Multicolor fluorescence in situ hybridization analysis of meiotic chromosome segregation in a 47,XYY male and a review of the literature

A patient with 47, XYY mosaic karyotype and congenital absence of bilateral vas deferens: a case report and literature review

Background

The incidence of 47, XYY syndrome in live-born male infants is 1/1000. Due to its variable clinical symptoms, the diagnosis is easy to miss. The incidence of congenital bilateral absence of the vas deferens (CBAVD) in infertile men is 1–2%. The main cause is the mutation of CFTR and ADGAG2 genes.

Case presentation

The patient was a 33-year-old man who visited a doctor 5 years ago due to infertility. The investigation revealed that the patient’s secondary sexual characteristics, testicular, and penis development were normal, and there was no gynecomastia, but the bilateral vas deferens and epididymis were not palpable. Transrectal ultrasound showed that the left seminal vesicle was missing, and the right seminal vesicle was atrophied. No abnormality was observed in Y chromosome microdeletion. Karyotype analysis indicated that the patient was 46, XY/47, XYY mosaic. Genetic testing found heterozygous mutations at two sites of CFTR (c263T > G and c2249C > T).

Conclusions

Herein, we report the rare case of a male patient with clinical manifestations of infertility, chromosome 46, XY/47, XXY mosaic type, simultaneously manifested as the absence of bilateral vas deferens. Two pathogenic heterozygous CFTR gene mutations were found. Given the low genetic risk of the disease, we recommend that patients undergo intracytoplasmic sperm injection (ICSI) for fertility assessment.

Reproductive outcomes of 3 infertile males with XYY syndrome: Retrospective case series and literature review

The aim of this study is to evaluate the pregnancy outcomes of males with a 47, XYY karyotype following assisted reproductive treatment.A retrospective study was performed using data from infertile men with 47, XYY at a center for reproductive medicine in 2004 to 2017. Of the 19,842 infertile males treated, a total of 21 showed the 47, XYY karyotype and were included in the present study. Clinical variables were collected. Three men were under treatment with their partner before either in vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI).The incidence of 47, XYY in infertile men is 1/945 (21/19842). Most men are azoospermic or severely oligospermic. Three men and their partners underwent IVF or ICSI treatment with fresh ejaculate samples. The fertilization rate was 52.94% to 83.33%. The embryo cleavage rate was 50% to 90%. One man had abnormal sex hormonal levels and his partner had no clinical pregnancy. The other 2 couples had healthy baby boys.Live spermatozoa can be gathered and fertility is possible for infertile males with 47, XYY syndrome when IVF or ICSI treatment is used. It is recommended that genetic counseling is provided in such cases.

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.

Preferential Y-Y pairing and synapsis and abnormal meiotic recombination in a 47,XYY man with non obstructive azoospermia

Back ground

Men with 47, XYY syndrome are presented with varying physical attributes and degrees of infertility. Little information has been documented regarding the meiotic progression in patients with extra Y chromosome along with the synapses and recombination between the two Y chromosomes.

Methods

Spermatocyte spreading and immunostaining were applied to study the behavior of the extra Y chromosome during meiosis I in an azoospermia patient with 47, XYY syndrome and results were compared with five healthy controls with proven fertility.

Results

The extra Y chromosome was present in all the studied spermatocytes of the patient and preferentially paired and synapsed with the other Y chromosome. Consistently, gamma-H2AX staining completely disappeared from the synapsed regions of Y chromosomes. More interestingly, besides recombination on short arms, recombination on the long arms of Y chromosomes was also observed. No pairing and synapsis defects between homologous autosomes were detected, while significantly reduced recombination frequencies on autosomes were observed in the patient. The meiotic prophase I progression was disturbed with significantly increased proportion of leptotene, zygotene cells and decreased pachytene spermatocytes in the patient when compared with the controls.

Conclusions

These findings highlight the importance of studies on meiotic behaviors in patients with an abnormal chromosomal constitution and provide an important framework for future studies, which may elucidate the impairment caused by extra Y chromosome in mammalian meiosis and fertility.

Electronic supplementary material

The online version of this article (doi:10.1186/s13039-016-0218-z) contains supplementary material, which is available to authorized users.

