FISH analysis of the chromosomal status of spermatozoa from three men with 45,XY,der(13;14)(q10;q10) karyotype

Bypassing Mendel's First Law: Transmission Ratio Distortion in Mammals

Mendel's law of segregation states that the two alleles at a diploid locus should be transmitted equally to the progeny. A genetic segregation distortion, also referred to as transmission ratio distortion (TRD), is a statistically significant deviation from this rule. TRD has been observed in several mammal species and may be due to different biological mechanisms occurring at diverse time points ranging from gamete formation to lethality at post-natal stages. In this review, we describe examples of TRD and their possible mechanisms in mammals based on current knowledge. We first focus on the differences between TRD in male and female gametogenesis in the house mouse, in which some of the most well studied TRD systems have been characterized. We then describe known TRD in other mammals, with a special focus on the farmed species and in the peculiar common shrew species. Finally, we discuss TRD in human diseases. Thus far, to our knowledge, this is the first time that such description is proposed. This review will help better comprehend the processes involved in TRD. A better understanding of these molecular mechanisms will imply a better comprehension of their impact on fertility and on genome evolution. In turn, this should allow for better genetic counseling and lead to better care for human families.

FISH analysis of numerical chromosomal abnormalities in the sperm of robertsonian translocation der(13; 14)(q10;q10) carriers

Fluorescence in situ hybridization analysis of numerical chromosomal abnormalities in the sperm of Robertsonian translocation der (13;14) (q10;q10) carriers has focused on a limited number of chromosomes mainly on chromosome 13, 18, 21, X, and Y. Here, we aimed to expand the analysis to all chromosomes by increasing the number of probes analyzed in fluorescence in situ hybridization. The incidence of numerical abnormalities of all chromosomes (1–22, X, and Y) was determined in sperm from 10 carriers of the Robertsonian translocation der(13;14)(q10;q10) and 10 normozoospermic males to fully assess the effect of translocation-derived chromosome on the segregation of all chromosomes during meiosis. Numerical abnormalities of the two translocated chromosomes were frequently detected in the sperm of der (13;14) translocation carriers, with an average frequency of 14.55% ± 6.00% for chromosome 13 and 13.27% ± 4.14% for chromosome 14. Numerical abnormalities of nontranslocated chromosomes, with an average frequency of 1.77% ± 0.62% (range, 1.16%–3.73%), was lower than that of translocated chromosome. However, the cumulative numerical abnormality of the 22 nontranslocated chromosomes was comparable to that of the two translocated chromosomes. Significantly increased numerical abnormalities in der(13;14) translocation carriers compared with those in normozoospermic males indicates the presence of translocation-derived chromosome disturbances, with translocated chromosomes being most affected; nontranslocated chromosomes were also affected, but to a lesser extent due to a mild interchromosomal effect.

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.

The impact of patient, embryo, and translocation characteristics on the ploidy status of young couples undergoing preimplantation genetic testing for structural rearrangements (PGT-SR) by next generation sequencing (NGS)

PURPOSE

To evaluate the factors that affect the incidence of euploid balanced embryos and interchromosomal effect (ICE) in carriers of different structural rearrangements.

METHODS

This retrospective study includes 95 couples with reciprocal translocations (RecT) and 36 couples with Robertsonian translocations (RobT) undergoing Preimplantation Genetic Testing for Structural Rearrangements (PGT-SR) between March 2016 and July 2019. Next-generation sequencing (NGS) was the technique used coupled with trophectoderm (TE) biopsy. Only cases with females under 38 years were included. A total of 532 blastocysts were evaluated.

RESULTS

The euploidy rate was similar in RobT when compared with RecT carriers [57/156 (36.5%) vs. 112/376 (29.8%), p = 0.127]. The pure ICE rate was significantly higher in RobT carriers [48/156 (30.8%) vs. 53/376 (14.1%), p < 0.001] than it was in RecT carriers. Female age was the independent factor for the probability of obtaining a euploid embryo in RecT and RobT carriers, and increasing female age decreases the probability of obtaining a euploid embryo. In RecT carriers, no significant differences were observed in euploidy rates, pure ICE, or combined ICE according to the length of the translocated fragment and the chromosome group. However, total ICE was significantly lower when there was a breakpoint in the short chromosome arm together with a breakpoint in the long arm [(44/158 (27.8%) for pq or qp, 51/155 (32.9%) for pp and 30/63 (47.6%) for qq; p = 0.02].

CONCLUSION

The incidence of euploid/balanced blastocysts was similar in both types of translocations. However, there was a significant increase in pure ICE in RobT compared to RecT carriers. In RecT carriers, the presence of the breakpoints in the long arm of the chromosomes involved in the rearrangement resulted in a higher total ICE.

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.

Genetic disorders and male infertility

BACKGROUND

At present, one out of six couples is infertile, and in 50% of cases, infertility is attributed to male infertility factors. Genetic abnormalities are found in 10%-20% of patients showing severe spermatogenesis disorders, including non-obstructive azoospermia.

METHODS

Literatures covering the relationship between male infertility and genetic disorders or chromosomal abnormalities were studied and summarized.

MAIN FINDINGS RESULTS

Genetic disorders, including Klinefelter syndrome, balanced reciprocal translocation, Robertsonian translocation, structural abnormalities in Y chromosome, XX male, azoospermic factor (AZF) deletions, and congenital bilateral absence of vas deferens were summarized and discussed from a practical point of view. Among them, understanding on AZF deletions significantly changed owing to advanced elucidation of their pathogenesis. Due to its technical progress, AZF deletion test can reveal their delicate variations and predict the condition of spermatogenesis. Thirty-nine candidate genes possibly responsible for azoospermia have been identified in the last 10 years owing to the advances in genome sequencing technologies.

