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The genomic architecture predisposed to the emergence of DNA copy number variation causing a new class of human chromosomal diseases-reciprocal microdeletion and microduplication syndromes- is reviewed in the paper. The molecular mechanisms of such chromosomal abnormalities are described. The problems of the interpretation of their clinical significance and genotype-phenotype correlations are discussed. The classification of phenotypes due to reciprocal chromosomal microdeletions and microduplications is shown. Published by 2015, reciprocal mutations associated with inherited and congenital human pathology and involving 58 chromosomal regions are summarized. [ABSTRACT FROM AUTHOR]

The contribution of chromosomal abnormalities to recurrent pregnancy loss (RLP) is reviewed in the paper. Data from conventional cytogenetic analysis of the karyotype of parents and spontaneous abortions, as well as the results of molecular cytogenetic investigations and preimplantation genetic diagnostics, are discussed. Information about the significance of epigenetic impairments (abnormalities of imprinting and X-chromosome inactivation) for recurrent pregnancy loss is also considered. Cytogenetic analysis of products of conception enables ascertainment of the causes of embryonic death in a large proportion of families, more accurate estimation of the therapeutic efficiency of treatment and drugs (when women with abnormal embryos were excluded), and a statistically valid prognosis about the next pregnancy outcome. [ABSTRACT FROM AUTHOR]

Karyotyping of noncultivated cells of 60 first-trimester spontaneous abortions (blighted ovum and missed abortions) was carried out using fluorescencein situ hybridization (FISH) with centromere-specific DNA probes for all chromosomes of the karyotype. Conventional cytogenetic study of these abortions was impossible because of cell culture failures. The algorithm is proposed for molecular cytogenetic FISH analysis of interphase karyotypes. Chromosome abnormalities were found in 32 fetuses (53.3%). In groups of missed abortions and blighted ovum, the frequency of numerical chromosome abnormalities was 50 and 60%, respectively. Both the numerical chromosome abnormalities typical of spontaneous human abortions (autosomal trisomies, sex chromosome aneuploidy, and polyploidy) and a relatively rare type of genomic imbalance unidentifiable by standard cytogenetic analysis (autosomal monosomies 7, 15, 21, and 22 in mosaic state) were observed. The frequency of these type of chromosome abnormalities comprised 19% of all known karyotype abnormalities determined in spontaneously aborted embryos. Note that the level of confined placental mosaicism in embryos with low cell proliferative activity was 25%, which is substantially higher than the corresponding parameter (1–2%) determined by prenatal diagnosis of chromosome abnormalities in developing embryos. The results of interphase FISH analysis of cells with low proliferative activity in vitro suggest that the pathology of early fetal development and missed abortion in humans are associated with a wider spectrum of chromosome abnormalities. [ABSTRACT FROM AUTHOR]

The level of chromosomal abnormalities in the somatic cells of adult individuals is characterized by significant interindividual variability, which may be partly affected by the genetic and epigenetic background. The epigenetic landscape in cells is largely determined by genome methylation. This study aimed to analyze the relationships between global genome methylation and the frequencies of chromosome abnormalities in lymphocytes of plutonium workers. The frequencies of chromosome aberrations, micronuclei, aneuploidy of chromosomes 2, 7, 8, 12, X, and Y and sister chromatid exchanges were analyzed in the lymphocytes of 40 male workers from a nuclear chemical facility (Seversk, Russia) with incorporated plutonium-239 and 49 healthy male volunteers who had no occupational exposure to ionizing radiation. The long interspersed nuclear elements-1 (LINE-1) methylation index was assessed as a well-known marker of global genome methylation. The frequencies of centromere-negative micronuclei (4.74 ± 2.26 vs. 3.02 ± 1.69‰), chromosome-type aberrations (0.81 ± 0.79 vs. 0.44 ± 0.69%), and total chromosome non-disjunction (0.93 ± 0.43 vs. 0.50 ± 0.25%) were significantly higher in the group of workers than in controls (p < 0.05). The LINE-1 methylation index did not differ significantly between the worker and control groups (74.93 ± 3.63 vs. 73.92 ± 4.62%). Correlations between LINE-1 methylation and the frequency of micronuclei (R = –0.35, p = 0.031) were observed in the control group, whereas correlations of LINE-1 methylation with chromatid-type aberrations (R = –0.42, p = 0.012) (but not chromosome-type aberrations) and with sister chromatid exchanges (R = –0.53, p = 0.004) were observed only in the group of plutonium workers. Thus, LINE-1 hypomethylation after plutonium exposure is associated mainly with chromatid breaks, either repaired or misrepaired. [ABSTRACT FROM AUTHOR]

