Type and frequency of chromosome aberrations in 781 couples undergoing intracytoplasmic sperm injection

Genetic and epigenetic risks of intracytoplasmic sperm injection method

Pregnancies achieved by assisted reproduction technologies, particularly by intracytoplasmic sperm injection (ICSI) procedures, are susceptible to genetic risks inherent to the male population treated with ICSI and additional risks inherent to this innovative procedure. The documented, as well as the theoretical, risks are discussed in the present review study. These risks mainly represent that consequences of the genetic abnormalities underlying male subfertility (or infertility) and might become stimulators for the development of novel approaches and applications in the treatment of infertility. In addition, risks with a polygenic background appearing at birth as congenital anomalies and other theoretical or stochastic risks are discussed. Recent data suggest that assisted reproductive technology might also affect epigenetic characteristics of the male gamete, the female gamete, or might have an impact on early embryogenesis. It might be also associated with an increased risk for genomic imprinting abnormalities.

Screening for chromosomal abnormalities in 2650 infertile couples undergoing ICSI

Chromosomal abnormalities are the major contributor to the genetic risks of infertility treatment associated with intracytoplasmic sperm injection (ICSI). The study objective was to assess prospectively the frequency of chromosomal aberrations in couples undergoing ICSI. A total of 2650 infertile couples (5300 patients) underwent chromosome analysis before undergoing ICSI in the Egyptian IVF-ET Centre. Heparinized blood samples were cultured, harvested and banded according to standard methods. Overall, 96.94% of the patients studied (5138/5300) had a normal karyotype, while the remaining 162 patients (3.06%) had an abnormal karyotype. Male patients constituted the majority of abnormalities; 138 males (85.19%) and 24 females (14.81%). These chromosomal aberrations included 117 cases (2.2%) of sex chromosome abnormalities; 113 males and four females. Forty-five patients (0.85%) had autosomal aberrations; 25 of them were males and 20 were females. The current data show that chromosomal abnormalities affect 3.06% of infertile patients, and occur in both sexes, but more predominantly in males undergoing ICSI for male factor infertility. It is recommended that chromosomal analysis be performed before undergoing ICSI, to identify patients who can be offered preimplantation genetic diagnosis.

Cytogenetic analyses in infertile men

In order to assess the significance of chromosome abnormalities and polymorphic chromosomal variants in male infertility, the results of cytogenetic studies of 90 patients (32 azoospermic and 58 oligozoospermic men) were compared with those of 30 control fertile men in Estonia. Total chromosome alterations were revealed in 47.8% of infertile men. Major chromosomal abnormalities had a 10-fold increase (13.4%) in infertile males (15.6% in azoospermics and 12% in oligozoospermics) compared to the control group. In azoospermics, the most prevalent were sex chromosomal abnormalities (47,XXY)(12%), whereas a Robertsonian translocation, t(13;14) was found in one patient (3.1). In contrast, in the oligospermia group the most frequent abnormalities were autosomal (10%), of which 6.9% were translocations. Sex chromosomal abnormalities were found very rarely (1.7%). Incidence of chromosomal variants was high (38%), but similar in all groups. The most frequently observed polymorphisms involved chromosome 9. In conclusion, chromosomal abnormalities found with a high frequency in infertile males are a major cause of male infertility, and justify the requirement of cytogenetic analysis in every infertile man.

Prevalence of chromosomal abnormalities in phenotypically normal and fertile adult males: large-scale survey of over 10,000 sperm donor karyotypes

BACKGROUND

Sperm donors represent an appropriate population for evaluating the frequency of chromosomal abnormalities in phenotypically normal and fertile adult males.

METHODS

A large multicentric retrospective study was made within the French CECOS (Centre d'Etude et de Conservation des ufs et du Sperme) for collecting cytogenetic, biological and familial data in sperm donors over a 25-year period.

RESULTS

As a whole, 10,202 karyotypes have been recorded. Thirty-eight karyotype aberrations (0.37%) have been diagnosed including 21 balanced chromosomal rearrangements (0.2%). These results are in agreement with those obtained in most large-scale studies performed in unselected newborns. Semen parameters were known for all men carrying an abnormal karyotype and showed normal sperm counts, suggesting that these types of chromosomal aberrations have no or poor consequences on spermatogenesis. Available familial data did not reveal any particular history of malformations, mental retardation or fetal losses.

CONCLUSION

This study is the first large-scale cytogenetic study made in normal and fertile males and shows that the frequency of chromosomal aberrations is not influenced by a previous normal fertility or by an uneventful familial history when compared to that found at birth.

