Citation

In addition to Fc?RI, a subtype of human mast cells (MCs) expresses Mas-related G-protein coupled receptor X2 (MRGPRX2, mouse counterpart MrgprB2). Although MrgprB2 contributes to IgE-mediated passive systemic anaphylaxis (PSA) in vivo, an MRGPRX2 inhibitor (C9) does not block MrgprB2-mediated or IgE-mediated MC degranulation in vitro.To generate mice expressing human MRGPRX2 to study receptor function in vitro and PSA in vivo.CRISPR/Cas9-mediated gene editing approach was utilized to replace endogenous MrgprB2 with human MRGPRX2 in mice (MRGPRX2-KI mice). MRGPRX2 expression in the skin, gingiva, trachea, and colon were evaluated using an anti-human MRGPRX2 antibody. Peritoneal MCs (PMCs) cultured from wild-type (WT), MRGPRX2-KI and MrgprB2-/- mice were used to study agonists-induced degranulation. The effects of selective MRGPRX2 inhibitors (C9 and C9-6) on substance P or IgE-mediated MC degranulation in vitro, and IgE-mediated passive systemic anaphylaxis (PSA) in vivo were tested.MRGPRX2-expressing MCs were present in tissues of MRGPRX2-KI mice. Most agonists tested induced greater degranulation at lower concentrations in PMCs from MRGPRX2-KI mice than cells from WT mice. Furthermore, C9 and C9-6 inhibited degranulation in MRGPRX2-KI PMCs in response to substance P. By contrast, they had no effect on IgE-mediated degranulation in vitro but inhibited PSA in MRGPRX2-KI mice in vivo.MRGPRX2-KI mice provide a readily available source of primary MCs for signaling studies. Furthermore, transactivation of MRGPRX2 contributes to IgE-mediated PSA, suggesting that MRGPRX2-KI mice could be utilized as a preclinical model for testing novel therapeutics targeting MRGPRX2 and its crosstalk with Fc?RI.