SEARCH · PubMed Health

Results for “Prophase”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 127 records · Page 7Linked to original sources

PubMed2005

HCP-4/CENP-C promotes the prophase timing of centromere resolution by enabling the centromere association of HCP-6 in Caenorhabditis elegans.

Prior to microtubule capture, sister centromeres resolve from one another, coming to rest on opposite surfaces of the condensing chromosome. Subsequent assembly of sister kinetochores at each sister centromere generates a geometry favorable for equal levels of segregation of chromatids. The holocentric chromosomes of Caenorhabditis elegans are uniquely suited for the study of centromere resolution and subsequent kinetochore assembly. In C. elegans, only two proteins have been identified as being necessary for centromere resolution, the kinase AIR-2 (prophase only) and the centromere protein HCP-4/CENP-C. Here we found that the loss of proteins involved in chromosome cohesion bypassed the requirement for HCP-4/CENP-C but not for AIR-2. Interestingly, the loss of cohesin proteins also restored the localization of HCP-6 to the kinetochore. The loss of the condensin II protein HCP-6 or MIX-1/SMC2 impaired centromere resolution. Furthermore, the loss of HCP-6 or MIX-1/SMC2 resulted in no centromere resolution when either nocodazole or RNA interference (RNAi) of the kinetochore protein KNL-1 perturbed spindle-kinetochore interactions. This result suggests that normal prophase centromere resolution is mediated by condensin II proteins, which are actively recruited to sister centromeres to mediate the process of resolution.

Adenosine Triphosphatases↗

PubMed1983

High-resolution idiogram of Giemsa R-banded human prophase chromosomes.

The schematic representation of RHG-banded chromosomes (R-banding was produced by heat denaturation followed by Giemsa staining (RHG) in the 850-band range per haploid set, was prepared showing the relative position, the specific size, and the characteristic staining intensity for each band. To this idiogram was adapted the new International Standard Cytogenetic Nomenclature. Our aim was to produce a realistic idiogram which could help in the preparation of R-banded prophase karyotypes and in the localization of chromosomal rearrangements. A comparative analysis of bands at prophase and metaphase revealed certain aspects of the dynamics involved in chromosome condensation and in R-band organization. The effect of chromosome elongation on the appearance of R-bands within heterochromatic regions has also been discussed.

Adult↗

PubMed1985

Analysis of high-resolution R-bands, obtained by heat-denaturation and Giemsa staining, on human prophase chromosomes.

RHG-bands (heat-denatured Giemsa R-bands) of human prophase chromosomes were analyzed at high resolution, and the banding patterns at prophase and metaphase are presented. The bands were compared with those of the International Standard Cytogenetic Nomenclature idiograms and of the G-band idiograms proposed by J. J. Yunis. The number, size, and position of the RHG-bands correspond rather well with their equivalent G-negative bands, but some differences were noted in the zones of preferential stretching, the juxtacentromeric regions, and the telomeres. Variations in the centromere index and the banding pattern in heterochromatin were also discussed.

Adult↗

PubMed2006

Genetics of meiotic prophase I in plants.

During meiotic prophase I, traits are reassorted as a result of a highly organized process involving sister chromatid cohesion, homologous chromosome alignment, pairing, synapsis, and recombination. In the past two years, a number of components involved in this pathway, including Structure Maintenance of Chromosomes (SMC), MRE11, the RAD51 homologs, BRCA2, MSH4, MER3, and ZIP1, have been characterized in plants; in addition, several genes that encode components unique to plants, such as POOR HOMOLOGOUS SYNAPSIS 1 and AMEIOTIC 1, have been cloned. Based on these recent data, essentially from maize and Arabidopsis, we discuss the conserved and plant-specific aspects of meiosis commitment and meiotic prophase I features.

Chromosomes, Plant↗

PubMed2001

Centromere and telomere redistribution precedes homologue pairing and terminal synapsis initiation during prophase I of cattle spermatogenesis.