Cytogenetic analysis of azoospermic patients: karyotype comparison of peripheral blood lymphocytes and testicular tissue

OBJECTIVE

The objective was to compare the results of a complete chromosomal, genetic and histological investigation in 13 azoospermic men with the results of the intracytoplasmic sperm injection (ICSI) procedure.

STUDY DESIGN

Peripheral blood samples were used for the measurement of follicle-stimulating hormone (FSH) levels, chromosomal analysis, microdeletions in the azoospermia factor (AZF) region of the Y chromosome and cystic fibrosis transmembrane conductance regulator (CFTR) mutation analysis. Testicular tissue was used for histological scoring and cytogenetic evaluation.

RESULTS

Peripheral blood cytogenetic analysis revealed a normal male karyotype in all cases. Chromosomal analysis from testicular tissue revealed a mosaicism for the terminal deletion of chromosome 22 with a breakpoint site at 22q13 in one patient with congenital bilateral absence of the vas deferens (CBAVD). Deletions in the AZFa, ATFb, and AZFc regions were not detected. The CFTR mutational analysis showed normal results in all patients.

CONCLUSIONS

Cytogenetic evaluation of testicular tissue should be performed in non-obstructive and obstructive azoospermic patients as well as in patients with multiple failed IVF and recurrent spontaneous abortion.

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.

Assisted reproduction: the epigenetic perspective

Developmental pathways in humans and other organisms are buffered against changes in genotype and environment. Therefore, it should not come as a surprise that most of the children conceived by assisted reproduction technology (ART) are healthy, although ART bypasses a lot of biological filters and subjects the gametes and the early embryo to environmental stress. If, however, the buffer breaks down, the development of certain tissues or organs may follow abnormal trajectories. We argue that both normal and abnormal development in children conceived by ART can be explained by epigenetic mechanisms, which control the establishment and maintenance of gene expression patterns in the placenta and fetus. Imprinted genes are of special importance in this respect. There is increasing evidence that genetic factors in infertile couples as well as environmental factors (hormones and culture media) can have adverse effects on epigenetic processes controlling implantation, placentation, organ formation and fetal growth. In addition, loss of epigenetic control may expose hidden genetic variation.

Low-level gonosomal mosaicism in women undergoing ICSI cycles

PURPOSE

Females with low-level gonosomal mosaicism (LLGM) scheduled for ICSI were retrospectively analyzed and compared to control groups. The prevalence of this mosaicism as well as its impact for an ICSI treatment were evaluated.

METHODS

Routine cytogenetic analysis was done in 891 females scheduled for ICSI treatment. For comparison 294 females with recurrent abortions and 104 women with clinical or cytogenetical affected children, who also had routine chromosome analysis, were acquired.

RESULTS

In the ICSI group the incidence of LLGM was significantly lower compared to the group of females with recurrent abortions (3.9% vs. 8.5%, p < 0.01). The incidence was similar between the groups of ICSI females and females with cytogenetical or clinically affected children (5.8%, p = 0.43). Neither anamnestic factors nor outcome parameters were different between females with and without LLGM undergoing ICSI.

CONCLUSION

There is no higher incidence of LLGM in females undergoing ICSI. In those who show LLGM, fertility capacity is not reduced.

[Genomic instability and male infertility]

Knowledge of the human genome has opened the genomic era. The genome instability, its causes and the possible consequences especially about fertility start to be understood. This instability can be observed on chromosome structure but also on genes. Different chromosomes rearrangements involved in infertility including translocations and Y chromosome deletions are described. The Y chromosome is a model of instability, and this instability is the source of its evolution. All those rearrangements are the results of illegitimate recombinations between homologous sequences. On genes we find punctual and dynamic mutations, polymorphisms and epigenetic abnormalities. They all are the results of ADN replication mistakes not corrected by the cellular machine. This machinery is the guardian of the genome integrity and in case of abnormality the programmed cellular death is induced. The knowledge of all these instability mechanisms is essential to appreciate the risk for the offspring after intracytoplasmic sperm injection. Indeed we go round physiological barriers without a complete understanding of the mechanisms involved. Thus, this is an important challenge for research teams but also for all assisted reproduction centers, dealing with ART. Genome is unstable - the very basis of its evolution. But this is also the cause of mistakes with pathological consequences like infertility and mental retardation.

Prevalence of chromosomal abnormalities in 2078 infertile couples referred for assisted reproductive techniques

BACKGROUND

This study analyses the prevalence of karyotype changes and Yq11 microdeletions among couples referred for assisted reproduction techniques.