CONCLUSION

Genetic testing for chromosomes and AZF deletions should be examined in cases of severe oligozoospermia and azoospermia. Genetic counseling should be offered before and after genetic testing.

Comprehensive Genome Profiling of Single Sperm Cells by Multiple Annealing and Looping-Based Amplification Cycles and Next-Generation Sequencing from Carriers of Robertsonian Translocation

Robertsonian translocation (RT) is a common cause for male infertility, recurrent pregnancy loss, and birth defects. Studying meiotic recombination in RT-carrier patients helps decipher the mechanism and improve the clinical management of infertility and birth defects caused by RT. Here we present a new method to study spermatogenesis on a single-gamete basis from two RT carriers. By using a combined single-cell whole-genome amplification and sequencing protocol, we comprehensively profiled the chromosomal copy number of 88 single sperms from two RT-carrier patients. With the profiled information, chromosomal aberrations were identified on a whole-genome, per-sperm basis. We found that the previously reported interchromosomal effect might not exist with RT carriers. It is suggested that single-cell genome sequencing enables comprehensive chromosomal aneuploidy screening and provides a powerful tool for studying gamete generation from patients carrying chromosomal diseases.

The incidence and type of chromosomal translocations from prenatal diagnosis of 3800 patients in the republic of macedonia

Robertsonian and reciprocal chromosomal translocations are the most frequent type of structural chromosomal aberrations in the human population. We report the frequency and type of detected translocations in 10 years of prenatal diagnosis of 3800 prenatal samples. The materials came from amniocentesis and chorionic villus samples (CVS). We detected seven Robertsonian translocations (0.18%), eight autosomal reciprocal translocations (0.21%) and one sex chromosome translocation (0.03%). The overall frequency of all translocations was 0.42%. Balanced state translocations were 0.29% and the frequency of translocations in an unbalanced state was 0.13%. There was one balanced de novo X-autosome translocation [46,X,t(X;10)(p11.23;q22.3)] and one balanced double translocation [46,XX,t(1;21);t(7;16)(1p21; 21q11) (7q31;16q23)] inherited from the mother. Most of the detected translocations were the result of unknown familial translocations, but some of them had been previously detected in one of the parents. In order to detect the recurrence risk for future pregnancies, we proposed genetic counseling in each of the cases and we established whether the parents were heterozygous for the same translocation. Histopatological findings for some unbalanced translocations correlated with phenotypes of detected unbalanced karyotypes.

Various endocrine disorders in children with t(13;14)(q10;q10) Robertsonian translocation

PURPOSE

45,XY,t(13;14)(q10;q10) karyotype can suggest infertility associated with more or less severe oligospermia in male adults. In addition, 45,XX,t(13;14)(q10;q10) karyotype carries reproductive risks such as miscarriage or infertility in female adults. However, reports on the phenotype of this karyotype in children are very rare. This study was done to observe various phenotypes of this karyotype in children.

METHODS

Between January 2007 and December 2012, children diagnosed with 45,XY,t(13;14)(q10;q10) or 45,XX,t(13;14)(q10;q10) karyotype by chromosome analysis were analyzed retrospectively.

RESULTS

Eight children (5 boys and 3 girls) were diagnosed with 45,XY,t(13;14)(q10;q10) or 45,XX,t(13;14)(q10;q10) karyotype. They ranged in age from 5 years and 6 months to 12 years and 4 months. The phenotypes of the study patients consisted of 1 hypogonadotrophic hypogonadism, 1 precocious puberty, 3 early puberty, 2 growth hormone deficiency (GHD) (partial) and 1 idiopathic short stature. As shown here t(13;14)(q10;q10) Robertsonian translocation shows a wide range of phenotypes.

CONCLUSION

It can be said that t(13;14)(q10;q10) Robertsonian translocation shows various phenotypes from GHD to precocious puberty in children. Further large-scale studies are necessary.

Chromosomal segregation in sperm of Robertsonian translocation carriers

PURPOSE

To study meiotic segregation patterns of Robertsonian translocations in sperm of male carriers and to assess the frequencies of unbalanced sperm formation.

METHODS

FISH with combination of probes to detect all the variants of meiotic segregation was performed on decondensed sperm nuclei of 5 carriers of der(13;14), 3 carriers of der(14;21) and one carrier of a rare der(13;21) translocation.

RESULTS

The frequency of sperm with alternate segregation and normal/balanced chromosomal complement ranged from 68 % to 94.4 % (mean 79.2 ± 8.4). Adjacent segregation was detected in 17.9 ± 7.3 % of sperm (from 5.6 % to 29 %). No significant differences in frequencies of gametes with nullisomies and disomies of chromosomes involved in translocations were observed. The mean frequency of 3:0 segregation products was 2.5 ± 1.4 %.

CONCLUSIONS

All analyzed patients showed homogenous segregation pattern with clear predominance of alternate segregation resulting in normal/balanced sperm production. Still, from 5.8-32 % (mean 20.4 ± 8.3 %) of sperm was unbalanced, which is the evidence of the increased risk of unbalanced offspring in carriers of Robertsonian translocations. Our results highlight the importance of genetic counseling of Robertsonian translocation carriers prior to ICSI or IVF.

