Cytogenetics
Wojciech Gorczyca in Atlas of Differential Diagnosis in Neoplastic Hematopathology, 2014
A karyotype is a set of chromosomes from one cell. There are 46 chromosomes occurring in 23 pairs (Figure 6.1). Chromosomes are distinct bodies found in the nucleus of cells, best visible in the phase of the cell cycle called metaphase. Chromosomes are composed of protein and DNA, and hold the genetic information in the form of linear sequences of four bases (A, T, C, and G). The DNA sequence for a single trait is called a gene. Each chromosome contains a few thousand genes, which range in size from a few thousand bases up to 2 million bases. The first 22 pairs are labeled longest to shortest. The last pair are called the sex chromosomes, which are labeled X or Y. Females have two X chromosomes (XX), and males have an X and a Y chromosome (XY). Each chromosome has a short or p (petit) arm and long or q (next letter in the alphabet) arm, which are separated by a region known as the centromere. The centromere is a condensed part of chromosome that binds together two sister chromatids and constitutes the attachment site for spindle fiber during cell division. Types of chromosomes are presented in Figure 6.2. Each chromosome arm is further defined by numbering the bands (light and dark bands visible under the microscope after staining with various dyes); the higher the number, the further the area is from the centromere. The band width and the order of bands are specific for each chromosome and allow their identification.
Molecular Biology
John C Watkinson, Raymond W Clarke, Louise Jayne Clark, Adam J Donne, R James A England, Hisham M Mehanna, Gerald William McGarry, Sean Carrie in Basic Sciences Endocrine Surgery Rhinology, 2018
Each DNA molecule is packaged into a chromosome by complex folding of the DNA around proteins. Diploid human cells contain 22 pairs of autosomes (1 to 22) and a pair of sex chromosomes (XX or XY) that determines the sex of the organism. One of each pair of chromosomes is maternally inherited and the other is paternally inherited. Each chromosome has a distinctive shape, size and banding pattern, but have the common appearance of two arms apparently separated by a constriction. The centromere is microscopically recognizable as the central constriction separating the chromosome into a long arm (q for queue) and a short arm (p for petit), but its biological role lies in anchoring the chromosome to the mitotic spindle for segregation during cell division. The ends of the chromosomes are capped by telomeres, which are specialized structures containing unique simple repetitive sequences. They maintain the structural integrity of the chromosome and provide a solution for complete replication of the extreme ends of the chromosome. The conventional nomenclature for chromosomal locus assignment is given by the chromosome number, followed by the arm and finally the position on the arm, for example, 3p21 indicates position 21(two-one) on the short arm of chromosome three.
Immunology of Scleroderma
Richard K. Burt, Alberto M. Marmont in Stem Cell Therapy for Autoimmune Disease, 2019
The centromere comprised of the kinetochore, which is a trilaminar disc-shaped structure, serves as the attachment site for the spindle microtubules. The microtubules facilitate the alignment and separation of the chromosome during mitosis.184,185 The prevalence of ACA in SSc varies but has been found to be strongly associated with the lcSSc.134 ACA has also been identified in normal individuals186 and patients with Raynaud’s,166,186 SLE,186 primary biliary cirrhosis,187 and morphea.187 ACA comprises at least 6 centromere polypeptides (CENP): CENP-A to CENP-F More than 90% of ACA-positive sera from SSc patients reacts with CENP-A, -B, and -C188 and studies have demonstrated that these antibodies are capable of disrupting mitosis.189 CENP-A is a protein that is very similar to histone H3 of the H3/H4 nucleosomal core and is approximately 18 kD in size. It copurifies with H3/H4, but it has a centromere specific binding domain and is therefore distinct from H3 and H4.190,191 CENP-B is a DNA binding protein of 80kD and can be identified in 100% of all ACA-positive sera. It is distributed throughout the centromeric alpha-satellite heterochromatin below the kinetochore.192 CENP-C is a 140 kD protein that is a component of the kinetochore plate, which is essential for normal centromere function.193
Mutant ATRX: uncovering a new therapeutic target for glioma
Published in Expert Opinion on Therapeutic Targets, 2018
Santiago Haase, María Belén Garcia-Fabiani, Stephen Carney, David Altshuler, Felipe J. Núñez, Flor M. Méndez, Fernando Núñez, Pedro R. Lowenstein, Maria G. Castro
The role of ATRX in the resolution of G4 and other non-B DNA secondary structures is essential in preserving genomic stability. Consequently, the accumulation of G4 and other secondary structures in ATRX-mutated cells may be a major contributor to genomic instability. ATRX appears to play a critical role in genomic stability preservation and contributes to chromosome dynamics during mitosis [60]. A study performed in HeLa cells shows that ATRX downregulation by siRNA results in abnormal chromosome congression during mitosis [108]. RNAi knock down of ATRX in mouse ES cells also induces a telomere-dysfunction phenotype and reduces chromobox homolog 5 (CBX5) enrichment at telomeres, suggesting that ATRX participates in telomere chromatin integrity maintenance [109]. In addition, studies in transgenic mice show that ATRX contributes to regulation of pericentric heterochromatin structure [110–112]. This is an essential mechanism that coordinates sister centromere cohesion and appropriate separation of chromatids during mitosis. The loss of this mechanism results in centromere instability and aneuploidy [106,113].
Favourable outcome of planned pregnancies in systemic sclerosis patients during stable disease
Published in Scandinavian Journal of Rheumatology, 2022
J Braun, A Balbir-Gurman, K Toledano, Y Tavor, Y Braun-Moscovici
Another issue is the impact of ACA positivity on conception and fertility. In our large cohort of SSc patients of fertile age, we identified eight ACA-positive patients. Four patients had failed repeated IVF attempts. Three other patients conceived spontaneously. Two patients underwent successful IVF with uneventful pregnancy and delivery of healthy babies. One of them had had two previous abortions and the IVF was with a donated oocyte. Two out of three patients with spontaneous abortions were positive for ACAs. Disorders of oocyte maturation and early embryonic development abnormalities have been observed in women with ACA positivity (14). ACA may be the essential marker for defective oocytes or embryos in infertile women with any type of ANA (15). The exact mechanism is unknown. In a study performed in mouse oocytes, microinjected centromere kinetochore antibodies were found to interfere with chromosome movement in meiotic and mitotic oocytes (16).
CDKN2A Depletion Causes Aneuploidy and Enhances Cell Proliferation in Non-Immortalized Normal Human Cells
Published in Cancer Investigation, 2018
Zofia Hélias-Rodzewicz, Nelson Lourenco, Mariama Bakari, Claude Capron, Jean-François Emile
Standard protocols were used for metaphase spreads and GTG (G-banding with trypsin-Giemsa) banding analyses. Trypsinized cells were incubated 10 minutes in a hypotonic solution and washed twice in a fixative mixture. After overnight incubation at +4°C, the cells were washed twice and metaphases were spread carefully onto the slides to avoid the unexpected chromosome losses or gains during metaphase preparations. Chromosome numbers were counted under a Zeiss Axioscope A1 microscope equipped with EC plan Neofluoar objectives (Zeiss, Marly le Roi, France). Centromere probes for chromosomes 6, 12, 16, and 17 were from Kreatech Biotechnology (Amsterdam, The Netherlands) and applied according to the manufacturer’s recommendations. Fluorescence signals were analyzed using a Leica DM4000B microscope equipped with appropriate filters and a DFC300FX camera under the control of LAS V4.0 software (Leica, Nanterre, France).