Alterations in nuclear topology associated with meiotic chromosome pairing were studied in premeiotic cells and spermatocytes I of adult bovine males. To this end, we performed FISH with chromosome, pericentromeric satellite-DNA and telomere-specific probes in combination with immunostaining of synaptonemal complex proteins (SCP3, SCP1) on testis tissue sections. Nuclei of premeiotic cells (spermatogonia) exhibited a scattered telomere distribution while pericentromeres formed a few intranuclear clusters. We observed that the chromosome pairing process in cattle prophase I is preceded by repositioning of centromeres and telomeres to the nuclear periphery during preleptotene. Clustering of chromosome ends (bouquet formation) was observed during the transition from leptonema to zygonema and coincided with pairing of a sub-centromeric marker of bovine chromosomes 7. Dissolution of bouquet topology during zygonema left perinuclear telomeres scattered over the nuclear periphery at pachynema. SCP3 staining in frozen tissue sections revealed the appearance of this axial element protein in intranuclear aggregates during preleptotene, followed by extensive axial element formation during leptotene. Synapsis as revealed by SCP1 staining initiated peripherally at earliest zygotene, at this stage nuclei still contained numerous SCP3 clusters. Our observations reveal prominent non-homologous satellite-DNA associations in spermatogonia and indicate the conservation of topological features of the meiotic chromosome pairing process among mammals. The comparison of telomere dynamics in mouse and cattle prophase I suggests that a larger number of chromosomes prolongs the duration of the bouquet stage.

Animals↗

PubMed2003

Chromatin dynamics in the male meiotic prophase.

During the male meiotic prophase in mouse and man, pairing and recombination of homologous chromosomes is accompanied by changes in chromatin structure. In this review, the dynamics of assembly and disassembly of the chromatin-associated complexes that mediate sister chromatid cohesion (cohesin) and maintain chromosome pairing (the synaptonemal complex) are described. Special features of the meiotic S phase are discussed, and also the dynamics of several key players that act together after the S phase at sites of meiotic double-strand break DNA repair. Current knowledge on histone modifications that occur during the male meiotic prophase is discussed, with special attention for the inactive chromatin of the X and Y chromosomes that constitutes the sex body. Finally, it is discussed that in the future, it will be possible to view the true chromatin dynamics during male meiosis in time, in living cells, through analysis of fluorescent-tagged proteins expressed in transgenic mice, using advanced fluorescent microscopy techniques.

Animals↗

PubMed1986

A human 9;20 reciprocal translocation associated with male infertility analyzed at prophase and metaphase I of meiosis.

Details are given of a meiotic prophase analysis, carried out by spreading, of a human 9;20 reciprocal translocation ascertained in a subfertile, oligospermic male. Air-dried meiotic preparations revealed the presence of translocation quadrivalents at metaphase I. Germ-cell degeneration was evident from the early prophase of meiosis onward. Associations between the translocation quadrivalent and XY bivalent at pachytene were seen in only 20% of the cells and seemed not to be the prime cause of germ-cell failure. Pairing disruption around the breakpoints of the translocation at pachytene and/or pairing failure in one arm of the pachytene cross was observed in a total of 87% of all cells analyzed. This could have contributed significantly to germ-cell atresia.

Cells, Cultured↗

PubMed1991

Chromosome condensation from prophase to late metaphase: relationship to chromosome bands and their replication time.

As chromosomes condense during early mitosis, their subbands fuse in a highly coordinated fashion. Subband fusion occurs when two large subbands flanking one minor subband come together to form one band, which takes on the cytological characteristics of the original flanking subbands. Using four different banding techniques--GTG (G-bands obtained with trypsin and Giemsa), GBG (G-bands obtained with BrdU and Giemsa), RHG (R-bands obtained by heating and Giemsa), and RBG (R-bands obtained with BrdU and Giemsa)--we studied subband fusion from prophase (1,250 bands per haploid set) to late metaphase (300 bands). To quantify the condensation process, a fusion index was established. We found that chromosomes contain preferential zones of condensation. From prophase to late metaphase, the early replicating subbands (R-subbands) fuse more readily with each other than do the late-replicating subbands (G-subbands). R-bands usually replicate early and condense late independently of the adjacent G-bands, which replicate late but condense early. Therefore, chromosome bands can undergo DNA replication and chromatin condensation relatively autonomously. Our data suggest that (1) chromosome replication and condensation are closely connected in time, (2) the metaphase bands represent independent units of chromatin condensation, and (3) the condensation process is an important feature of chromosome organization.

Cells, Cultured↗

PubMed1995

Precise ordering of 26 cosmid markers on chromosome region 3p23-->p21.3 by two-color FISH on human prophase chromosomes and stretched DNAs.

