Heterochromatic Variations and Pregnancy Losses in Humans

Characterization of Chromosomal Instability in Glioblastoma

Glioblastoma multiforme (GBM) is a malignant tumor of the central nervous system (CNS). The poor prognosis of GBM due to resistance to therapy has been associated with high chromosomal instability (CIN). Replication stress is a major cause of CIN that manifests as chromosome rearrangements, fragility, and breaks, including those cytologically expressed within specific chromosome regions named common fragile sites (CFSs). In this work, we characterized the expression of human CFSs in the glioblastoma U-251 MG cell line upon treatment with the inhibitor of DNA polymerase alpha aphidicolin (APH). We observed 52 gaps/breaks located within previously characterized CFSs. We found 17 to be CFSs in GBM cells upon treatment with APH, showing a frequency equal to at least 1% of the total gaps/breaks. We report that two CFSs localized to regions FRA2E (2p13/p12) and FRA2F (2q22) were only found in U-251 MG cells, but not lymphocytes or fibroblasts, after APH treatment. Notably, these glioblastoma-specific CFSs had a relatively high expression compared to the other CFSs with breakage frequency between ∼7 and 9%. Presence of long genes, incomplete replication, and delayed DNA synthesis during mitosis (MiDAS) after APH treatment suggest that an impaired replication process may contribute to this loci-specific fragility in U-251 MG cells. Altogether, our work offers a characterization of common fragile site expression in glioblastoma U-251 MG cells that may be further exploited for cytogenetic and clinical studies to advance our understanding of this incurable cancer.

Clinical Manifestations of Chromosomal Anomalies and Polymorphic Variations in Patients Suffering from Reproductive Failure

Background:

Human reproduction is the most intricate event as ~ 20% of human pregnancies end in miscarriages for which chromosomal anomalies are a common factor. The chromosomal variations associated with reproductive failures include translocations, inversions, supernumerary marker chromosomes, heterochromatic polymorphisms, etc., Till date, the significance of heteromorphic variants in reproductive failures is unclear.

Aim:

The aim of this study is to investigate the role of chromosomal anomalies and polymorphic variations in reproductive failure.

Materials and Methods:

Chromosomal analysis using GTG banding was performed on 638 couples (1276 individuals).

Results:

In the present study, 138 of 1276 individuals showed chromosomal variations with respect to heterochromatic variants and Robertsonian translocations. The most common variants observed across the population studied were the pericentric inversion of the chromosome 9 [inv(9)(p11q13), 3.68%] followed by pstk + on the short arm of chromosome 15 (15pstk+, 1.95%) and Robertsonian translocation of chromosomes 13 and 14 [rob(13;14)(q10;q10), 1.25%]. The maximum percentage of heterochromatic variation was observed in females with recurrent pregnancy loss (Groups A, 4.78%) and males with wives having recurrent miscarriages (Group B, 3.68%) and the minimum was recorded in patients with in vitro fertilization (IVF) failures (Group C, 0.23%) and couples having a history of the malformed child (Group F, 0.23%).

Conclusions:

High level of chromosomal polymorphic variations in patients with reproductive failures warrants their in-depth analysis to nail down the causative factors. Hence, cytogenetic analysis coupled with genetic counseling becomes indispensable for patients suffering from infertility, reproductive failures and pregnancy losses before IVF treatment to rule out the carrier status.

The type and prevalence of chromosomal abnormalities in couples with recurrent first trimester abortions: A Turkish retrospective study

OBJECTIVE

Chromosomal abnormalities are more common in the first trimester abortions. We aimed to investigate the types and prevalence of chromosomal abnormalities in couples with recurrent first trimester miscarriages in Sivas, Turkey.

MATERIALS AND MEDHODS

Three hundred couples (600 individuals) who had a story of recurrent abortion were included in the study. Chromosome analysis was performed after the preparation of lymphocyte culture with the standard method. Karyotype analyses were supported by FISH and aCGH studies.

RESULTS

Total 26 chromosome abnormalities (8.7%) were found in the couples (19 females and 7 males). Fifteen cases (57.7%) were structural anomalies and eleven cases (42.3%) were numerical chromosomal aberrations. We detected 5 balanced translocations (33.3%), 4 Robertsonian translocations (26.7%), 3 inversions (20%), 2 duplications (13.3%) and one deletion (6.7%) among the structural anomalies. Mosaic monosomy X in five cases (45.4%), the combination of mosaic monosomy-trisomy X in three cases (27.3%), the combination of mosaic monosomy-trisomy and tetrasomy X in two cases (18.2%) and mosaic pentasomy X in only one individual (9.1%) were encountered as numerical chromosome aberrations. 19 cases had heterochromatic changes or other chromosomal variations (satellite increments and inv9).

