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

Chromosomal segregation and recombination in human sperm cells from reciprocal translocation carriers

PURPOSE

To determine whether recombination occurring around the breakpoints of translocated chromosomes may affect the accuracy of the current linkage analysis-based diagnosis of reciprocal translocation (RT) embryos.

METHODS

Here, we have selected 688 single sperm cells sampled from 14 RT carriers with signed informed consent before semen collection and systematically investigated their chromosomal segregation patterns and potential recombination of translocated chromosomes.

RESULTS

We found that 39.96% of sperm cells showed alternative segregation patterns to produce normal and chromosomally balanced sperm cells, while 39.01% presented with an adjacent-1 segregation pattern, and 16.06% presented with an adjacent-2 segregation pattern, and 4.59% presented with a 3:1 segregation pattern. Moreover, we discovered a previously unknown segregation pattern at 0.38% occurrence. Notably, of the 887 recombination events on RT-associated chromosomes identified, 18 recombination events were located within the range of 5 Mb around breakpoints, among which 10/18 (55.6%) were located within 1-3 Mb of the breakpoint.

CONCLUSION

Our study provides evidence for recombination within the 5 Mb region flanking the breakpoints of translocated chromosomes, and these results suggest a non-negligible risk in the accurate diagnosis of chromosomal translocation in embryos through current linkage analysis-based diagnostic methods.

Single Nucleotide Polymorphism array analysis for fetuses from balanced translocation carriers at the second trimester

Prenatal diagnosis is crucial for pregnancies from couples with a carrier of a balanced translocation. We retrospectively reviewed 195 pregnancies from 189 couples with a balanced translocation carrier. Of these, 126 were from natural conception, while 69 were conceived through assisted reproductive technology (ART) with preimplantation genetic diagnosis (PGD). Both single nucleotide polymorphism (SNP) array analysis and conventional karyotyping were conducted on all pregnancies, and karyotype-visible imbalances and pathogenic/likely pathogenic copy number variations (CNVs) were categorized as clinically significant abnormalities. In natural conception group, couples with a female carrier experiencing more than two miscarriages accounted for 30.2 %, significantly higher than the 14.0 % in male carrier couples (p < 0.05). In the PGD group, similar difference was observed between female and male carrier couples (p < 0.05). In the natural pregnancies, SNP array analysis yielded additional 12 cases of CNVs, including two cases of pathogenic (P)/likely pathogenic (LP) aberrations, four variants with uncertain significance (VUS), and six likely benign variants. Only two CNVs were found to be associated with translocation breakpoints, which were finally confirmed to be of parental inheritance. In the PGD pregnancies, two cases of VUS unrelated to the translocation breakpoints were revealed. Taken together, repeated miscarriage was more frequently observed in couples where the carrier was female than male. Conventional SNP array analysis in prenatal diagnosis indicated insufficient evidence to support the notion that balanced translocations increase the likelihood of fetuses having clinically significant CNVs.

Sperm Meiotic Segregation Analysis of Reciprocal Translocations Carriers: We Have Bigger FISH to Fry

Reciprocal translocation (RT) carriers produce a proportion of unbalanced gametes that expose them to a higher risk of infertility, recurrent miscarriage, and fetus or children with congenital anomalies and developmental delay. To reduce these risks, RT carriers can benefit from prenatal diagnosis (PND) or preimplantation genetic diagnosis (PGD). Sperm fluorescence in situ hybridization (spermFISH) has been used for decades to investigate the sperm meiotic segregation of RT carriers, but a recent report indicates a very low correlation between spermFISH and PGD outcomes, raising the question of the usefulness of spermFISH for these patients. To address this point, we report here the meiotic segregation of 41 RT carriers, the largest cohort reported to date, and conduct a review of the literature to investigate global segregation rates and look for factors that may or may not influence them. We confirm that the involvement of acrocentric chromosomes in the translocation leads to more unbalanced gamete proportions, in contrast to sperm parameters or patient age. In view of the dispersion of balanced sperm rates, we conclude that routine implementation of spermFISH is not beneficial for RT carriers.

Are ovarian responses and the number of transferable embryos different in females and partners of male balanced translocation carriers?

PURPOSE

To compare ovarian response and the number of transferable embryos between women with balanced autosomal translocations and women whose partners carry the translocation (control group). To investigate the predictive value of metaphase II (MII) oocyte number and biopsied embryo number for gaining at lowest one transferable embryo.