Function of the sex chromosomes in mammalian fertility

The sex chromosomes play a highly specialized role in germ cell development in mammals, being enriched in genes expressed in the testis and ovary. Sex chromosome abnormalities (e.g., Klinefelter [XXY] and Turner [XO] syndrome) constitute the largest class of chromosome abnormalities and the commonest genetic cause of infertility in humans. Understanding how sex-gene expression is regulated is therefore critical to our understanding of human reproduction. Here, we describe how the expression of sex-linked genes varies during germ cell development; in females, the inactive X chromosome is reactivated before meiosis, whereas in males the X and Y chromosomes are inactivated at this stage. We discuss the epigenetics of sex chromosome inactivation and how this process has influenced the gene content of the mammalian X and Y chromosomes. We also present working models for how perturbations in sex chromosome inactivation or reactivation result in subfertility in the major classes of sex chromosome abnormalities.

Rate of X chromosome aneuploidy in young fertile women: Comparison of cultured and uncultured cell preparations using fluorescence in situ hybridisation

BACKGROUND

X chromosome aneuploidy <10% in female patients is a routinely used reporting limit in diagnostic cytogenetics. X aneuploidy (<10%) is commonly detected in women investigated for infertility or recurrent miscarriages. It is unclear if this aneuploidy is causally relevant or related to the culture process. Information about the background rate of X aneuploidy in young fertile women would be helpful in resolving this issue.

AIM

This study aimed to investigate the rate of X aneuploidy in young fertile women in cultured and uncultured samples to determine if the commonly used <10% limit is relevant.

METHOD

Volunteers (aged 22-40 years) with proven fertility (n = 78) participated. The number of X chromosome signals in 500 cultured and 500 uncultured preparations were enumerated using FISH.

RESULTS

Significantly, all participants had <5% X aneuploidy in both preparations, X chromosome loss occurred (2.4%) more frequently than gain (0.7%). Cultured preparations had a mean of 2.1% cells with X chromosome aneuploidy (95% CI 1.9-2.3%) compared with a mean rate of 0.9% aneuploidy in uncultured preparations (95% CI 0.7-1.1%). The relative risk for cultured preparations having X aneuploidy compared with uncultured cells was 2.33 (P < 0.001) (95% CI 2.1-2.6).

CONCLUSION

Young fertile women had <5% X aneuploidy. The rate of X aneuploidy was higher in cultured (2.1%) compared with uncultured (0.9%) preparations (P < 0.001). This data may provide useful background information when considering low level X aneuploidy in other groups of women with clinical indications for karyotype.

Evidence that meiotic sex chromosome inactivation is essential for male fertility

The mammalian X and Y chromosomes share little homology and are largely unsynapsed during normal meiosis. This asynapsis triggers inactivation of X- and Y-linked genes, or meiotic sex chromosome inactivation (MSCI). Whether MSCI is essential for male meiosis is unclear. Pachytene arrest and apoptosis is observed in mouse mutants in which MSCI fails, e.g., Brca1(-/-), H2afx(-/-), Sycp1(-/-), and Msh5(-/-). However, these also harbor defects in synapsis and/or recombination and as such may activate a putative pachytene checkpoint. Here we present evidence that MSCI failure is sufficient to cause pachytene arrest. XYY males exhibit Y-Y synapsis and Y chromosomal escape from MSCI without accompanying synapsis/recombination defects. We find that XYY males, like synapsis/recombination mutants, display pachytene arrest and that this can be circumvented by preventing Y-Y synapsis and associated Y gene expression. Pachytene expression of individual Y genes inserted as transgenes on autosomes shows that expression of the Zfy 1/2 paralogs in XY males is sufficient to phenocopy the pachytene arrest phenotype; insertion of Zfy 1/2 on the X chromosome where they are subject to MSCI prevents this response. Our findings show that MSCI is essential for male meiosis and, as such, provide insight into the differential severity of meiotic mutations' effects on male and female meiosis.