Interchromosomal effect analyses by sperm FISH: incidence and distribution among reorganization carriers

Structural reorganization carriers usually present compromised fertility accompanied by an increased risk of producing gametes with chromosomal abnormalities that can be transmitted to the offspring. In part these imbalances are ascribed to result from the occurrence of meiotic disturbances produced by the rearrangements in the proper segregation of other chromosome pairs. This phenomenon of interference has been called interchromosomal effect (ICE). Several studies have been performed to assess the occurrence of ICE in structural reorganization carriers by analyzing the frequencies of numerical abnormalities in the gametes. Nevertheless, the occurrence and distribution of these disturbing events still is a controversial issue. In this work we present compiled data from 130 sperm fluorescent in situ hybridization (FISH) studies performed in carriers of the most frequent structural rearrangements in humans: 44 Robertsonian translocations, 66 reciprocal translocations and 13 inversions. Data from 7 complex/multiple rearrangements will be considered in a separate group. Significant increases of gametes with numerical abnormalities have been detected in all types of reorganization carriers. Among the groups of non-complex/multiple rearrangements, Robertsonian translocations appear to be the most prone to produce such interference (54.5%) closely followed by reciprocal translocations (43.9%). In contrast, ICE's were only detected in 7.7% of the inversion carriers analyzed. The presence of complex/multiple rearrangements seems to be an important factor for promoting ICE, as 71.4% of these carriers presented increased rates of gametes with numerical abnormalities. Altogether, almost half of the structural reorganization carriers (45.4%) present a higher reproductive risk of producing aneuploid/diploid spermatozoa compared to the general population. This high incidence has been obtained by analyzing a small set of chromosomes, suggesting that underlying meiotic disorders could be present in these individuals. Further ICE studies in structural reorganization carriers will help to clarify the still unknown predisposing cytogenetic features that promote this phenomenon.

Analysis using fish of sperm and embryos from two carriers of rare rob(13;21) and rob(15;22) robertsonian translocation undergoing PGD

The majority of fluorescence in situ hybridization (FISH) studies on the meiotic segregation of Robertsonian translocations focus on the most common types, rob(13; 14) and rob(14; 21). Here we report the first study for carriers of rare Robertsonian translocations rob(13; 21) and rob(15; 22) combining analysis of meiotic segregation in sperm and blastomeres following pre-implantation genetic diagnosis (PGD). Dual-colour FISH was applied to nuclei from spermatozoa and blastomeres from PGD embryos using two subterminal contig probes for each translocation, and a second round with probes for chromosomes 16 and 18. Patient 1 had a rob(13; 21) and patient 2 had a rob(15; 22), and 86.3% and 87.5% of gametes respectively were consistent with meiotic segregation resulting in a normal or balanced chromosome complement. Analysis of embryos showed that for patient 1 and 2 respectively, 25% and 46% were balanced, and of the unbalanced embryos, 50% and 31% were mosaic or chaotic. Our patients with a rob(13; 21) and rob(15; 22) were found to have a similar meiotic segregation pattern to that for male carriers of the common Robertsonian translocations. The observed rate in unbalanced embryos being mosaic or chaotic may result in an increased risk of chromosomal abnormalities. Our results may help to improve the genetic counseling for carriers of rare Robertsonian translocations.

Chromosomal segregation in spermatozoa of five Robertsonian translocation carriers t(13;14)

PURPOSE

To analyse the segregation of a Robertsonian translocation t(13;14) in five male carriers, and to verify a possible inter-chromosomal effect (ICE) of the Robertsonian translocation on chromosomes 18, X, and Y.

METHODS

The spermatozoa of these patients (n = 5) and of 15 donors with normal semen parameters and 46,XY karyotype were analysed using triple colour FISH with locus specific probes for chromosomes 13, 14, and 21 and by triple colour FISH for chromosomes X, Y, and 18.

RESULTS

The frequency of balanced spermatozoa resulting from alternate segregation varied between 62.16% and 81.70% with a mean of 71.5%. The rates of unbalanced spermatozoa resulting from adjacent segregation varied between 13.4% and 25.1% with a mean of 18.26%. Triple colour FISH X-Y-18 showed a significant increase in disomy frequencies of these chromosomes in comparison with controls, indicating an ICE.

CONCLUSION

In spite of the high number of normal/balanced frequencies, there remain many unbalanced spermatozoa resulting from adjacent mode of segregation. This raises the question of the unbalanced chromosomal risk for the offspring of 45,XY, t(13;14) males and the importance of the genetic counselling prior to ICSI or IVF treatment for couples where the male is a Robertsonian translocation carrier.

Meiotic segregation of Robertsonian translocations ascertained in cleavage-stage embryos--implications for preimplantation genetic diagnosis

BACKGROUND

The aim of this study was to ascertain the prevalence of meiotic segregation products in embryos from carriers of 13/14 and 14/21 Robertsonian translocations and to estimate the predictive value of testing single cells using the fluorescence in situ hybridization (FISH) technique, to provide more information for decision-making about PGD.

METHODS

In this prospective cohort study, the copy number of translocation chromosomes in nuclei from lysed blastomeres of cleavage-stage embryos was ascertained using locus-specific FISH probes. Logistic regression analysis, controlling for translocation type, female age and fertility status, was used to calculate the odds ratio (OR) of unbalanced segregation products for female and male heterozygotes. The primary diagnostic measure was the predictive value of the test result. The primary outcome measure was the live birth rate per couple.

RESULTS

Female carriers were four times more likely than male carriers to produce embryos with an unbalanced translocation product (OR 3.8, 95% confidence interval 2.0-7.2, P < 0.001). The prevalence of abnormality for the chromosomes tested in embryos from female or male heterozygotes was estimated to be 43 or 28%, respectively, while estimates of the predictive value were 93-100 or 96-100% for a normal test result and 79 or 57% for an abnormal test result. The live birth rate per couple was 58% for female carriers and 50% for male carriers.

CONCLUSIONS

For female carriers, PGD using FISH could reduce the risk of miscarriage from either translocation or the risk of Down syndrome from the 14/21 Robertsonian translocation. PGD using FISH for male carriers is unlikely to be indicated given the relatively low prevalence of chromosome imbalance and low predictive value.

