Somatic chromosomal abnormalities in infertile men and women

Genomic aspects in reproductive medicine

Infertility is a complex disease characterized by extreme genetic heterogeneity, compounded by various environmental factors. While there are exceptions, individual genetic and genomic variations related to infertility are typically rare, often family-specific, and may serve as susceptibility factors rather than direct causes of the disease. Consequently, identifying the cause of infertility and developing prevention and treatment strategies based on these factors remain challenging tasks, even in the modern genomic era. In this review, we first examine the genetic and genomic variations associated with infertility, and subsequently summarize the concepts and methods of preimplantation genetic testing in light of advances in genome analysis technology.

Swimming trapper decreases the proportion of chromosomally unbalanced spermatozoa in human Robertsonian translocation carriers

BACKGROUND

Carriers of reciprocal translocations often have more unbalanced spermatozoa and higher DNA fragmentation rates, elevating reproductive risk. The simple swim-up method (SSUM) can decrease the amount of spermatozoa with abnormal chromatin structure and fragmented DNA, however, it has limited efficacy in eliminating chromosomally unbalanced sperm.

METHODS

The spermatozoa of eight Robertsonian translocation (Rob) carriers were split into three groups: original raw semen group (control group); SSUM and swimming trapper method group (STM) processed semen samples. After different semen preparation procedures, semen qualities, sperm chromosomal aneuploidy, and sperm fragmented DNA were evaluated.

RESULTS

Although spermatozoa with higher motility was obtained by both SSUM and STM, the population of faster forward moving sperm was greater with STM as compared to SSUM. While the rates of DNA fragmentation were statistically much lower in both groups than ejaculated semen sample, our data showed better effect on the decrease of DNA fragmentation index (DFI) after selection by STM for patients who have high DFI (>20%) in neat semen. For all patients, significant decrease in the frequency of chromosomally unbalanced spermatozoa was observed after selection using STM. Although similar trends can be seen in the SSUM group, a significant difference was identified in one patient only.

CONCLUSIONS

Use of swimming trapper (STM) is superior for enriching high-motile and genetically competent sperm in comparison with SSUM.

Preimplantation genetic testing in couples with balanced chromosome rearrangement: a four-year period real world retrospective cohort study

BACKGROUND

Couples with balanced chromosome rearrangement (BCR) are at high risk of recurrent miscarriages or birth defects due to chromosomally abnormal embryos. This study aimed to provide real-world evidence of the euploidy rate of blastocysts from couples with BCR using preimplantation genetic testing (PGT) and to guide pretesting genetic counselling.

METHODS

A continuous four-year PGT data from couples with BCR were retrospectively analyzed. Biopsied trophectoderm cells were amplified using whole genome amplification, and next-generation sequencing was performed to detect the chromosomal numerical and segmental aberrations. Clinical data and molecular genetic testing results were analyzed and compared among the subgroups.

RESULTS

A total of 1571 PGT cycles with 5942 blastocysts were performed chromosomal numerical and segmental aberrations detection during the four years. Of them, 1034 PGT cycles with 4129 blastocysts for BCR couples were included; 68.96% (713/1034) PGT cycles had transferable euploid embryos. The total euploidy rate of blastocysts in couples carrying the BCR was 35.29% (1457/4129). Couples with complex BCR had euploid blastocyst rates similar to those of couples with non-complex BCR (46.15% vs. 35.18%, P > 0.05). Chromosome inversion had the highest chance of obtaining a euploid blastocyst (57.27%), followed by Robertsonian translocation (RobT) (46.06%), and the lowest in reciprocal translocation (RecT) (30.11%) (P < 0.05). Couples with males carrying RobT had higher rates of euploid embryo both in each PGT cycles and total blastocysts than female RobT carriers did, despite the female age in male RobT is significant older than those with female RobT (P < 0.05). The proportions of non-carrier embryos were 52.78% (95/180) and 47.06% (40/85) in euploid blastocysts from couples with RecT and RobT, respectively (P > 0.05). RecT had the highest proportion of blastocysts with translocated chromosome-associated abnormalities (74.23%, 1527/2057), followed by RobT (54.60%, 273/500) and inversion (30.85%, 29/94) (P < 0.05).

CONCLUSIONS

In couples carrying BCR, the total euploidy rate of blastocysts was 35.29%, with the highest in inversion, followed by RobT and RecT. Even in couples carrying complex BCR, the probability of having a transferable blastocyst was 46.15%. Among the euploid blastocysts, the non-carrier ratios in RecT and RobT were 52.78% and 47.06%, respectively. RecT had the highest proportion of blastocysts with translocated chromosome-associated abnormalities.

Identification and interruption of inheritance of familial cryptic translocations: A case report

BACKGROUND

Cryptic translocations can be identified via genetic analysis of aborted tissues or malformed infants, but it is difficult to deduce the parental origins of the translocations. In the absence of such information, it is not easy to distinguish translocations from normal embryos during pre-implantation genetic testing, that seeks to block familial transmission of translocations.

METHODS

Here, we present a new method that detects cryptic translocations and blocks familial transmission thereof. Whole-genome, low-coverage mate-pair sequencing (WGLMPS) revealed chromosome breakpoint sequences, and preimplantation genetic haplotyping (PGH) was then used to discard embryos with cryptic translocations.

RESULTS

Cryptic translocations were found in all four families, and familial transmission was successfully blocked in one family.

CONCLUSION

Whole-genome, low-coverage mate-pair sequencing combined with preimplantation genetic haplotyping methods powerfully and practically identify cryptic translocations and block familial transmissions.

The effect of carrier characteristics and female age on preimplantation genetic testing results of blastocysts from Robertsonian translocation carriers

PURPOSE

To analyze factors affecting segregation and ploidy results from Robertsonian carriers, and determine chromosomes involved impact chromosome stability during meiosis and mitosis.

METHODS

This retrospective study include 928 oocyte retrieval cycles from 763 couples with Robertsonian translocations undergoing preimplantation genetic testing for structural rearrangements (PGT-SR) using next-generation sequencing (NGS) between December 2012 and June 2020.The segregation patterns of the trivalent of 3423 blastocysts were analyzed according to the carrier's sex and age. A total of 1492 couples who received preimplantation genetic testing for aneuploidy (PGT-A) were included as the control group and matched according to maternal age and testing time stage.