Clinical Review#: State of the art for genetic testing of infertile men

Intracytoplasmic sperm injection (ICSI) now provides fertility in many cases of severe idiopathic spermatogenic failure and obstructive azoospermia. Genetic causes must be sought by systematic evaluation of infertile men and affected couples informed about the implications of such diagnoses for assisted reproductive technology outcome and their potential offspring. This review discusses established and emerging genetic disorders related to fertility practice. Chromosomal anomalies are found in about 7% men with idiopathic spermatogenic failure, predominantly numerical/structural in azoospermic men and translocations/inversions in oligospermic men. Routine karyotyping of men with sperm densities less than 10 million/ml, even in the absence of other clinical presentations, is recommended because infertility is associated with higher rates of aneuploidy in ejaculated or testicular sperm and increased chromosomal defects in ICSI offspring. The long arm of the Y chromosome microdeletions are the most common recognized genetic cause of infertility and are found in about 4% men with sperm densities less than 5 million/ml. Routine testing using strict quality assurance procedures is recommended. Azoospermia factor (AZF)-c deletions, the most common form of the long arm of the Y chromosome microdeletions, are usually associated with low levels of sperm in the ejaculate or in testis biopsies, whereas men with AZFa or AZFb+c deletions usually produce no testicular sperm. When AZF-deleted sperm are available and used for ICSI, fertility defects in male offspring seem inevitable. Bilateral congenital absence of the vas is associated with heterozygosity for cystic fibrosis transmembrane receptor mutations making routine gene screening and genetic counseling of the couple essential. Testing for less common genetic associations/defects linked with different reproductive dysfunction may be applicable to specific patients but have not entered routine practice.

Underlying karyotype abnormalities in IVF/ICSI patients

Cytogenetic investigations are performed in couples asking for IVF or intracytoplasmic sperm injection (ICSI) treatment. These serve a diagnostic purpose because male or female infertility might have a chromosomal origin. Chromosomal aberrations found in these patients include numerical abnormalities, such as Klinefelter syndrome, XYY karyotype or Turner syndrome and its variants; sex reversions, such as XX males or XY females; and also structural abnormalities, such as Robertsonian or reciprocal translocations and inversions. Finding the chromosomal origin of infertility in a patient also has a prognostic value because it aids the management of pregnancies obtained after IVF or ICSI and may lead to a proposal of prenatal or preimplantation genetic diagnosis.

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.

Sperm ultrastructure and meiotic segregation in an infertile 47, XYY man

The majority of 47, XYY males are fertile and contribute to produce chromosomally normal children. In 47, XYY carriers, most meiotic studies indicated that the extra Y chromosomes were lost in the pre-meiotic stages, but in some cases the presence of one X and the two Y chromosomes has been detected during prophase I as an X univalent plus a YY bivalent. The aim of this study was to describe sperm parameters and meiotic segregation in a case of an infertile man with a 47, XYY karyotype. Sperm morphology was evaluated for the first time by transmission electron microscopy highlighting apoptosis and necrosis as the most frequent pathologies. Meiotic segregation was explored by fluorescence in situ hybridisation technique, which makes us capable of detecting aneuploidies of sex chromosomes. The fact that the frequency of 1818XY diploidy was very high reveals an error occurring during first meiotic division. Polymerase chain reaction analysis did not show any Y microdeletion. The combination of these two techniques led us to clarify the status of the spermatogenic process, showing an altered meiotic segregation concomitant with the presence of sperm apoptosis and necrosis in a patient 47, XYY.

Aneuploidy study in sperm and preimplantation embryos from nonmosaic 47,XYY men

OBJECTIVE

To determine gonosomal and autosomal aneuploidy rate in sperm and preimplantation embryos from nonmosaic 47,XYY males.

DESIGN

Sperm and blastomere analysis by fluorescence in situ hybridization.

SETTING

Fertility clinic, academic hospital.

PATIENT(S)

Two 47,XYY men undergoing preimplantation genetic diagnosis (PGD) and eight 46,XY males distributed in two control groups (fertile and infertile).

INTERVENTION(S)

Sperm-sample collection for fluorescence in situ hybridization and PGD.

MAIN OUTCOME MEASURE(S)

Aneuploidy frequencies for chromosomes X, Y, 13, 16, 18, 21, and 22 in sperm and embryos.

RESULT(S)

Patients with 47,XYY presented global sperm gonosomal and autosomal aneuploidy frequency of 37.23%-37.80%, with XY disomy being the most frequent abnormality (16.70%-19.01%). This aneuploidy rate was statistically significantly different from that found in both 46,XY infertile controls (1.07%) and 46,XY fertile controls (1.04%). In total, 47 preimplantation embryos were analyzed, of which 32 were classified as normal (68%) and 15 as aneuploid (32%). Among the abnormal embryos, 9 presented gonosomal abnormalities, and 6, autosomal abnormalities.