To construct a detailed cytogenetic map of human chromosome region 3p23-->p21.3, we determined the order of 26 cosmid markers (cCI 3 series) previously localized within this region by fluorescence in situ hybridization (FISH). Two-color pairwise FISH analysis of prophase chromosomes provided the order of these markers as follows: pter - 245 (D3S647) - 872 (D3S1018) - 818 (D3S996) - 905 (D3S1022) - 515 (D3S685) - 1195 (D3S1125) - 718 (D3S935) - 911 (D3S1025) - 878 (D3S1020) - 717 (D3S934) - 401 (D3S664) - [708 (D3S926)/524 (D3S686)] - 848 (D3S1011) - 771 (D3S966) - 917 (D3S1029) - 533 (D3S688) - 470 (D3S676) - 940 (D3S1037) - 785 (D3S974) - 810 (D3S988) - 9 (D3S643) - 382 (D3S660) - 769 (D3S965) - 792 (D3S978) - 604 (D3S705) - cen. The two-color signals of 524 (D3S686) and 708 (D3S926) were visualized as an overlapping pattern on prophase chromosomes, and, further, the string signals also overlapped on stretched DNAs, allowing us to determine their precise order as pter - D3S926 - D3S686 - cen. The precise order of 26 DNA markers on 3p23-->p21.3 can provide useful information for the positional cloning of tumor suppressor gene(s) and cancer breakpoint(s) encompassed in this region.

Chromosome Mapping↗

PubMed2003

The p27cip/kip ortholog dacapo maintains the Drosophila oocyte in prophase of meiosis I.

Animal oocytes undergo a highly conserved developmental arrest in prophase of meiosis I. Often this marks a period of rapid growth for the oocyte and is necessary to coordinate meiotic progression with the developmental events of oogenesis. In Drosophila, the oocyte develops within a 16-cell germline cyst. Throughout much of oogenesis, the oocyte remains in prophase of meiosis I. By contrast, its 15 mitotic sisters enter the endocycle and become polyploid in preparation for their role as nurse cells. How germline cysts establish and maintain these two independent cell cycles is unknown. We demonstrate a role for the p21(CIP)/p27(Kip1)/p57(Kip2)-like cyclin-dependent kinase inhibitor (cki) dacapo in the maintenance of the meiotic cycle in Drosophila oocytes. Our data indicate that it is through the differential regulation of the cki Dacapo that two modes of cell-cycle regulation are independently maintained within the common cytoplasm of ovarian cysts.

Animals↗

PubMed2005

SPO11 is required for sex-body formation, and Spo11 heterozygosity rescues the prophase arrest of Atm-/- spermatocytes.

SPO11 introduces double-strand breaks (DSBs) that trigger the phosphorylation of H2AX during meiotic prophase. In mice, SPO11 is strictly required for initiation of meiotic recombination and synapsis, yet SPO11 is still considered to be dispensable for sex-body formation in mouse spermatocytes. We provide conclusive evidence showing that functional SPO11, and consequently recombination and synapsis, are required for phosphorylation of H2AX in the X-Y chromatin and for sex-body formation in mouse spermatocytes. We investigated the role in meiosis of the three kinases [ATM (ataxia telangiectasia mutated), ATR (ataxia-telangiectasia- and Rad-3-related) and DNA-PKcs (DNA-dependent-protein-kinase catalytic subunit)] known to phosphorylate H2AX in mitotic cells. We found that DNA-PKcs can be ruled out as an essential kinase in this process, whereas ATM is strictly required for the chromatin-wide phosphorylation of H2AX occurring in leptotene spermatocytes in response to DSBs. Remarkably, we discovered that Spo11 heterozygosity can rescue the prophase-I-arrest characteristic of ATM-deficient spermatocytes. Characterization of the rescued Atm-/- Spo11+/- mutant indicates that ATM is dispensable for sex-body formation and phosphorylation of H2AX in this subnuclear domain. The co-localization of ATR, phosphorylated H2AX and the sex chromatin observed in the Atm-/- Spo11+/- mutant, along with ATR transcription kinetics during the first wave of spermatogenesis, confirm and expand recent findings indicating that ATR is the kinase involved in H2AX phosphorylation in the sex body.

Animals↗

PubMed1998

Oscillatory nuclear movement in fission yeast meiotic prophase is driven by astral microtubules, as revealed by continuous observation of chromosomes and microtubules in living cells.