Clinical outcomes of preimplantation genetic diagnosis (PGD) and analysis of meiotic segregation modes in reciprocal translocation carriers

Balanced reciprocal translocation is the most common chromosome rearrangement, with an incidence of 1 out of 625 newborns. In reciprocal translocation carriers, genetically unbalanced gametes can be produced through three principal modes of segregation: adjacent-1, adjacent-2 and 3:1. In this study, we reviewed 133 cycles of preimplantation genetic diagnosis (PGD) for 65 couples with reciprocal translocation and analyzed pregnancy outcomes and the meiotic segregation mode of gametes of the translocation carriers using fluorescent in situ hybridization (FISH). We found that 285 of 1,508 embryos (18.9%) were normal or balanced. Thirty-three clinical pregnancies, including eight spontaneous abortions (21.6% per couple), were established. According to the meiotic segregation analysis, the frequencies of 3:1 and 4:0 segregation modes were significantly higher (P < 0.05) in female carriers, and the frequencies of adjacent-1 and chaotic segregation modes were significantly higher (P < 0.05) in male carriers. Our results indicate that meiotic segregation might be affected by the carrier's sex but not by the carrier's age or breakpoints.

Meiotic segregation and interchromosomal effect in the sperm of a double translocation carrier: a case report

BACKGROUND

Infertility is a natural mechanism of selection intended to prevent the delivery of a child with malformations or mental retardation. Male infertility is closely related to chromosomal abnormalities. This study was focused on the analysis of meiotic segregation involving a Robertsonian translocation, 45,XY,der(13;13) [56]/45,XY,der(13;14) [44] and the evaluation of possible interchromosomal effects.

RESULTS

Hybridisation with LSI 13q14 and subtelomere 14q probes and WCP13 SpectrumGreen and WCP14 SpectrumOrange probes showed a high proportion of unbalanced gametes, corresponding to 71.2% of the spermatozoa. The disomic frequencies of the sexual chromosomes and chromosome 18 of the patient were higher (5.28% and 2.55%, respectively) than those of the control (0.6% and 0.59%, respectively).

CONCLUSION

Meiotic segregation studies in sperm are an important tool for genetic counselling of chromosomal aberrations, allowing for a prediction of the risks and consequent implications for the reproductive life. The patient with this rare translocation exhibited meiotic segregation fidelity, and a high rate of unbalanced gametes with disomic spermatozoa.

Cytogenetic determinants of male fertility

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Analysis of meiotic segregation patterns and interchromosomal effects in sperm from six males with Robertsonian translocations

PURPOSE

To provide more genetic information about meiotic segregation behavior and the possibility of interchromosomal effects (ICE) in spermatozoa from carriers of Robertsonian (Rob) translocations.

MATERIALS AND METHODS

Meiotic segregation behavior in spermatozoa from six carriers of Rob translocations, four t(13;14), one t(14;22) and one t(13;21), was investigated by dual fluorescence in-situ hybridization (FISH). Aneuploidy for chromosomes 18, X and Y was studied by triple FISH.

RESULTS

The rate of normal/balanced spermatozoa resulting from alternate segregation ranged from 78.14 to 86.88%. The frequency of unbalanced spermatozoa resulting from adjacent segregation varied between 11.70 and 19.53%. The higher frequencies of aneuploidy for sex chromosome were observed in three Rob translocation carriers. In addition, the increased rates of diploid were found in two t(13;14) carriers.

CONCLUSIONS

Alternate segregation is dominant in the different types of Rob translocations. Some carriers may be at an increased risk for ICE.

Fertility testing and ICSI sperm selection by hyaluronic acid binding: clinical and genetic aspects

The testis-expressed chaperone protein, HspA2 (previously creatine kinase M isoform) was established as a measure of human sperm cellular maturity, function and fertility. The presence of HspA2 in the synaptonemal complex is likely to link low HspA2 expression and increased frequency of chromosomal aneuploidies in arrested-maturity spermatozoa. A relationship also exists between HspA2 expression in elongating spermatids and the associated spermatogenetic events, including plasma membrane remodelling and the formation of zona pellucida and hyaluronic acid (HA) binding sites. The HA receptor of mature spermatozoa, when coupled with HA-coated slides and/or Petri dishes, allows visual observation of sperm-HA binding, providing a basis for sperm maturity testing, a major improvement in semen evaluation, and selection of mature spermatozoa for intracytoplasmic sperm injection (ICSI). Thus, in HA-selected spermatozoa the frequency of chromosomal disomy and diploidy is reduced 4- to 6-fold compared with semen sperm fractions. This reduction is similar to the increase in numerical chromosomal aberrations in ICSI children. Combined studies of sperm shape and chromosome probes demonstrated that sperm morphology does not aid selection of haploid spermatozoa. The HA-mediated sperm selection is a novel and efficient technique that may alleviate potential problems related to ICSI fertilization with visually selected spermatozoa.

The impact of male factor on recurrent pregnancy loss

PURPOSE OF REVIEW

The present paper reviews the current literature on the impact of male factor on recurrent pregnancy loss.

RECENT FINDINGS

Most clinicians focus their evaluation of recurrent pregnancy loss on the female, without much, if any, consideration of the other half of the couple - the male. Yet, the male contributes one-half of the genes for the embryo. Recent literature demonstrates that the male contributes to recurrent pregnancy loss due to genetic factors, semen factors or due to other factors such as age.

SUMMARY

Recurrent pregnancy loss results as a factor of a couple. This paper emphasizes the contribution of the male to implantation failure, miscarriage, and congenital anomalies suggested by recent literature. The current data are preliminary. With further investigation, evaluation of the male may be considered a routine part of the evaluation in the near future.

