Chromosomal Aberrations and Aneuploidies of Spermatozoa

Does reciprocal translocation affect the meiotic segregation products of non-translocation chromosomes?

This retrospective cohort study aimed to assess the effect of chromosomal reciprocal translocation on meiotic segregation products of non-translocation chromosomes. A total of 744 reciprocal translocation carriers and 875 non-carriers were included in this study. A total of 6,832 blastocysts were biopsied and tested by next-generation sequencing. Blastocysts from the carrier group were classified into five subgroups according to the theoretical segregation pattern of quadrivalent structure. For carrier patients, normal meiotic segregation products of the non-translocation chromosome were classified after excluding the segregation modes of the quadrivalent structure. The proportion of normal non-translocation chromosome meiotic segregation products was similar between the carrier and noncarrier groups (p = 0.69). The generalized Estimation Equation revealed that there was no correlation between reciprocal translocation and meiotic segregation products of non-translocation chromosomes. Moreover, subgroup analyses showed that the segregation modes of quadrivalent structure (p = 0.00) and carrier's gender (p = 0.00) may affect the meiotic segregation products of non-translocation chromosomes. In conclusion, reciprocal translocation does not directly reduce the proportion of normal segregation products of non-translocation chromosomes. The difference among subgroups of different quadrivalent segregation patterns implied that interchromosomal effect may exist but the high incidence of chromosomal abnormalities for reciprocal translocation carriers should not be attributed to interchromosomal effect.

Sperm and Oocyte Chromosomal Abnormalities

Gametogenesis, the process of producing gametes, differs significantly between oocytes and sperm. Most oocytes have chromosomal aneuploidies, indicating that chromosomal aberrations in miscarried and newborn infants are of oocyte origin. Conversely, most structural anomalies are of sperm origin. A prolonged meiotic period caused by increasing female age is responsible for an increased number of chromosomal aberrations. Sperm chromosomes are difficult to analyze because they cannot be evaluated using somatic cell chromosome analysis methods. Nevertheless, researchers have developed methods for chromosome analysis of sperm using the fluorescence in situ hybridization method, hamster eggs, and mouse eggs, allowing for the cytogenetic evaluation of individual sperm. Reproductive medicine has allowed men with severe spermatogenic defects or chromosomal abnormalities to have children. However, using these techniques to achieve successful pregnancies results in higher rates of miscarriages and embryos with chromosomal abnormalities. This raises questions regarding which cases should undergo sperm chromosome analysis and how the results should be interpreted. Here, we reviewed clinical trials that have been reported on oocyte and sperm chromosome analyses. Examination of chromosomal abnormalities in gametes is critical in assisted reproductive technology. Therefore, it is necessary to continue to study the mechanism underlying gametic chromosomal abnormalities.

Effect of chronic sleep deprivation on acrosomal integrity and functional parameters of murine sperm

OBJECTIVE

To evaluate the effect of chronic sleep deprivation on sperm function quality in mice.

DESIGN

Experimental study.

SETTING

Not applicable.

ANIMALS

Spermatozoa from twenty-four 10-week-old C57BL/6J male mice.

INTERVENTION(S)

The sleep deprivation group underwent gentle handling for 6 hours for 5 consecutive days. The mice in the sleep recovery group were allowed to sleep during the 24-hour period after the sleep deprivation protocol.

MAIN OUTCOME MEASURE(S)

After euthanasia, the spermatozoa were collected for analysis. Sperm motility was evaluated using computer-assisted sperm analyzer. Intracellular superoxide anion (O₂^-) activity, acrosome integrity, mitochondrial activity, and DNA fragmentation assays were conducted afterward.

RESULT(S)

Sleep deprivation and sleep recovery groups presented a lower percentage of spermatozoa with an intact acrosome, compared with the respective control groups. Regarding DNA fragmentation, a decreased proportion of spermatozoa with Comet I class intact DNA was observed in the sleep recovery group, compared with the recovery control group. Beat cross frequency was increased in the sleep recovery group.

CONCLUSION(S)

Sleep deprivation can reduce sperm quality, impairing acrosome integrity. Sleep recovery decreased DNA integrity and increased beat cross frequency.

