title: The X-chromosomal human biglycan gene BGN is subject to X inactivation but is transcribed like an X-Y homologous gene.
abstract: We report the mRNA and protein expression levels of human biglycan (BGN) in patients with different numbers of sex chromosomes. BGN maps to the distal long arm of the X chromosome, band Xq28, near the second pseudoautosomal region. BGN expression levels are reduced in 45,X Turner patients and increased in patients with additional sex chromosomes. This is suggestive of a pseudoautosomal gene or a gene that escapes X inactivation and that has an active Y chromosomal copy. However, we also provide evidence from hybrid cell lines that BGN is subject to X inactivation and that there is no homolog on the Y chromosome. This evidence excludes an escape from X inactivation. Moreover, additional Y chromosomes increase BGN expression levels, despite the absence of a Y chromosomal BGN gene. Therefore, another explanation has to be invoked. The "pseudoautosomal expression" of BGN may be attributed to a gene or genes that escape X inactivation and that regulate the transcriptional activity of BGN. This is the first report concerning an X chromosomal gene that does not show the conventional correlation between gene dosage and expression rate known from other X chromosomal genes.
authors.affiliation: Abteilung Medizinische Genetik der Universität Ulm, Germany.
authors.forename: C
authors.initials: C
authors.lastname: Geerkens
authors.forename: U
authors.initials: U
authors.lastname: Vetter
authors.forename: W
authors.initials: W
authors.lastname: Just
authors.forename: N S
authors.initials: NS
authors.lastname: Fedarko
authors.forename: L W
authors.initials: LW
authors.lastname: Fisher
authors.forename: M F
authors.initials: MF
authors.lastname: Young
authors.forename: J D
authors.initials: JD
authors.lastname: Termine
authors.forename: P G
authors.initials: PG
authors.lastname: Robey
authors.forename: D
authors.initials: D
authors.lastname: Wöhrle
authors.forename: W
authors.initials: W
authors.lastname: Vogel
mesh_terms: D000328:Adult; D001483:Base Sequence; D058578:Biglycan; D002648:Child; D058575:Decorin; D004303:Dosage Compensation, Genetic; D016326:Extracellular Matrix Proteins; D006801:Humans; D007223:Infant; D008875:Middle Aged; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D011509:Proteoglycans / Q000235:genetics*; D012689:Sequence Homology, Nucleic Acid; D012867:Skin / Q000737:chemistry; D014158:Transcription, Genetic / Q000235:genetics*; D014960:X Chromosome; D014998:Y Chromosome
chemical_list: C546884:BGN protein, human; D058578:Biglycan; C546878:DCN protein, human; D058575:Decorin; D016326:Extracellular Matrix Proteins; D011509:Proteoglycans