: Bruton's component B tyrosine kinase (Btk) is a critical of signaling pathways that regulate B cell development and function. Mutations in Btk cause the cell immunodeficiency's X-linked a gammaglobulinemia (XLA) in humans and X-linked immunodeficiency (xid) in mice. Btk is also required for the production of autoantibodies and the efficient degranulation of mast cells. A thorough understanding of the signaling pathways downstream of Btk is likely to reveal new therapeutic targets for B cell immunodeficiencies,autoimmunity, and allergy. This study will test the hypothesis that impaired regulation of gene expression in response to BCR crosslinking results in the B cell developmental and functional defects observed in the absence of Btk. B cells from wild type and Btklo mice, which express a limiting dosage of Btk, will be compared. Unlike Btk-/- or xid mice, Btklo mice have normal numbers of mature B cells. These cells remain functionally impaired due to insufficient levels of Btk, allowing Btk-dependent signaling events to be identified in mature B cells. We have begun to characterize Btk-dependent changes in BCR-induced gene expression using cDNA microarray analysis.
Our first aim i s to confirm these results using real-time RT-PCR and Western blots and to define which branches of Btk signaling pathways are involved in the regulation of these genes. The role of Btk-regulated genes in mediating various functional outcomes of Btk-initiated signals will be assessed as follows. Btk-regulated genes will be expressed as transgenes in Btk-/-, Btk lo, and wild type mice and their ability to restore Btk-dependent defects in conventional B cell development and function observed. To assess the role of Btk-regulated genes in B-1 cell differentiation, transgenes expressing Btk regulated genes will be crossed to Btk-/-, Btklo, and wild type mice carrying a VH12 anti-phosphatidylcholine Ig transgene. This transgene drives the clonal expansion of phosphatidylcholine-specific B cells and their differentiation into the B-1 compartment in a Btk-dependent manner. These studies will define the mechanism by which Btk-mediated transmission of BCR signals regulates the development and function of both conventional B and B-1 cells and potentially identify novel therapeutic approaches for diseases involving B cell disregulation.

Agency
National Institute of Health (NIH)
Institute
National Institute of Allergy and Infectious Diseases (NIAID)
Type
Research Project (R01)
Project #
5R01AI049248-03
Application #
6847829
Study Section
Immunobiology Study Section (IMB)
Program Officer
Miller, Lara R
Project Start
2003-02-01
Project End
2008-01-31
Budget Start
2005-02-01
Budget End
2006-01-31
Support Year
3
Fiscal Year
2005
Total Cost
$312,000
Indirect Cost
Name
University of Texas Sw Medical Center Dallas
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
800771545
City
Dallas
State
TX
Country
United States
Zip Code
75390
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Hinman, Rochelle M; Nichols, Whitney A; Diaz, Tracy M et al. (2009) Foxo3-/- mice demonstrate reduced numbers of pre-B and recirculating B cells but normal splenic B cell sub-population distribution. Int Immunol 21:831-42
Contreras, Cristina M; Halcomb, Kristina E; Randle, Lindsey et al. (2007) Btk regulates multiple stages in the development and survival of B-1 cells. Mol Immunol 44:2719-28
Halcomb, Kristina E; Contreras, Cristina M; Hinman, Rochelle M et al. (2007) Btk and phospholipase C gamma 2 can function independently during B cell development. Eur J Immunol 37:1033-42
Hinman, Rochelle M; Bushanam, Jessica N; Nichols, Whitney A et al. (2007) B cell receptor signaling down-regulates forkhead box transcription factor class O 1 mRNA expression via phosphatidylinositol 3-kinase and Bruton's tyrosine kinase. J Immunol 178:740-7