The relevance of sperm morphology in male infertility

This brief report concerns the role of human sperm morphology assessment in different fields of male infertility: basic research, genetics, assisted reproduction technologies, oxidative stress. One of the best methods in studying sperm morphology is transmission electron microscopy (TEM) that enables defining the concept of sperm pathology and classifying alterations in non-systematic and systematic. Non-systematic sperm defects affect head and tail in variable ratio, whereas the rare systematic defects are characterized by a particular anomaly that marks most sperm of an ejaculate. TEM analysis and fluorescence in situ hybridization represent outstanding methods in the study of sperm morphology and cytogenetic in patients with altered karyotype characterizing their semen quality before intracytoplasmic sperm injection. In recent years, the genetic investigations on systematic sperm defects, made extraordinary progress identifying candidate genes whose mutations induce morphological sperm anomalies. The question if sperm morphology has an impact on assisted fertilization outcome is debated. Nowadays, oxidative stress represents one of the most important causes of altered sperm morphology and function and can be analyzed from two points of view: 1) spermatozoa with cytoplasmic residue produce reactive oxygen species, 2) the pathologies with inflammatory/oxidative stress background cause morphological alterations. Finally, sperm morphology is also considered an important endpoint in in vitro experiments where toxic substances, drugs, antioxidants are tested. We think that the field of sperm morphology is far from being exhausted and needs other research. This parameter can be still considered a valuable indicator of sperm dysfunction both in basic and clinical research.

Growth performance and reproductive function impairment of glyphosate-based herbicide in male guinea pig (Cavia porcellus)

Glyphosate formulations, widely applied non-selective systemic herbicides, are progressively becoming the most controversial pesticides on the market due the adverse effects they pose to humans and environment. The information on these potential hazardous effects to the handlers of the pesticide remains obscure. This study investigated effects of glyphosate-based herbicide on growth performance, seminal parameters and hemato-biochemical profiles in male guinea pig. Forty sexually mature male guinea pigs weighing between 393.3 and 418.4 g were divided into four groups of 10 animals each and orally administered 0, 186, 280 and 560 mg/kg body weight of WILLOSATE daily for 60 days. Daily feed intake and body weight gain were recorded. At the end of experimental period all animals were humanely sacrificed, and blood samples and vital organs were collected for appropriate analysis. Results showed a significant decrease (p < 0.05) in body weight gain (-102.2%), final body weight (-9.8%) and feed intake (-13.1%) of animals following sub-chronic exposure of WILLOSATE. The weights of the liver and kidney increased significantly (p < 0.05) by 25.4% and 28.8%, respectively, while testicular weights decreased (p < 0.05) by 24% with increasing doses of WILLOSATE. A decrease in sperm motility (-67.9%), viability (-52.7%) and concentration per vas deferens (-40.7%), and an increase in sperm major (28.1%) and minor (45.3%) morphological aberrations were recorded in WILLOSATE - exposed guinea pigs when compared to controls. There was a dose-dependent increase (p < 0.05) in MCV and WBC and a decrease in Hb content and RBC, as well as serum content in total protein (-11.8%). The serum content of cholesterol (37.8%), urea (87.1%), creatinine (22.4%), ALAT (74.2%) and ASAT (88.7%) were significantly higher in treated groups compared to controls. These results point toward the toxic effects of WILLOSATE on vital organs and reproductive function of the body at high doses and long-term exposure.

Frequency of Sperm Aneuploidy in Oligoasthenoteratozoospermic (OAT) Patients by Comprehensive Chromosome Screening: A Proof of Concept

Background:

Embryonic aneuploidy usually results in implantation failure and miscarriage. Considering significantly high frequency of sperm aneuploidy reported in oligoasthenoteratozoospermia (OAT) using fluorescence in situ hybridization (FISH) in limited number of chromosomes and lack of comprehensive chromosome screening (CCS) in OAT, the aim of this study was applying CCS in OAT sperm and comparison of the results with FISH findings.

Methods:

Five OAT patients with normal blood karyotypes and history of implantation failure were included. The successfully amplified samples, each containing two sperm, were analyzed by array comparative genomic hybridization (aCGH). FISH was utilized mainly depending on the aneuploidies found by aCGH to assess their frequencies in total sperm population.

Results:

In aCGH for 30 sperm, aneuploidy was found in 66% of samples. Following the study of 4300 sperm by FISH, an average of 55.46% aneuploidy was observed. No pregnancy was resulted with normal partners.

