biostudies-literaturePatzelt THelmholtz-GemeinschaftDeutsche ForschungsgemeinschaftEuropean Research CouncilDeutsche Krebshilfe3120-3125https://www.ebi.ac.uk/biostudies/studies/S-EPMC5866538biostudies-literatureUnknown115(12)The transcription factor Foxp1 is critical for early B cell development. Despite frequent deregulation of Foxp1 in B cell lymphoma, the physiological functions of Foxp1 in mature B cells remain unknown. Here, we used conditional gene targeting in the B cell lineage and report that Foxp1 disruption in developing and mature B cells results in reduced numbers and frequencies of follicular and B-1 B cells and in impaired antibody production upon T cell-independent immunization in vivo. Moreover, <i>Foxp1</i>-deficient B cells are impaired in survival even though they exhibit an increased capacity to proliferate. Transcriptional analysis identified defective expression of the prosurvival Bcl-2 family gene <i>Bcl2l1</i> encoding Bcl-xl in Foxp1-deficient B cells, and we identified Foxp1 binding Proceedings of the National Academy of Sciences of the United States of AmericaFoxp1 controls mature B cell survival and the development of follicular and B-1 B cells.PMC5866538SFB746111026ImmunoSensationPCCC/WP8EXC294SFB1054/B0170112036RU 695/6-1TRR130322865322972Patzelt TGorka OThoene SWartewig TReth MRuland JKeppler SJLang RBuchner MForster IfalseFoxp1 controls mature B cell survival and the development of follicular and B-1 B cells.The transcription factor Foxp1 is critical for early B cell development. Despite frequent deregulation of Foxp1 in B cell lymphoma, the physiological functions of Foxp1 in mature B cells remain unknown. Here, we used conditional gene targeting in the B cell lineage and report that Foxp1 disruption in developing and mature B cells results in reduced numbers and frequencies of follicular and B-1 B cells and in impaired antibody production upon T cell-independent immunization in vivo. Moreover, <i>Foxp1</i>-deficient B cells are impaired in survival even though they exhibit an increased capacity to proliferate. Transcriptional analysis identified defective expression of the prosurvival Bcl-2 family gene <i>Bcl2l1</i> encoding Bcl-xl in Foxp1-deficient B cells, and we identified Foxp1 binding 2018-01-01T00:00:00Z2018 Mar2026-05-01T20:11:27.283Z2019-03-26T23:47:20ZS-EPMC58665382950722610.1073/pnas.1711335115