RESULTS

A total of 1728 (50.5%) normal/balanced embryos were identified from 3423 embryos diagnosed. The rate of alternate segregation in male Robertsonian translocation carriers was significantly higher than that in female carriers (82.3% vs. 60.0%, P < 0.001). However, the segregation ratio exhibited no difference between young and older carriers. Further, increasing maternal age decreased the proportion of transferable embryo cycle in both female and male carriers. And the ratio of chromosome mosaic from the Robertsonian translocation carrier group was significantly higher than that in the PGT-A control group (1.2% vs. 0.5%, P < 0.01).

CONCLUSIONS

The meiotic segregation modes were affected by the carrier sex and were independent of the carrier's age. Advanced maternal age decreased the probability of obtaining a normal/balanced embryo. In additional, the Robertsonian translocation chromosome could increase the possibility of chromosome mosaicism during mitosis in blastocysts.

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.

Pseudodicentric Chromosome Originating from an X-Autosome Translocation in a Male Patient with Cryptozoospermia

Genetic factors are responsible for 15% of male infertility conditions. Numerical and structural chromosomal anomalies are validated genetic factors leading to spermatogenic quantitative defects, with a frequency depending on the severity of the phenotype. Among the structural chromosomal rearrangements, dicentric chromosomes are generally observed in robertsonian translocations or in cases of Y chromosome isodicentrics. In X-autosome translocations, male carriers are generally infertile, regardless of the position of the breakpoint, due to interrupted spermatogenesis. We report an infertile man bearing an unusual balanced (X;22) translocation, with a centromeric X breakpoint generating a derivative pseudodicentric chromosome psu dic(22;X). Extensive cytogenetic analyses were necessary to determine the precise nature of the derivative chromosome. The likely cause of the reproductive phenotype of the patient is discussed based on meiotic chromosomal conformation.

Analysis of clinical outcomes and meiotic segregation modes following preimplantation genetic testing for structural rearrangements using aCGH/NGS in couples with balanced chromosome rearrangement

Purpose

To retrospectively evaluate the effectiveness of PGT‐SR by array comparative genomic hybridization (aCGH) or next‐generation sequencing (NGS) in preventing recurrent miscarriages.

Methods

Thirty one couples with balanced translocation who underwent 68 PGT‐SR cycles between 2012 and 2020 were evaluated. A total of 242 blastocysts were biopsied for aCGH or NGS. The genetically transferable blastocysts were transferred in the subsequent frozen‐thawed single embryo transfer cycle.

Results

The genetically transferable blastocyst rate was 21.2% (51/241). Thirty five genetically transferable blastocysts were transferred into the uterine cavity. The clinical pregnancy rate was 57.1% (20/35), and the ongoing pregnancy rate was 100.0% (20/20). The incidence of interchromosomal effect (ICE) was influenced by ovarian stimulation protocol, female age, and carrier's gender, but dependent on the types of balanced translocation carriers. Furthermore, there was no significant difference in meiotic segregation modes in ovarian stimulation protocols and carrier's gender. Interestingly, the incidence of adjacent‐1 segregation in ≧40 years group increased significantly compared with <35 years group.

Conclusions

For the first time in Japan, we show the effectiveness of PGT‐SR using aCGH or NGS, which enables comprehensive analysis of chromosomes, in the prevention of recurrent miscarriages. Furthermore, our results may support better genetic counseling of balanced translocation carriers for PGT‐SR cycles.

The fertility preservation decision-making and testicular sperm retrieval outcome in older adolescents with nonmosaic Klinefelter syndrome and azoospermia

BACKGROUND

This study aims to analyze the fertility preservation decision-making and the sperm retrieval rate (SRR) in older adolescents (age 15-19 years) with nonmosaic Klinefelter syndrome (KS) and azoospermia in a male reproductive clinic, and to determine the accumulated SRR in older adolescents by literature review.

METHODS

Older adolescents with nonmosaic KS and azoospermia referred for hypogonadism and fertility concerns were enrolled. Reproductive counseling and fertility preservation options were offered to patients/parents. The acceptability and the reasons affecting the reproductive decision-making were analyzed. Patients/parents who agreed on fertility preservation received microdissection testicular sperm extraction (mTESE) and cryopreservation. A comprehensive literature review regarding the SRRs in older adolescents with KS was conducted.

RESULTS

A total of eight older adolescents were enrolled. After fertility preservation counseling, three patients/parents (37.5%) agreed to receive mTESE, and spermatozoa were successfully retrieved in two. "Lack of interest" and "inconsistent sperm retrieval result" were the main reasons for refusal. A total of 89 older adolescents from nine articles, and ours were collected for SRR analysis. Most of the reports had a limited number of cases, and none of them described the acceptance rate of sperm retrieval in adolescents. Forty-three out of 89 older adolescents (48.3%) had successful sperm retrieval, and there was no significant difference in the SRR between the mTESE and conventional TESE.

CONCLUSION

Successful testicular sperm retrieval in older adolescents with KS is not superior to those reported in adults. Adolescents and their parents should undergo a detailed reproductive consultation process and shared decision-making discussion before considering testicular sperm retrieval.

Optimization of the sperm processing protocol for subsequent molecular cytogenetic studies

One of the causes of spontaneous pregnancy termination, infertility, and birth of children with development delay and malformations are chromosomal abnormalities (CA) as well as spontaneous aneuploidies in gametes of phenotypically normal parents. Often couples with reproductive problems, as well as spouses one of whom is a carrier of CA, turn to the programs of assisted reproductive technologies (ART) for preimplantation evaluation of the zygote chromosomal status. As part of ART programs, parental gametes are examined to assess the level of spontaneous aneuploidy. As a rule, the most accessible material for analysis is the ejaculate. Fluorescent in situ hybridization (FISH) is used to examine male gametes obtained from the ejaculate. However, this FISH-analysis has a number of limitations and difficulties because of the peculiarities of the sperm head structure, namely the supercondensed state of chromosome chromatin. In order to optimize the FISH protocol, five different protocols were used for pre-hybridization processing of ejaculate samples obtained from nine phenotypically normal men. A comparative analysis of hybridization efficiency showed that the protocol using tris(2-carboxyethyl)phosphine hydrochloride (TCEP) as a decondensation agent was the most effective for subsequent molecular cytogenetic studies. The developed hybrid protocol combining proteolytic pretreatment, TCEP and thermal decondensation can be used when other protocols for pre-hybridization treatment of ejaculate preparations are not effective.

Effect of carriers' sex on meiotic segregation patterns and chromosome stability of reciprocal translocations

RESEARCH QUESTION

Does the sex of reciprocal translocation carriers affect meiotic segregation patterns and stability of non-translocated chromosomes during meiosis?

