Published online
doi:10.1084/jem.20070318
The Journal of Experimental Medicine, Vol. 204, No. 11, 2615-2627
The Rockefeller University Press, 0022-1007 $30.00
© Hövelmeyer et al.
Regulation of B cell homeostasis and activation by the tumor suppressor gene CYLD
Nadine Hövelmeyer1,
F. Thomas Wunderlich2,5,
Ramin Massoumi4,
Charlotte G. Jakobsen1,
Jian Song1,5,
Marcus A. Wörns1,
Carsten Merkwirth2,5,
Andrew Kovalenko6,
Monique Aumailley3,5,
Dennis Strand1,
Jens C. Brüning2,5,
Peter R. Galle1,
David Wallach6,
Reinhard Fässler4, and
Ari Waisman1
1 I. Medical Department, Johannes Gutenberg-University Mainz, Verfügungsgebäude, 55131 Mainz, Germany
2 Institute for Genetics and 3 Center for Biochemistry, Medical Faculty, University of Cologne, 50674 Cologne, Germany
4 Department of Molecular Medicine, Max Planck Institute of Biochemistry, 82152 Martinsried, Germany
5 Center for Molecular Medicine Cologne, University of Cologne, 50931 Cologne, Germany
6 Department of Biological Chemistry, The Weizmann Institute of Science, 76100 Rehovot, Israel
CORRESPONDENCE Ari Waisman: waisman{at}uni-mainz.de
B cell homeostasis is regulated by multiple signaling processes, including nuclear factor-
B (NF-
B), BAFF-, and B cell receptor signaling. Conditional disruption of genes involved in these pathways has shed light on the mechanisms governing signaling from the cell surface to the nucleus. We describe a novel mouse strain that expresses solely and excessively a naturally occurring splice variant of CYLD (CYLDex7/8 mice), which is a deubiquitinating enzyme that is integral to NF-
B signaling. This shorter CYLD protein lacks the TRAF2 and NEMO binding sites present in full-length CYLD. A dramatic expansion of mature B lymphocyte populations in all peripheral lymphoid organs occurs in this strain. The B lymphocytes themselves exhibit prolonged survival and manifest a variety of signaling disarrangements that do not occur in mice with a complete deletion of CYLD. Although both the full-length and the mutant CYLD are able to interact with Bcl-3, a predominant nuclear accumulation of Bcl-3 occurs in the CYLD mutant B cells. More dramatic, however, is the accumulation of the NF-
B proteins p100 and RelB in CYLDex7/8 B cells, which, presumably in combination with nuclear Bcl-3, results in increased levels of Bcl-2 expression. These findings suggest that CYLD can both positively and negatively regulate signal transduction and homeostasis of B cells in vivo, depending on the expression of CYLD splice variants.
Abbreviations used: CBA, cytometric bead assay; EMSA, electrophoretic mobility shift assay; MAPK, mitogen-activated protein kinase; MEF, mouse embryonic fibroblast; MZ, marginal zone; NEMO, NF-
B essential modulator; NP-CG, nitrophenol-conjugated chicken
-globulin; PC, peritoneal cavity; TD, T cell–dependent; TI, T cell–independent; TLR, Toll-like receptor.
N. Hövelmeyer and F.T. Wunderlich contributed equally to this paper.
R. Massoumi's present address is Division of Experimental Pathology, Malmö University Hospital, Malmö, Sweden.

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