Robust evidence reveals the reliable rate of normal/balanced embryos for identifying reciprocal translocation and Robertsonian translocation carriers

We aimed to evaluate the reliable rate of normal/balanced embryos for reciprocal translocation and Robertsonian translocation carriers and to provide convincing evidence for clinical staff to conduct genetic counselling regarding common structural rearrangements to alleviate patient anxiety. The characteristics of 39,459 embryos that were sourced from unpublished data and literature were analyzed. The samples consisted of 17,536 embryo karyotypes that were not published and 21,923 embryo karyotypes obtained from the literature. Using the PubMed, Cochrane Library, Web of Science, and Embase databases, specific keywords were used to screen the literature for reciprocal translocation and Robertsonian translocation. The ratio of normal/balanced embryos in the overall data was calculated and analyzed, and we grouped the results according to gender to confirm if there were gender differences. We also divided the data into the cleavage stage and blastocyst stage according to the biopsy period to verify if there was a difference in the ratio of normal/balanced embryos. By combining the unpublished data and data derived from the literature, the average rates of normal/balanced embryos for reciprocal translocation and Robertsonian translocation carriers were observed to be 26.96% (7953/29,495) and 41.59% (4144/9964), respectively. Reciprocal translocation and Robertson translocation exhibited higher rates in male carriers than they did in female carriers (49.60% vs. 37.44%; 29.84% vs. 27.67%). Additionally, the data for both translocations exhibited differences in the normal/balanced embryo ratios between the cleavage and blastocyst stages of carriers for both Robertsonian translocation and reciprocal translocation (36.07% vs 43.43%; 24.88% vs 27.67%). The differences between the two location types were statistically significant (P < 0.05). The normal/balanced ratio of embryos in carriers of reciprocal and RobT was higher than the theoretical ratio, and the values ranged from 26.96% to 41.59%. Moreover, the male carriers possessed a higher number of embryos that were normal or balanced. The ratio of normal/balanced embryos in the blastocyst stage was higher than that in the cleavage stage. The results of this study provide a reliable suggestion for future clinic genetic consulting regarding the rate of normal/balanced embryos of reciprocal translocation and Robertsonian translocation carriers.

Decrease of spermatozoa with an unbalanced chromosome content after cell sorting in men carrying a structural chromosomal abnormality

BACKGROUND

We showed that in men with a constitutional chromosomal abnormality, DNA fragmentation was significantly higher in chromosomally unbalanced spermatozoa than in spermatozoa with a normal or balanced chromosomal content. These results could be explained by a phenomenon already described in infertile men: abortive apoptosis.

OBJECTIVES

To determine whether magnetic-activated cell separation could select spermatozoa with lower levels of DNA fragmentation and unbalanced chromosome content in men carrying a structural chromosomal abnormality.

MATERIALS AND METHODS

The spermatozoa of ten males with a chromosomal rearrangement were separated into two populations using magnetic-activated cell separation (annexin V (-) and annexin V (+) fractions), in order to study meiotic segregation by fluorescence in situ hybridization, the percentage of spermatozoa with an externalization of phosphatidylserine by annexin V staining and DNA fragmentation by TdT-mediated dUTP nick-end labeling on the whole ejaculate and on selected spermatozoa in the same patient.

RESULTS

For all patients, the percentage of spermatozoa with externalization of phosphatidylserine decreased in the annexin V (-) fraction and increased in the annexin V (+) fraction as compared to the frozen-thawed semen sample. The rates of DNA fragmentation were statistically much lower in the annexin V (-) fraction when compared to the rate before magnetic-activated cell separation for all but one patient. Conversely, we observed a statistically significantly higher rate of DNA fragmentation in the annexin V (+) fraction for six patients. After magnetic-activated cell separation, there was a significant increase of normal/balanced spermatozoa in the fraction of annexin V (-) for all patients. Conversely, we observed a significant decrease in the fraction of annexin V (+) for seven patients.