Using a computerized fluorescence microscope system to observe fluorescently stained cellular structures in vivo, we have examined the dynamics of chromosomes and microtubules during the process of meiosis in the fission yeast Schizosaccharomyces pombe. Fission yeast meiotic prophase is characterized by a distinctive type of nuclear movement that is led by telomeres clustered at the spindle-pole body (the centrosome-equivalent structure in fungi): the nucleus oscillates back and forth along the cell axis, moving continuously between the two ends of the cell for some hours prior to the meiotic divisions. To obtain a dynamic view of this oscillatory nuclear movement in meiotic prophase, we visualized microtubules and chromosomes in living cells using jellyfish green fluorescent protein fused with alpha-tubulin and a DNA-specific fluorescent dye, Hoechst 33342, respectively. Continuous observation of chromosomes and microtubules in these cells demonstrated that the oscillatory nuclear movement is mediated by dynamic reorganization of astral microtubules originating from the spindle-pole body. During each half-oscillatory period, the microtubules extending rearward from the leading edge of the nucleus elongate to drive the nucleus to one end of the cell. When the nucleus reversed direction, its motion during the second half of the oscillation was not driven by the same microtubules that drove its motion during the first half, but rather by newly assembled microtubules. Reversible inhibition of nuclear movement by an inhibitor of microtubule polymerization, thiabendazole, confirmed the involvement of astral microtubules in oscillatory nuclear movement. The speed of the movement fluctuated within a range 0 to 15 micron/minute, with an average of about 5 microm/minute. We propose a model in which the oscillatory nuclear movement is mediated by dynamic instability and selective stabilization of astral microtubules.

Cell Division↗

PubMed2002

Homolog pairing and two kinds of bouquets in the meiotic prophase of rye, Secale cereale.

Chromosome configurations and structures during meiotic prophase were investigated by staining large repeated DNA sequences localized in the subtelomeric regions of all the chromosomes in rye, Secale cereale, in order to clarify when and how homolog pairing and bouquet formation occur. The changes of the spatial locations of chromosomes in the nucleus were investigated by the use of laser confocal microscopy, together with the surface-spreading method of silver nitrate staining to detect the formation of the synaptonemal complex. Homolog pairing in which homologs of four chromatids of a pair of homologs were coaligned in parallel but remained distinctly separate was microscopically detected for the first time in the present study. Homolog pairing showed the following characteristics: (1) it occurred at the leptotene-zygotene transition stage, prior to the formation of nodules and the synaptonemal complex; (2) the chromatin structure of chromosomes was in a state of decondensation; (3) it required no telomere clustering. These data suggest that homolog pairing represents a structure that indicates incipient recombination. After the homolog pairing stage, two kinds of bouquet configuration were found in zygotene. The commonly observed type was a loose bouquet, in which the subtelomeric regions were loosely aggregated. The other type was a definite bouquet, in which almost all the subtelomeric regions were conjugated, but this type was observed only in a limited number of the meiotic prophase cells of some individuals. It was concluded that the former represents the configuration of homologous recombination and the latter that of ectopic recombination.

Cell Nucleus↗

PubMed1992

[Changes in the relative arrangement of the chromosomes and nucleolus in developing mammalian oocytes during meiotic prophase I in relation to functional changes in the oocytes].

Data on chromosome transformation in meiotic prophase I during mammalian oogenesis are summarized. The main peculiarity of the female meiosis in mammals is an unusually long diplotene stage which may be subdivided into four periods: 1) the early diplotene (up to the beginning of follicle formation); 2) the dictyotene or "diffuse diplotene", implying primordial follicle oocytes; 3) the most pronounced lampbrush chromosome stage coinciding with the large growth period; 4) the stage of chromosome inactivation and karyosphere formation corresponding to the terminal stage of oocyte development before ovulation. These stages are associated with changes in the transcriptional chromosome activity. A correlation is revealed between the spatial chromosome arrangement in the oocyte nucleus and the transcriptional activity. Some regularities are followed in the transformation of the main nucleolar component arrangement during meiotic prophase I in mammalian oocytes. At the late pachytene and at the early diplotene, a segregation of the main nucleolar components has been observed. These components are disposed in the direction: chromatin--fibrillar center--dense fibrillar component--granulo-fibrillar component. At the dictyotene, signs of nucleolar segregation are still observed. At the lampbrush chromosome stage, when the nucleus is most highly transcriptionally active, an integration of nucleolar components occurs. At the late diplotene--prediakinesis stage, i.e. in the course of transcriptional activity lowering and karyosphere formation, the secondary segregation of the main nucleolar components occurs. These move to the nucleolar periphery to be disposed around a large fibrillar mass which is gradually displacing the rest of the nucleolar components. The fibrillar mass formation in the preovulatory oocyte nucleoli is one of the peculiarities of the diplotene and prediakinetic mammalian oocytes.