CONCLUSION(S)

High rate of gonosomal and autosomal aneuploidy was observed in sperm and preimplantation embryos from nonmosaic 47,XYY males. The offspring of this category of patients may be at higher risk of chromosomal abnormalities, and therefore PGD can be suggested to these patients.

Gender effects on the incidence of aneuploidy in mammalian germ cells

Aneuploidy occurs in 0.3% of newborns, 4% of stillbirths, and more than 35% of all human spontaneous abortions. Human gametogenesis is uniquely and gender-specific susceptible to errors in chromosome segregation. Overall, between 1% and 4% of sperm and as many as 20% of human oocytes have been estimated by molecular cytogenetic analysis to be aneuploid. Maternal age remains the paramount aetiological factor associated with human aneuploidy. The majority of extra chromosomes in trisomic offspring appears to be of maternal origin resulting from nondisjunction of homologous chromosomes during the first meiotic division. Differences in the recombination patterns between male and female meiosis may partly account for the striking gender- and chromosome-specific differences in the genesis of human aneuploidy, especially in aged oocytes. Nondisjunction of entire chromosomes during meiosis I as well as premature separation of sister chromatids or homologues prior to meiotic anaphase can contribute to aneuploidy. During meiosis, checkpoints at meiotic prophase and the spindle checkpoint at M-phase can induce meiotic arrest and/or cell death in case of disturbances in pairing/recombination or spindle attachment of chromosomes. It has been suggested that gender differences in aneuploidy may result from more permissive checkpoints in females than males. Furthermore, age-related loss of chromosome cohesion in oocytes as a cause of aneuploidy may be female-specific. Comparative data about the susceptibility of human male and female germ cells to aneuploidy-causing chemicals is lacking. Increases of aneuploidy frequency in sperm have been shown after exposure to therapeutic drugs, occupational agents and lifestyle factors. Conversely, data on oocyte aneuploidy caused by exogenous agents is limited because of the small numbers of oocytes available for analysis combined with potential maternal age effects. The vast majority of animal studies on aneuploidy induction in germ cells represent cause and effect data. Specific studies designed to evaluate possible gender differences in induction of germ cell aneuploidy have not been found. However, the comparison of rodent data available from different laboratories suggests that oocytes are more sensitive than male germ cells when exposed to chemicals that effect the meiotic spindle. Only recently, in vitro experiments, analyses of transgenic animals and knockdown of expression of meiotic genes have started to address the molecular mechanisms underlying chromosome missegregation in mammalian germ cells whereby striking differences between genders could be shown. Such information is needed to clarify the extent and the mechanisms of gender effects, including possible differential susceptibility to environmental agents.

Chromosome abnormalities in one thousand infertile males with nonobstructive sperm disorders

One hundred thirty-five in 1,000 (13.5%) Tunisian male infertile patients with nonobstructive spermatogenesis disorders were found to have chromosomal abnormalities.

Meiosis and sex chromosome aneuploidy: how meiotic errors cause aneuploidy; how aneuploidy causes meiotic errors

As a group, sex chromosome aneuploidies - the 47,XXY, 47,XYY, 47,XXX and 45,X conditions - constitute the most common class of chromosome abnormality in human live-births. Considerable attention has been given to the somatic abnormalities associated with these conditions, but less is known about their meiotic phenotypes; that is, how does sex chromosome imbalance influence the meiotic process. This has become more important with the advent of assisted reproductive technologies, because individuals previously thought to be infertile can now become biological parents. Indeed, there are several recent reports of successful pregnancies involving 47,XXY fathers, and suggestions that cryopreservation of ovarian tissue might impart fertility to at least some Turner syndrome individuals. Thus, the possible consequences of sex chromosome aneuploidy on meiotic chromosome segregation need to be explored.