METHODS

Prior to receiving either IVF or ICSI treatment, each partner of 2078 infertile couples was screened for karyotype changes by GTG-banding technique on peripheral lymphocytes. No subject presented with obvious phenotype of chromosomal rearrangement. All the oligo/azoospermic men with normal karyotype were further investigated by PCR for Yq11 microdeletions.

RESULTS

Eighty-two out of 2078 couples (3.95%) had one partner carrying a chromosomal change, and 10 out of 202 (4.95%) men showed Yq11 microdeletions. The chromosomal rearrangements were 44 (2.1%) translocations, 23 (1.1%) gonosomal mosaics, six (0.3%) 47,XXY, five (0.24%) marker chromosomes, three (0.14%) inversions and one (0.05%) duplication. Frequency of anomalies in men and women were similar: 42 and 40 cases respectively.

CONCLUSIONS

Partners of infertile couples requiring IVF or ICSI treatment appear to be affected by higher frequency of chromosomal rearrangements than the general population. Categories with greater risk were represented by men with sperm cell count <20 x 10(6) sperm/ml, and women with history of pregnancy loss.

Chromosomal abnormalities in couples undergoing intracytoplasmic sperm injection. A study of 370 couples and review of the literature

Intracytoplasmic sperm injection (ICSI) is now widely acknowledged as the most effective therapeutic approach to severe male infertility or unsuccessful in vitro fertilization. Cytogenetic investigations were performed in 370 females and 335 males prior to ICSI between January 1997 and April 2003. Nine men (2.7%) and 48 women (13%) had an abnormal karyotype, 44 females having some degree of numerical sex chromosome mosaicism. A review of the literature showed the prevalence of all types of chromosomal abnormalities to be much higher among male and female partners of couples examined prior to ICSI than among newborns. As most ICSIs are performed with ejaculated spermatozoa from oligospermic men, the distribution and the prevalence of the several types of chromosomal abnormalities are closer to those of oligospermic rather than azoospermic males. Our results combined with those of the literature stress the importance of karyotyping both male and female partners before ICSI is started. Adequate genetic counselling, possibly followed by prenatal diagnosis, should be offered if a chromosomal anomaly is detected.

Causes of azoospermia and their management

Azoospermia may occur because of reproductive tract obstruction (obstructive azoospermia) or inadequate production of spermatozoa, such that spermatozoa do not appear in the ejaculate (non-obstructive azoospermia). Azoospermia is diagnosed based on the absence of spermatozoa after centrifugation of complete semen specimens using microscopic analysis. History and physical examination and hormonal analysis (FSH, testosterone) are undertaken to define the cause of azoospermia. Together, these factors provide a >90% prediction of the type of azoospermia (obstructive v. non-obstructive). Full definition of the type of azoospermia is provided based on diagnostic testicular biopsy. Obstructive azoospermia may be congenital (congenital absence of the vas deferens, idiopathic epididymal obstruction) or acquired (from infections, vasectomy, or other iatrogenic injuries to the male reproductive tract). Couples in whom the man has congenital reproductive tract obstruction should have cystic fibrosis (CF) gene mutation analysis for the female partner because of the high risk of the male being a CF carrier. Patients with acquired obstruction of the male reproductive tract may be treated using microsurgical reconstruction or transurethral resection of the ejaculatory ducts, depending on the level of obstruction. Alternatively, sperm retrieval with assisted reproduction may be used to effect pregnancies, with success rates of 25–65% reported by different centres. Non-obstructive azoospermia may be treated by defining the cause of low sperm production and initiating treatment. Genetic evaluation with Y-chromosome microdeletion analysis and karyotype testing provides prognostic information in these men. For men who have had any factors potentially affecting sperm production treated and remain azoospermic, sperm retrieval from the testis may be effective in 30–70% of cases. Once sperm are found, pregnancy rates of 20–50% may be obtained at different centres with in vitro fertilisation and intracytoplasmic sperm injection.

Uniparental disomy and Robertsonian translocations: risk estimation and prenatal testing

BACKGROUND

Uniparental disomy (UPD) is defined by the inheritance of both homologous chromosomes from only one parent, resulting in an imbalance of the expression of imprinted genes. With the recent identification of several diseases associated with UPD, the diagnostic significance of this molecular finding is a focus of interest. Acrocentric chromosomes involved in Robertsonian translocations (RTs) are particularly prone to being affected by mis-segregation events, possibly resulting in UPD. While UPDs of chromosomes 13, 21, and 22 have no clinical consequences, and therefore have no diagnostic impact despite of homozygosity of recessive alleles, prenatal testing for UPDs 14 or 15 is becoming increasingly asked for.

