cells. Here we provide methods and protocols to isolate pure populations of multipotent precursors to T cells and innate lymphoid cells (ILCs) from adult mouse bone marrow, using flow cytometric sorting. These include precursors to all lymphocytes (viz., LMPPs and ALPs) and multipotent precursors to ILCs that have been recently refined (viz., specified EILPs, committed EILPs, and ILCPs).
© 2023. This is a U.S. government work and not under copyright protection in the U.S.; foreign copyright protection may apply.

BTB domain And CNC Homolog 2 (Bach2) is a transcription repressor that actively participates in T and B lymphocyte development, but it is unknown if Bach2 is also involved in the development of innate immune cells, such as natural killer (NK) cells. Here, we followed the expression of Bach2 during murine NK cell development, finding that it peaked in immature CD27+CD11b+ cells and decreased upon further maturation. Bach2 showed an organ and tissue-specific expression pattern in NK cells. Bach2 expression positively correlated with the expression of transcription factor TCF1 and negatively correlated with genes encoding NK effector molecules and those involved in the cell cycle. Lack of Bach2 expression caused changes in chromatin accessibility of corresponding genes. In the end, Bach2 deficiency resulted in increased proportions of terminally differentiated NK cells with increased production of granzymes and cytokines. NK cell-mediated control of tumor metastasis was also augmented in the absence of Bach2. Therefore, Bach2 is a key checkpoint protein regulating NK terminal maturation.
© 2022, Li et al.