title: High RAD51 mRNA levels in young rabbit appendix. A role in B-cell gene conversion?
abstract: The rabbit has a limited number of VH genes that rearrange. As in the chicken, the 3'-most VH1 gene is rearranged in most B lymphocytes. This laboratory reported that by 6 weeks after birth, diversification of rearranged VH genes occurs, at least in part, by gene conversion-like events in the appendix, suggesting that this organ is a homologue of the avian bursa of Fabricius. Rad51 contributes to the repair of double-strand breaks in DNA during somatic and meiotic recombination. The gene was first identified in lower eukaryotes, and later in vertebrates including chicken, as encoding an Escherichia coli RecA-like protein. We report the cloning and sequencing of RAD51 from the rabbit. Because the chicken bursa was shown to express high levels of RAD51 message, we investigated the expression of RAD51 in the rabbit appendix and other tissues. Using a quantitative polymerase chain reaction mimic assay and conventional northern analyses, we found high RAD51 expression in young rabbit appendix comparable to levels in testis where there is an abundance of meiotic recombination. RAD51 levels were three times higher in appendix B lymphocytes compared with T lymphocytes and were lower in adult appendix, as well as in spleen and Peyer's patches of young rabbits. We measured the levels of message in several appendix cell sub-populations obtained by fluorescence-activated cell sorting and found that sub-populations of B lymphocytes corresponding to different stages of B-cell development as well as B cells undergoing isotype switch did not have significantly different mRNA levels.
authors.affiliation: Molecular Immunogenetics Section, Laboratory of Immunology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892-1892, USA.
authors.forename: E
authors.initials: E
authors.lastname: Schiaffella
authors.forename: P
authors.initials: P
authors.lastname: Fuschiotti
authors.forename: S J
authors.initials: SJ
authors.lastname: Bensinger
authors.forename: R G
authors.initials: RG
authors.lastname: Mage
mesh_terms: D000367:Age Factors; D000595:Amino Acid Sequence; D000818:Animals; D015703:Antigens, CD; D001065:Appendix / Q000166:cytology / Q000276:immunology*; D030161:Avian Proteins; D001402:B-Lymphocytes / Q000276:immunology*; D001483:Base Sequence; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics; D004268:DNA-Binding Proteins / Q000096:biosynthesis* / Q000235:genetics; D005785:Gene Conversion; D007070:Immunoglobulin A / Q000302:isolation & purification; D017578:Immunoglobulin Class Switching / Q000235:genetics*; D007075:Immunoglobulin M / Q000302:isolation & purification; D051917:Leukosialin; D008969:Molecular Sequence Data; D011817:Rabbits; D051135:Rad51 Recombinase; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D012795:Sialoglycoproteins / Q000302:isolation & purification; D013601:T-Lymphocytes / Q000276:immunology; D014018:Tissue Distribution
chemical_list: D015703:Antigens, CD; D030161:Avian Proteins; D018076:DNA, Complementary; D004268:DNA-Binding Proteins; D007070:Immunoglobulin A; D007075:Immunoglobulin M; D051917:Leukosialin; D012795:Sialoglycoproteins; C495150:RAD51 protein, Gallus gallus; D051135:Rad51 Recombinase