DESIGN

A total of 790 couples who underwent preimplantation genetic testing for reciprocal translocations by using the single nucleotide polymorphism (SNP) array platform between October 2016 and December 2019 were included. Among them, 294 couples had their euploid embryos distinguished between normal euploidies and balanced translocation carriers.

RESULTS

Female translocation carriers had a significantly lower incidence of alternate segregation pattern than male carriers (43.26% versus 47.98%, P = 0.001), but a higher incidence of 3:1 segregation pattern (6.70% versus 4.29%, P < 0.001). Stratified analysis showed only female translocation carriers with acrocentric chromosome (Acr-ch) involved had a lower incidence of alternate segregation pattern and a higher incidence of 3:1 segregation pattern compared with male carriers (41.63% versus 47.73%, P = 0.012; 9.32% versus 5.03%, P = 0.001). In 2233 embryos of 294 couples with identification of normal and balanced embryos, no significant differences were found in the paternal-origin aneuploidy rate (5.61% versus 5.82%, P = 0.861) and the maternal-origin aneuploidy rate (12.82% versus 12.08%, P = 0.673) in both male and female carriers. After excluding segmental aneuploidies, no differences were found between male and female carriers in both paternal-origin aneuploidy rate (2.14% versus 1.75%, P = 0.594) and maternal-origin aneuploidy rate (11.75% versus 11.06%, P = 0.683).

CONCLUSION

The sex of the translocation carriers affected meiotic segregation patterns with no effect on the stability of non-translocated chromosomes during meiosis.

Hypogonadotropic hypogonadism associated with another small supernumerary marker chromosome (sSMC) derived from chromosome 22, a case report

The idiopathic hypogonadotropic hypogonadism (IHH) is portrayed as missing or fragmented pubescence, cryptorchidism, small penis, and infertility. Clinically it is characterized by the low level of sex steroids and gonadotropins, normal radiographic findings of the hypothalamic-pituitary areas, and normal baseline and reserve testing of the rest of the hypothalamic-pituitary axes. Delay puberty and infertility result from an abnormal pattern of episodic GnRH secretion. Mutation in a wide range of genes can clarify ~40% of the reasons for IHH, with the majority remaining hereditarily uncharacterized. New and innovative molecular tools enhance our understanding of the molecular controls underlying pubertal development. In this report, we aim to present a 26-year-old male of IHH associated with a small supernumerary marker chromosome (sSMC) that originated from chromosome 22. The G-banding analysis revealed a karyotype of 47,XY,+mar. High-throughput DNA sequencing identified an 8.54 Mb duplication of 22q11.1-q11.23 encompassing all the region of 22q11 duplication syndrome. Pedigree analysis showed that his mother has carried a balanced reciprocal translocation between Chromosomes 22 and X[t(X;22)]. To the best of our knowledge, this is the second confirmed case of IHH with an sSMC deriving from chromosome 22. Based on our study, the duplicated chromosome fragment 22q11.1-q11.23 might be the reason for the phenotype of our case. Meanwhile, High-throughput DNA sequencing combined with cytogenetic analysis can provide a more accurate clinical diagnosis for patients carrying sSMCs.

Analysis of sperm chromosomes in six carriers of rare and common Robertsonian translocations

Introduction: Robertsonian translocation (RobT) is the central fusion of the long arms of two acrocentric chromosomes, leading to 45 chromosomes in humans. The most common ones are rob(13;14) and rob(14;21) (91%). Other types of RobT are so-called rare cases. In the general population RobTs occur with a frequency of approximately 0.123%, but among men with reproductive failure this value rises 9-fold. Infertility in RobT carriers is associated with the formation of unbalanced spermatozoa resulting from segregation of the chromosomes involved in trivalent during the meiotic prophase. In spermatozoa of many RobT carriers an increased level of chromosomal aneuploidy is observed. Materials and Methods: We examined the hyperhaploidy level of chromosomes 7, 9, 18, 21, 22, X and Y in spermatozoa of 6 RobT unrelated carriers: two carriers with rare rob(13;15), one with rare rob(13;22), and three of the common rob(13;14). Results were compared with the control data from a group of 7 fertile men with a normal karyotype. Fluorescent in situ hybridization (FISH) was applied. Results: We found an increased level of sperm aneuploidy regarding at least one of the analyzed chromosomes in each of the carriers, while in rare RobTs interchromosomal effect (ICE) was observed. Meiotic segregation pattern of a rare rob(13;15) carrier revealed the 76% of normal /balanced spermatozoa. Disucussion: Due to the relatively high population frequency of RobTs, their influence on reproductive failure, hight risk of imbalancement in prenatal diagnosis (7%), and small amount of data for rare RobTs, each newly characterized case is valuable in genetic counseling.

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.

Clinical Evaluation of a Custom Gene Panel as a Tool for Precision Male Infertility Diagnosis by Next-Generation Sequencing

BACKGROUND

Up to 15% of couples are infertile and male factor infertility accounts for approximately 50% of these cases. Male infertility is a multifactorial pathological condition. The genetic of male infertility is very complex and at least 2000 genes are involved in its etiology. Genetic testing by next-generation sequencing (NGS) technologies can be relevant for its diagnostic value in male infertile patients. Therefore, the aim of this study was to implement the diagnostic offer with the use of an NGS panel for the identification of genetic variants.

METHODS

We developed an NGS gene panel that we used in 22 male infertile patients. The panel consisted of 110 genes exploring the genetic causes of male infertility; namely spermatogenesis failure due to single-gene mutations, central hypogonadism, androgen insensitivity syndrome, congenital hypopituitarism, and primary ciliary dyskinesia.

RESULTS

NGS and a subsequent sequencing of the positive pathogenic or likely pathogenic variants, 5 patients (23%) were found to have a molecular defect. In particular, pathogenic variants were identified in TEX11, CCDC39, CHD7, and NR5A1 genes. Moreover, 14 variants of unknown significance and 7 novel variants were found that require further functional studies and family segregation.

CONCLUSION

This extended NGS-based diagnostic approach may represent a useful tool for the diagnosis of male infertility. The development of a custom-made gene panel by NGS seems capable of reducing the proportion of male idiopathic infertility.

Role of treatment with human chorionic gonadotropin and clinical parameters on testicular sperm recovery with microdissection testicular sperm extraction and intracytoplasmic sperm injection outcomes in 184 Klinefelter syndrome patients

OBJECTIVE

To investigate whether preoperative human chorionic gonadotropin (hCG) treatment can help predict the outcomes of microdissection testicular sperm extraction (micro-TESE) and affect fertility outcomes in non-mosaic Klinefelter syndrome (KS) patients.