Conclusion:

Using aCGH, some abnormalities were observed that are not typically considered in sperm FISH studies. Despite small sample size of the comprehensive study, like other similar studies, the frequency of aneuploidies was considerable and similar to FISH. Aneuploidies revealed by aCGH at single sperm resolution were different from sperm population detected by FISH. Considering high frequency of aneuploidy in OATs sperm, preimplantation genetic testing for aneuploidy (PGT-A) can be used for in transfer of chromosomally normal embryos.

How much, if anything, do we know about sperm chromosomes of Robertsonian translocation carriers?

In men with oligozoospermia, Robertsonian translocations (RobTs) are the most common type of autosomal aberrations. The most commonly occurring types are rob(13;14) and rob(14;21), and other types of RobTs are described as 'rare' cases. Based on molecular research, all RobTs can be broadly classified into Class 1 and Class 2. Class 1 translocations produce the same breakpoints within their RobT type, but Class 2 translocations are predicted to form during meiosis or mitosis through a variety of mechanisms, resulting in variation in the breakpoint locations. This review seeks to analyse the available data addressing the question of whether the molecular classification of RobTs into Classes 1 and 2 and/or the type of DD/GG/DG symmetry of the involved chromosomes is reflected in the efficiency of spermatogenesis. The lowest frequency value calculated for the rate of alternate segregants was found for rob(13;15) carriers (Class 2, symmetry DD) and the highest for rob(13;21) carriers (Class 2, DG symmetry). The aneuploidy values for the rare RobT (Class 2) and common rob(14;21) (Class 1) groups together exhibited similarities while differing from those for the common rob(13;14) (Class 1) group. Considering the division of RobT carriers into those with normozoospermia and those with oligoasthenozoospermia, it was found that the number of carriers with elevated levels of aneuploidy was unexpectedly quite similar and high (approx. 70%) in the two subgroups. The reason(s) that the same RobT does not always show a similar destructive effect on fertility was also pointed out.

Sperm chromosome abnormalities in patients with normal karyotype and in translocation carriers: clinical relevance for assisted reproductive technology

RESEARCH QUESTION

What is the proportion of chromosomally abnormal spermatozoa in men with a history of reproductive failure, including patients with normal karyotype and carriers of translocations? Should this analysis be included in a clinical setting to define the best treatment options for infertile couples?

DESIGN

Aneuploidy for chromosomes XY, 13, 15, 16, 17, 18, 21, 22 was tested by fluorescent in-situ hybridization (FISH) in 1665 samples from couples with normal karyotype having had at least three previous IVF failures, miscarriages, or both (group-A). A FISH test was also carried out in 76 samples from carriers of translocations (group B) to detect the proportion of spermatozoa with unbalanced rearrangement.

RESULTS

In group A, the lowest incidence of aneuploid sperm cells was found in men with normozoospermia (1.3%, range 0.09-6.31%) compared with men with moderate oligoasthenoteratozoospermia (2.1%, range 0.41-16.6%, P < 0.001), severe oligoasthenoteratozoospermia (4.7%, range 0.53-30.77, P < 0.001), microepididymal sperm aspiration (3.1%, range 1.19-24.24, P < 0.001) and testicular sperm extraction samples (5.8%, range 1.54-33.3, P < 0.001). In group B, the proportion of spermatozoa with unbalanced rearrangement was significantly higher in reciprocal (63%, range 10.0-87.6%) than in Robertsonian translocations (16%, range 4.3-51.0%, P < 0.001).

CONCLUSIONS

Patients with poor prognosis of term pregnancy tend to generate high proportions of chromosomally abnormal spermatozoa, especially in severe male factor cases. Corresponding frequencies occur at wide ranges; therefore, the FISH test is needed to assess the proportion of spermatozoa with altered chromosome condition. A flowchart, which included the FISH test, was designed to assist clinicians guide couples with poor prognosis of pregnancy, on the most indicated treatment options.

