title: Transcription of a protein-coding gene on B chromosomes of the Siberian roe deer (Capreolus pygargus).
abstract: BACKGROUND
  Most eukaryotic species represent stable karyotypes with a particular diploid number. B chromosomes are additional to standard karyotypes and may vary in size, number and morphology even between cells of the same individual. For many years it was generally believed that B chromosomes found in some plant, animal and fungi species lacked active genes. Recently, molecular cytogenetic studies showed the presence of additional copies of protein-coding genes on B chromosomes. However, the transcriptional activity of these genes remained elusive. We studied karyotypes of the Siberian roe deer (Capreolus pygargus) that possess up to 14 B chromosomes to investigate the presence and expression of genes on supernumerary chromosomes.
  
  
  RESULTS
  Here, we describe a 2 Mbp region homologous to cattle chromosome 3 and containing TNNI3K (partial), FPGT, LRRIQ3 and a large gene-sparse segment on B chromosomes of the Siberian roe deer. The presence of the copy of the autosomal region was demonstrated by B-specific cDNA analysis, PCR assisted mapping, cattle bacterial artificial chromosome (BAC) clone localization and quantitative polymerase chain reaction (qPCR). By comparative analysis of B-specific and non-B chromosomal sequences we discovered some B chromosome-specific mutations in protein-coding genes, which further enabled the detection of a FPGT-TNNI3K transcript expressed from duplicated genes located on B chromosomes in roe deer fibroblasts.
  
  
  CONCLUSIONS
  Discovery of a large autosomal segment in all B chromosomes of the Siberian roe deer further corroborates the view of an autosomal origin for these elements. Detection of a B-derived transcript in fibroblasts implies that the protein coding sequences located on Bs are not fully inactivated. The origin, evolution and effect on host of B chromosomal genes seem to be similar to autosomal segmental duplications, which reinforces the view that supernumerary chromosomal elements might play an important role in genome evolution.
authors.affiliation: Institute of Molecular and Cellular Biology SВ RAS, Novosibirsk, Russia. vlad@mcb.nsc.ru
authors.forename: Vladimir A
authors.initials: VA
authors.lastname: Trifonov
authors.forename: Polina V
authors.initials: PV
authors.lastname: Dementyeva
authors.forename: Denis M
authors.initials: DM
authors.lastname: Larkin
authors.forename: Patricia C M
authors.initials: PC
authors.lastname: O'Brien
authors.forename: Polina L
authors.initials: PL
authors.lastname: Perelman
authors.forename: Fengtang
authors.initials: F
authors.lastname: Yang
authors.forename: Malcolm A
authors.initials: MA
authors.lastname: Ferguson-Smith
authors.forename: Alexander S
authors.initials: AS
authors.lastname: Graphodatsky
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002417:Cattle; D002874:Chromosome Mapping; D022202:Chromosomes, Artificial, Bacterial / Q000235:genetics; D033481:Chromosomes, Mammalian / Q000235:genetics*; D003001:Cloning, Molecular; D056915:DNA Copy Number Variations / Q000235:genetics; D003670:Deer / Q000235:genetics*; D005260:Female; D018628:Gene Dosage / Q000235:genetics; D015723:Gene Library; D017404:In Situ Hybridization, Fluorescence; D008297:Male; D008969:Molecular Sequence Data; D009713:Nucleotidyltransferases / Q000235:genetics; D016366:Open Reading Frames / Q000235:genetics*; D016133:Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D012800:Siberia; D013045:Species Specificity; D014158:Transcription, Genetic
chemical_list: D009713:Nucleotidyltransferases
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