DESIGN

Retrospective cohort study.

SETTING

University-affiliated fertility center.

PATIENT(S)

A total of 184 non-mosaic KS patients who underwent micro-TESE with or without preoperative hCG treatment from January 2016 to July 2019.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Sperm retrieval rate (SRR) with and without hCG treatment, logistic models analysis.

RESULT(S)

Eighty KS patients (43.5%) had successful sperm retrievals after micro-TESE. There was no statistically significant difference in the SRR between the group who received hCG treatment and the group that did not (44.0% vs. 43.3%). Logistic regression analyses demonstrated that the hCG treatment had no statistically significant effect on successful sperm retrieval. However, higher preoperative testosterone (T) levels seemed to be associated with a higher probability of successful sperm retrieval (multivariate adjusted odds ratio 1.09; 95% confidence interval [CI], 1.04-1.16). The prediction model for SRR on KS patients had an area under the curve of 67.3% (95% CI, 59.3-75.3%). In the hCG treatment group, the data indicated that the three parameters of testicular volume, pretreatment T level, and alterations of T were associated with the probability of successful sperm retrieval. Moreover, hCG therapy did not affect intracytoplasmic sperm injection (ICSI) outcomes. No differences in the pregnancy rate or live-birth rate were observed between the two groups.

CONCLUSION(S)

Therapy with hCG does not affect SRR or ICSI outcomes of non-mosaic KS patients. However, preoperative T levels, whether treated with hCG or not, can predict the chance of sperm retrieval with micro-TESE.

Small supernumerary marker chromosomes (sSMC) and male infertility: characterization of five new cases, review of the literature, and perspectives

PURPOSE

To characterize small supernumerary marker chromosomes (sSMC) in infertile males RESEARCH QUESTION: Are molecular cytogenetic methods still relevant for the identification and characterization of sSMC in the era of next-generation sequencing?

METHODS

In this paper, we report five males with oligoasthenozoospermia or azoospermia with a history of recurrent pregnancy loss in partnership in four cases. R-banding karyotyping and fluorescence in situ hybridization (FISH) analysis were performed and showed sSMC in all five cases. Microdissection and reverse-FISH were performed in one case.

RESULTS

One sSMC, each, was derived from chromosome 15 and an X-chromosome; two sSMC were derivatives of chromosome 22. The fifth sSMC was a ring chromosome 4 complemented by a deletion of the same region 4p14 to 4p16.1 in one of the normal chromosomes 4. All markers were mosaics except one of sSMC(22).

CONCLUSION

Through this study, we emphasize the necessity of a proper combination of high-throughput techniques with conventional cytogenetic and FISH methods. This could provide a personalized diagnostic and accurate results for the patients suffering from infertility or RPL. We also highlight FISH analyses, which are essential tools for detecting sSMC in infertile patients. In fact, despite its entire composition of heterochromatin, sSMC can have effects on spermatogenesis by producing mechanical perturbations during meiosis and increasing meiotic nondisjunction rate. This would contribute to understand the exact chromosomal mechanism disrupting the natural and the assisted reproduction leading to offer a personalized support.

Familial Infertility (Azoospermia and Cryptozoospermia) in Two Brothers-Carriers of t(1;7) Complex Chromosomal Rearrangement (CCR): Molecular Cytogenetic Analysis

Structural aberrations involving more than two breakpoints on two or more chromosomes are known as complex chromosomal rearrangements (CCRs). They can reduce fertility through gametogenesis arrest developed due to disrupted chromosomal pairing in the pachytene stage. We present a familial case of two infertile brothers (with azoospermia and cryptozoospermia) and their mother, carriers of an exceptional type of CCR involving chromosomes 1 and 7 and three breakpoints. The aim was to identify whether meiotic disruption was caused by CCR and/or genomic mutations. Additionally, we performed a literature survey for male CCR carriers with reproductive failures. The characterization of the CCR chromosomes and potential genomic aberrations was performed using: G-banding using trypsin and Giemsa staining (GTG banding), fluorescent in situ hybridization (FISH) (including multicolor FISH (mFISH) and bacterial artificial chromosome (BAC)-FISH), and genome-wide array comparative genomic hybridization (aCGH). The CCR description was established as: der(1)(1qter->1q42.3::1p21->1q42.3::7p14.3->7pter), der(7)(1pter->1p2 1::7p14.3->7qter). aCGH revealed three rare genes variants: ASMT, GARNL3, and SESTD1, which were ruled out due to unlikely biological functions. The aCGH analysis of three breakpoint CCR regions did not reveal copy number variations (CNVs) with biologically plausible genes. Synaptonemal complex evaluation (brother-1; spermatocytes II/oligobiopsy; the silver staining technique) showed incomplete conjugation of the chromosomes. Associations between CCR and the sex chromosomes (by FISH) were not found. A meiotic segregation pattern (brother-2; ejaculated spermatozoa; FISH) revealed 29.21% genetically normal/balanced spermatozoa. The aCGH analysis could not detect smaller intergenic CNVs of few kb or smaller (indels of single exons or few nucleotides). Since chromosomal aberrations frequently do not affect the phenotype of the carrier, in contrast to the negative influence on spermatogenesis, there is an obvious need for genomic sequencing to investigate the point mutations that may be responsible for the differences between the azoospermic and cryptozoospermic phenotypes observed in a family. Progeny from the same parents provide a unique opportunity to discover a novel genomic background of male infertility.

Analysis of meiotic segregation modes in biopsied blastocysts from preimplantation genetic testing cycles of reciprocal translocations

Purpose

To analyse the meiotic segregation modes of chromosomal structural rearrangements (PGT-SR) of reciprocal translocation in biopsied blastocysts from preimplantation genetic testing and to investigate whether any features of reciprocal translocation, such as carrier gender or the presence of acrocentric chromosomes or terminal breakpoints, affect meiotic segregation modes.

Methods

Comprehensive chromosomal screening was performed by next generation sequencing (NGS) on 378 biopsied blastocysts from 102 PGD cycles of 89 reciprocal translocation carriers. The segregation modes of a quadrivalent in 378 blastocysts were analysed according to the carrier’s gender, chromosome type and the location of chromosome breakpoints.

