Meiotic segregation analysis of reciprocal translocations both in sperms and blastomeres

Reproductive Risk Estimation Calculator for Balanced Translocation Carriers

Balanced translocation carriers experience elevated reproductive risks, including pregnancy loss and children with anomalies due to generating chromosomally unbalanced gametes. While understanding the likelihood of producing unbalanced conceptuses is critical for individuals to make reproductive decisions, risk estimates are difficult to obtain as most balanced translocations are unique. To improve reproductive risk estimates, Drs. Trunca and Mendell created models based on a logistic regression analysis of a dataset of over 6000 individuals from over 1000 translocation families. While risk assessments using these models have been offered as a free service for years, this protocol aims to create a sustainable model for genetics professionals to obtain risk estimates for their patients directly. This protocol guides the user through collecting clinical information, using a risk-generating Java program based on the models, and interpreting the program outputs. A practice tutorial is provided to ensure competency in interpretation prior to use. © 2022 Wiley Periodicals LLC. Basic Protocol 1: Estimation of reproductive risks for balanced translocation carriers Basic Protocol 2: Practical examples of typical patient encounters with instructive interpretations.

Chromosome 17 translocation affects sperm morphology: Two case studies and literature review

We present two cases of infertile males with teratozoospermia stemming from chromosome 17 translocation. The patients present karyotypes that have not been previously reported. Genes located on breakpoints (17p11.2, 9q31, and 11p15) were analysed to find the probable mechanism affecting sperm morphology. Our results suggest that ALKBH5, TOP3A, and LLGL1 interactions may be an underlying cause of abnormal sperm head morphology. Translocation of chromosome 17 occurred in conjunction with chromosome 9 and chromosome 11 translocation in the two cases, resulting in oligozoospermia and asthenozoospermia, respectively. These abnormal phenotypes may involve meiosis- and motility-related genes such as LDHC, DNHD1, UBQLN3, and NUP98. Translocation is thus a risk factor for sperm morphological abnormalities and motility deficiency. The interaction network of 22 genes on breakpoints suggests that they contribute to spermatogenesis as a group. In conclusion, this study highlighted the importance of investigating genes linked to sperm morphology, together with chromosome 17 translocation and reproductive risks. For patients interested in screening before a future pregnancy, we recommend preimplantation genetic diagnosis to reduce the risk of karyotypically unbalanced foetuses and birth defects.

Conventional ICSI improves the euploid embryo rate in male reciprocal translocation carriers

PURPOSE

To evaluate whether the morphologically normal spermatozoa selected for intracytoplasmic sperm injection (ICSI) under microscope had a higher rate of normal/balanced chromosome contents than that in the whole unselected sperm from reciprocal translocation carriers.

METHODS

Five hundred unselected spermatozoa from each of 40 male translocation carriers were performed with fluorescence in situ hybridization (FISH), to determine the rates of gametes with different meiotic contents of translocated chromosomes. Meanwhile, 3030 biopsied blastocysts from 239 male and 293 female reciprocal translocation carriers were detected with the microarray technique to analyze the rates of embryos with different translocated chromosome contents.

RESULTS

The D3 embryo rate, blastocyst formation rate, and euploid rate of blastocysts were remarkably higher in male carriers than those in female (p = 0.001, p = 0.004, and p = 0.035, respectively). In addition, the percentages of alternate products, which contained normal/balanced chromosome contents, in embryos from male carriers were markedly higher than those in sperm FISH (p = 2.48 × 10^-5 and p = 2.88 × 10^-10), while the percentages of adjacent-2 and 3:1 products were lower than those in sperm FISH (p = 0.003 and p = 5.28 × 10^-44). Moreover, consistent results were obtained when comparing the rates of products in embryos between male and female carriers. Specifically, the incidence of alternate products in male carriers was higher than those in female carriers (p = 0.022). However, no similar differences were seen between sperm and embryos of female carriers.

CONCLUSION

ICSI facilitates the selection of spermatozoa with normal/balanced chromosome contents and improves the D3 embryo rate, blastocyst formation rate, and the euploid embryo rate in male carriers.

Clinical feature of infertile men carrying balanced translocations involving chromosome 10: Case series and a review of the literature

RATIONALE

Infertile male carrying balanced translocations can be broadly divided into two types: pregestational and gestational infertility. Chromosome and breakpoints involved translocation should be considered in genetic counselling for these patients. To date, > 100 cases have been described with carrying balanced translocations involving chromosome 10 in fertile male.

