Arhgap25deficiency leads to decreased numbers of peripheral blood B cells and defective germinal center reactions

Abstract

30Rho family GTPases are critical for normal B cell development and function and their activity is 31 regulated by a large and complex network of guanine nucleotide exchange factors (GEFs) and 32 GTPase activating proteins (GAPs). However, the role of GAPs in B cell development is poorly 33 understood. Here we show that the novel Rac-GAP ARHGAP25 is important for B cell 34 development in mice in a CXCR4-dependent manner. We show that Arhgap25 deficiency leads 35 to a significant decrease in peripheral blood B cell numbers, as well as defects in mature B cell 36 differentiation. Arhgap25 -/-B cells respond to antigen stimulation in vitro and in vivo but have 37 impaired germinal center formation and decreased IgG1 class switching. Additionally, 38 Arhgap25 -/-B cells exhibit increased chemotaxis to CXCL12. Taken together, these studies 39 demonstrate an important role for Arhgap25 in peripheral B cell development and antigen 40 response. 41 demonstrate that Arhgap25 plays an important role in terminal B cell differentiation and B cell 64 activation by influencing CXCL12-CXCR4 signaling. 65 In particular, Arhgap25-deficient mice have significantly fewer peripheral blood mature B cells 66 than wild-type controls. Additionally, Arhgap25-deficient B cells have defects in germinal center 67 formation in response to in vivo immunization, with fewer and smaller splenic germinal centers 68 in Arhgap25 -/mice than wild-type mice after NP-CGG injection. These defects may be 69 attributable to increased responsiveness of Arhgap25 -/-B cells to CXCL12, which may keep 70 germinal center B cells sequestered in the dark zone (DZ)(23). We observed increased numbers 71 of DZ B cells in Arhgap25 -/mice, as well as decreased numbers of plasma cells and diminished 72 IgG1 secretion. Taken together, these findings indicate that Arhgap25 plays an important role in 73 regulating B cell chemotaxis and the germinal center reaction via the CXCL12-CXCR4 pathway. 74 5 MATERIALS AND METHODS 75 Mice 76 Arhgap25 -/mice (CSD28473) were obtained as cryopreserved embryos from the NIH Knockout 77 Mouse Project (KOMP) repository, recovered using standard techniques, and housed in specific-78 pathogen-free barrier facilities at City of Hope. C57Bl/6N mice were purchased from Taconic 79 Biosciences and bred under specific-pathogen-free conditions at City of Hope. Unless otherwise 80 stated, 7-12 week old gender-matched mice were used for all experiments. Every animal was 81 maintained and handled in accordance with City of Hope Institutional Animal Care and Use 82 Committee (IACUC) guidelines and protocols. 83 Flow Cytometry Analysis 84 Single cell suspensions were prepared by mechanical dissociation and then strained through a 85 70µm mesh. Red blood cells were lysed in RBC lysis buffer (00-4300-54, eBioscience, San 86 Diego CA) per manufacturer's directions. Cells were then strained through a 40µm cell strainer 87 and then stained in phosphate-buffered saline (PBS) with 5% fetal bovine serum (FBS) in 5 ml 88 polystyrene round-bottom tubes. Prior ...

Chromosome‐scale genomes reveal genomic consequences of inbreeding in the South China tiger: A comparative study with the Amur tiger

“…MyH10 (Kim et al, 2018), CP (Fleming & Gitlin, 1990), RCOR1 (Yao et al, 2014), DENND1A (Shi et al, 2019), RAD51D (Pittman & Schimenti, 2000) and PAPPA2 (Fujimoto et al, 2020) were related to fetal growth and survival. Deletions or mutations in SKOR2 (Wang et al, 2011), GNAO1 (Danti et al, 2017), GFRA1 (Arora et al, 2021), ARHGAP25 (Lindner et al, 2020), SALL2 (Kelberman et al, 2014), ABCB5 (Bruce et al, 2014) and MYOF (Doherty et al, 2005) would lead to abnormal growth of tissues and organs (Table S21).…”