Bruton's tyrosine kinase regulates the activation of gene rearrangements at the lambda light chain locus in precursor B cells in the mouse
Bruton's tyrosine kinase (Btk) is a nonreceptor tyrosine kinase involved in precursor B (pre-B) cell receptor signaling. Here we demonstrate that Btk-deficient mice have an approximately 50% reduction in the frequency of immunoglobulin (Ig) lambda light chain expression, already at the immature B cell stage in the bone marrow. Conversely, transgenic mice expressing the activated mutant Btk(E41K) showed increased lambda usage. As the kappa/lambda ratio is dependent on (a) the level and kinetics of kappa and lambda locus activation, (b) the life span of pre-B cells, and (c) the extent of receptor editing, we analyzed the role of Btk in these processes. Enforced expression of the Bcl-2 apoptosis inhibitor did not alter the Btk dependence of lambda usage. Crossing 3-83mudelta autoantibody transgenic mice into Btk-deficient mice showed that Btk is not essential for receptor editing. Also, Btk-deficient surface Ig(+) B cells that were generated in vitro in interleukin 7-driven bone marrow cultures manifested reduced lambda usage. An intrinsic defect in lambda locus recombination was further supported by the finding in Btk-deficient mice of reduced lambda usage in the fraction of pre-B cells that express light chains in their cytoplasm. These results implicate Btk in the regulation of the activation of the lambda locus for V(D)J recombination in pre-B cells.
|Keywords||*Gene Rearrangement, B-Lymphocyte, Light Chain, Animals, Antigens, CD19, B-Lymphocytes/*immunology, Bone Marrow Cells, Enzyme Activation, Female, Genes, bcl-2, Hematopoietic Stem Cells/*immunology, Mice, Protein-Tyrosine Kinase/*metabolism, RNA Editing, Receptors, Antigen, B-Cell/genetics, Research Support, Non-U.S. Gov't|
Dingjan, G.M., Middendorp, S., Dahlenborg, K., Maas, A., Hendriks, R.W., & Grosveld, F.G.. (2001). Bruton's tyrosine kinase regulates the activation of gene rearrangements at the lambda light chain locus in precursor B cells in the mouse. The Journal of Experimental Medicine. Retrieved from http://hdl.handle.net/1765/9639