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Drouin R, Holmquist GP, Richer CL. High-resolution replication bands compared with morphologic G- and R-bands. ADVANCES IN HUMAN GENETICS 1994; 22:47-115. [PMID: 7762454 DOI: 10.1007/978-1-4757-9062-7_2] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Affiliation(s)
- R Drouin
- Division of Biology, Beckman Research Institute of the City of Hope, Duarte, California 91010-0269, USA
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2
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Webb T. Delayed replication of Xq27 in individuals with the fragile X syndrome. AMERICAN JOURNAL OF MEDICAL GENETICS 1992; 43:1057-62. [PMID: 1415338 DOI: 10.1002/ajmg.1320430633] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The timing of late replicating bands on the X chromosome has been studied in individuals with the fragile X [fra(X)] syndrome. Compared to controls both affected individuals and symptomless carriers of the syndrome show delayed replication of the Xq27 region as shown by 2 different methods. The implications of this finding are discussed in relation to the proposal [Laird et al., 1987] that the fraX syndrome is associated with a failure to reactivate the Xq27 band correctly after it has been inactivated in a female.
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Affiliation(s)
- T Webb
- Department of Clinical Genetics, University of Birmingham, Birmingham Maternity Hospital, Edgbaston, England, United Kingdom
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3
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Izumikawa Y, Naritomi K, Hirayama K. Replication asynchrony between homologs 15q11.2: cytogenetic evidence for genomic imprinting. Hum Genet 1991; 87:1-5. [PMID: 2037275 DOI: 10.1007/bf01213082] [Citation(s) in RCA: 31] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Replication kinetics of the Prader-Willi syndrome critical region (15q11.2) was investigated in seven normal healthy adult females using RBG replication bands. Replication asynchrony between homologs 15q11.2 was identified consistently in about 40% of cells in all individuals. It was limited to the stages in which Xp22, Xp11, Xq13 and Xq24/26 were visible in the late-replicating X chromosome. This asynchrony suggested that replication timing overlapped between 15q11.2 and the early replicating R-bands of the late X chromosome in some cells, and that the difference in replication timing between homologs was probably related to genomic imprinting; the latter has been suggested as a pathogenetic basis of Prader-Willi syndrome. As a result of an analysis of the proportions of asynchronous and synchronous cells in each replication stage, two types of cells were deduced providing 1:1 methylation mosaicism of genomic imprinting was assumed. The first type was composed of cells with normal replication in one homolog and delayed replication in the other. The second type was composed of cells with normal replication in both homologs. Our results provide cytogenetic evidence of methylation mosaicism for mammalian genomic imprinting.
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Affiliation(s)
- Y Izumikawa
- Department of Pediatrics, University of the Ryukyus School of Medicine, Okinawa, Japan
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Schmidt M, Migeon BR. Asynchronous replication of homologous loci on human active and inactive X chromosomes. Proc Natl Acad Sci U S A 1990; 87:3685-9. [PMID: 2339112 PMCID: PMC53967 DOI: 10.1073/pnas.87.10.3685] [Citation(s) in RCA: 57] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The two X chromosomes in mammalian females replicate asynchronously, the inactive later than the active one. Using BrdUrd-sensitive restriction and UV irradiation to identify newly synthesized DNA directly on Southern blots, and restriction fragment length differences to discriminate alleles on active and inactive human X chromosomes, we examined the replication of hypoxanthine phosphoribosyltransferase (HPRT) and clotting factor IX (F9) loci in clonal populations of mouse-human hybrids. We find that HPRT replicates at different times during the period of DNA synthesis (S phase), depending on its activity: It replicates in early S phase, when expressed (on the active X chromosome), and in late S phase when silent (on the inactive X chromosome). Furthermore, when reactivated, the derepressed locus is earlier replicating, supporting a relationship between replication and transcription. Neither F9 allele is expressed in these cells, and both replicate in the second half of S phase, (slightly earlier on active than on inactive X chromosome).