METHODS

Thirty-one fetuses with nonhomologous balanced RTs involving chromosome 14 were tested for UPD14 by microsatellite typing.

RESULTS

No cases of maternal UPD14 were detected among the 31 fetuses analyzed.

CONCLUSIONS

Based on our own data from molecular testing in 31 prenatal RT cases and findings in the published literature, we delineated a risk of 0.3% for a UPD with clinical consequences for prenatally detected carriers of a nonhomologous RT. Prenatal UPD testing is not associated with any additional risk to the pregnancy once invasive prenatal testing has been carried out. However, the possibly conflicting consequences in the case of a prenatal UPD identification should be discussed in advance. Furthermore, risk figures in specific clinical cohorts, such as couples prior to intracytoplasmic sperm injection, as well as questions of prenatal diagnostic management, will be discussed.

Reciprocal translocation associated with multiple exostoses in seven members of a three generation family and discovered through an infertile male

We report a four generations family with multiple exostoses segregating with a reciprocal translocation t(8;19)(q24.11;q13.13) in 8 members of three generations. FISH investigations detected a breakage of the dosage-sensitive EXT1 gene. Although three members of the family died perinatally from unknown causes and one carrier had four spontaneous abortions, the translocation was discovered only when the cytogenetic analysis was requested in an affected male because of oligozoospermia. In fact, it is well known that infertile males may be carriers of reciprocal or Robertsonian translocations with a higher frequency than the general population. This family stresses the importance of requesting the cytogenetic analysis in all cases in which a dominant disease segregates with repeated miscarriages and/or newborn deaths of unknown cause.

Fetal chromosomal analysis of pregnancies following intracytoplasmic sperm injection with amniotic tissue culture

OBJECTIVES

The objective of this study was to determine the incidence of chromosomal anomalies in a complete cohort of ICSI pregnancies.

METHODS

From January 1996 to December 2000, 1500 consecutive patients who had become pregnant after Intracytoplasmic Sperm Injection (ICSI) were given prenatal genetic counseling and 98 of them (6.5%) who accepted amniocentesis were studied. Amniocentesis was performed between 14 and 20th weeks of their pregnancy. Amniotic tissue cultures were processed according to Hoehn et al. A minimum of 20 metaphases were examined on each preparation. Both parents were also evaluated with peripheral blood karyotyping.

RESULTS

Amniocentesis and karyotyping was performed to evaluate the 142 fetuses from 98 ICSI pregnancies. Karyotypes from peripheral leucocytes of the parents were also evaluated. Chromosomal anomalies were detected from 6 out of the 142 (4.2%) fetuses. The anomalies were as follows, '46,XX/69,XXX/92,XXXX', '46,XY/69,XXY/92,XXYY', '47,XY + 21', '46,XY/47,XY + 7', '47,XXY', and '45,X0'. All except one pregnancy were terminated with the consent of the couples. Fetal tissue cultures were also studied after the termination of the pregnancy in order to confirm prenatal diagnosis. We did not detect abnormal karyotype from the parents of these fetuses.

CONCLUSIONS

The ratio of chromosomal abnormalities seems to be slightly increased in ICSI pregnancies. Paternal factors due to morphologically abnormal spermatozoa, maternal factors due to increased mother age and more frequently, de novo occurring sex chromosomal abnormalities may be responsible for this outcome.

[Value of karyotyping women patients of couples referred for sterility]

It has been known for some 25 years that there is a causal relation between chromosomal aberrations and male infertility and that the major indication for karyotyping an infertile man is still usually an abnormal sperm analysis. The value of karyotyping women in the routine work-up of couples referred for sterility has long been debated. A French recent cytogenetic study found an overall increased frequency of chromosomal aberrations in the female and confirmed that in some cases of poor reproductive outcome there may be a contribution of maternal chromosome aberrations. Indeed, the existence of a chromosome abnormality in the female partner was associated with the group of infertile men in which there was no apparent cause of infertility. These results emphasise the need for thorough genetic work-up in couples referred for sterility. This work-up should include karyotyping of the female for some indications explained in this work.

Genetic counseling in translocations

Advances in the treatment of male infertility-specifically intracytoplasmic sperm injection have now resulted in greater recognition of the clinical significance of genetic translocations. This article focuses on the different types of translocations (Robertsonian, reciprocal) as well as on the prevalence and incidence of translocations in infertile and other populations. The authors contrast theoretical and empiric meiotic segregation patterns in the different clinical settings of traditional prenatal genetic diagnosis and preimplantation genetic diagnosis. In particular, the significance of a higher prevalence of unbalanced blastomeres is discussed.