CONCLUSION

Chromosome analysis in couples with recurrent miscarriage is necessary for possible preimplantation genetic diagnosis. As well as numerical and structural chromosome abnormalities, some chromosomal variations (heterochromatin and satellite increments etc.) may also contribute to recurrent miscarriages. Numerical chromosomal abnormalities are often associated with sex chromosomes and usually seen in females.

Cytogenetic abnormalities in couples with a history of primary and secondary recurrent miscarriage: a Brazilian Multicentric Study

Objective: To evaluate the difference between chromosomal abnormalities between the gender of couples affected by Recurrent miscarriage (RM) and if there is an association between previous obstetric history and chromosomal abnormalities of the parents.Methods: Multicenter, retrospective, observational study from seven different RM clinics between 2006 and 2016. We enrolled 707 couples (1014 participants) with a history of RM. We compared the frequency of chromosomal abnormalities between groups of couples with primary and secondary RM and separated between women and their partners. Furthermore, we compared the prevalence of chromosomal abnormalities between groups based on the number of previous spontaneous abortions.Results: The overall prevalence of all cytogenetic abnormalities was 5.59% (n = 1414, women and their partners). Excluding cases of polymorphism and inversion of chromosome 9, which are considered variants of normality, the prevalence in all individuals was 2.26% (n = 32/1414). The comparative analysis of cases of chromosomal abnormalities among couples with primary and secondary RM based on the number of previous miscarriages (PM) revealed a similar frequency between groups. The statistical analysis of the total cases (primary PM + secondary PM) in these three groups were as follows: (a) couple, 2 pm versus 3 pm vs. ≥4 PM, p = .514; (b) women, 2 pm versus 3 pm vs. ≥4 PM, p = .347; and (3) partner, 2 pm versus 3 pm vs. ≥4 PM, p = .959. Chromosomal abnormalities were significantly more prevalent among women than among their partners (6.9 versus 4.2%; p = .027). Moreover, the distribution of leading chromosomal abnormalities among women was different compared with their partners. Among women, we observed these abnormalities in the following frequency order: mosaicism (38.8%), polymorphism (32.6%), translocation (16.3%), and inversion (12.3%). Among their partners, these abnormalities were polymorphism (73.3%), inversion (13.3%), mosaicism (6.7%), and translocation (6.7%).Conclusion: The number of PM and the history of full-term pregnancy does not correlate with an increase or decrease in the prevalence of cytogenetic abnormalities in couples with RM.

The incidence of long heterochromatic polymorphism variants in infants conceived through assisted reproductive technologies

Long heterochromatic variants on chromosomes 1, 9, 16 and Y are suspected to be implicated in infertility and early pregnancy loss, but little is known about how these variants are inherited in children conceived by infertile couples through assisted reproductive technologies. In this case-control study, the incidence of these variants was compared between infants conceived using intracytoplasmic sperm injection (ICSI), IVF and natural intercourse by karyotyping lymphocytes from cord blood or peripheral blood. This study included a total of 647 infants, including 189 conceived by ICSI, 177 by IVF, and 281 naturally conceived (NC). Variants were observed in 13.23% of ICSI, 15.82% of IVF and 12.46% of NC infants, showing that the incidence of variants does not appear to be significantly different between infants conceived using assisted reproductive technologies and infants conceived naturally. Because the parents of these infants were not karyotyped, we can only speculate as to whether these variants were directly inherited. This study concludes that infants born from infertile parents using assisted reproductive technologies to achieve pregnancy do not appear to be any more likely than NC infants of fertile parents to possess long heterochromatic variants.

Effect of chromosomal polymorphisms of different genders on fertilization rate of fresh IVF-ICSI embryo transfer cycles

To explore whether chromosomal polymorphisms of different genders affect outcomes of fresh IVF and intracytoplasmic sperm injection (ICSI) embryo transfer cycles differently, 37 couples with chromosomal polymorphisms were identified out of 614 infertile couples undergoing IVF-ICSI treatments. Group 1 included 20 couples in which only the male carried chromosomal polymorphisms; group 2 included 17 couples with female carriers only; group 3 included 19 infertile couples with normal karyotypes randomly selected as controls. A significantly lower fertilization rate was found in group 1 compared with groups 2 and 3 (56.68% in Group 1, 78.02% in group 2 and 71.74% in group 3; group 1 versus group 2, P < 0.001; group 1 versus group 3, P = 0.001; respectively). When stratified according to fertilization method, the fertilization rate in IVF cycles of group 1 was significantly lower than group 3 (50.00% in Group 1, 73.89% in Group 3, P < 0.001). Fertilization rates in ICSI cycles between groups 1 and 3 were not significantly different. This study suggests that male chromosomal polymorphisms adversely influence fertilization rates of IVF cycles. The use of ICSI may improve the success of infertility treatment by increasing the fertilization rate for men with chromosomal polymorphisms.