Somatic chromosomal abnormalities in infertile men and women

Infertility--the inability to achieve conception or sustain a pregnancy through to live birth--is very common and affects about 15% of couples. While chromosomal or genetic abnormalities associated with azoospermia, severe oligozoospermia or primary ovarian failure were of no importance for reproduction prior to the era of in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI), advances in assisted reproductive techniques (ART) now enable many infertile couples to have children. These developments have raised the question of the genetic consequences of ICSI: concerns of the potential harm of the invasive procedure and concerns about the genetic risk. The infertile male and female definitely have an increased risk to carry a chromosomal abnormality. Detection of such an abnormality is of fundamental importance for the diagnosis of infertility, the following treatment, the evaluation of the risk for the future child and the appropriate management of the pregnancy to be obtained. Therefore, cytogenetic screening of both partners is mandatory prior to any type of ART. The present review is based on several surveys on male and female infertility and analyzes the types and frequencies of the different reported chromosome abnormalities according to the type of impairment of spermatogenesis and the type of treatment planned or performed. With regard to assisted reproductive techniques (especially ICSI) the main types of chromosomal abnormalities are discussed and their potential risks for ICSI. If available, reported cases of performed ICSI and its outcome are presented. The detection of an abnormal karyotype should lead to comprehensive genetic counselling, which should include all well-known information about the individual type of anomaly, its clinical relevance, its possible inheritance, the genetic risk of unbalanced offspring, and the possibilities of prenatal diagnosis. Only this proceeding allows at-risk couples to make an informed decision regarding whether or not to proceed with ART. These decisions can be made only when both partners have clearly understood the genetic risks and possible consequences when ART is used.

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.

Meiotic segregation of sex chromosomes in mosaic and non-mosaic XYY males: case reports and review of the literature

The aim of this study was to determine the incidence of sex chromosome aneuploidy in spermatozoa of two males with a 47,XYY karyotype and one male with a 46,XY/47,XYY constitution. Spermatozoa obtained from two oligospermic patients and one volunteer semen donor were studied by multicolour fluorescence in situ hybridization. In the XY/XYY male, the frequencies of X-bearing to Y-bearing sperm were significantly different from the 1 : 1 expected ratio. Significantly increased frequencies were found in the mosaic and non-mosaic males for 24,XX and 24,YY sperm when compared with control donors. The number of 24,XY sperm was significantly different from the controls in the XYY males, but not in the mosaic male. The incidence of disomy 18 and the rate of diploidy also increased in the three patients. However, the mosaic male had the lowest cumulative rate of disomic and diploid spermatozoa when compared with the two XYY patients. Our data suggest that: (i) chromosome abnormalities observed in spermatozoa of the two XYY oligoasthenoteratospermic (OAT) males arise through segregation errors in XY germ cells rather than normal meiosis of XYY germ cells, (ii) mosaic XYY males with normal semen parameters have a lower risk of producing offspring with a sex chromosomal abnormality than OAT males with XYY karyotype.

[Genetic origin of spermatogenesis impairments: clinical aspects and relationships with mouse models of infertility]

Human spermatogenesis failures appear frequently as idiopathic and may be due to genetic causes. Mutations of genes involved in the hypothalamic/pituitary control of spermatogenesis have been described and account for several types of hypogonadotropic hypogonadism. Chromosomal abnormalities found in infertile patients are either gonosomal aneuploidies or structural anomalies which interfere with the normal chromosome behaviour at meiosis and lead to germ cell breakdown. Microdeletions of the Y chromosome are often undetectable at karyotype and are responsible for the loss of genes which compose the AZF factor. The increase in the number of mouse models of infertility will allow the description of many human genes involved in the spermatogenesis process provided that a detailed analysis of their genotype-phenotype relationships is performed.

Current and future genetic screening for male infertility

Although much of male infertility is currently unexplained, it is likely that underlying defects in critical genes or entire gene pathways are responsible. Because powerful technologies exist to bypass severe male-factor infertility, improving the diagnosis of genetic infertility is important for the infertile couple, not only to explain the problem but also to inform them of conditions potentially transmissible to offspring.

PRINS tandem labeling of satellite DNA in the study of chromosome damage

Tandem labeling of satellite DNA was proposed a few years ago (1) for evaluating preferential chromosome breaks in the pericentromeric regions of mammalian chromosomes, and (2) for distinguishing chromosome breaks from chromosome segregation errors in interphase cells. In the presence of primers and modified nucleotides, primed in situ labeling (PRINS) tags repetitive DNA sequences, and serves as a useful alternative to fluorescence in situ hybridization (FISH). We developed a two-color method for PRINS tandem labeling of centromeric and pericentromeric sequences. The method, which appears to be more sensitive than FISH, was used to assay micronuclei in mouse splenocytes and early spermatids, and it provided insight into mechanisms of induction of chromosome damage in these cells. We compared the sensitivity of this method and of a different two-color approach, based on simultaneous labeling of centromeric and telomeric sequences.