Analysis of human unfertilized oocytes and pronuclear zygotes—Correlation between chromosome/chromatin status and patient-related factors

Zhivkova, R; Delimitreva, S; Toncheva, Draga; Vatev, I

doi:10.1016/j.ejogrb.2006.03.022

Cited by 10 publications

(8 citation statements)

References 22 publications

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“…Interestingly, children born after ICSI appear to have a wider range of telomere lengths than controls (Robinson et al ., 2005). Human embryos display a wide variety of genetic abnormalities; however, end-to-end joining has not been reported as a common occurrence in humans (Zhivkova et al ., 2007). This finding might be taken to imply that the human oocyte effectively avoids such an eventuality under normal circumstances, although chromosome fusion can be induced in mouse embryos by exposure to toxic mitochondrial uncouplers (Liu et al ., 2002b) or cigarette smoke condensate (Huang et al ., 2010).…”

Section: Discussionmentioning

confidence: 99%

Telomere lengths in human oocytes, cleavage stage embryos and blastocysts

Turner

Wong

Rai

et al. 2010

Molecular Human Reproduction

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Telomeres are repeated sequences that protect the ends of chromosomes and harbour DNA repair proteins. Telomeres shorten during each cell division in the absence of telomerase. When telomere length becomes critically short, cell senescence occurs. Telomere length therefore reflects both cellular ageing and capacity for division. We have measured telomere length in human germinal vesicle (GV) oocytes and preimplantation embryos, by quantitative fluorescence in situ hybridization (Q-FISH), providing baseline data towards our hypothesis that telomere length is a marker of embryo quality. The numbers of fluorescent foci suggest that extensive clustering of telomeres occurs in mature GV stage oocytes, and in preimplantation embryos. When calculating average telomere length by assuming that each signal presents one telomere, the calculated telomere length decreased from the oocyte to the cleavage stages, and increased between the cleavage stages and the blastocyst (11.12 versus 8.43 versus 12.22 kb, respectively, P < 0.001). Other methods of calculation, based upon expected maximum and minimum numbers of telomeres, confirm that telomere length in blastocysts is significantly longer than cleavage stages. Individual blastomeres within an embryo showed substantial variation in calculated average telomere length. This study implies that telomere length changes according to the stage of preimplantation embryo development.

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Section: Discussionmentioning

confidence: 99%

Telomere lengths in human oocytes, cleavage stage embryos and blastocysts

Turner

Wong

Rai

et al. 2010

Molecular Human Reproduction

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“…Of note, we not only included PNs of equal and different sizes but also those zygotes with a single PN, as more than 80% proceed from fertilized oocytes (Munne et al ., 1993), and in FISH studies concerning ploidy status of 1PN-derived embryos displayed a normal ploidy number of chromosomes in nearly half of them. Probably some monopronuclear stage can be mis-defined because of the clustering of some vacuolar or pronuclear membrane remnants and the cells have a 1PN appearance at the time of observation (Zhivkova, 2007). In circumstances of extremely limited availability of zygotes, we may be forced to use those with a single PN.…”

Section: Discussionmentioning

confidence: 99%

Human zygote morphological indicators of higher rate of arrest at the first cleavage stage

Zamora

Sánchez

Pérez

et al. 2010

Zygote

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A little studied aspect of developmental arrest (DA) in ART is zygote arrest (ZA). Etiologically, blockage at the first cleavage stage includes molecular and chromosomal anomalies, some of which manifest morphologically. Given considerations on embryo culture, transfer and cryopreservation, optimal zygote selection is very important. The aim of this study was to ascertain whether zygote morphological features were indicators of increased ZA. In this study we performed a prospective, observational study of 2105 zygotes obtained from consecutive patients who were undergoing IVF/ICSI treatment, of which 43 (2%) suffered ZA. Morphological features observed under the inverted microscope were qualitatively categorized: pronuclear size, nucleolar precursor bodies (NPB) alignment, light and dark halos, polar body placement and fragmentation observed at 16-18 h post-insemination. We compared these features in blocked versus cleaved zygotes at 48 h and found significant correlations (p < 0.05) between ZA and three features: the absence of a light halo (p = 0.001), the absence of a dark halo (p < 0.005), and non-aligned NPB (p < 0.05). We can say that certain morphological features are indicators of significantly increased zygote arrest. These findings may be of utility for optimal zygote selection and culture strategies, especially in countries under restrictive conditions.

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“…It is evident that the compact morphology of oocyte chromosomes does not allow the detection of complex rearrangements such as translocations and inversions. As suggested by Zhivkova et al (2007), further frequent errors may comprise the confusion of single chromatids and small acrocentric chromosomes and the interpretation of chromatid separation as hyperhaploidy.…”

Section: Discussionmentioning

confidence: 99%

“…Currently, it is not clear whether additional techniques will completely supersede the conventional approach of homogeneous staining. The latter may indeed have advantages for the analysis of compact chromosomes and the detection of fragments (Zhivkova et al 2007). However, to improve the scientific value of corresponding studies, strict and uniform criteria should be followed, not only when analysing cytogenetic preparations but also in presenting the results (Rosenbusch 2007).…”

Section: Discussionmentioning

confidence: 99%

Human oocyte chromosome analysis: complicated cases and major pitfalls

Rosenbusch

Schneider²,

Michelmann

2008

J Genet

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Human oocytes that remained unfertilized in programmes of assisted reproduction have been analysed cytogenetically for more than 20 years to assess the incidence of aneuploidy in female gametes. However, the results obtained so far are not indisputable as a consequence of difficulties in evaluating oocyte chromosome preparations. Because of the lack of guidelines, we decided to summarize for the first time, the possible pitfalls in human oocyte chromosome analysis. Therefore, we screened the material from our previous studies and compiled representative, complicated cases with recommendations for their cytogenetic classification. We point out that maturity and size of the oocyte are important parameters and that fixation artefacts, as well as the particular structure of oocyte chromosomes, may predispose one to misinterpretations. Moreover, phenomena related to oocyte activation and fertilization are illustrated and explained. This compilation may help to avoid major problems in future studies and contribute to a more precise, and uniform assessment of human oocyte chromosomes.

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Analysis of human unfertilized oocytes and pronuclear zygotes—Correlation between chromosome/chromatin status and patient-related factors

Cited by 10 publications

References 22 publications

Telomere lengths in human oocytes, cleavage stage embryos and blastocysts

Telomere lengths in human oocytes, cleavage stage embryos and blastocysts

Human zygote morphological indicators of higher rate of arrest at the first cleavage stage

Human oocyte chromosome analysis: complicated cases and major pitfalls

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