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Affiliation(s)
- M Schmidt
- Department of Pediatrics, Johns Hopkins University School of Medicine, Baltimore, MD 21205
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5
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Schwemmle S, Mehnert K, Vogel W. How does inactivation change timing of replication in the human X chromosome? Hum Genet 1989; 83:26-32. [PMID: 2767677 DOI: 10.1007/bf00274142] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The kinetics of replication of the inactive (late replicating) X chromosome (LRX) were studied in karyotypically normal lymphocytes and human amniotic fluid cells. Both cell types were successively pulse labeled with 1-h or 1/2-h thymidine pulses in an otherwise BrdU-substituted S phase after partial synchronization of the cultures at G1/S. For the first time with this technique, the entire sequence of replication was analyzed for the LRX from the beginning to the end of the S phase, with special reference to mid S (R-band to G-band transition replication). The inactive X is the last chromosome of the metaphase to start replication, with a delay of 1 or 2 h, after which time a thymidine pulse results in R-type patterns. In mid S, the inactive X is the first chromosome to switch to G-type replication (without overlapping of both types and without any detectable replication pause). Until the end of S, a thymidine pulse results in G-type patterns. To rule out artifacts that might arise by the synchronization of cultures in these experiments, controls were carried out with BrdU pulses and the BrdU antibody technique without synchronization. In the course of replication, no fundamental difference was seen between the two different cell types examined. In contrast to studies using continuous labeling, this study did not reveal an interindividual difference of replication kinetics in the LRXs of the seven individuals studied; thus it is concluded that the inactive X chromosome shows only one characteristic course of replication.
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Affiliation(s)
- S Schwemmle
- Abteilung Klinische Genetik der Universität, Ulm, Federal Republic of Germany
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Reddy KS, Savage JR, Papworth DG. Replication kinetics of X chromosomes in fibroblasts and lymphocytes. Hum Genet 1988; 79:44-8. [PMID: 3366462 DOI: 10.1007/bf00291708] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The kinetics of replication for early and late replicating X chromosomes in karyotypically normal fibroblasts and lymphocytes was studied using terminal bromodeoxyuridine (BrdU) treatment followed by Hoechst/light/Giemsa staining. Although the order of band appearance differs between the two tissues, the programme (order and interval between band appearances) for early replicating bands (dark R-bands) is identical in the two homologues. This is probably also the case for later replicating bands (dark G-bands) though the criteria for determining mean band appearance times are less reliable for these bands when terminal BrdU treatment is used. This means that the late X has a delayed start but thereafter proceeds at the same pace as its early counterpart.
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Affiliation(s)
- K S Reddy
- MRC Radiobiology Unit, Chilton, Didcot, UK
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Yamamoto Y, Suzuki N, Matsuyama S, Koizumi T. DNA replication study in a female infant with a karyotype of 45,X/46,X, psu dic(X) (p22::p22) and review of the literature. JINRUI IDENGAKU ZASSHI. THE JAPANESE JOURNAL OF HUMAN GENETICS 1987; 32:97-105. [PMID: 3325667 DOI: 10.1007/bf01893163] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
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Babu A, Verma RS. Chromosome structure: euchromatin and heterochromatin. INTERNATIONAL REVIEW OF CYTOLOGY 1987; 108:1-60. [PMID: 2822591 DOI: 10.1016/s0074-7696(08)61435-7] [Citation(s) in RCA: 66] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Affiliation(s)
- A Babu
- Division of Cytogenetics, Interfaith Medical Center, Brooklyn, New York
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Evidence for a relationship between DNA methylation and DNA replication from studies of the 5-azacytidine-reactivated allocyclic X chromosome. Exp Cell Res 1985; 158:301-10. [PMID: 2408909 DOI: 10.1016/0014-4827(85)90455-0] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
We examined the sequence of DNA synthesis of the human active, inactive and reactivated X chromosomes in mouse-human hybrid cells. The two independent reactivants, induced by 5-azacytidine (5-azaC), expressed human hypoxanthinephosphoribosyl transferase (HPRT), and one also expressed human glucose-6-phosphate dehydrogenase (G6PD) and phosphoglycerate kinase (PGK). Restriction enzyme analysis of DNA methylation at the re-expressed loci revealed hypomethylation of CpG clusters, that characterizes the relevant genes on the active X. The transfer of active and inactive X chromosomes from the native environment of the human fibroblast to the foreign environment of the hybrid cell did not affect the specific replication sequence of either human X chromosome. The silent X chromosome when reactivated, remained allocyclic, and the first bands to replicate were the same as prior to reactivation. In one reactivant, however, further progression of replication was significantly altered with respect to the order in which bands were synthesized. This alteration in the replication of the silent X following 5-azaC-induced reactivation suggests that DNA methylation may modulate the replication kinetics of chromosomal DNA.
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Debiec-Rychter M, Kałuzewski B, Bugała I, Zajazkowska D. Isochromosome X in acute myeloblastic leukemia. CANCER GENETICS AND CYTOGENETICS 1985; 15:137-41. [PMID: 3855374 DOI: 10.1016/0165-4608(85)90141-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
An aberrant leukemic clone with a 46,X,i(Xq) karyotype appeared at the first relapse of the disease in a case of acute myeloblastic leukemia (AML). The DNA replication pattern displayed asynchronous late termination within the homologous arms of the isochromosome in all investigated metaphases. The origin of asynchrony in the isochromosome's DNA replication pattern is discussed.