Studying meiosis: a review of FISH and M-FISH techniques used in the analysis of meiotic processes in humans

It is well known that chromosome in situ hybridization allows the unequivocal identification of targeted human somatic chromosomes. Different fluorescent in situ hybridization (FISH) techniques have been developed throughout the years and, following the mitotic studies, meiotic analyses have been performed using these different techniques. The introduction of M-FISH techniques to the analysis of meiotic cells has allowed the study of meiotic processes for every individual human chromosome. In this paper, we review the different FISH and M-FISH techniques that have been used on human meiotic cells in both men and women.

Rare Robertsonian translocations and meiotic behaviour: sperm FISH analysis of t(13;15) and t(14;15) translocations: a case report

t(13;15) and t(14;15) are two rare Robertsonian translocations. Meiotic segregation was studied in four males heterozygous for the rare Robertsonian translocations t(13;15) and t(14;15). Both locus-specific probes (LSPs) and whole chromosome painting (WCP) probes, specific to chromosomes 13, 14 and 15, were used in this study. The number of spermatozoa scored for each carrier ranged from 891 to 5000. The frequencies of normal and balanced sperm resulting from the alternate mode of segregation ranged from 77.6 to 92.8%, confirming the prevalence of alternate segregation over other segregation modes in all Robertsonian translocations. The incidences of unbalanced complements ranged from 6.7 to 20.4%, with a significant excess of disomy rates over the complementary frequencies of nullisomy. This variability might reflect differences in the location of breakpoints in translocated chromosomes, leading to the variable production of unbalanced gametes and the variable alterations of semen parameters in Robertsonian translocation carriers.

Chromosomal segregation in spermatozoa of 14 Robertsonian translocation carriers

Male carriers of Robertsonian (Rob) translocations can have fertility problems associated with low sperm counts and abnormal sperm morphology. In this study, spermatozoa from 14 Rob translocation carriers, seven der(13;14), two der(13;15), two der(14;15), two der(14;21) and one der(21;22), were tested by fluorescence in-situ hybridization (FISH) for the chromosomes involved, to study meiotic segregation behaviour. It was shown that in each type of Rob translocation, meiotic segregation behaviour is similar, comparable and occurs non-randomly. Most of the spermatozoa results from alternate segregation (range: 76-89.47%). There is, however, still much unbalanced spermatozoa resulting from adjacent segregation mode (range: 10.24-23.41%). These data provide useful information for genetic counselling purposes. Moreover, aneuploidy for chromosomes 13,18, 21, X and Y was studied in five patients and suggested an inter-chromosomal effect.

Sperm nuclei analysis of 1/29 Robertsonian translocation carrier bulls using fluorescence in situ hybridization

In 1964, Gustavsson and Rockborn first described the 1/29 Robertsonian translocation in cattle. Since then, several studies have demonstrated the negative effect of this particular chromosomal rearrangement on the fertility of carrier animals. During the last decade, meiotic segregation patterns have been studied on human males carrying balanced translocations using FISH on decondensed sperm nuclei. In this work, we have applied the 'Sperm-FISH' technique to determine the chromosomal content of spermatozoa from two bulls heterozygous for the 1/29 translocation and one normal bull (control). 5425 and 2702 sperm nuclei were scored, respectively, for the two heterozygous bulls, using whole chromosome painting probes of chromosomes 1 and 29. Very similar proportions of normal (or balanced) spermatozoa resulting from alternate segregation were observed (97.42% and 96.78%). For both heterozygous bulls, the proportions of nullisomic and disomic spermatozoa did not follow the theoretical 1:1 ratio. Indeed, proportions of nullisomic spermatozoa were higher than those of disomic sperma tozoa (1.40% vs 0.09% (bull 1) and 1.29% vs 0.15% (bull 2) for BTA1, and 0.65% vs 0.40% (bull 1) and 1.11% vs 0.63% (bull 2) for BTA29). The average frequencies of disomic and diploid spermatozoa in the normal bull were 0.11% and 0.05%, respectively.

Segregation of chromosomes in sperm of Robertsonian translocation carriers

Robertsonian translocations are the most frequent structural chromosomal abnormalities in humans and can affect fertility, with various degrees of sperm alterations in men; or the pregnancy outcome of the carriers. The studies on meiotic segregation of chromosomes in sperm of Robertsonian translocation males find a majority of normal or balanced spermatozoa for the chromosomes related to the translocation (mean 85.42%; range 60-96.60%). Furthermore, recent studies suggest an interchromosomal effect. Studies on spermatozoa from translocation carriers, and in mouse models help the comprehension of the meiotic segregation mechanisms. Results of meiotic segregation analysis in man could be integrated in genetic counselling especially when assisted reproductive technology is required.

Intracytoplasmic sperm injection: a novel selection method for sperm with normal frequency of chromosomal aneuploidies

OBJECTIVE

To test a newly invented intracytoplasmic sperm injection (ICSI) sperm selection method based on sperm hyaluronic acid (HA) binding.

DESIGN

Comparison of chromosomal disomy and diploidy frequencies in sperm arising from semen and in HA-bound sperm.

SETTING

Academic andrology laboratory.

PATIENT(S)

Men presenting for semen analysis.

INTERVENTION(S)

Washed sperm fractions of 32 semen samples were applied to Petri dishes or glass slides coated with immobilized HA. The unbound sperm were rinsed gently, and the HA-bound sperm were removed with an ICSI pipette. The control sperm population was the unselected sperm. Both HA-selected and unselected sperm were treated with fluorescence in situ hybridization with centromeric probes for the X, Y, and 17 chromosomes.