DISCUSSION AND CONCLUSIONS

Magnetic-activated cell separation is a promising tool for increasing the selection of healthy spermatozoa, with a decrease in the number of spermatozoa with externalization of phosphatidylserine, DNA fragmentation, and chromosome unbalance, for use in assisted reproductive technologies such as intracytoplasmic sperm injection for males with a chromosomal structural abnormality.

Clinical features of carriers of reciprocal chromosomal translocations involving chromosome 2: report of nine cases and review of the literature

OBJECTIVE

To explore the clinical features of carriers of chromosome 2 translocations, enabling informed genetic counseling of these patients.

MATERIALS AND METHODS

Eighty-two male carriers of a translocation who were infertile or receiving fertility counseling were recruited. Cytogenetic analyses were performed using G-banding. A search of PubMed was performed to determine whether the identified translocations on chromosome 2 are involved in male infertility. The relationships of translocation breakpoints with male infertility and recurrent pregnancy loss were analyzed.

RESULTS

Of the 82 translocation carriers, 9 (11%) were carriers of a chromosome 2 translocation. Four cases had oligozoospermia or infertility, while five had normal semen. In an analysis of the literature, 55 patients who were carriers of chromosome 2 translocations were also reviewed. Breakpoints at 2p13 and 2q31 were observed in six patients each, and were the most common. Breakpoints at 2p23, 2p13, 2p11.2, 2q31, and 2q37 were associated to both pre-gestational and gestational infertility, while other breakpoints were associated with gestational infertility.

CONCLUSIONS

All breakpoints at chromosome 2 were correlated with gestational infertility. Carriers of chromosome 2 translocations should therefore receive counseling to continue with natural conception and use of different technologies available via assisted reproductive technology, such as preimplantation genetic diagnosis.

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.

Sperm nuclear architecture is locally modified in presence of a Robertsonian translocation t(13;17)

In mammals, the non-random organization of the sperm nucleus supports an early function during embryonic development. Altering this organization may interfere with the zygote development and reduce fertility or prolificity. Thus, rare studies on sperm cells from infertile patients described an altered nuclear organization that may be a cause or a consequence of their respective pathologies. Thereby, chromosomal rearrangements and aneuploidy can be studied not only for their adverse effects on production of normal/balanced gametes at meiosis but also for their possible impact on sperm nuclear architecture and the epigenetic consequences of altered chromosome positioning. We decided to compare the global architecture of sperm nuclei from boars, either with a normal chromosome composition or with a Robertsonian translocation involving chromosomes 13 and 17. We hypothesized that the fusion between these chromosomes may change their spatial organization and we examined to what extend it could also modify the global sperm nuclear architecture. Analysis of telomeres, centromeres and gonosomes repartition does not support a global nuclear disorganization. But specific analysis of chromosomes 13 and 17 territories highlights an influence of chromosome 17 for the positioning of the fused chromosomes within the nucleus. We also observed a specific clustering of centromeres depending of the chromosome subtypes. Altogether our results showed that chromosome fusion does not significantly alter sperm nucleus architecture but suggest that centromere remodelling after chromosome fusion locally impacts chromosome positioning.

Impact of reciprocal translocation t (18; 21) on male infertility and embryo development: lessons from an oocyte-donating ICSI cycle

PURPOSE

To report the outcome of intracytoplasmic sperm injection (ICSI) cycles of an oligozoospermic man with reciprocal translocation.

METHODS

Two ICSI cycles were given to a 29-year-old man with severe oligozoospermia and reciprocal translocation t(18;21)(p11;q21) and his wife. In the first cycle, no sperm were found in his semen and all 15 oocytes retrieved were donated to another infertile couple suffering from oligozoospermia and premature ovarian failure. In the second cycle, sperm from the husband's ejaculate were used to fertilize 13 retrieved oocytes.

RESULTS

Eleven embryos were acquired and a healthy girl was born in the oocyte-donated ICSI cycle. In the second cycle, 6 embryos were acquired and only biochemical pregnancy was achieved after three times of embryo transfer.