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Lalande M, Kunkel LM, Flint A, Latt SA. Development and use of metaphase chromosome flow-sorting methodology to obtain recombinant phage libraries enriched for parts of the human X chromosome. CYTOMETRY 1984; 5:101-7. [PMID: 6232119 DOI: 10.1002/cyto.990050202] [Citation(s) in RCA: 35] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Metaphase chromosomes isolated from human lymphoblastoid cell lines containing structurally abnormal X chromosomes have been stained with the bisbenzimidazole dye Hoechst 33258 and analyzed on a FACS II flow system equipped with a 5-W all-lines argon ion laser. The chromosomal fluorescence has been highly resolved at flow rates of 1,000-3,000 chromosomes per second. With the goal of obtaining recombinant DNA libraries from parts of the human X chromosome, fluorescence populations enriched for a dicentric X (Xpter- greater than Xq24::Xq24-greater than Xpter) chromosome and an isochromosome of the long arm of the X [i(Xq)] have been identified. The dicentric X chromosome has been resolved as a discrete peak in the fluorescence flow histogram. In contrast, the fluorescence intensity of the isochromosome is indistinguishable from that of chromosomes 3 and 4. Recombinant DNA libraries from the flow-sorted chromosomes have been constructed in the lambda phage, Charon 21A, and consist of 1.6 X 10(5) and 0.7 X 10(5) plaque-forming units in the case of the dicentric X and the isochromosome, respectively. Ninety percent of the phage in both recombinant libraries contain inserts which hybridize to highly repetitive human DNA sequences. The recombinant phage library from the flow-sorted dicentric X chromosome, which could be assigned to a discrete fluorescence peak, has been further characterized and shows at least a tenfold enrichment for X chromosome-specific DNA sequences as determined by Southern blot hybridization of cloned fragments.
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Schmidt M, Stolzmann WM. Replication variants of the human inactive X chromosome. II. Frequency and replication rate relative to the other chromosomes of the complement. Chromosoma 1984; 89:68-75. [PMID: 6538134 DOI: 10.1007/bf00302353] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Replication variants of the inactive X chromosome were investigated in lymphocytes from six donors by means of terminal BrdU or thymidine incorporation. There were interindividual differences in the incidence of particular variants. In endoreduplicated and tetraploid cells both allocyclic X chromosomes showed the same replication sequence. The Xp22 band of the allocyclic X chromosome seemed to replicate later than the homologous material in some cells. Initiation time of DNA synthesis within the inactive X chromosome was found to be stable; termination time, however, varied greatly relative to the other chromosomes. Early completion of replication within the heterochromatic X chromosome could be demonstrated preferentially for the Xq25-27 terminal sequence, but other variants expressed the phenomenon also. A variable replication rate of the inactive X chromosome is believed to be responsible for its asynchronous, independent replication. The biological significance of the phenomenon is discussed with respect to cell differentiation.
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Lindgren V, Farber RA. Chromosome replication in normal and transformed human lymphocytes. CANCER GENETICS AND CYTOGENETICS 1983; 9:71-9. [PMID: 6601510 DOI: 10.1016/0165-4608(83)90027-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
We analyzed the late-replication patterns of human B-lymphocyte chromosomes before and after transformation by Epstein-Barr virus. There were no statistically significant differences between normal cells and transformed cells derived from the same male individual; therefore, the order of termination of chromosome replication was unchanged by transformation. We also examined the replication patterns of T lymphocytes from the same donor and found no differences between normal B and T cells.
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Kunkel LM, Tantravahi U, Eisenhard M, Latt SA. Regional localization on the human X of DNA segments cloned from flow sorted chromosomes. Nucleic Acids Res 1982; 10:1557-78. [PMID: 6461845 PMCID: PMC320550 DOI: 10.1093/nar/10.5.1557] [Citation(s) in RCA: 170] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Fluorescence activated sorting of chromosomes from 49,XXXXY human lymphoblasts has been used to obtain DNA enriched for the human X. This DNA was cloned in lambda phage Charon 21A to obtain a library of approximately 60,000 pfu. Phage inserts free of human highly repeated DNA sequences are localized to different regions of the human X by two independent hybridization analyses. The first utilized comparative hybridization to rodent-human hybrid cell DNA samples containing all or known portions of the human X, while the second was based on hybridization dosage to DNA samples from human cell lines differing in the number of X chromosomes or X chromosome segments. Of five unique sequence inserts tested, three were X chromosome specific and were localized to regions Xpter leads to Xcen, Xql leads to Xq22 and Xq24 leads to Xqter, respectively. The library presented here represents a highly enriched source of human X chromosome-specific DNA sequences.
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