Results

The results showed that 122 out of 378 blastocysts (32.3%) were normal or balanced, 209 (55.3%) were translocated chromosomal abnormalities, and 47 (12.4%) were abnormalities of non-translocated chromosomes. The proportion of translocated chromosomal abnormalities in translocations without acrocentric chromosomes was significantly higher than that in blastocysts from carriers with acrocentric chromosomes (14.8% versus 5.9%, P = 0.032). Translocation with acrocentric chromosomes exhibited a significantly higher proportion of 3:1 segregation (24.8% versus 5.1%, P < 0.0001) and a lower rate of 2:2 segregation (70.3% versus 87.0%, P = 0.00028) compared with the proportions in blastocysts from carriers without acrocentric chromosomes. The frequency of adjacent-2 segregation was significantly different in translocations with terminal breakpoints compared to the frequency in blastocysts from carriers without terminal breakpoints (6.7% versus 15.5%, P = 0.013).

Conclusions

This study indicates that the segregation modes in blastocysts were affected by the presence of acrocentric chromosomes and terminal breakpoints, but not by the carrier’s sex. Our data may be useful for predicting the segregation pattern of a reciprocal translocation and could support genetic counselling for balanced translocation carriers for PGT cycles using blastocyst biopsy.

The effect of Robertsonian translocations on the intranuclear positioning of NORs (nucleolar organizing regions) in human sperm cells

Only a few studies have described sperm chromosome intranuclear positioning changes in men with reproductive failure and an incorrect somatic karyotype. We studied the influence of Robertsonian translocations on the acrocentric chromosome positioning in human sperm cells. The basis of the analysis was the localization of NORs (nucleolar organizing regions) in sperm nuclei from three Robertsonian translocation carriers, namely, rob(13;22), rob(13;15) and rob(13;14), with a known meiotic segregation pattern. All three carriers presented with a similar percentage of genetically normal sperm cells (i.e., approximately 40%). To visualize NORs, we performed 2D-FISH with directly labelled probes. We used the linear and radial topologies of the nucleus to analyse the NORs distribution. We found an affected positioning of NORs in each case of the Robertsonian translocations. Moreover, the NORs tended to group, most often in two clusters. Both in Robertsonian carriers and control sperm cells, NORs mostly colocalized in the medial areas of the nuclei. In the case of the Roberstonian carriers, NORs were mostly concentrated in the peripheral part of the medial area, in contrast to control sperm cells in which the distribution was more dispersed towards the internal area.

Chromosome (re)positioning in spermatozoa of fathers and sons - carriers of reciprocal chromosome translocation (RCT)

Background

Non-random chromosome positioning has been observed in the nuclei of several different tissue types, including human spermatozoa. The nuclear arrangement of chromosomes can be altered in men with decreased semen parameters or increased DNA fragmentation and in males with chromosomal numerical or structural aberrations. An aim of this study was to determine whether and how the positioning of nine chromosome centromeres was (re)arranged in the spermatozoa of fathers and sons – carriers of the same reciprocal chromosome translocation (RCT).

Methods

Fluorescence in situ hybridization (FISH) was applied to analyse the positioning of sperm chromosomes in a group of 13 carriers of 11 RCTs, including two familial RCT cases: t(4;5) and t(7;10), followed by analysis of eight control individuals. Additionally, sperm chromatin integrity was evaluated using TUNEL and Aniline Blue techniques.

Results

In the analysed familial RCT cases, repositioning of the chromosomes occurred in a similar way when compared to the data generated in healthy controls, even if some differences between father and son were further observed. These differences might have arisen from various statuses of sperm chromatin disintegration.

Conclusions

Nuclear topology appears as another aspect of epigenetic genomic regulation that may influence DNA functioning. We have re-documented that chromosomal positioning is defined in control males and that a particular RCT is reflected in the individual pattern of chromosomal topology. The present study examining the collected RCT group, including two familial cases, additionally showed that chromosomal factors (karyotype and hyperhaploidy) have superior effects, strongly influencing the chromosomal topology, when confronted with sperm chromatin integrity components (DNA fragmentation or chromatin deprotamination).

Electronic supplementary material

The online version of this article (10.1186/s12920-018-0470-7) contains supplementary material, which is available to authorized users.

Analysis of segregation patterns of quadrivalent structures and the effect on genome stability during meiosis in reciprocal translocation carriers

STUDY QUESTION

Do specific factors affect the segregation patterns of a quadrivalent structure and can the quadrivalent affect genome stability during meiosis?

SUMMARY ANSWER

Meiotic segregation patterns can be affected by the carrier's gender and age, location of breakpoints and chromosome type, and the quadrivalent structure can increase genome instability during meiosis.

WHAT IS KNOWN ALREADY

Carriers of reciprocal translocations have an increased genetic reproductive risk owing to the complex segregation patterns of a quadrivalent structure. However, the results of previous studies on the factors that affect segregation patterns seem to be contradictory, and the effect of a quadrivalent on genome stability during meiosis is unknown.

STUDY DESIGN, SIZE, DURATION

We designed a retrospective study to analyze the segregation patterns of 24 chromosomes from reciprocal translocation and non-translocation patients. Data for 356 reciprocal translocation carriers and 53 patients with the risk to transmit monogenic inherited disorders (RTMIDs) undergoing PGD-single nucleotide polymorphism array analysis were collected. The study was performed between March 2014 and July 2017.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Segregation patterns of a quadrivalent in 1842 blastocysts from 466 assisted reproduction cycles of reciprocal translocation carriers were analyzed according to the location of chromosome breakpoints, the carrier's gender and age, and chromosome type. In addition, to analyze the effect of quadrivalent structure on genome stability, segregation products of chromosomes which are not involved in the translocation from translocation carriers were compared with those of 23 pairs of chromosomes in 318 blastocysts from 72 assisted reproduction cycles of patients with RTMIDs.

MAIN RESULTS AND THE ROLE OF CHANCE

The percentage of adjacent-2 products with severe asymmetric quadrivalent was significantly higher than those with mild asymmetric quadrivalent (P = 0.020) while, in contrast, the incidence of 4:0/others was lower (P = 0.030). The frequencies of adjacent-1, adjacent-2 and 3:1 products differed between male and female carriers (P < 0.001, P = 0.015 and P = 0.001, respectively), and also for adjacent-1 and 4:0/others products in young versus older carriers (P = 0.04 and P = 0.002, respectively). In addition, adjacent-1 products of a quadrivalent with an acrocentric chromosome were significantly higher than those of a quadrivalent without an acrocentric chromosome (P = 0.001). Moreover, a quadrivalent could significantly increase the frequencies of abnormal chromosomes compared to patients with RTMIDs (P = 0.048, odds ratio (OR) = 1.43, 95% CI = 1.01-2.43), especially for the male carriers (P = 0.018, OR = 1.58, 95% CI = 1.08-2.25). In contrast, for older carriers, no difference was found in both aneuploidy and segmental anomalies compared to patients with RTMIDs.

