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Preimplantation Genetic Testing for Structural Rearrangements
Published in Carlos Simón, Carmen Rubio, Handbook of Genetic Diagnostic Technologies in Reproductive Medicine, 2022
Inmaculada Campos-Galindo, Vanessa Peinado
Cytogenetics is the study of chromosome structure and properties that capitalizes on the constant morphology and size of normal chromosomes to detect abnormalities [9]. Karyotyping is a useful cytogenetic tool that uses in vitro culture and banding techniques to perform structural and numerical chromosomal analyses in metaphases to describe normal or abnormal chromosome complement of an individual, tissue, or cell line [10]. Currently, karyotyping of peripheral blood samples remains the first-line method for detecting chromosomal abnormalities in infertile couples.
Emerging Risks and Final Thoughts
Published in Ted W. Simon, Environmental Risk Assessment, 2019
Epigenetics refers to alterations in DNA structure, chromosome structure, and gene/protein expression without a change in the DNA sequence. These changes fall into three broad categories—DNA methylation, histone modifications and non-coding microRNAs (miRNAs)—that alter gene expression and nucleosome positioning.2–4 A comparison of neurodevelopmental effects of arsenic with epigenetic markers was shown in Chapter 5. Epigenetic changes associated with arsenic exposure and possibly linked to disease have been documented for a number of endpoints.5–14 The mode of action for arsenic is binding to sulfhydryl groups; this event in turn affects coordinated gene expression via Nrf2.15–18
DNA Double Strand Breaks and Chromosomal Aberrations
Published in K. H. Chadwick, Understanding Radiation Biology, 2019
The unineme concept of chromosome structure, which visualises the DNA double helix running from one telomere end of the chromosome to the other telomere end, identifies a DNA double strand break as a chromatid arm break and its repair as the rejoining of chromatid arms. The chromosome carrying the double strand break has apparently no template to copy for the repair. Errors in the rejoining of chromatid arms lead to the formation of chromosomal aberrations which can be seen in the microscope at mitosis.
The effect of ionomycin-induced oocyte activation on multiple morphological abnormalities of the sperm flagella
Published in Systems Biology in Reproductive Medicine, 2023
Zhiren Liu, Yujia Guo, Xingting Chen, Chen Lin, Xinxin Guo, Mingting Jiang, Qicai Liu
Day 6 embryos with blastulation failure are suitable for the comparison. Through the transcriptome analysis of day 6 embryos, GO analysis showed that AOA had effects on the terms of ‘protein-DNA complex’, ‘nucleosome’, and ‘DNA packaging complex’. It indicated that AOA had an effect on the chromosome structure of the day 6 embryo. The change in chromosome structure can further affect transcriptional regulation and selective expression of genes. Cell differentiation depends on gene-specific expression. Therefore, cell differentiation may also be affected by AOA. It may be why the blastocysts of AOA groups had more differentiation failure cells. In addition, in the ‘protein heterodimerization activity’ term, except for the genes involved in chromosome structure, most of the rest of the genes are involved in transcriptional regulation. These genes included USF1, NFYB, METTL3, LSM6, GTF2A1, FMR1, CREB3L3, CEBPB, and BHLHE40 (Table 2 and Supplementary Table 3). METTL3 has been shown to be involved in the differentiation of embryonic stem cells (Geula et al. 2015). Therefore, AOA also has a direct effect on transcriptional regulation.
Heterochromatin extension: a possible cytogenetic fate of primary amenorrhea along with normal karyotype
Published in Journal of Obstetrics and Gynaecology, 2022
Bishal Kumar Dey, Shanoli Ghosh, Ajanta Halder, Somajita Chakraborty, Sanchita Roy
The region of heterochromatin also acts as a key part in chromosome structure, histone modification and gene regulation. There is evidence from where we come to know that there may be displacement of heterochromatin from one chromosome to another. Perhaps, this displacement is helping in the extension of a particular chromosome at the heterochromatin portion of the long arm (Bannister and Kouzarides 2011). The mechanisms of spindle fibres, chromosome movement, meiosis crossover and change of sister chromatids are considered to be the integral region as heterochromatin for a chromosome. At the time of meiosis, there may be a change in area of synapses of homologous chromosomes in the polymorphic heterochromatin region. The heterochromatin in chromosomal polymorphism can also regulate gene expression by reversible transformation between heterochromatin (non-coding DNA sequences) and euchromatin (expressed DNA sequences) thus justifying certain clinical expression like short stature or PA. It was also postulated that defective histone protein methylation due to presence of heteromorphic variants may play a more crucial role in ovarian failure. Association of heterochromatin polymorphism with ovarian dysgenesis may be a reason for the occurrence of PA. For that, we need to study on a greater number of patients on the basis of their nucleosome’s functionality and heteromorphic polymorphism by sequencing.
In vitro-derived platelets: the challenges we will have to face to assess quality and safety
Published in Platelets, 2020
S. Mookerjee, H. R. Foster, A. K Waller, C. J. Ghevaert
Therefore, it is crucial that we quantify genomic instability of both seed material or cellular intermediates as nucleated cells will inevitably find their way into the final product. Recent work has shown that cells acquire mutations directly as a result of adaptation to the tissue culture process, as there are no cell-extrinsic mechanisms (e.g. an immune system) to remove any cells that might have the potential to become dangerous. In fact, between 12.5% and 34% of all human pluripotent stem cell lines acquire specific nonrandom chromosomal abnormalities over time (particularly in chromosome structure and number in chromosomes 1, 12, 17 and 20) that were reminiscent of changes also observed in cancers[16]. Additionally, immortalized cells have had their cell-intrinsic mechanisms for DNA damage control suppressed. Studies on other cell types, forced to overexpress c-Myc, show that this can directly drive the formation of tumors in vivo, making it vital that we are vigilant of this in our cell banks if we are to use these immortalized cells as a source [17,18].