title: Generation of a novel Cr2 gene allele by homologous recombination that abrogates production of Cr2 but is sufficient for expression of Cr1.
abstract: The enhancing effects of the complement system for humoral immunity have primarily focused upon the recognition of complement-bound foreign antigens by a co-receptor complex of the antigen-specific B cell receptor (BCR) and complement receptor 2 (Cr2). In vivo experiments using Cr2 gene deficient mice (which lack the expression of both the Cr1 and Cr2 proteins) do demonstrate depressed humoral responses to immunization but cannot be used to define specific contributions of the singular Cr1 or Cr2 proteins on B cell functions. To study the effect of a Cr2 deficiency in a Cr1 sufficient environment we created a mouse line in which the alternative splice site required for the expression of the Cr2 isoform was removed. This mouse line, Cr2KO, still expressed Cr1 on B cells but was deficient for the full length Cr2 protein. Surprisingly a new alternative splice within the Cr2 gene created a truncated product that encoded a novel protein termed iCr2 that was expressed on the surface of the cells. The Cr2KO mouse thus provides a new model system for the analysis of Cr1 and Cr2 functions in the immune response of the mouse.
authors.affiliation: Division of Microbiology and Immunology, Department of Pathology, University of Utah School of Medicine, Salt Lake City, UT 84112, United States.
authors.forename: Luke R
authors.initials: LR
authors.lastname: Donius
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Orlando
authors.forename: Janis J
authors.initials: JJ
authors.lastname: Weis
authors.forename: John H
authors.initials: JH
authors.lastname: Weis
mesh_terms: D000483:Alleles; D017398:Alternative Splicing / Q000235:genetics / Q000276:immunology*; D000818:Animals; D001402:B-Lymphocytes / Q000276:immunology / Q000378:metabolism; D015153:Blotting, Western; D002462:Cell Membrane / Q000276:immunology / Q000378:metabolism; D003713:Dendritic Cells / Q000276:immunology / Q000378:metabolism; D005434:Flow Cytometry; D015870:Gene Expression / Q000276:immunology; D059765:Homologous Recombination / Q000235:genetics / Q000276:immunology*; D007150:Immunohistochemistry; D051379:Mice; D018345:Mice, Knockout; D020033:Protein Isoforms / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D017463:Receptors, Complement 3b / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D017464:Receptors, Complement 3d / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013154:Spleen / Q000166:cytology / Q000276:immunology / Q000378:metabolism
chemical_list: D020033:Protein Isoforms; D017463:Receptors, Complement 3b; D017464:Receptors, Complement 3d
keywords: Alternative splicing; B cell receptor; B cells; BCR; C3; Complement; Complement receptors; Cr1/CR1; Cr2/CR2; Follicular dendritic cells; IC; PCR; SCR; SS; TK; WT; complement component 3; complement receptor 1; complement receptor 2; follicular dendritic cell; gMFI; geometric mean fluorescent intensity; iCr2; incomplete Cr2; isotype control; polymerase chain reaction; s; short consensus repeat; signal sequence; thymidine kinase; wild type