ABSTRACT
The protein tyrosine phosphatase CD45 is expressed as a series of isoforms whose tissue and differentiation stage specificity is broadly conserved in evolution. CD45 has been shown to be an important regulator of a variety of functions in many different hemopoietic lineages. We have chosen an in vivo genetic complementation strategy to investigate the differential functions between isoforms. In this study, we report the characterization of transgenic mice which express the isoforms CD45RO or CD45RB as their only CD45 molecules, at a variety of expression levels and in the majority of hemopoietic lineages. Both CD45RO and CD45RB isoforms reconstitute thymocyte development in a CD45-null mouse background when expressed above a threshold level. The resulting mature T cells populate the peripheral lymphoid organs where they are found at normal frequency. Both CD45RO and CD45RB isoforms also permit T cell function in the periphery, although the threshold for normal function here appears to be set higher than in the thymus. In contrast, neither isoform is capable of fully restoring peripheral B cell maturation, even at levels approaching those in heterozygous CD45(+/-) mice in which maturation is normal. In vitro activation of B cells by Ag-receptor stimulation is only minimally complemented by these CD45RO and CD45RB transgenes. Our results suggest that CD45 isoforms play unique roles which differ between the T and B lineages.
Subject(s)
B-Lymphocytes/cytology , B-Lymphocytes/immunology , Cell Cycle Proteins , Gene Deletion , Leukocyte Common Antigens/physiology , T-Lymphocyte Subsets/cytology , T-Lymphocyte Subsets/immunology , Animals , Antibody Formation/genetics , B-Lymphocytes/metabolism , Cell Differentiation/genetics , Cell Differentiation/immunology , Crosses, Genetic , Dinitrophenols/immunology , Female , Gene Expression Regulation/immunology , Hematopoietic Stem Cells/immunology , Hematopoietic Stem Cells/metabolism , Humans , Immunoglobulin Class Switching/genetics , Leukocyte Common Antigens/biosynthesis , Leukocyte Common Antigens/genetics , Lymphocyte Activation/genetics , Mice , Mice, Inbred C57BL , Mice, Inbred CBA , Mice, Inbred DBA , Mice, Transgenic , Protein Isoforms/biosynthesis , Protein Isoforms/deficiency , Protein Isoforms/genetics , Protein Isoforms/physiology , Proto-Oncogene Proteins/biosynthesis , Proto-Oncogene Proteins/genetics , Proto-Oncogene Proteins c-vav , Serum Albumin, Bovine/immunology , T-Lymphocyte Subsets/metabolism , Thymus Gland/cytology , Thymus Gland/immunology , Thymus Gland/metabolism , Transgenes/immunologyABSTRACT
Cre transgenic mice can be used to delete gene sequences flanked by loxP sites in specific somatic tissues. We have generated vavCre transgenic mice, which can be used to inactivate genes specifically in adult hematopoietic and endothelial cells. In these animals, a Cre transgene is expressed under control of murine vav gene regulatory elements. To assess their usefulness, vavCre transgenic mice were bred with R26R mice, which express a lacZ reporter gene only in cells where Cre-mediated recombination has occurred. VavCre/R26R double-heterozygous offspring were analyzed by beta-galactosidase histochemistry and flow cytometry. VavCre-mediated recombination occurred in most hematopoietic cells of all hematopoietic organs, including the hematopoietic progenitor-rich bone marrow. Recombination also occurred in most endothelial and germ cells, but only rarely in other cell types. The recombination in both hematopoietic and endothelial lineages may partly reflect their putative shared ontogeny and provides a unique tool for simultaneous pan-hematopoietic and endothelial mutagenesis.