LIMITATIONS, REASONS FOR CAUTION

The study contained appropriate controls, yet the analysis was limited by a small number of control patients and embryos.

WIDER IMPLICATIONS OF THE FINDINGS

Until now, there had been no definite report about the effect of quadrivalents on genome stability in reciprocal translocation carriers compared with control samples, and in the present study the large sample size ensured a detailed analysis of factors with a possible impact on segregation patterns. These data provide a better insight into the meiotic mechanisms involved in non-disjunction events in gametes from reciprocal translocation carriers. In addition, our results will help to provide each reciprocal translocation carrier couple undergoing PGD with more appropriate genetic counseling and a better understanding of the large numbers of abnormal embryos with chromosome aneuploidy.

STUDY FUNDING/COMPETING INTEREST(S)

The research was supported by the Research Funding of Shanghai Ji Ai Genetics & IVF Institute and the authors declare a lack of competing interests in this study.

A Familial Case Report of a 13;22 Chromosomal Translocation with Recurrent Intracytoplasmic Sperm Injection Failure

The importance of cytogenetic analysis in a family with reproductive failure in two siblings is highlighted, where two siblings and their mother presented with a balanced translocation between chromosomes 13;22. The clinical evaluation had shown the female to be normal and the male to be oligoasthenoteratozoospermic despite repeated semen analysis. The couple was referred to our laboratory after three consecutive intracytoplasmic sperm injection (ICSI) failures at a local assisted reproductive technique (ART) center. Peripheral blood lymphocytes, obtained for karyotyping, were studied by a standard G-banding technique. Chromosomal analysis of the members of the pedigree, including the probands, showed the presence of the same translocation, t(13;22)(q21.2;q13.3), carried by three generations of the family. The sister and the mother of the proband had multiple spontaneous abortions in the first trimester. The spouses, when examined cytogenetically, were found to be normal. We propose the involvement of a balanced t(13;22)(q21.2;q13.3) chromosomal translocation in the pathogenesis of recurrent ART or spontaneous reproductive failures. Hence, it is suggested that all cases with structural chromosomal abnormalities be counseled prior to opting for ART and undergoing pre-implantation genetic diagnosis (PGD). This would prevent recurrent financial, physical and emotional stress in couples seeking ART.

DNA Damage and Repair in Human Reproductive Cells

The fundamental underlying paradigm of sexual reproduction is the production of male and female gametes of sufficient genetic difference and quality that, following syngamy, they result in embryos with genomic potential to allow for future adaptive change and the ability to respond to selective pressure. The fusion of dissimilar gametes resulting in the formation of a normal and viable embryo is known as anisogamy, and is concomitant with precise structural, physiological, and molecular control of gamete function for species survival. However, along the reproductive life cycle of all organisms, both male and female gametes can be exposed to an array of “stressors” that may adversely affect the composition and biological integrity of their proteins, lipids and nucleic acids, that may consequently compromise their capacity to produce normal embryos. The aim of this review is to highlight gamete genome organization, differences in the chronology of gamete production between the male and female, the inherent DNA protective mechanisms in these reproductive cells, the aetiology of DNA damage in germ cells, and the remarkable DNA repair mechanisms, pre- and post-syngamy, that function to maintain genome integrity.

Analysis of Meiotic Segregation Pattern and Interchromosomal Effects in a Bull Heterozygous for a 3/16 Robertsonian Translocation

Robertsonian translocations are the most frequent chromosomal rearrangements detected in cattle. Here, we report on the detection of a new Robertsonian translocation between chromosomes BTA3 and BTA16. This rob(3;16) was dicentric, suggesting that its occurrence was recent. FISH analysis of decondensed sperm nuclei revealed a relatively low rate of unbalanced gametes produced by adjacent segregation (5.87%). In addition, and for the first time in bovines, a significant interchromosomal effect (ICE) was detected for 2 different autosomes: BTA17 (global disomy + nullisomy rate of 9%) and BTA20 (1.8%). These results suggest that ICE should be taken into consideration when assessing the putative effect of Robertsonian translocations on reproduction.

Impaired Spermatogenesis due to Small Supernumerary Marker Chromosomes: The Reason for Infertility Is Only Reliably Ascertainable by Cytogenetics

Infertile male with small supernumerary marker chromosomes (sSMCs) were studied. Overall, 37 own patients and 166 cases from the literature were included. sSMCs of our own cases were characterized by multicolor-FISH probe sets. Available clinical data of the infertile males were also evaluated, and meta-analysis on suitability of molecular karyotyping for sSMC characterization was done. As a result, sSMCs can be optimally characterized by single-cell directed (molecular) cytogenetics. In infertile males, sSMCs derive predominantly from one of the acrocentric chromosomes, mainly chromosomes 15, 14, and 22. Interestingly, altered spermiograms were found in 62% of the males with an sSMC, while the remainder cases had infertility in connection with recurrent spontaneous abortions. Meta-analysis for detectability of sSMCs by aCGH revealed that 81-87% of the cases would have not been picked up by exclusive use of that approach. Thus, as impaired spermatogenesis is known to be indicative for gross chromosomal anomalies in infertile male patients, it can be concluded from this study that the presence of sSMCs also needs to be considered. However, sSMCs can only be reliably detected by standard karyotyping and not by modern high throughput approaches like aCGH and next-generation sequencing.

Comprehensive genetic testing for female and male infertility using next-generation sequencing

PURPOSE

To develop a comprehensive genetic test for female and male infertility in support of medical decisions during assisted reproductive technology (ART) protocols.

METHODS

We developed a next-generation sequencing (NGS) gene panel consisting of 87 genes including promoters, 5' and 3' untranslated regions, exons, and selected introns. In addition, sex chromosome aneuploidies and Y chromosome microdeletions were analyzed concomitantly using the same panel.

RESULTS

The NGS panel was analytically validated by retrospective analysis of 118 genomic DNA samples with known variants in loci representative of female and male infertility. Our results showed analytical accuracy of > 99%, with > 98% sensitivity for single-nucleotide variants (SNVs) and > 91% sensitivity for insertions/deletions (indels). Clinical sensitivity was assessed with samples containing variants representative of male and female infertility, and it was 100% for SNVs/indels, CFTR IVS8-5T variants, sex chromosome aneuploidies, and copy number variants (CNVs) and > 93% for Y chromosome microdeletions. Cost analysis shows potential savings when comparing this single NGS assay with the standard approach, which includes multiple assays.