MAIN OUTCOME MEASURE(S)

Chromosomal disomy and diploidy frequencies.

RESULT(S)

In the HA-bound sperm (495-2,079 per man, 41,670 in all) compared with unselected sperm (4,770 per man, 162,210 in all), the chromosomal disomy frequencies were reduced to 0.16% from 0.52%, diploidy to 0.09% from 0.51%, and sex chromosome disomy to 0.05% from 0.27% (a 5.4-fold reduction vs. 4-fold respective increase in ICSI offspring).

CONCLUSION(S)

The HA sperm selection method for ICSI, which is based on a relationship between sperm receptors for zona pellucida and HA, will likely reduce the potential genetic complications and adverse public health effects of ICSI.

Meiotic segregation patterns and ICSI pregnancy outcome of a rare (13;21) Robertsonian translocation carrier: a case report

t(13;21) is an uncommon Robertsonian translocation (RT) with limited information in the literature. Hereby, we assessed the meiotic segregation and interchromosomal effect (ICE) in sperm nuclei from a t(13;21) carrier. The pregnancy outcome following ICSI was also included as reference for physicians and patients. Dual-colour fluorescent in situ hybridization (FISH) was carried out to analyse the segregation pattern of chromosomes 13 and 21, while triple-colour FISH was used to investigate the possible concurrence of ICE. With respect to chromosomal constitutions of 13 and 21, 88.39% of the spermatozoa were normal or balanced due to alternative segregations, and 11.08% showed nullisomy or disomy as a result of adjacent segregations. However, for chromosome 18 and sex chromosomes, the proportion of normal haploids was 98.79%. The rate of disomy was not significantly higher than the controls for either chromosome 18 or X/Y. The rare t(13;21) case exhibited a similar pattern of meiotic segregation as in the common RTs. ICEs were not observed in the current case.

Interchromosomal effect in sperm of males with translocations: report of 6 cases and review of the literature

Somatic chromosomal abnormalities are frequently found in infertile men, particularly in those with low sperm count and/or seeking intracytoplasmic sperm injection. These abnormalities mostly consist of numerical sex chromosome abnormalities and translocations (Robertsonian or reciprocal). In this study, we searched for the occurrence of non-disjunction of chromosomes not involved in translocations during meiosis, phenomenon called interchromosomal effect (ICE) and first described by Lejeune (1965). Ejaculate samples of two patients carrying a Robertsonian translocation and four a reciprocal translocation patients and four controls (men with a 46,XY karyotype and normal sperm parameters) were studied in dual FISH 7-9, dual FISH 13-21 and triple FISH X-Y-18. A statistically significant increase of disomy X, Y and XY (P = 0.009, P = 0.004, P < 0.001) was found in the Robertsonian der(13;14)(q10;q10) carrier but not in the der(14;21)(q10;q10) carrier compared with controls. Among reciprocal translocation carriers, a significant increase of disomy 21 (P = 0.033) was observed in a sole patient with a t(9;22)(q21;q11.2). The increase of meiotic non-disjunction for chromosome 21 and sex chromosomes is a recurrent event found in other studies. According to our results and published data, the ICE on some specific chromosomes is likely in men carrier of a translocation, although it cannot be excluded that the aneuploidy is related to the oligoasthenoteratozoospermia usually present in these men. Moreover, this phenomenon showed interindividual variations which cannot be predicted. The risk of aneuploidy in sperm of males used for ICSI need to be evaluated. It could be superadded to that of meiotic segregation of the translocation to give a more precise and personalized risk assessment of aneuploidy in the offspring of those men.

FISH studies of chromosome abnormalities in germ cells and its relevance in reproductive counseling

Chromosome abnormalities are one of the major causes of human infertility. In infertile males, abnormal karyotypes are more frequent than in the general population. Furthermore, meiotic disorders affecting the germ cell-line have been observed in men with normal somatic karyotypes consulting for infertility. In both cases, the production of unbalanced spermatozoa has been demonstrated. Basically addressed to establish reproductive risks, fluorescence in situ hybridization (FISH) on decondensed sperm heads has become the most frequently used method to evaluate the chromosomal constitution of spermatozoa in carriers of numerical sex chromosome abnormalities, carriers of structural chromosome reorganizations and infertile males with normal karyotype. The aim of this review is to present updated figures of the information obtained through sperm FISH studies with an emphasis on its clinical significance. Furthermore, the incorporation of novel FISH-based techniques (Multiplex-FISH; Multi-FISH) in male infertility studies is also discussed.

Analysis of chromosome segregation during preimplantation genetic diagnosis in both male and female translocation heterozygotes

Individuals carrying translocations suffer from reduced fertility or spontaneous abortions and seek help in form of assisted reproductive technology (ART) and preimplantation genetic diagnosis (PGD). While most translocations are relatively easy to detect in metaphase cells, the majority of embryonic cells biopsied in the course of in vitro fertilization (IVF) procedures are in interphase. These nuclei are thus unsuitable for analysis by chromosome banding or painting using fluorescence in situ hybridization (FISH). Thus several methods have been devised to detect translocation imbalance through FISH in single cells for purpose of PGD, among them polar body chromosome painting, interphase FISH with combination of subtelomeric and centromeric probes, breakpoint spanning probes, and cell conversion. Results with PGD indicate a significant decrease in spontaneous abortions, from 81% before PGD to 13% after PGD. They also indicate very high rates of chromosome abnormalities in embryos from translocation carriers, 72% for Robertsonian translocations and 82% for reciprocal translocations. Sperm analysis was found to be a good predictor of IVF and PGD outcome, with samples with more than 60% abnormal forms indicating poor prognosis. Similarly, the predictability from first PGD cycle results for future cycles was 90%. In summary, PGD can help translocation carriers to achieve viable pregnancies, but the success of the process is conversely related to the baseline of unbalanced gametes.