DESIGN

We retrospectively analyzed 1942 preimplantation genetic testing for structural rearrangements (PGT-SR) cycles of 1505 balanced autosomal translocation couples over 8 years. All cycles were divided into two subgroups: Robertsonian and reciprocal translocations (ROBT and ReBT). Receiver operator characteristic (ROC) curves were plotted to ascertain a cutoff of MII oocytes and biopsied embryos as predictors of gaining at lowest one transferable embryo.

RESULT

There were no statistical differences in baseline features or ovarian response indicators regarding the number of retrieved/MII oocytes, E2 level on the day of HCG, and ovarian sensitivity index (OSI) between women with balanced autosomal translocations and control group (P > 0.05). A decreased number of transferable embryos were found in women with balanced autosomal translocations regardless of the type of translocation. The cutoff values for gaining at lowest one transferable embryo are 12.5 MII oocytes and 4.5 biopsied embryos, respectively.

CONCLUSION

Women with balanced autosomal translocations have a normal ovarian response, but fewer transferable embryos, meaning that higher gonadotropin (Gn) doses may be required to increase transferable embryos. When fewer than 12.5 MII oocytes or 4.5 blastocysts are obtained in a PGT-SR cycle, couples should be notified that the likelihood of gaining a transferable embryo is low.

Protamines and DNA integrity as a biomarkers of sperm quality and assisted conception outcome

Present research aim was to identify functional tests in semen associated with DNA damage and chromatin maturity (protamination) which predict the outcome in assisted reproduction. Couples were grouped according to male partner semen parameters, into normozoospermia (NZs), severe male factor (SMF) and mild male factor (MMF). DNA fragmentation index (DFI) in spermatozoa was analysed by sperms chromatin dispersion (SCD), sperm chromatin structure assay (SCSA) and acridine orange testing (AOT). Chromomycin A3 (CMA3) and toluidine blue (TB) staining to measure sperm chromatin maturity (CM). DFI and chromatin decondensation were significantly lower in N compared to male factor categories (MMF and SMF). Aneuploidy embryos were significantly higher in couples with male factor infertility (MMF and SMF). A positive correlation was observed between fertilization rate (FR) and live birth rate (LBR) with sperm concentration, motility, vitality, normal sperm morphology and negative correlation between sperm DFI and sperm CM. No correlation was observed between embryo aneuploidy and sperm DFI or CM. Lower percentage of spermatozoa chromatin integrity are associated with low fertilization and live birth rate. Male factor infertility, due to impaired semen parameters and chromatin defects could be regarded in future as an indication of IVF/ICSI, and predictor of assisted reproductive techniques outcome.

Effect of parental origin and predictors for obtaining a euploid embryo in balanced translocation carriers

RESEARCH QUESTION

What is the effect of parental origin of translocation and predictors for obtaining a euploid embryo in preimplantation genetic testing for chromosomal structural rearrangements (PGT-SR) for balanced translocation carriers?

DESIGN

A total of 179 PGT-SR cycles and 614 blastocysts from 123 couples carrying a balanced translocation were retrospectively analysed. Next-generation sequencing (NGS) was performed after trophectoderm biopsy.

RESULTS

There were no differences in ovarian stimulation parameters or PGT-SR outcomes regarding the number of oocytes retrieved (11.95 ± 5.71 versus 11.82 ± 6.26), blastulation rate (0.42 ± 0.27 versus 0.45 ± 0.28), biopsy cancellation rate (11.7% versus 12.9%), the number of blastocysts for biopsy (3.70 ± 2.58 versus 4.04 ± 3.51), or the proportion of euploid embryos (23.80% versus 25.42%), aneuploid embryos (58.10% versus 57.52%) and mosaic embryos (18.10% versus 17.06%) between female carriers and male partner carriers. In a multivariate logistic regression model, the number of blastocysts for biopsy (adjusted odds ratio 1.752; 95% confidence interval 1.359-2.259; P < 0.001) was significantly associated with the chance of obtaining at least one euploid embryo. Receiver operating characteristic analysis with a threshold of 3.5 was conducted to calculate the number of blastocysts required for biopsy to obtain at least one euploid embryo.

CONCLUSIONS

The parental origin of translocation does not significantly affect the PGT-SR outcomes for young balanced translocation carriers. At least 3.5 blastocysts are required to obtain one euploid embryo. Couples should be informed that the probability of obtaining one euploid embryo is low when fewer than 4 blastocysts are obtained in one PGT cycle.