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Title: Identification of imprinted genes using a novel screening method based on asynchronous DNA replication

Abstract

Genomic imprinting refers to the process of epigenetic change that occurs during germ cell development that results in either maternal- or paternal-specific gene expression. Identification of imprinted genes is of primary importance to the understanding of imprinting mechanisms and the role of specific imprinted genes in human disease. Recently, it has been established that chromosomal regions known to contain imprinted genes replicate asynchronously. We propose a novel screening method to identify imprinted genes based on replication asynchrony as a marker for imprinted domains. Dividing human cells were pulse-labeled with BrdU and separated into different fractions of S-phase by flow cytometry. A library of late-replicating inter-Alu sequences should be enriched in gene-associated sequences that replicate early on one chromosome and late on the other homologue. Clones were analyzed for replication timing by hybridization to inter-Alu replication profiles. Candidates for replication asynchrony exhibited broad or biphasic replication timing, and these were analyzed for chromosomal location by hybridizations to inter-Alu products from a hybrid mapping panel. Initial screening of 123 clones resulted in 3 asynchronously-replicating clones that localized to single chromosomes. Chromosome 17 and chromosome 19 candidates might be located in regions thought to be imprinted by synteny with mouse chromosomes. A chromosomemore » 15 clone was further characterized because of its possible localization to the Prader-Willi/Angelman locus. This sequence was localized outside the region deleted in Prader-Willi patients, and was found to be expressed in human cell lines. Replication asynchrony for this sequence appears to be polymorphic because cells derived from some individuals indicated synchronous replication. This appears to be the first example of a polymorphism in replication asynchrony.« less

Authors:
; ;  [1]
  1. Univ. of Washington, Seattle, WA (United States)
Publication Date:
OSTI Identifier:
134231
Report Number(s):
CONF-941009-
Journal ID: AJHGAG; ISSN 0002-9297; TRN: 95:005313-0967
Resource Type:
Journal Article
Resource Relation:
Journal Name: American Journal of Human Genetics; Journal Volume: 55; Journal Issue: Suppl.3; Conference: 44. annual meeting of the American Society of Human Genetics, Montreal (Canada), 18-22 Oct 1994; Other Information: PBD: Sep 1994
Country of Publication:
United States
Language:
English
Subject:
55 BIOLOGY AND MEDICINE, BASIC STUDIES; GENES; GENETICS; GENE REGULATION; STRUCTURE-ACTIVITY RELATIONSHIPS; HEREDITARY DISEASES; DNA; DNA REPLICATION; SCREENING; BIOLOGICAL MARKERS; MUTATIONS; GERM CELLS; CELL DIVISION; HUMAN CHROMOSOMES; GENETIC MAPPING; CELL FLOW SYSTEMS; POLYMERASE CHAIN REACTION; HETEROCHROMATIN; DNA SEQUENCING; DNA HYBRIDIZATION; DNA-CLONING