Sperm studies in heterozygote inversion carriers: a review

The risk of producing unbalanced gametes in heterozygous inversion carriers mostly depends on the occurrence of recombination events within the inverted segment. Recombination determines the possibility of producing chromosomes with duplications/deficiencies (pericentric inversions) or with duplications/deficiencies which furthermore appear as dicentric and acentric fragments (paracentric inversions). In this work, a general description of the close relationship between the occurrence of crossovers in pericentric and paracentric inversions and the final segregation outcome is presented. After this introduction, a compilation of inversion segregation data and interchromosomal effect results from previously published sperm studies have been reviewed. Segregation results indicate a great heterogeneity in the percentage of unbalanced gametes, from 0 to 37.38%. The size of the inverted segments and their proportion in the chromosome are two parameters closely related with the incidence of recombination (P < 0.0001; using a quadratic model and Pearson's correlation test). These results suggest that the production of a significant level of unbalanced gametes would require a minimum inversion size of 100 Mbp and the inversion of at least 50% of the chromosome. Interchromosomal effects are seldom observed in chromosomal inversions. Finally, implications of the meiotic behavior of the inversions in the progeny of the carriers and the incorporation of sperm FISH segregation analysis for reproductive genetic counseling are discussed.

Fluorescence in situ hybridization sperm analysis of six translocation carriers provides evidence of an interchromosomal effect

OBJECTIVE

To investigate the existence of an interchromosomal effect in balanced reciprocal translocation carriers and to evaluate their risk of having an affected child or repeated spontaneous abortions.

DESIGN

Analysis of chromosomal sperm content by fluorescence in situ hybridization (FISH) using probes for chromosomes 1, 15, 16, 17, 18, X, and Y.

SETTING

University hospital.

PATIENT(S)

Six male carriers of balanced chromosome rearrangements, one with normal sperm parameters and five with oligoasthenoteratozoospermia, and seven fertile controls.

INTERVENTION(S)

Fluorescence in situ hybridization for chromosomal enumeration on sperm samples.

MAIN OUTCOME MEASURE(S)

Rate of disomy for the studied chromosomes.

RESULT(S)

A total of 123,842 spermatozoa were scored (82,181 for controls and 41,661 for patients). For each patient, at least one chromosome studied presented a significantly increased rate of disomy. One patient showed a clear interchromosomal effect for at least three of the six chromosomes studied. Disomy rates were statistically significantly and inversely correlated with the total progressive motility of spermatozoa.

CONCLUSION(S)

The observed interchromosomal effect seems to be translocation, patient, and chromosome dependent. Variable effects were observed, according to the chromosome studied. When we looked at patients carrying the same translocation, the level of disomy rate was variable and affected different chromosomes.

Molecular cytogenetics analysis with whole chromosome paint probes of sperm nuclei from a (13;15) Robertsonian translocation carrier

Meiotic segregation of a Robertsonian translocation (13;15) was assessed in sperm nuclei using dual-color fluorescent in situ hybridization (FISH) with whole-chromosome paint probes. Most spermatozoa in the (13;15) translocation carrier resulted from alternate segregation. Although an increased frequency of unbalanced gametes was observed, spontaneous pregnancy led to the birth of a boy with a normal karyotype.

Ultrastructural studies of spermatozoa from infertile males with Robertsonian translocations and 18, X, Y aneuploidies

BACKGROUND

In order to clarify the relationship between chromosomal rearrangements, sperm morphology and interchromosomal effects (ICE), we studied the spermatogenetic defects in seven infertile Robertsonian translocation carriers.

METHODS

Lymphocyte karyotypes were evaluated using Giemsa-Trypsin-Giemsa banding and fluorescence in-situ hybridization (FISH). Semen analysis was performed by light and transmission electron microscopy. FISH of sperm nuclei was carried out to detect possible ICE.

RESULTS

Lymphocyte karyotype analysis revealed five t(13;14), one t(13;21) and one t(14;22) carriers. Sperm ultrastructural examination highlighted a higher percentage of immaturity, apoptosis and necrosis than in controls. Aneuploidies of gonosomes were detected in sperm from five out of six carriers of Robertsonian translocation, whereas aneuploidy of chromosome 18 was evident in three out of six carriers. The frequencies of diploidy were altered in all cases.

CONCLUSIONS

Since these infertile patients showed severe spermatogenetic impairment from the morphological and meiotic points of view, we recommend detailed sperm ultrastructural and chromosomal analysis before undertaking ICSI cycles in Robertsonian translocation carriers.

Sperm segregation analysis of a (13;22) Robertsonian translocation carrier by FISH: a comparison of locus-specific probe and whole chromosome painting

BACKGROUND

The t(13;22) Robertsonian translocation constitutes a rare form of rearrangement between acrocentric human chromosomes. Most of the meiotic segregation studies of human Robertsonian translocations have been performed on common t(13;14) and t(14;21) translocations. Analysis of the chromosomal constitution in sperm of Robertsonian translocation carriers is of great interest for assessing the risk of unbalanced forms and adapting genetic counselling. In the present study, we present the first meiotic segregation study of a t(13;22) Robertsonian translocation in human sperm.

METHODS

A total of 11 787 sperm nuclei were scored using two distinct FISH labelling techniques, i.e. the locus-specific probes (LSI) method and the whole chromosome painting (WCP) technique.