Genetics in human reproduction

Approximately 50% of the causes of infertility are of genetic origin. The objective of this study was to analyze the role of genetics in human reproduction by reviewing the main genetic causes of infertility and the use of preimplantation genetic testing in Brazil. This literature review comprised articles in English and Portuguese published on databases PubMed, Scielo, and Bireme from 1990 to 2019. Randomized clinical trials and specialized guidelines were given preference whenever possible. Genetic cause can be traced back to up to 20% of the cases of severe azoospermia or oligozoospermia. Subjects with these conditions are good candidates for genetic screening. In women, genetic causes of infertility (fragile X syndrome, X-trisomy, and Turner's syndrome, some of which diagnosed with karyotyping) culminate with premature ovarian failure. Genetic screening helps advise couples of the risk of experiencing early reproductive capacity loss and of the chances of their offspring carrying genetic disorders. In addition to enhancing the prevention of serious diseases in the offspring of couples at increased risk of genetic diseases, preimplantation genetic screening improves the success rates of assisted reproduction procedures by allowing the selection of euploid embryos for transfer. The interface between genetics and human reproduction has gained significant relevance, but discussions are still needed on which procedures are clinically and ethically acceptable and how they should be regulated.

Interchromosomal effect: Report of a father and son, bearing different translocations of the same chromosome, and a review of the current literature

Interchromosomal effect is a controversial phenomenon postulating that during gametogenesis of translocation carriers, aside from the unbalanced segregation of chromosomes involved in the translocation, other, structurally normal chromosomes might also be affected and segregated abnormally. Here, we present a balanced reciprocal translocation carrier t(15;20)(q11;p13), and his son, bearing a different translocation of chromosome 15, t(15;Y)(q11;q12). To further elucidate the so-far-controversial interchromosomal effect phenomenon, published original articles and case reports about interchromosomal effect were reviewed. The father was a carrier of t(15;20)(q11;p13). His wife's karyotype was normal. During a pregnancy occurred without any preceding procedure, amniocentesis was recommended to the family and performed. Result of the amniocentesis revealed a different translocation of chromosome 15; t(15;Y)(q11;q12). To our knowledge, this is the first report of two generations within a family, bearing different translocations of a chromosome. On top of all previous studies investigating ICE, our case adds an important finding, showing not only the rate of aneuploidies of structurally normal chromosomes, but also the rate of this 'alternating translocations' might be increased in translocation carriers, and this could be an important clue about interchromosomal effects.

Male Infertility in Robertsonian Translocation: A Case Report

Case series

Patients: Male, 34-year-old • Male, 35-year-old

Final Diagnosis: Primary infertility • Robertsonian translocation

Symptoms: Asymptomatic

Medication: —

Clinical Procedure: —

Specialty: Urology

The role of total chromosomal disomy in human spermatozoa as a predictor of the outcome of pre-implantation genetic screening

OBJECTIVE

To assess the efficacy of sperm disomy rate as a predictor of preimplantation genetic screening (PGT-A) outcomes.

DESIGN

Retrospective cohort study.

SETTING

Andrology laboratory and in vitro fertilization center.

PATIENT(S)

All patients (n = 123) who underwent sperm fluorescence in situ hybridization and PGT-A at the China International Trust and Investment Corporation Xiangya Reproductive and Genetic Hospital between January 2015 and November 2018 were included.

INTERVENTION(S)

Sperm samples of all patients evaluated for elevated disomy levels of 24 chromosomes using multicolor sperm fluorescence in situ hybridization and all embryos were cultured and biopsied at the blastocyst stage for PGT-A.

MAIN OUTCOME MEASURE(S)

The relationship between the whole genome of sperm disomy rate and PGT-A outcome and the predictive effect of the whole genome of sperm disomy rate on PGT-A outcome.

RESULT(S)

A statistically significant correlation was observed between the sperm disomy rate and PGT-A outcome. Many confounders were considered, such as patients' factors, semen or laboratory characteristics, which may affect PGT-A outcome. Regression analysis excluding these confounding factors indicated a 2.071-fold decrease in odds of probability of not obtaining any euploid embryo to transfer for every 1% decrease in total disomy rate. Based on a total disomy rate threshold of 4.84%, the prediction ability of total disomy rate on PGT-A outcome reached 75.6%.

CONCLUSION(S)

There is a negative correlation between the whole genome of sperm disomy rate and PGT-A outcome. It is a potential role for whole genome of sperm disomy rate in the PGT-A patients as a predictor, as well as in future genetic counselling. Based on these results, genetic counselors can advise couples on the risk of not obtaining any euploid embryo and help them choose the best reproductive and diagnostic method.

The use of fluorescence in situ hybridization analysis on sperm: indications to perform and assisted reproduction technology outcomes

PURPOSE

To determine the consequences of an altered sperm fluorescence in situ hybridization (FISH) result for ART outcomes and the indications for a sperm FISH analysis.