Citation Formats

Kawame, H., Hansen, R.S., and Gartler, S.M.. Identification of imprinted genes using a novel screening method based on asynchronous DNA replication. United States: N. p., 1994. Web.
Kawame, H., Hansen, R.S., & Gartler, S.M.. Identification of imprinted genes using a novel screening method based on asynchronous DNA replication. United States.
Kawame, H., Hansen, R.S., and Gartler, S.M.. Thu . "Identification of imprinted genes using a novel screening method based on asynchronous DNA replication". United States. doi:.
@article{osti_134231,
title = {Identification of imprinted genes using a novel screening method based on asynchronous DNA replication},
author = {Kawame, H. and Hansen, R.S. and Gartler, S.M.},
abstractNote = {Genomic imprinting refers to the process of epigenetic change that occurs during germ cell development that results in either maternal- or paternal-specific gene expression. Identification of imprinted genes is of primary importance to the understanding of imprinting mechanisms and the role of specific imprinted genes in human disease. Recently, it has been established that chromosomal regions known to contain imprinted genes replicate asynchronously. We propose a novel screening method to identify imprinted genes based on replication asynchrony as a marker for imprinted domains. Dividing human cells were pulse-labeled with BrdU and separated into different fractions of S-phase by flow cytometry. A library of late-replicating inter-Alu sequences should be enriched in gene-associated sequences that replicate early on one chromosome and late on the other homologue. Clones were analyzed for replication timing by hybridization to inter-Alu replication profiles. Candidates for replication asynchrony exhibited broad or biphasic replication timing, and these were analyzed for chromosomal location by hybridizations to inter-Alu products from a hybrid mapping panel. Initial screening of 123 clones resulted in 3 asynchronously-replicating clones that localized to single chromosomes. Chromosome 17 and chromosome 19 candidates might be located in regions thought to be imprinted by synteny with mouse chromosomes. A chromosome 15 clone was further characterized because of its possible localization to the Prader-Willi/Angelman locus. This sequence was localized outside the region deleted in Prader-Willi patients, and was found to be expressed in human cell lines. Replication asynchrony for this sequence appears to be polymorphic because cells derived from some individuals indicated synchronous replication. This appears to be the first example of a polymorphism in replication asynchrony.},
doi = {},
journal = {American Journal of Human Genetics},
number = Suppl.3,
volume = 55,
place = {United States},
year = {Thu Sep 01 00:00:00 EDT 1994},
month = {Thu Sep 01 00:00:00 EDT 1994}
}
  • The GABRB3 and GABRA5 genes are organized as a cluster in chromosome 15q11-q13. The genes are separated by around 100 kb and arranged in opposite transcriptional orientations. The GABA{sub A} receptor cluster lies near the Angelman and Prader-Willi loci and displays asynchronous DNA replication, suggesting that this region is subject to parental imprinting. In order to further study the association between DNA replication and imprinting, allele-specific replication was assayed by fluorescence in situ hybridization with {lambda}-phage probes from the GABRB3/A5 region and a D15Z1 satellite probe to identify the parental origin of each chromosome. The replication kinetics of each allelemore » was determined by using a flow sorter to fractionate mitogen-stimulated lymphocytes on the basis of cell cycle progression prior to FISH analysis. These kinetic studies reveal a 50-150 kb chromosomal domain extending from the middle of the GABRB3/A5 intergenic region into the GABRA5 5{prime}-UTR which displays maternal replication in early S with paternal replication delayed until the end of S. In contrast, genomic regions on either side of this maternal early replication domain exhibit the opposite pattern with paternal before maternal replication and both alleles replicating in the latter half of S. These results indicate that the GABRB3/A5 region is divided into domains in which replication timing is determined by parental origin. In addition to a loss of asynchronous replication, organization into replication timing domains is also lost in lymphocytes from maternal and paternal uniparental disomy 15 patients suggesting that a chromosome contribution from both parents is required for the establishment of the imprinted replication domains.« less
  • No abstract prepared.
  • We used a combination of subtractive hybridization and differential screening strategies to identify genes that may function normally in hearing and, when mutated, result in deafness. A human fetal cochlear (membranous labyrinth) cDNA library was subtracted against total human fetal brain RNAs by an avidin-biotin-based procedure to enrich for cochlear transcripts. Subtracted cochlear clones were differentially screened with {sup 32}P-labeled total cochlear and total brain cDNA probes. Sequence analysis of clones that hybridized more intensely with cochlear than with brain cDNA probes revealed some previously characterized genes, including mitochondrial sequences, collagen type I {alpha}-2 (COL1A2), collagen type II {alpha}-1 (COL2A1),more » collagen type III {alpha}-1 (COL3A1), spermidine/spermine N{sup 1}-acetyltransferase (SAT), osteonectin (SPARC), and peripheral myelin protein 22 (PMP22). Also identified were clones that are potential novel cochlear genes. Northern blots of cochlear and brain RNAs probed with COL1A2, COL2A1, COL3A1, SAT, SPARC, PMP22, and a novel sequence, designated Coch-5B2, confirm results of the subtractive procedure by showing preferential cochlear expression. A number of these genes serve structural or regulatory functions in extracellular matrix or neural conduction; defects in some of these genes are associated with disorders involving hearing loss. Partial sequence analysis of Coch-5B2 reveals a von Willebrand factor type A-like domain in this cDNA. To assess the cochlear specificity of Coch-5B2, a Northern blot panel of 14 human fetal tissue RNAs was probed with Coch-5B2, showing differential expression of this novel gene in the cochlea. 68 refs., 3 figs.« less
  • The timing of DNA replication of the human {beta}-globin gene locus has been studied by blot hybridization of newly synthesized BrdUrd-substituted DNA from cells in different stages of the S phase. Using probes that span >120 kilobases across the human {beta}-globin gene locus, the authors show that the majority of this domain replicates in early S phase in the human erythroleukemia cell line K562 and in middle-to-late S phase in the lymphoid cell line Manca. However, in K562 cells three small regions display a strikingly different replication pattern than adjacent sequences. These islands, located in the inter-{gamma}-globin gene region andmore » approximately 20 kilobases 5' to the {epsilon}-globin gene and 20 kilobases 3' to the {beta}-globin gene, replicate later and throughout S phase. A similar area is also present in the {alpha}-globin gene region in K562 cells. They suggest that these regions may represent sites of termination of replication forks.« less
  • DNA polymerases delta and ..cap alpha.. were purified from CV-1 cells, and their sensitivities to the inhibitors aphidicolin, (p-n-butylphenyl) deoxyguanosine triphosphate (BuPdGTP), and monoclonal antibodies directed against DNA polymerase ..cap alpha.. were determined. The effects of these inhibitors on DNA replication, measured with (/sup 3/H)TTP, in permeabilized CV-1 cells were studied to investigate the potential roles of polymerases delta and ..cap alpha.. in DNA replication. Aphidicolin was shown to be a more potent inhibitor of DNA replication than of DNA polymerase ..cap alpha.. or delta activity. Inhibition of DNA replication by various concentrations of BuPdGTP was intermediate between inhibition ofmore » purified polymerase ..cap alpha.. or delta activity. Concentrations of BuPdGTP which totally abolished DNA polymerase ..cap alpha.. activity were much less effective in reducing DNA replication, as well as the activity of DNA polymerase delta. Monoclonal antibodies which specifically inhibited polymerase ..cap alpha.. activity reduced, but did not abolish, DNA replications in permeable cells. BuPdGTP, as well as anti-polymerase ..cap alpha.. antibodies, inhibited DNA replication in a nonlinear manner as a function of time. A concentration of BuPdGTP which abolished polymerase ..cap alpha.. activity reduced, but did not abolish, both the synthesis and maturation of nascent DNA fragments. This information suggests that polymerases ..cap alpha.. and delta are involved in both the synthesis and maturation of nascent DNA. This is the first report to present evidence suggesting that both polymerases ..cap alpha.. and delta play a significant role in mammalian DNA replication.« less