Human induced pluripotent stem cells (iPSCs) are a promising source of cells for regenerative medicine, study of the pathogenesis of various diseases, screening of pharmacological drugs, and other clinical and basic research. However, the maintenance of the genetic stability of the cells during reprogramming, long-term culture, and directed differentiation is necessary for the use of iPSCs. Large chromosomal aberrations affect the quality of iPSCs most adversely, so the review focuses on the analysis of chromosomal abnormalities, including the recurrent aneuploidy; the sources of its origin, the effect of reprogramming, and long-term culture on the accumulation of chromosome aberrations are discussed. Cases of spontaneous correction of the iPSCs karyotype and the possibility of induced correction of the large chromosomal abnormalities by removing or silencing the extra homologue are considered. [ABSTRACT FROM AUTHOR]

Risks related to occupational exposure of humans to ionizing radiation remains a focus of attention. Of special importance is the poorly understood effect of ionizing radiation on the rate of numerical chromosome aberrations in human somatic cells. The purpose of this study was characterization of a radiation-induced increase in the rate of aneuploidy induced by incorporated plutonium-239 (Pu) in somatic cells of chemonuclear industry workers. Significant differences in the chromosome 2, 7, 8, 12, and Y aneuploidy rate have been found between subjects with incorporated Pu and control subjects have been demonstrated. Chromosome nondisjunction has been found to be the main mechanism of aneuploidy induced by incorporated Pu. [ABSTRACT FROM AUTHOR]

Early stages of human embryonic development are characterized by the spatiotemporal coincidence of events of total epigenetic genome reprogramming and elevated level of mosaic forms of numerical chromosome abnormalities. It is possible that the abnormal reprogramming of various regions of the genome can lead to violations of local epigenetic chromatin organization and gene expression, which affect the correct chromosome segregation during mitosis. In this study, a comparative analysis of the methylation index of LINE-1 retrotransposon, which largely reflects the methylation profile of the genome, is performed in placental tissues of spontaneous abortions with complete and mosaic forms of aneuploidy and with a normal karyotype, as well as in the control group of induced abortions of the first trimester of pregnancy. It was shown that extraembryonic mesoderm and chorionic cytotrophoblast of spontaneous abortions with chromosomal mosaicism are characterized by the highest index of LINE-1 methylation among all studied groups. At the same time, the excessive hypomethylation of transposable genetic element was registered in spontaneous abortions with normal karyotype. We hypothesize that violations of parental genome demethylation during epigenetic reprogramming at preimplantation stages of development may be associated with an increased frequency of mitotic errors in chromosome segregation, which leads to the formation of a mosaic karyotype. [ABSTRACT FROM AUTHOR]

The present work was aimed at generating the dynamic standard reference intervals (DSRI) and their application for chromosomal-aberration (CA) analysis. The evaluation of the generated DSRI was performed using the DNA samples from four patients with already known CA. High-resolution comparative genomic hybridization analysis (HR-CGH) allowed us to not only identify all of the CAs that were not revealed by CGH, but also to detect the breakpoints and to determine the size of chromosomal imbalance. [ABSTRACT FROM AUTHOR]

The methylation status of the cell cycle control gene RB1 has been studied in placental tissues of spontaneous abortions of the first trimester of pregnancy with mosaic variants of numerical chromosomal abnormalities verified by a molecular cytogenetic examination. Aberrant methylation of the gene promoter region has been revealed for the first time in 20% of embryos with chromosomal mosaicism that died in utero. A maximum frequency of epimutations was recorded in a group of embryos with a low level of abnormal cells for which mitotic errors are most likely to determine the formation of mosaic aneuploidy in primary euploid zygotes. It has been suggested that aberrant epigenetic genomic modifications at early stages of human embryonic development can be one of the mechanisms promoting genomic instability realized in the form of mosaic abnormalities of the karyotype that are incompatible with the normal course of embryogenesis. [ABSTRACT FROM AUTHOR]