METHODS

Data from 439 infertile men were collected. Bivariate analyses were performed to determine the association of men's age, seminal alterations, and sperm FISH indication, with the incidence of X, Y, 13, 18, and 21 sperm chromosomal abnormalities. A multivariate logistic regression analysis was performed to establish the most predictive variables for altered sperm FISH. Results from the IVF/ICSI cycles were collected for 248 out of 439 patients. Two distinct groups were established: 151 couples that used their own oocytes and 97 couples involved in egg donation programs. In both groups, ART outcomes were compared between normal and altered sperm FISH.

RESULTS

Teratozoospermia and oligozoospermia were associated with sperm chromosome anomalies (p < 0.05). Indications for sperm FISH analysis with the highest predictability were teratozoospermia, male age, oligozoospermia, and implantation failure (AUC = 0.702). Embryo quality (p = 0.096), pregnancy rate (p = 0.054), and implantation rate (p = 0.089) were higher in own-oocytes couples with normal sperm FISH than in altered sperm FISH couples, although differences were not statistically significant. In donor-oocytes couples, in which high-quality embryos were transferred later than in own-oocytes couples (3.8 vs. 3.0 days), we did not identify differences in the ART outcome between normal and altered sperm FISH couples. In both groups, the possible interference of woman age was negligible.

CONCLUSIONS

Sperm FISH is indicated in middle-aged oligoteratozoospermic patients with implantation failures in previous IVF/ICSI cycles. Sperm chromosome anomalies have a moderate detrimental impact on embryo quality, implantation, and pregnancy rates.

Male infertility: establishing sperm aneuploidy thresholds in the laboratory

PURPOSE

Fluorescence in situ hybridization (FISH) in spermatozoa provides an estimate of the frequency of chromosomal abnormalities, but there is not a clinical consensus on how to statistically analyze sperm FISH results. We therefore propose a statistical approach to establish sperm aneuploidy thresholds in a fertile population.

METHODS

We have determined the distribution and variation of the frequency of nullisomy, disomy, and diploidy for a set of 13 chromosomes (1, 2, 9, 13, 15, 16, 17, 18, 19, 21, 22, X, and Y) in sperm nuclei from 14 fertile men by means of automatized FISH. The dispersion of data has been analyzed by the non-parametric Wilcoxon Rank Sum test. We have established the threshold values for each chromosome and aneuploidy type on the basis of the confidence interval values (99.9%).

RESULTS

Nullisomy thresholds ranged from 0.49% for chromosome 19 to 3.09% for chromosome 22; disomy thresholds ranged from 0.30% for chromosome 21 to 1.47% for chromosome 15; diploidy thresholds ranged from 0.24% for the 9/19 chromosome set to 1.21% for the 13/21 chromosome set.

CONCLUSIONS

Applying this approach with clinical purposes will enable us to categorize the patient as altered or normal regarding his sperm aneuploidy. Any result surpassing the cited threshold values indicates a 99.9% probability of being significantly different from fertile controls.

A novel male 2;4;14 complex chromosomal translocation with normal semen parameters but 100% embryonic aneuploidy

We report a case of a couple with a history of six spontaneous miscarriages in which a novel complex chromosomal rearrangement was detected in the male partner who had a totally normal semen analysis. Preimplantation genetic testing of their embryos demonstrated 100% aneuploidy.

Sperm DNA fragmentation and sex chromosome aneuploidy after swim-up versus density gradient centrifugation

OBJECTIVE

The aim of this study was to compare the efficacy of swim-up and density gradient centrifugation (DGC) for reducing the amount of sperm with fragmented DNA, sex chromosome aneuploidy, and abnormal chromatin structure.

METHODS

Semen samples were obtained from 18 healthy male partners who attended infertility clinics for infertility investigations and were processed with swim-up and DGC. The percentages of sperm cells with fragmented DNA measured by the sperm chromatin dispersion test, normal sex chromosomes assessed by fluorescence in situ hybridization, and abnormal chromatin structure identified by toluidine blue staining were examined.

