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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
Paracentric inversions occur after a two-break event in the same chromosome arm, and inversion and rejoining of the segment between two breakpoints (Figure 12.3b) [40]. Paracentric inversions produce gametes that have either no centromere (acentric) or two centromeres (dicentric) and are not viable. Therefore, most paracentric inversions are considered harmless. However, a possible meiotic crossover in the inverted segment may generate chromosomally unbalanced gametes. Most zygotes resulting from chromosomally unbalanced gametes are lost very early, even before implantation, but there is still a risk of having a phenotypically abnormal child [40,41]. Spontaneous abortion, infertility, and mental retardation and/or congenital malformation of offspring have also been reported among paracentric inversion carriers [41], and the pooled risk of unbalanced viable offspring has been reported in 4% [22,42].
Habitual Abortion
Published in E. Nigel Harris, Thomas Exner, Graham R. V. Hughes, Ronald A. Asherson, Phospholipid-Binding Antibodies, 2020
Dwight D. Pridham, Christine L. Cook
Inversions are less frequent, but occur in about 1% of couples with HAB. Inversions involve breakage at two points within a chromosome with subsequent reversal of the gene sequence between the breaks. In pericentric inversion, the centromere is involved in the reversal, and the abnormality usually can be recognized by altered arm length of the involved chromosome. Paracentric inversions are limited to one arm of a chromosome and may be harder to recognize unless the banding pattern is altered. This form of inversion may therefore be more prevalent than is currently believed. Either form of inversion causes formation of an inversion loop during meiosis (Figure 3). If crossing over occurs within the loop, unbalanced duplication or deletion of genetic material usually occurs resulting in nonviable or severely abnormal embryos.
Chromosome abnormalities
Published in Angus Clarke, Alex Murray, Julian Sampson, Harper's Practical Genetic Counselling, 2019
Figure 4.5 shows the arrangement of chromosomes with either a pericentric or a paracentric inversion at meiosis. Having this diagram ‘available’ to you is, again, helpful in explaining the outcomes of chiasma formation at meiosis in the offspring of those who carry such inversions.
Abnormal chromosomes identification using chromosomal microarray
Published in Journal of Obstetrics and Gynaecology, 2022
Yunfang Shi, Xiaozhou Li, Duan Ju, Yan Li, Xiuling Zhang, Ying Zhang
Indeed, there are discordant results between karyotype analysis and CMA, which require further postnatal investigation. For case 6, karyotype indicated a structural abnormality on chromosome X, while CMA detected an 80.0 Mb deletion in Xq13.3q28 not consistent with karyotype analysis. The couples refused further examination and were lost in the follow-up. On this basis, we could not accurately diagnose the abnormality of chromosome X. In a previous study, Zhang et al. (2018) investigated a derivative X chromosome using karyotype analysis, FISH and SNP-array, which showed unbalanced derivative X chromosome with complex inversion, translocation and deletion, notably exhibiting a pericentric inversion between Xp22.3 and Xq28, as well as fragment translocation between Yq11.21 and q11.23 except the SRY gene. Different genetic testing methods have their advantages, disadvantages and applications. Therefore, it is recommended that the incorporation of multiple genetic techniques, such as karyotype, FISH, QF-PCR, MLPA or CMA, is essential for prenatal diagnosis, especially in the presence of an uncommon chromosome aberration (Liu et al. 2019). This may accurately reveal the nature, sources and manifestations of the derivative chromosome abnormalities and avoid the birth of children with defects.
Genetic aspects of idiopathic asthenozoospermia as a cause of male infertility
Published in Human Fertility, 2020
Zohreh Heidary, Kioomars Saliminejad, Majid Zaki-Dizaji, Hamid Reza Khorram Khorshid
In a study of 17 men with AZS showed that approximately 12 (∼70%) of them had chromosome aberrations mostly associated with repeated failures in assisted reproductive technologies (ART). Most of the chromosomal abnormality in these men were structural including microdeletions in chromosome 2, 3, 13 and 22, and also del 21qter, and pericentric del(9)(p12→q13) (Shah & Arole, 2014). However, the rate of the chromosome abnormality was very high perhaps due to low sample size, selection criteria or methodological issues. Interestingly, in studying the reproductive condition in six infertile men with a pericentric inversion of chromosome 9, Sasagawa et al. (1998) found that three of them were AZS patients. Analysis of the karyotypes of 300 infertile couples with at least three years of infertility revealed a total of 2.5% inversions, among these, 4.69% men were inversion 9 carriers, while one female patient was affected (0.33%). The incidence of inversion 9 in male patients was significantly higher than that of the normal population (2%). Inversion 9 may often cause infertility in men due to spermatogenic disturbances, which arise by the loops or acentric fragments formed in meiosis (Mozdarani, Meybodi, & Karimi, 2007). Supernumerary marker chromosome derived from chromosome 22 was found in an OAS patient (Perrin et al., 2012), and complex rearmament, which is usually associated with infertility or subfertility in male carriers, have also been reported in one AZS and one OAS patient (Asia et al., 2014; Olszewska et al., 2014).
A retrospective exploratory study of fetal genetic invasive procedures at a University Hospital
Published in Journal of Obstetrics and Gynaecology, 2018
Chitra Andrew, Teena Koshy, Shivani Gopal, Solomon Franklin Durairaj Paul
The chorionic villi, amniotic fluid and cord blood samples were cultured for conventional cytogenetic analysis using standard protocols (Barch et al. 1997). The chromosomes obtained in the metaphase were subjected to giemsa staining after trypsin treatment and analysed on the Cytovision karyotyping platform. The results of chromosome analyses were grouped as normal or abnormal. The abnormal group was further categorised into: (i) numerical and structural abnormalities, (ii) autosomal and sex chromosomal abnormalities and (iii) balanced and unbalanced structural rearrangements. Normal variations in chromosomal structures, such as pericentric inversion of chromosome 9, enlarged heterochromatin on various chromosomes and enlarged satellites, which are generally considered to be clinically insignificant, were excluded. Fluorescent in situ hybridisation (FISH) was performed as per the manufacturer’s protocol for aneuploidy screening for chromosomes 13, 18, 21, X and Y and for the microdeletion 22q11.2 using commercially available probes from Vysis©. While aneuploidy FISH was offered to all the cases, it was performed only for those who were willing to do the test in addition to karyotyping. For cases of cardiac anomalies, though FISH for microdeletion 22q11.2 was strongly recommended, only 5 of the 11 couples in this study agreed to the test.