PATIENT CONCERNS

We report 11 cases translocation carriers involving chromosome 10, and review 99 carriers of chromosome 10 translocation from reported literature.

DIAGNOSES

Eleven cases of chromosomal translocation were diagnosed by cytogenetic analysis. Three of these men had azoospermia or oligozoospermia, while eight had normal semen. Of these latter cases, their partners were able to conceive, but had a tendency to miscarry or have a stillbirth.

INTERVENTIONS

Chromosome breakpoints should be considered in genetic counseling. Preimplantation genetic diagnosis should be performed to decrease the high risk of miscarriage and to minimize the genetic risks to offspring for patients with gestational infertility.

OUTCOMES

The most common translocations and breakpoints were at t(4;10) and 10q24, observed in 12 and 10 patients respectively. Breakpoints at 10p15.1, 10p12, 10q10, 10q22.1, 10q24.2, and 10q26.3 were linked to pregestational infertility; breakpoints at 10p12.1, 10q11, 10q21.2, and 10q23.3 were associated with gestational infertility; the other breakpoints were connected with both forms of infertility.

LESSONS

Breakpoints at 10p12 and 10q26.3 were associated with pregestational infertility. Other breakpoints at chromosome 10 were correlated with gestational infertility. These breakpoints should be considered when counseling men with chromosome 10 translocations should be informed of their options.

Meiotic segregation analyses of reciprocal translocations in spermatozoa and embryos: no support for predictive value regarding PGD outcome

Translocation heterozygotes have an increased risk of producing gametes with unbalanced chromosome content. This often leads to reproductive problems such as infertility, repeated miscarriages or birth of an affected child. To increase the chances of having a healthy live-born child, translocation heterozygotes often opt for preimplantation genetic diagnosis (PGD). The aim of this study was to investigate whether there is a correlation between chromosome segregation in spermatozoa from translocation heterozygotes and the number of balanced embryos produced during PGD that may be used to predict the PGD outcome. Ten male reciprocal translocation heterozygotes that went through PGD at a Stockholm PGD centre were included. We analysed 1000 spermatozoa from each patient and between 3 and 29 embryos from the total of PGD cycles that the couples went through. Fluorescence in-situ hybridization (FISH) analysis of spermatozoa and embryos was performed with the same DNA probes. We found that the proportion of balanced spermatozoa was much higher than the proportion of balanced embryos during PGD. Our results indicate that a sperm FISH analysis prior to PGD is not a reliable predictor of the PGD outcome. PGD is a valuable reproductive alternative for translocation heterozygotes with reproductive problems and should be offered to these couples.

Quadrivalent asymmetry in reciprocal translocation carriers predicts meiotic segregation patterns in cleavage stage embryos

The effect of quadrivalent geometry on meiotic behaviour was evaluated. Segregation patterns of 404 cleavage stage embryos from 40 reciprocal translocation carriers undergoing 75 PGD cycles were analysed according to the asymmetric degree of quadrivalent. The percentage of alternate products with severe asymmetric quadrivalents was significantly lower than patients with mild asymmetric quadrivalents (22.5% versus 38.7%, P = 0.001). The incidence of 3:1 products was significantly higher in patients with severe compared with mild asymmetric quadrivalents (23.1% versus 12.2%, P = 0.004). The incidence of adjacent 1 (25.8% versus 24.3%), 2 (11.5% versus 12.6%) and 4:0/other segregation products (17.0% versus 12.2%) were not statistically significantly different between embryos from patients with severe or mild asymmetric quadrivalents. After adjusting for the confounder of sex using a logistic regression model, the odds of alternate embryos is about one-half for carriers classified as severe (OR 0.456, 95% CI 0.291 to 0.705), and the odds of 3:1 embryos is 2.2 times higher for carriers with severe asymmetric quadrivalents (OR 2.235, 95% CI 1.318 to 3.846). Our results suggest that the meiotic segregation pattern is related to the degree of asymmetry of specific quadrivalents. Severe asymmetric quadrivalents increases the risk of abnormal embryos.