RESULTS

The percentage of sperm cells with fragmented DNA was significantly lower in the swim-up fraction (9.7%, p=0.001) than in the unprocessed fraction (27.0%), but not in the DGC fraction (27.8%, p=0.098). The percentage of sperm cells with normal X or Y chromosomes was comparable in the three fractions. The percentage of sperm cells with abnormal chromatin structure significantly decreased after DGC (from 15.7% to 10.3%, p=0.002). The swim-up method also tended to reduce the percentage of sperm cells with abnormal chromatin structure, but the difference was not significant (from 15.7% to 11.6%, p=0.316).

CONCLUSION

The swim-up method is superior for enriching genetically competent sperm.

Preliminary analysis of numerical chromosome abnormalities in reciprocal and Robertsonian translocation preimplantation genetic diagnosis cases with 24-chromosomal analysis with an aCGH/SNP microarray

PURPOSE

The aim of this study was to determine whether an interchromosomal effect (ICE) occurred in embryos obtained from reciprocal translocation (rcp) and Robertsonian translocation (RT) carriers who were following a preimplantation genetic diagnosis (PGD) with whole chromosome screening with an aCGH and SNP microarray. We also analyzed the chromosomal numerical abnormalities in embryos with aneuploidy in parental chromosomes that were not involved with a translocation and balanced in involved parental translocation chromosomes.

METHODS

This retrospective study included 832 embryos obtained from rcp carriers and 382 embryos from RT carriers that were biopsied in 139 PGD cycles. The control group involved embryos obtained from age-matched patient karyotypes who were undergoing preimplantation genetic screening (PGS) with non-translocation, and 579 embryos were analyzed in the control group. A single blastomere at the cleavage stage or trophectoderm from a blastocyst was biopsied, and 24-chromosomal analysis with an aCGH/SNP microarray was conducted using the PGD/PGS protocols. Statistical analyses were implemented on the incidences of cumulative aneuploidy rates between the translocation carriers and the control group.

RESULTS

Reliable results were obtained from 138 couples, among whom only one patient was a balanced rcp or RT translocation carrier, undergoing PGD testing in our center from January 2012 to June 2014. For day 3 embryos, the aneuploidy rates were 50.7% for rcp carriers and 49.1% for RT carriers, compared with the control group, with 44.8% at a maternal age < 36 years. When the maternal age was ≥ 36 years, the aneuploidy rates were increased to 61.1% for rcp carriers, 56.7% for RT carriers, and 60.3% for the control group. There were no significant differences. In day 5 embryos, the aneuploidy rates were 24.5% for rcp carriers and 34.9% for RT carriers, compared with the control group with 53.6% at a maternal age < 36 years. When the maternal age was ≥ 36 years, the aneuploidy rates were 10.7% for rcp carriers, 26.3% for RT carriers, and 57.1% for the control group. The cumulative aneuploidy rates of chromosome translocation carriers were significantly lower than the control group. No ICE was observed in cleavage and blastocyst stage embryos obtained from these carriers. Additionally, the risk of chromosomal numerical abnormalities was observed in each of the 23 pairs of autosomes or sex chromosomes from day 3 and day 5 embryos.

CONCLUSION

There was not enough evidence to prove that ICE was present in embryos derived from both rcp and RT translocation carriers, regardless of the maternal age. However, chromosomal numerical abnormalities were noticed in 23 pairs of autosomes and sex chromosomes in parental structurally normal chromosomes. Thus, 24-chromosomal analysis with an aCGH/SNP microarray PGD protocol is required to decrease the risks of failure to diagnose aneuploidy in structurally normal chromosomes.

Genetic diagnostics of male infertility in clinical practice

Approximately 15% of couples are infertile. Male factors contribute to infertility in over 50% of cases. Identifiable genetic abnormalities contribute to 15%-20% of the most severe forms of male infertility, azoospermia. In this chapter, we explore known genetic causes of male infertility such as Klinefelter syndrome, XYY men, Kallmann syndrome, y-microdeletions, Robertsonian translocations, autosomal inversions, mixed gonadal dysgenesis, x-linked and autosomal gene mutations, and cystic fibrosis transmembrane conductance regulator abnormalities. We also briefly comment on novel biomarkers for male infertility.

The Importance of Cytogenetics and Associated Molecular Techniques in the Management of Patients Carrying Robertsonian Translocation and Their Pregnancy Outcome by Intracytoplasmic Sperm Injection

Objective

The present study outlines three cases of a Robertsonian translocation and the consequences for the initiation of pregnancy by intracytoplasmic sperm injection (ICSI). Three case histories are presented documenting structural chromosome abnormalities in infertile males.

