The B cell-restricted adaptor BASH is required for normal development and antigen receptor-mediated activation of B cells

Katsuhiko Hayashi, Ryo Nittono, Noriaki Okamoto, Sachiyo Tsuji, Yasushi Hara, Ryo Goitsuka, Daisuke Kitamura

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Abstract

B cell antigen receptor signals development, activation, proliferation, or apoptosis of B cells depending on their condition, and its proper signaling is critical for activation and homeostasis of the immune system. The B cell-restricted adaptor protein BASH (also termed BLNK/SLP-65) is rapidly phosphorylated by the tyrosine kinase Syk after BCR ligation and binds to various signaling proteins. BASH structurally resembles SLP-76, which is essential for T cell development and T cell receptor signaling. To evaluate the role for BASH in B cell development and function in vivo, we disrupted BASH alleles in embryonic stem cells by means of homologous recombination and used these cells to complement lymphocyte-incompetent blastocysts from RAG2-deficient mice. In the resultant chimeric mice, T cell development was apparently normal, but B cell development was impaired, and a normally rare population of large preB cells expressing preB cell receptor dominated in the bone marrow in place of small preB cells, although they were mostly noncycling. In addition, the mature B cell populations in the periphery and the bone marrow profoundly decreased in size, as did B-1 cells in the peritoneal cavity, and serum Ig was severely reduced. The BASH- deficient B cells scarcely proliferated or up-regulated B7-2 in response to BCR ligation and poorly proliferated upon CD40 ligation or lipopolysaccharide stimulation. This phenotype indicates that BASH is critical for preB cell receptor signaling inducing proliferation of large preB cells and the following differentiation, for peripheral B cell maturation, and for BCR signaling inducing activation/proliferation of B cells.

Original languageEnglish
Pages (from-to)2755-2760
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume97
Issue number6
DOIs
Publication statusPublished - Mar 14 2000
Externally publishedYes

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