title: Duplication of a gene-rich cluster between 16p11.1 and Xq28: a novel pericentromeric-directed mechanism for paralogous genome evolution.
abstract: We have identified a 26.5 kb gene-rich duplication shared by human Xq28 and 16p11.1. Complete comparative sequence analysis of cosmids from both loci has revealed identical Xq28 and 16p11.1 genomic structures for both the human creatine transporter gene (SLC6A8) and five exons of the CDM gene (DXS1357E). Overall nucleotide similarity within the duplication was found to be 94.6%, suggesting that this interchromosomal duplication occurred within recent evolutionary time (7-10 mya). Based on comparisons between genomic and cDNA sequence, both the Xq28 creatine transporter and DXS1357E genes are transcriptionally active. Predicted translation of exons and RT-PCR analysis reveal that chromosome 16 paralogs likely represent pseudogenes. Comparative fluorescent in situ hybridization (FISH) analyses of chromosomes from various primates indicate that this gene-rich segment has undergone several duplications. In gorilla and chimpanzee, multiple pericentromeric localizations on a variety of chromosomes were found using probes from the duplicated region. In other species, such as the orangutan and gibbon, FISH signals were only identified at the distal end of the X chromosome, suggesting that the Xq28 locus represents the ancestral copy. Sequencing of the 16p 11.1/Xq28 duplication breakpoints has revealed the presence of repetitive immunoglobulin-like CAGGG pentamer sequences at or near the paralogy boundaries. The mobilization and dispersal of this gene-rich 27 kb element to the pericentromeric regions of primate chromosomes defines an unprecedented form of recent genome evolution and a novel mechanism for the generation of genetic diversity among closely related species.
authors.affiliation: Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA.
authors.forename: E E
authors.initials: EE
authors.lastname: Eichler
authors.forename: F
authors.initials: F
authors.lastname: Lu
authors.forename: Y
authors.initials: Y
authors.lastname: Shen
authors.forename: R
authors.initials: R
authors.lastname: Antonacci
authors.forename: V
authors.initials: V
authors.lastname: Jurecic
authors.forename: N A
authors.initials: NA
authors.lastname: Doggett
authors.forename: R K
authors.initials: RK
authors.lastname: Moyzis
authors.forename: A
authors.initials: A
authors.lastname: Baldini
authors.forename: R A
authors.initials: RA
authors.lastname: Gibbs
authors.forename: D L
authors.initials: DL
authors.lastname: Nelson
mesh_terms: D000818:Animals; D001483:Base Sequence; D002352:Carrier Proteins / Q000235:genetics*; D002503:Centromere / Q000235:genetics; D002874:Chromosome Mapping; D002885:Chromosomes, Human, Pair 16 / Q000235:genetics*; D003360:Cosmids / Q000235:genetics; D003401:Creatine; D019143:Evolution, Molecular; D005091:Exons / Q000235:genetics; D015186:Hominidae / Q000235:genetics; D006801:Humans; D006922:Hylobates / Q000235:genetics; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D008957:Models, Genetic; D008969:Molecular Sequence Data; D005810:Multigene Family / Q000235:genetics*; D011506:Proteins / Q000235:genetics*; D012091:Repetitive Sequences, Nucleic Acid / Q000235:genetics; D017422:Sequence Analysis, DNA; D012689:Sequence Homology, Nucleic Acid; D014960:X Chromosome / Q000235:genetics*
chemical_list: C091247:BCAP31 protein, human; D002352:Carrier Proteins; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D011506:Proteins; C080679:creatine transporter; D003401:Creatine