Materials and Methods

Semen analysis was performed according to the World Health Organization guidelines. Chromosome analysis was performed using G-banding. Y chromosome microdeletions were detected by multiplex polymerase chain reaction assays.

Results

Cytogenetic analysis revealed Robertsonian translocation 45,XY,der(14;21)(q10;q10) in a male with severe oligoasthenoteratozoospermia (SOAT) after three subsequent ICSI treatments were unsuccessful. The second case involved a Robertsonian translocation 45,XY,der(13,14)(q10;q10) with SOAT detected in a male after one pregnancy loss. Third case involved a Robertsonian translocation 45,XY,der(13,14)(q10;q10) with SOAT.

Conclusion

This case series emphasize the necessity of cytogenetic analysis of couples with primary infertility and recurrent miscarriages before any assisted reproductive technology is performed. For couples in whom one or more partners have a translocation, prenatal genetic diagnosis/preimplantation genetic diagnosis is recommended.

PARP3 is a promoter of chromosomal rearrangements and limits G4 DNA

Chromosomal rearrangements are essential events in the pathogenesis of both malignant and nonmalignant disorders, yet the factors affecting their formation are incompletely understood. Here we develop a zinc-finger nuclease translocation reporter and screen for factors that modulate rearrangements in human cells. We identify UBC9 and RAD50 as suppressors and 53BP1, DDB1 and poly(ADP)ribose polymerase 3 (PARP3) as promoters of chromosomal rearrangements across human cell types. We focus on PARP3 as it is dispensable for murine viability and has druggable catalytic activity. We find that PARP3 regulates G quadruplex (G4) DNA in response to DNA damage, which suppresses repair by nonhomologous end-joining and homologous recombination. Chemical stabilization of G4 DNA in PARP3-/- cells leads to widespread DNA double-strand breaks and synthetic lethality. We propose a model in which PARP3 suppresses G4 DNA and facilitates DNA repair by multiple pathways.

Meiotic pairing and gene expression disturbance in germ cells from an infertile boar with a balanced reciprocal autosome-autosome translocation

Individuals carrying balanced constitutional reciprocal translocations generally have a normal phenotype, but often present reproductive disorders. The aim of our research was to analyze the meiotic process in an oligoasthenoteratospermic boar carrying an asymmetric reciprocal translocation involving chromosomes 1 and 14. Different multivalent structures (quadrivalent and trivalent plus univalent) were identified during chromosome pairing analysis. Some of these multivalents were characterized by the presence of unpaired autosomal segments with histone γH2AX accumulation sometimes associated with the XY body. Gene expression in spermatocytes was studied by RNA-DNA-FISH and microarray-based testis transcriptome analysis. Our results revealed a decrease in gene expression for chromosomes 1 and 14 and an up-regulated expression of X-chromosome genes for the translocated boar compared with normal individuals. We hypothesized that the observed meiotic arrest and reproductive failure in this boar might be due to silencing of crucial autosomal genes (MSUC) and disturbance of meiotic sex chromosome inactivation (MSCI). Further analysis revealed abnormal meiotic recombination (frequency and distribution) and the production of a high rate of unbalanced spermatozoa.

Disruption of dmc1 Produces Abnormal Sperm in Medaka (Oryzias latipes)

DMC1 is a recombinase that is essential for meiotic synapsis. Experiments in extensive species of eukaryotes have indicated the independent role of DMC1 in repairing double strand breaks (DSBs) produced during meiosis I. Mutation of dmc1 in mice and human often leads to obstacles in spermatogenesis and male sterility. Here, we report on the disruption of dmc1 in male medaka (Oryzias latipes). Synapsis was disturbed in the mutant medaka testis nuclei, as observed in mice and other organisms. Unexpectedly, the mutant medaka could produce a few sperm and, although most of these had multiple tail or multiple head malformations, some of them could swim, and few of them even had insemination ability. Our transcriptome analysis showed that there was not a remarkable change in the expression of most of the genes involved in the pathways associated with the meiotic DNA repair and flagella assembly. Our results provided an indication of the accessory mechanisms that might be involved in the repair of DSBs during meiosis. In a species besides humans, we provided evidence that disorders in meiosis recombination might lead to the malformation of sperm.