CONCLUSIONS

By the unusual oocyte-donating ICSI procedures, impact of the new reported reciprocal translocation t (18; 21) (p11; q21) on male fertility and embryo development was suggested.

A t(5;16)(p15.32;q23.3) generating 16q23.3 --> qter duplication and 5p15.32 --> pter deletion in two siblings with mental retardation, dysmorphic features, and speech delay

We report on two siblings (half brothers on the paternal side) with a syndrome consisting of delayed development, cardiac anomalies, chest deformity, hip rotation, metatarsus adductus, genital hypoplasia, dysmorphic face, depressed nasal bridge, mental retardation, and speech delay. All metaphases examined showed a normal karyotype in the patients, their father, and both mothers. High-resolution array CGH examination revealed a 16q (6 Mb) duplication dup(16)(16q23.3 --> 16qter) and a 5p (0.97 Mb) terminal deletion del(5)(p15.32 --> pter) in both affected boys but not their healthy siblings or parents. Interphase fluorescence in situ hybridization (FISH) confirmed both the 16q duplicated region and the 5p terminal deletion. Clinical abnormalities in the patients included thin upper lip, clinodactyly, and foot deformity, which were reported previously with duplications in 16q23.3. Pectus excavatum, hip rotation, metatarsus adductus, umbilical hernia, brachycephaly, and esotropia were not reported previously in chromosome 16q duplications but may be features that occur intermittently. The 5p deleted region has been associated previously only with speech delay, which was present in both patients. These patients display certain phenotypic characteristics not reported previously in 16q duplication and confirm 5p terminal deletion as an important chromosome anomaly for speech delay.

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.

Diagnostic applications of fluorescence in situ hybridization

BACKGROUND

Fluorescence in situ hybridization (FISH) assays are indispensable in diagnostics and research. Routine application of this so-called molecular cytogenetic technique on human chromosomes started in 1986. Since then, a huge variety of different approaches for chromosomal differentiation based on FISH has been described. It was established to characterize marker chromosomes identified in conventional banding analysis as well as cryptic rearrangements not resolved by standard cytogenetics.

OBJECTIVE/METHOD

Even though molecular cytogenetics, like banding cytogenetics for almost 40 years, is often called dead now, it offers unique possibilities of single cell analysis. Thus, a review is presented here on the available diagnostic-relevant FISH methods and probe sets applied in routine pre- and postnatal clinical as well as tumor cytogenetics.

CONCLUSION

Molecular cytogenetics is a fast, straightforward and reliable tool that is indispensable in cytogenetic diagnostics. It is and will continue to be of high clinical impact in diagnostics, especially in the overwhelming majority of routine cytogenetic laboratories that cannot afford and do not need high-throughput chip-based platforms for their daily work.

Interindividual differences and alterations in the topology of chromosomes in human sperm nuclei of fertile donors and carriers of reciprocal translocations

Recently it has been shown that the nucleus of the human spermatozoon appears to possess a specific architecture. The current prevailing view is that spatial organization of the male genome contains information critical for the spermatozoon's function as well as for early embryonic development. The purpose of this study was to determine whether there are alterations in intranuclear localization of centromeres in spermatozoa of chromosomes associated with particular reciprocal chromosome translocations (RCT). We analyzed the longitudinal and spatial localization of centromeres of selected chromosomes in sperm nuclei of four control males with normal karyotypes as well as in six carriers of reciprocal chromosome translocations: t(1;7), t(7;2), t(7;13), t(7;9), t(9;14), and t(4;13). Our study revealed that chromosomes with translocations may have shifted their intranuclear localization and that these translocations may influence the localization of other chromosomes in sperm nuclei. The chromocenter in sperm nuclei of translocation carriers was widened toward the apical side in comparison with chromocenter sites visible in control males. Our study also revealed interindividual differences in the localization of the Y chromosome centromere in the chromocenter area of sperm from fertile individuals.