title: Immunoglobulin double-isotype expression by trans-mRNA in a human immunoglobulin transgenic mouse.
abstract: We have studied immunoglobulin double-isotype expression in a transgenic mouse (TG.SA) in which expression of the endogenous immunoglobulin heavy chain locus is almost completely excluded by a nonallelic rearranged human mu transgene. By flow-cytometric analyses, we have shown that a small, but significant, portion (about 4%) of transgenic spleen cells expresses human mu (transgene) and mouse gamma (endogenous) chains when cultured in vitro with bacterial lipopolysaccharide and interleukin 4. By using amplification of cDNA by the polymerase chain reaction, followed by cloning and sequencing of the amplified cDNA fragment, we have demonstrated expression of trans-mRNA consisting of the transgenic variable and endogenous constant (gamma 1) region sequences. Such trans-mRNA could be produced by either switch recombination or trans-splicing between the transgene and endogenous sterile gamma 1-gene transcripts. These results indicate that trans-splicing might be a possible mechanism for the immunoglobulin double-isotype expression in normal B lymphocytes that have not rearranged the second expressed constant region gene.
authors.affiliation: Center for Molecular Biology and Genetics, Kyoto University, Japan.
authors.forename: A
authors.initials: A
authors.lastname: Shimizu
authors.forename: M C
authors.initials: MC
authors.lastname: Nussenzweig
authors.forename: T R
authors.initials: TR
authors.lastname: Mizuta
authors.forename: P
authors.initials: P
authors.lastname: Leder
authors.forename: T
authors.initials: T
authors.lastname: Honjo
mesh_terms: D000818:Animals; D001483:Base Sequence; D005091:Exons; D005434:Flow Cytometry; D015870:Gene Expression; D005803:Genes, Immunoglobulin; D006801:Humans; D007143:Immunoglobulin Heavy Chains / Q000235:genetics; D007132:Immunoglobulin Isotypes / Q000235:genetics*; D007148:Immunoglobulin mu-Chains / Q000235:genetics; D008214:Lymphocytes / Q000276:immunology*; D051379:Mice; D008822:Mice, Transgenic; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D012326:RNA Splicing; D012333:RNA, Messenger / Q000235:genetics*; D013154:Spleen / Q000276:immunology; D014158:Transcription, Genetic
chemical_list: D007143:Immunoglobulin Heavy Chains; D007132:Immunoglobulin Isotypes; D007148:Immunoglobulin mu-Chains; D012333:RNA, Messenger