Fertility Assessment in Sorraia Stallions by Sperm-Fish and Fkbp6 Genotyping

The Sorraia, a critically endangered indigenous Iberian horse breed, is characterized by low genetic variability, high rate of inbreeding, bad sperm quality and subfertility. Here, we studied 11 phenotypically normal but subfertile Sorraia stallions by karyotyping, sex chromosome sperm-FISH and molecular analysis of FKBP6 - a susceptibility locus for impaired acrosome reaction (IAR). The stallions had normal sperm concentration (>300 million cells/ml), but the numbers of progressively motile sperm (21%) and morphologically normal sperm (28%) were invariably low. All stallions had a normal 64,XY karyotype. The majority of sperm (89%) had normal haploid sex chromosome content, although 11% of sperm carried various sex chromosome aneuploidies. No correlation was found between the percentage of sperm sex chromosome abnormalities and inbreeding, sperm morphology or stallion age. Direct sequencing of FKBP6 exon 4 for SNPs g.11040315G>A and g.11040379C>A revealed that none of the stallions had the susceptibility genotype (A/A-A/A) for IAR. Instead, all animals had a G/G-A/A genotype - a testimony of low genetic variability. The findings ruled out chromosomal abnormalities and genetic predisposition for IAR as contributing factors for subfertility. However, low fertility of the Sorraia stallions could be partly attributed to relatively higher rate of sex chromosome aneuploidies in the sperm.

Is the interchromosomal effect present in embryos derived from Robertsonian and reciprocal translocation carriers particularly focusing on chromosome 10 rearrangements?

The aim of this study was to analyse the possible occurrence of the interchromosomal effect (ICE) in human preimplantation embryos obtained from Robertsonian and reciprocal translocation carriers focusing on ones with chromosome 10 rearrangements who were undergoing preimplantation genetic diagnosis (PGD) and to investigate whether offering aneuploidy screening would be beneficial to these patients. Cleavage stage embryos from translocation carriers undergoing PGD were biopsied. Multicolour fluorescence in situ hybridisation for the chromosomes involved in the translocation in addition to nine more chromosomes (13, 15, 16, 17, 18, 21, 22, X and Y) was used in the analysis. The control group involved embryos obtained from age-matched patients undergoing preimplantation genetic screening (PGS). Cumulative aneuploidy rate in embryos derived from both Robertsonian and reciprocal translocation carriers was found to be similar with the control group. Therefore no ICE was observed in cleavage stage embryos obtained from these carriers. More than half of the embryos with chromosome 10 rearrangements had aneuploidy for which an increased aneuploidy rate was more apparent in male carriers. Thus, it is possible that there is a risk of ICE in reciprocal carriers with chromosome 10 rearrangements. This study showed that there is no ICE in embryos derived from Robertsonian and reciprocal translocation carriers. However high rates of aneuploidy in structurally normal chromosomes were detected in embryos derived from these carriers and thus aneuploidy screening in addition to PGD may increase the pregnancy rates of these patients.

Clinical genetic testing for male factor infertility: current applications and future directions

Spermatogenesis involves the aggregated action of up to 2300 genes, any of which, could, potentially, provide targets for diagnostic tests of male factor infertility. Contrary to the previously proposed common variant hypothesis for common diseases such as male infertility, genome-wide association studies and targeted gene sequencing in cohorts of infertile men have identified only a few gene polymorphisms that are associated with male infertility. Unfortunately, the search for genetic variants associated with male infertility is further hampered by the lack of viable animal models of human spermatogenesis, difficulty in robustly phenotyping infertile men and the complexity of pedigree studies in male factor infertility. In this review, we describe basic genetic principles involved in understanding the genetic basis of male infertility and examine the utility and proper clinical use of the proven genetic assays of male factor infertility, specifically Y chromosome microdeletions, chromosomal translocations, karyotype, cystic fibrosis transmembrane conductance regulator mutation analysis and sperm genetic tests. Unfortunately, these tests are only able to diagnose the cause of about 20% of male factor infertility. The remainder of the review will be devoted to examining novel tests and diagnostic tools that have the potential to explain the other 80% of male factor infertility that is currently classified as idiopathic. Those tests include epigenetic analysis of the spermatozoa and the evaluation of rare genetic variants and copy number variations in patients. Success in advancing to the implementation of such areas is not only dependent on technological advances in the laboratory, but also improved phenotyping in the clinic.