Animals↗

PubMed1990

The mechanism of kinetochore-spindle attachment and polewards movement analyzed in PtK2 cells at the prophase-prometaphase transition.

PtK2 cells at the prophase-prometaphase transition were analyzed to study the origin of kinetochore microtubules, the mode of kinetochore fiber construction and the mechanism of polewards movement. Attention was focused on chromosomes which, as deduced from video time-lapse tapes, had just started their initial characteristic movement towards one of the poles. In the same cell, the arrangement of microtubules in the vicinity of the kinetochore region was visualized either with indirect immunofluorescence and confocal fluorescence microscopy, or with electron microscopy in semithin sections of cells, immunostained for microtubules and embedded in epon. The results strengthen the evidence that kinetochore microtubules are nucleated in the centrosomal region. Bundles of microtubules, some ending at the kinetochore and others passing beyond it, are formed rapidly, seemingly without influencing the rapid rate of movement. They also show that microtubules often establish contact with kinetochores by lateral interaction, prior to kinetochore-pole orientation, and that kinetochores can move polewards along the microtubule wall of attached microtubules, independently of the latter's dynamics. These findings confirm and extend to the earliest chromosome movements at the prophase-prometaphase transition, the results of Rieder and Alexander (J. Cell Biol. 110, 81-95, (1990)), who studied the attachment and polewards movement of chromosomes strongly delayed in forming an attachment to the spindle. They are discussed in the light of recent evidence for the localization of dynein to kinetochores and contemporary models for kinetochore structure and function.

Animals↗

PubMed1986

[Electron microscopic study of preleptotene-stage oocyte nuclei in the prophase of meiosis in the hen].

The morphology of oocyte nuclei at preleptotene and early leptotene stages of meiotic prophase I in the chick embryo was examined by electron microscopy and light cytochemistry. The intrenuclear fibrillar body (IFB) of proteinaceous nature is described. The IFB has a spherical or irregular form and consists of the disoriented fibrils ranging from 3 to 18 nm in diameter and of globules lying along the course of fibrils. The condensed chromatin in the oocyte nuclei at the early--late preleptotene stages and the thread-like chromosomes in the oocyte nuclei at the middle preleptotene--early leptotene stages either closely adjoin to IFB, localized in the centre of the nucleus, or are situated at some distance from it, and then the fibrils or fibrillar filaments are seen between chromosome material and IFB. The chromosomes are attached to IFV by the telomer or interstitial segment. The chromosomes lose the connection with IFB after the attachment of both the telomeres to the nuclear envelope (middle--late leptotene), and IFB removes from the centre of the nucleus to its periphery. It is supposed that IFB represents a nuclear skeleton element and takes part in the spatial organization of the chromosomes in the oocyte nuclei at the early stages of meiotic prophase I.

Animals↗

PubMed1979

A method for the in vivo experimental study of meiotic prophase in the golden hamster (Mesocricetus auratus).

Gonads of 15 day-old hamster fetuses were grafted under the kidney capsule of adult ovariectomized females. In 81.8% of the grafts, the germ cells developed and completed meiotic prophase; they reached the diplotene stage and gave rise to primordial follicles. These grafts could survive well in the host for at least 20 days. Meiotic prophase was not initiated within 24 h of grafting in contrast to the in vivo condition where it is observed 24 h after birth. In grafted ovaries, 69% of the germ cells were at the leptotene stage on day 3. By day 5, most of them were either at the zygotene (15%) or pachytene stages (60%). Oocytes at the diplotene stage were found from day 5 onwards and on day 7, 30% of the germ cells had already reached this stage. The highest numbers of atretic germ cells could be found on days 1, 9 and 10 post graft. It is noteworthy that the number of germinal cells remaining in the ovary 10 and 20 days after grafting were 11.4% and 12.9% of the total number of germinal cells present in normal animals of the same ages post-partum. This point is discussed in detail.

Animals↗

PubMed1984

[Female germ cell development during the meiotic prophase in the rat: criteria for cytoplasmic and nuclear identification of the different stages on thin histological slides].

The different stages of meiotic prophase in germ cells of the rat ovary were studied cytologically at definite times when there was a dominant nuclear stage. Each stage was identified in 1 mu sections. The usual references for the definition of meiotic nuclear stages according to chromosomal structures wee used and have been described in more detail. It has also been shown that cytological observations such as the organization and distribution of cytoplasmic organelles (mitochondria, Golgi apparatus) equally contributes to the identification of the stages of meiotic prophase.

Animals↗