CONCLUSIONS

A single, comprehensive, NGS panel can simplify the ordering process for healthcare providers, reduce turnaround time, and lower the overall cost of testing for genetic assessment of infertility in females and males, while maintaining accuracy.

Is sperm FISH analysis still useful for Robertsonian translocations? Meiotic analysis for 23 patients and review of the literature

Background

Robertsonian translocations (RobT) are common structural chromosome rearrangements where carriers display a majority of chromosomally balanced spermatozoa from alternate segregation mode. According to some monotony observed in the rates of balanced segregation, is sperm FISH analysis obsolete for RobT carriers?

Methods

Retrospective cohort research study on 23 patients analyzed in our center from 2003 to 2017 and compared to the data of 187 patients in literature from 1983 to 2017.

Robertsonian translocation carriers were divided in six groups according to the chromosomes involved in the translocation: 9 patients from our center and 107 from literature carrying 45,XY,der(13;14) karyotype, 3 and 35 patients respectively with 45,XY,der(14;21), 5 and 11 patients respectively with 45,XY,der(13;15), 4 and 7 patients respectively with 45,XY,der(14;15), 1 and 4 patients respectively with 45,XY,der(13;22),and 1 and 10 patients respectively with 45,XY,der(14;22).

Results

Alternate segregation mode is predominant in our group of Robertsonian translocation carriers with 73.45% ±8.05 of balanced spermatozoa (min 50.92%; max 89.99%). These results are compliant with the data from literature for all translocations types (p > 0.05) and are consistent among the different types of Robertsonian translocations (p > 0.05) except for der(13;15) that exhibit lower balanced spermatozoa rates (p < 0.05 versus der(13;14), der(14;21), (13;21) and der(15;22)). Normozoospermic patients also display a significantly (p < 0.01) higher rate of balanced sperm cells than patients with abnormal seminograms whatever the defect implied.

Conclusions

According to the discrepancies observed between der(13;15) and all the other Rob T carriers, the differences observed among patients presenting normal and abnormal sperm parameters and the input in genetical counselling, sperm FISH does not seem obsolete for these patients. Moreover, it seems important to collect more data for rare RobT.

Cytogenetic Abnormalities Found in Patients with Reproductive Problems

Introduction

One of the important causes of male infertility is aberration at the chromosomes.

Aim

The main purpose of this study was to determine the frequency and types of chromosomal aberration in infertile/sterile men whose samples were analyzed in the Center for Cytogenetics of Faculty of Medicine University of Sarajevo in the last four years.

Methods

A total of 353 infertile/sterile men, between the ages of 22-55 years, referred for cytogenetic analysis to the Center for Genetics of Faculty of Medicine during the period 2013-2016. Karyotyping was performed on peripheral blood lymphocytes by using the Giemsa trypsin banding (GTG) technique.

Results

The structural and numerical chromosomal aberration in infertility/ sterility of men found with the incidence of 6% (20/353). Out of the 20 patients with abnormal cytogenetic diagnosis, structural chromosome abnormalities were observed in 17 (85%) patients and 3 (15%) with numerical aberrations. The type of aberrations mostly found were Robertsonian and reciprocal translocations (35%, 35%, respectively).

Conclusions

The incidence of chromosomal abnormalities in infertile/sterile males suggests that the cytogenetics analysis is an important in male infertility, especially if it will be used for the purpose of assisted reproduction techniques.

Sperm fluorescent in situ hybridisation study of interchromosomal effect in six Tunisian carriers of reciprocal and Robertsonian translocations

Carriers of structural chromosomal anomalies, translocations and inversions are at increased risk of aneuploid gametes production. Besides the direct effect on the involved chromosomes, these rearrangements might disturb the segregation of other structurally normal chromosomes during meiosis. Such event is known as interchromosomal effect. In this study, six male carriers of translocations, four reciprocals and two Robertsonians, were investigated. In addition, seven fertile men with normal 46,XY karyotypes and normal sperm characteristics were enrolled as a control group. Spermatic fluorescent in situ hybridisation specific for chromosomes X, Y, 18, 21 and 22 was carried out. The Mann-Whitney U-test was used to compare the aneuploidy rates between patients and controls. All translocation carriers showed significantly increased frequencies of disomy of all investigated chromosomes, and diploid gametes compared with the control group (p < .05). However, disomy XY was not significantly different between controls and patients (p > .05). We have also observed a considerable interindividual variability in disomy and diploidy rates. These results confirm that the interchromosomal effect seems to exist and could contribute to higher rates of abnormal prenatal aneuploidy, resulting in a small increase in the risk of miscarriage and birth of children with congenital abnormalities and a potential reduction in fertility.

Male infertility associated with de novo pericentric inversion of chromosome 1

Inversion occurs after two breaks in a chromosome have happened and the segment rotates 180° before reinserting. Inversion carriers have produced abnormal gametes if there is an odd number crossing- over between the inverted and the normal homologous chromosomes causing a duplication or deletion. Reproductive risks such as infertility, abortion, stillbirth and birth of malformed child would be expected in that case. A 54-year- old male patient was consulted to our clinic for primary infertility. The routine chromosome study were applied using peripheral blood lymphocyte cultures and analyzed by giemsa-trypsin-giemsa (GTG) banding, and centromer banding (C-banding) stains. Y chromosome microdeletions in the azoospermia factor (AZF) regions were analyzed with polymerase chain reaction. Additional test such as fluorescence in situ hybridization (FISH) was used to detect the sex-determining region of the Y chromosome (SRY). Semen analysis showed azoospermia. A large pericentric inversion of chromosome 1 46,XY, inv(1) (p22q32) was found in routine chromosome analysis. No microdeletions were seen in AZF regions. In our patient the presence of SRY region was observed by using FISH technique with SRY-specific probe. Men who have pericentric inversion of chromosome 1, appear to be at risk for infertility brought about by spermatogenic breakdown. The etiopathogenic relationship between azoospermia and pericentric inversion of chromosome 1 is discussed.

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.