RESULTS

The frequency of normal or balanced sperm resulting from alternate meiotic segregation was 86%. Incidences of unbalanced complements resulting from adjacent segregation modes were 12.79% and 14.36% in LSI and WCP assays, respectively. No significant excess of nullisomy or disomy for the affected chromosomes was observed.

CONCLUSIONS

Similar results in segregation were obtained with the two techniques, demonstrating the efficiency of the two strategies for the direct segregation analysis of Roberstsonian translocations. The results obtained indicated a moderate meiotic production of imbalance. This study shows that the rare Robertsonian translocation (13;22) displays a similar distribution of balanced and unbalanced sperm patterns as the common Robertsonian translocations previously studied. This suggests that the behaviour of acrocentric chromosomes was similar in all cases of centric fusion.

Negligible interchromosomal effect in embryos of Robertsonian translocation carriers

It has been suggested that translocations, and perhaps other chromosome rearrangements, disturb meiotic disjunction of chromosome pairs not involved in the translocation, resulting in non-disjunction in those chromosomes (interchromosomal effect) and predisposition to trisomy offspring. Other reports have suggested an increased risk of mosaicism and chaotic embryos in translocation carriers. This study was designed to determine if such interchromosomal effects are producing significantly more chromosome abnormalities than those expected from unbalanced gametes. For that purpose, two groups of PGD patients were compared, Robertsonian translocation carriers (RBT) and carriers of X-linked diseases (XLI), of similar age. Both groups were analysed by FISH with similar DNA probes. The results indicate that overall, the higher rate of chromosome abnormalities in the RBT group was solely due to unbalanced gametes and not to an interchromosomal effect or higher incidence of mosaicism. If unbalanced and normal were combined, this proportion was 53% in XLI and 59% in RBT. However, when specific RBT translocations were studied, only a slight increase in embryos with aneuploidy for chromosome 22 was found for the t(13;14) translocation carriers, while a higher rate of post-zygotic abnormalities was observed in the more rare RBT. In conclusion, the overall rate of non-translocation related abnormalities was not increased in the RBT group compared with the control group, but a slight interchromosomal effect may exist, as some Robertsonian translocations may be more prone to produce mosaic and chaotic embryos.

Meiotic segregation of translocations during male gametogenesis

Balanced reciprocal and Robertsonian translocations are the most common structural chromosomal abnormalities in humans. Generally, they are without consequence for the carrier, but for various degrees of oligoasthenoteratozoospermia in men. As these carriers can produce a significant percentage of gametes with an unbalanced combination of the parental rearrangement, there is a more or less significant risk, according to cases, of chromosomal imbalances for their offspring. Therefore, techniques were developed to study the meiotic segregation of these translocations in males. Direct investigation of human sperm chromosomes became possible by karyotyping spermatozoa after penetration of zona-free hamster oocytes and, more recently, using fluorescent in situ hybridization (FISH). This paper reviews the results obtained using these techniques in Robertsonian and reciprocal translocations. The studies on spermatozoa from translocation carriers help the comprehension of the mechanisms of the meiotic segregation. They should be integrated in the genetic exploration of the infertile men, in order to give them a personalized risk assessment of unbalanced spermatozoa, specially as a correlation was found recently between the percentage of abnormal spermatozoa and that of abnormal embryos.

Genetic analysis of sperm and implications of severe male infertility--a review

The use of fluorescence in situ hybridization (FISH) on decondensed sperm heads has allowed to analyse the chromosome constitution of spermatozoa in different populations. In controls, the mean incidence of disomy (including all chromosomes) is about 6.7 per cent; diploidy increases with age, and some individuals may show a special tendency to nondisjunction. Carriers of numerical sex chromosome anomalies show a low incidence of sex chromosome disomies (2.54-7.69 per cent), and the need to screen ICSI candidates for these conditions has to be reconsidered. Carriers of inversions produce from 0 to 54.3 per cent abnormal sperm. Carriers of Robertsonian translocations produce from 3.4 to 36.0 per cent abnormal sperm, and carriers of reciprocal translocations produce from 47.5 to 81.0 per cent abnormal spermatozoa. However, carriers of translocations usually produce more abnormal embryos than expected from these figures. This may be partly related to interchromosomal effects induced by some structural reorganizations. Males with oligoasthenozoospermia, low motility and/or high FSH concentrations show frequent synaptic anomalies, resulting in the production of aneuploid and diploid sperm. Testicular sperm show extremely high rates of chromosomal abnormalities. The risk of recurrent abortion is increased by the presence of chromosome abnormalities in sperm.

Preferential alternate segregation in the common t(11;22)(q23;q11) reciprocal translocation: sperm FISH analysis in two brothers

Segregation behaviour studies in t(11;22) carriers have reported controversial results. Whereas some authors have detected a preponderance of 3:1 products, no evidence of such prevalence was found by others. This study reports a fluorescence in-situ hybridization (FISH) segregation analysis on decondensed spermatozoa in two brothers, carriers of the same t(11;22)(q23;q11) rearrangement. Data revealed a similar meiotic segregation pattern in both carriers, 2:2 Alternate segregation being the most frequent (42.94 and 45%), while 3:1 genotypes were the least frequent in both patients, with percentages around 10%. The production of three chiasmata, based on the presence of G-light bands along the translocated segments and the presence of recombination sites at 11q and 22q distal regions, are proposed as the cause of a preponderance of the Alternate segregation. Interchromosomal effects involving chromosomes 13, 18, 21, X and Y were also evaluated. An increased frequency of sex chromosome disomies was detected in one patient. Reviewing the literature, a relationship between this phenomenon and the involvement of acrocentric chromosomes in the reorganization is suggested. FISH segregation and interchromosomal effects studies in spermatozoa are encouraged to gather information to establish the best approach for preimplantational genetic diagnosis in reorganization carriers.