title: Expression of mRNA for a newly identified Pax5 exon is reduced in multiple myeloma.
abstract: Pax5 is a transcription factor that is critical in the bone marrow for differentiation and proliferation of B cells until the plasma cell stage. In Pax5(-/-) mice, B-cell development stalls at the pro-B-cell stage. Messenger RNA profiles of alternatively spliced isoforms of Pax5 in bone marrow frequently differ between multiple myeloma (MM) patients and healthy donors. We sought to determine if Pax5 mRNA profiles also differed in blood and unexpectedly detected the presence of a previously unreported exon that alters the amino acid code for the transactivating domain of Pax5 in CD138(-) B cells. This unique exon escapes detection by conventional analyses of RT-PCR products and may serve as a prototype for other exons, in other genes, that escape RT-PCR detection. Eight percent of tested human subjects were heterozygous for an allele with a nonsynonymous nucleotide substitution in the new exon, and one MM patient was homozygotic for this base difference. Subsequent analysis of plasma and B-cell populations from bone marrow revealed a markedly reduced mRNA expression of the new isoform in cells from MM patients when compared to cells from normal subjects.
authors.affiliation: Department of Immunology, Mayo Clinic, Rochester, Minnesota, 55901, USA. borson.nancy@mayo.edu
authors.forename: Nancy D
authors.initials: ND
authors.lastname: Borson
authors.forename: Martha Q
authors.initials: MQ
authors.lastname: Lacy
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Wettstein
mesh_terms: D017398:Alternative Splicing; D000595:Amino Acid Sequence; D001402:B-Lymphocytes / Q000378:metabolism; D001483:Base Sequence; D005091:Exons / Q000235:genetics*; D015972:Gene Expression Regulation, Neoplastic; D006579:Heterozygote; D006720:Homozygote; D006801:Humans; D008969:Molecular Sequence Data; D009101:Multiple Myeloma / Q000235:genetics* / Q000378:metabolism; D051757:PAX5 Transcription Factor / Q000235:genetics* / Q000378:metabolism; D010950:Plasma Cells / Q000378:metabolism; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism*; D012334:RNA, Neoplasm / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D051757:PAX5 Transcription Factor; C497281:PAX5 protein, human; D020033:Protein Isoforms; D012333:RNA, Messenger; D012334:RNA, Neoplasm