Chromosomal Translocation t (10;19) (q11.2;q13.4) in an Infertile Male

Chromosomal rearrangements are usually associated with male factor infertility. We report here a 34-year-old man suffering from primary infertility for 15 years. The cytogenetic analysis and investigation of Y-chromosome microdeletions were performed. A reciprocal balanced translocation t (10;19) (q11.2;q13.4) was found in oligozoospermic infertile men with no Y-chromosome microdeletions. In this case, we aimed to evaluate the 46,XY,t (10;19) (q11.2;q13.4) karyo-type, which was detected through a cytogenetic analysis of a person referred to our genetic laboratory due to primary infertility, in the light of the literature.

Predictive value of sperm-FISH analysis on the outcome of preimplantation genetic diagnosis (PGD) for a pericentric inversion inv5(p15.3q11.2) carrier

BACKGROUND

Pericentric inversions (PIs) are structural chromosomal abnormalities, potentially associated with infertility or multiple miscarriages. More rarely, at meiosis, odd numbers of genetic recombinations within the inversion loop produce recombinant gametes which may lead to aneusomy of recombination in the offspring.

METHODS

We report a FISH segregation analysis of an inv5(p15.3q11.2) carrier, both in sperm and blastomeres. In sperm, we directly evaluated the proportion of recombinant gametes and compared the results with chromosomal abnormalities found in blastomeres collected from embryos obtained following a preimplantation genetic diagnosis (PGD) procedure.

RESULTS

A total of 7006 sperm nuclei were analyzed. The size of the inverted segment represented 27% of the total length of chromosome 5. The frequencies of balanced chromosomes (normal or inverted), recombinant chromosomes and unbalanced combinations were 97.1, 0.17 and 2.73%, respectively. Of six embryos, PGD FISH analysis revealed that one was a balanced embryo, whereas five were unbalanced and there were no recombinants.

CONCLUSIONS

This study demonstrated the value of sperm-FISH analysis in providing reproductive genetic counseling for PI carriers. Our study also highlights the clinical relevance of performing PGD instead of prenatal diagnosis.

18, X, Y aneuploidies and transmission electron microscopy studies in spermatozoa from five carriers of different reciprocal translocations

We analysed ejaculated spermatozoa from five infertile men with different balanced reciprocal translocations to contribute to the study of meiotic segregation of chromosomes 18, X and Y and also to evaluate sperm morphology by transmission electron microscopy (TEM) analysis. Conventional lymphocyte karyotype analyses highlighted different reciprocal balanced translocations: t(12;13), t(4;9), t(X;8), t(8;10) and t(3;16). Semen analysis was performed by light and TEM. Fluorescence in situ hybridization was performed directly on sperm nuclei using centromeric probes for chromosomes 18, X and Y. The carriers of the balanced reciprocal translocations considered in the present study showed a very similar pattern of sperm pathologies: diffused presence of apoptosis and immaturity. All patients showed meiotic segregation derangements, highlighted by the presence of sperm diploidies and sex chromosome disomies particularly related to the failure of the first meiotic division. However, an increased incidence of chromosome 18 aneuploidy was detected in spermatozoa from t(X;8) and t(8;10) carriers. We have also reported values from sex chromosomes such as t(X;8), although the X chromosome was involved in translocation. Since patients with reciprocal translocations and spermatogenetic impairment are candidates for intracytoplasmic sperm injection cycles, the study of sperm parameters, and particularly of the level of aneuploidy rates, would provide better information for couples at risk and would contribute to the data in the literature for a better understanding of the effects of chromosomal rearrangement on the whole meiotic process and, in particular, on chromosomes not involved in translocation.

Cytogenetic determinants of male fertility

BACKGROUND

Cytogenetic abnormalities have been known to be important causes of male infertility for decades.

METHODS

Research publications from 1978 to 2008, from PubMed, have been reviewed.

RESULTS

These studies have greatly improved our information on somatic chromosomal abnormalities such as translocations, inversions and sex chromosomal anomalies, and their consequences to the cytogenetic make-up of human sperm. Also, we have learned that infertile men with a normal somatic karyotype have an increased risk of chromosomally abnormal sperm and children. New techniques such as single sperm typing and synaptonemal complex analysis have provided valuable insight into the association between meiotic recombination and the production of aneuploid sperm. These meiotic studies have also unveiled errors of chromosome pairing and synapsis, which are more common in infertile men.

CONCLUSIONS

These studies allow us to provide more precise information to infertile patients, and further our basic knowledge in the causes of male infertility.