Mice Lacking the CARD of CARMA1 Exhibit Defective B Lymphocyte Development and Impaired Proliferation of Their B and T Lymphocytes

AbstractCARMA1 (originally called CARD11) is a membrane-associated guanylate kinase family member that is required for T cell receptor (TCR)-induced NF-κB activation in T cell leukemia lines [1–5]. It uses its N-terminal caspase activation and recruitment domain (CARD) to interact with the CARD in the downstream adaptor Bcl-10. We show that primary B and T lymphocytes from knock-in mice expressing only a CARDless form of CARMA1 (ΔCARD) are defective at mitogen-induced NF-κB activation and fail to proliferate. CARMA1 mutant mice exhibited normal T but impaired B cell development; CD5+ peritoneal B cells were absent, and serum immunoglobulin levels were markedly reduced. A lacZ reporter gene knocked into the CARMA1 locus confirmed lymphocyte-specific expression of CARMA1. Thus, CARMA1 has an essential role in mediating B and T lymphocyte proliferation and requires its CARD to engage downstream signaling components