Murine Bone Marrow Stromally Derived BMS2 Adipocytes Support Differentiation and Function of Osteoclast-Like Cellsin Vitro1

Neutrophils are important innate immune cells that tackle invading pathogens with different effector mechanisms. They acquire this antimicrobial potential during their maturation in the bone marrow, where they differentiate from hematopoietic stem cells in a process called granulopoiesis. Mature neutrophils are terminally differentiated and short-lived with a high turnover rate. Here, we show a critical role for linker histone H1 on the differentiation and function of neutrophils using a genome-wide CRISPR/Cas9 screen in the human cell line PLB-985. We systematically disrupted expression of somatic H1 subtypes to show that individual H1 subtypes affect PLB-985 maturation in opposite ways. Loss of H1.2 and H1.4 induced an eosinophil-like transcriptional program, thereby negatively regulating the differentiation into the neutrophil lineage. Importantly, H1 subtypes also affect neutrophil differentiation and the eosinophil-directed bias of murine bone marrow stem cells, demonstrating an unexpected subtype-specific role for H1 in granulopoiesis.

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Arhgap21 Deficiency Results in Increase of Osteoblastic Lineage Cells in the Murine Bone Marrow Microenvironment

Frontiers in Cell and Developmental Biology ◽

10.3389/fcell.2021.718560 ◽

2021 ◽

Vol 9 ◽

Author(s):

Mariana Ferreira Pissarra ◽

Cristiane Okuda Torello ◽

Rafael Gonçalves Barbosa Gomes ◽

Rodrigo Naoto Shiraishi ◽

Irene Santos ◽

...

Keyword(s):

Bone Marrow ◽

Osteogenic Differentiation ◽

Hematopoietic Stem ◽

Knockout Mouse Model ◽

Murine Bone Marrow ◽

Osteoblastic Lineage ◽

Bm Niche ◽

Stem And Progenitor Cells ◽

And Function

ARHGAP21 is a member of the RhoGAP family of proteins involved in cell growth, differentiation, and adhesion. We have previously shown that the heterozygous Arhgap21 knockout mouse model (Arhgap21+/−) presents several alterations in the hematopoietic compartment, including increased frequency of hematopoietic stem and progenitor cells (HSPC) with impaired adhesion in vitro, increased mobilization to peripheral blood, and decreased engraftment after bone marrow transplantation. Although these HSPC functions strongly depend on their interactions with the components of the bone marrow (BM) niche, the role of ARHGAP21 in the marrow microenvironment has not yet been explored. In this study, we investigated the composition and function of the BM microenvironment in Arhgap21+/− mice. The BM of Arhgap21+/− mice presented a significant increase in the frequency of phenotypic osteoblastic lineage cells, with no differences in the frequencies of multipotent stromal cells or endothelial cells when compared to the BM of wild type mice. Arhgap21+/− BM cells had increased capacity of generating osteogenic colony-forming units (CFU-OB) in vitro and higher levels of osteocalcin were detected in the Arhgap21+/− BM supernatant. Increased expression of Col1a1, Ocn and decreased expression of Trap1 were observed after osteogenic differentiation of Arhgap21+/− BM cells. In addition, Arhgap21+/− mice recipients of normal BM cells showed decreased leucocyte numbers during transplantation recovery. Our data suggest participation of ARHGAP21 in the balanced composition of the BM microenvironment through the regulation of osteogenic differentiation.

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