Cytoskeletal alterations associated with donor age and culture interval for equine oocytes and potential zygotes that failed to cleave after intracytoplasmic sperm injection

Intracytoplasmic sperm injection (ICSI) is an established method to fertilise equine oocytes, but not all oocytes cleave after ICSI. The aims of the present study were to examine cytoskeleton patterns in oocytes after aging in vitro for 0, 24 or 48h (Experiment 1) and in potential zygotes that failed to cleave after ICSI of oocytes from donors of different ages (Experiment 2). Cytoplasmic multiasters were observed after oocyte aging for 48h (P<0.01). A similar increase in multiasters was observed with an increased interval after ICSI for young mares (9-13 years) but not old (20-25 years) mares. Actin vesicles were observed more frequently in sperm-injected oocytes from old than young mares. In the present study, multiasters appeared to be associated with cell aging, whereas actin vesicles were associated with aging of the oocyte donor.

Altered bivalent positioning in metaphase I human spermatocytes from Robertsonian translocation carriers

PURPOSE

The study aims to determine whether there is an altered bivalent positioning in metaphase I human spermatocytes from Robertsonian translocation carriers.

METHODS

Metaphase I human spermatocytes from three 45,XY,der(13;14)(q10;q10) individuals and a 45,XY,der(14;15)(q10;q10) individual were analyzed. Proximity relationships of bivalents were established by analyzing meiotic preparations combining Leishman staining and multiplex-FISH procedures. Poisson regression model was used to determine proximity frequencies between bivalents and to assess associations with chromosome size, gene density, acrocentric morphology, and chromosomes with heterochromatic blocks. The hierarchical cluster Ward method was used to characterize the groups of bivalents with preferred proximities in a cluster analysis. Bivalent groups obtained were individually compared with those obtained in normal karyotype individuals evaluated in a previous study.

RESULTS

A total of 1288 bivalents were examined, giving a total of 2289 proximity data. Only four positive significant proximities were detected for each type of Robertsonian translocation. Significant bivalent associations were only observed by small-size chromosomes for MI,22,XY,III(13q14q). These results were clearly divergent from 46,XY individuals. Moreover, cluster analysis revealed that about 30 % of the bivalents showed changes in their proximity relationships in metaphase I.

CONCLUSIONS

The territorial organization of bivalents in metaphase I human spermatocytes changes in the presence of a Robertsonian translocation.

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.

FISH and array CGH characterization of de novo derivative Y chromosome (Yq duplication and partial Yp deletion) in an azoospermic male

This study presents a 28-year-old infertile male who was referred to the cytogenetic laboratory for chromosomal analysis after 4 years of regular unprotected intercourse in whom non-obstructive azoospermia was revealed. Standard cytogenetic G-banding was performed on metaphase spreads and a de-novo karyotype 46,X,der(Y)(q11.22;p11.3) was identified. This analysis was followed by flourescence in-situ hybridization(FISH) and array comparative genomic hybridization (aCGH). Finally, the patient's karyotype was identified as 46,X,der(Y)(qter→q11.221::p11.31→qter).ish der(Y) (qter+,pter-,SHOX+,SRY+,Ycen+,DYZ3+;DYZ1+,qter+).arrYq11.221q12(14,448,863-59,288,511) x2, Yp11.32p11.31(104,062-266,388) x0. It is proposed that de-novo derivative monocentric Y chromosome with duplicated region Y qter→q11.221::p11.31→qter with partial deletion of Yp PAR1 region most probably can perturb the conjugation of sex chromosomes during first meiotic division of spermatogenic arrested differentiation (development).

Outcome of testicular sperm extraction in nonmosaic Klinefelter syndrome patients: what is the best approach?

Klinefelter syndrome (KS) is the most common chromosomal disorder associated with male hypogonadism and infertility. Parenthood can be achieved in men with KS by intracytoplasmic sperm injection (ICSI) using testicular spermatozoon. The aim of this study was to evaluate surgical sperm retrieval (SSR) rate in patients with KS and to investigate the approach associated with the highest SSR. This is a retrospective study where all medical records of patients with KS who underwent SSR for ICSI, in our centre in the past 14 years, were reviewed. Forty-three patients were included in this study. Twenty-three underwent conventional testicular sperm extraction (TESE), while 20 patients underwent microsurgical TESE (Micro-TESE). The SSR was significantly higher in the Micro-TESE group when compared with the TESE group (30% versus 0% respectively). In the Micro-TESE group, hormonal stimulation was given to 16 patients, while no treatment was given to four patients. SSR was only successful in hormonally treated patients (6/16). When the type of hormone stimulation was evaluated, SSR was higher in patients receiving aromatase inhibitors (27.8%). SSR in patients with KS is significantly higher when using hormonal stimulation by aromatase inhibitors followed by microsurgical testicular sperm extraction.

Impact of chromosomal translocations on male infertility, semen quality, testicular volume and reproductive hormone levels

OBJECTIVE

To analyse the relationship between male infertility and chromosomal translocations, and the influence of different types of chromosomal translocations on semen quality, testicular volume and hormone levels.

METHODS

A retrospective cohort of infertile men was recruited for chromosomal analysis using standard Giemsa stain banding. Physical examinations, semen analysis, hormonal analysis and the detection of azoospermia factor (AZF) microdeletions were carried out. Men with normal fertility were used as controls.

RESULTS

Among the 1056 infertile men, 22 had chromosomal translocations (2.1%), including seven with Robertsonian translocations (0.7%), 11 with autosome-autosome reciprocal translocations (1.0%) and four with gonosome-autosome reciprocal translocations (0.4%). Left and right testicular volumes of patients with chromosomal translocations were significantly smaller than those in the fertile control group. There were no significant differences in hormone levels between patients with chromosomal translocations and fertile controls, except for significantly lower testosterone levels in patients with Robertsonian and gonosome-autosome reciprocal translocations compared with the controls. All AZF microdeletion analyses showed normal results.

CONCLUSIONS

Chromosomal translocations may cause reductions in testicular volume and testosterone level, which may impact spermatogenesis, resulting in azoospermia or oligozoospermia and male infertility.

Azoospermia due to spermatogenic failure

This article summarizes the current literature regarding azoospermia caused by spermatogenic failure. The causes and genetic contributions to spermatogenic failure are reviewed. Medical therapies including use of hormonal manipulation, whether guided by a specific abnormality or empiric, to induce spermatogenesis are discussed. The role of surgical therapy, including a discussion of varicocelectomy in men with spermatogenic failure, as well as an in-depth review of surgical sperm retrieval with testicular sperm extraction and microdissection testicular sperm extraction, is provided. Finally, future directions of treatment for men with spermatogenic failure are discussed, namely, stem cell and gene therapy.