Comprehensive office evaluation in the new millennium

The success of a comprehensive office-based evaluation of male-factor infertility depends on the physician's thorough understanding of risk assessment in the history, identification of pertinent physical examination findings, and correct assessment of laboratory data. Office-based ultrasonographic techniques have already increased the urologist's ability to visualize suspected anatomic abnormalities, and the use of functional tests of sperm has given greater depth to the limited, but essential, prognostic capabilities of the routine semen analysis.

Guidelines for the appropriate use of genetic tests in infertile couples

Research on genetic causes of male and female infertility rapidly expanded in the last years, following the development of in vitro fertilising techniques. Genetic tests are now available to explore the cause of the infertility and assess the risk of a given couple to transmit its genetic characteristics. This allows at-risk couples to take an informed decision when electing for a medically assisted reproduction. It also allows the professionals to offer a prenatal diagnosis when appropriate. Thus, the genetic work-up of the infertile couple has become good practice for an appropriate diagnosis, treatment and prognostic assessment. The lack of national or international rules for the genetic approach to the infertile couple, prompted the Italian community of professionals in the field of reproductive medicine to join and set up guidelines for the genetic diagnosis of male and female infertility. The group of clinical and research experts is representative of 12 national scientific societies and was supported by external experts from four international societies. We examine the clinically relevant genetic causes of male and female infertility and suggest the category of patients for which each genetic test is recommended or optional, both for an accurate diagnosis and prior to ART.

Comparative genomic hybridization analysis of sperm DNA apoptosis after exposure to heat shock

PURPOSE

A DNA disc chip assay based on comparative genomic hybridization (CGH) was developed to measure sperm DNA integrity. The objective was to correlate DNA integrity of heat-treated sperm with the sperm capacitation index (CI) determined from the sperm penetration assay.

METHODS

Basic semen and kinematic parameters were measured (N = 6). Sperm were washed in two-layer colloid suspensions and split portions incubated at either 3 degrees C (control) or 40 degrees C for 4 h. Single-stranded DNA of heated sperm were stained in SYBR Gold and hybridized to bisbenzimide (Hoechst 33342) stained control DNA in a membrane disc. Fluorescent intensities of the discs were measured and correlation analyses with sperm parameters performed.

RESULTS

Sperm CI was positively correlated (R = 0.737) with sperm DNA integrity. Two populations of sperm could be discerned: low capacitating sperm that initiated apoptosis and high capacitating sperm unaffected by heat shock treatment. The remaining parameters were not related to sperm DNA stability.

CONCLUSIONS

Fragile DNA were found in a population of sperm associated with poor capacitation characteristics and apoptosis was observed after heat treatment. The results suggested that sperm dysfunction might be due to apoptotic sperm DNA resulting from an elevated temperature in the surroundings. The data suggested that the second population of high capacitating sperm induced chaperones such as heat shock proteins hsp 70 to protect against apoptosis.

Neonatal data on a cohort of 2889 infants born after ICSI (1991-1999) and of 2995 infants born after IVF (1983-1999)

BACKGROUND

To evaluate the safety of ICSI, this study compared data of IVF and ICSI children by collecting data on neonatal outcome and congenital malformations during pregnancy and at birth.

METHODS

The follow-up study included agreement to genetic counselling and eventual prenatal diagnosis, followed by a physical examination of the children after 2 months, after 1 year and after 2 years. 2840 ICSI children (1991-1999) and 2955 IVF children (1983-1999) were liveborn after replacement of fresh embryos. ICSI was carried out using ejaculated, epididymal or testicular sperm.

RESULTS

In the two cohorts, similar rates of multiple pregnancies were observed. ICSI and IVF maternal characteristics were comparable for medication taken during pregnancy, pregnancy duration and maternal educational level, whereas maternal age was higher in ICSI and a higher percentage of first pregnancies and first children born was observed in the ICSI mothers. Birthweight, number of neonatal complications, low birthweight, stillbirth rate and perinatal death rate were compared between the ICSI and the IVF groups and were similar for ICSI and IVF. Prematurity was slightly higher in the ICSI children (31.8%) than in the IVF children (29.3%). Very low birthweight was higher in the IVF pregnancies (5.7%) compared with ICSI pregnancies (4.4%). Major malformations (defined as those causing functional impairment or requiring surgical correction), were observed at birth in 3.4% of the ICSI liveborn children and in 3.8% of the IVF children (P = 0.538). Malformation rate in ICSI was not related to sperm origin or sperm quality. The number of stillbirths (born > or =20 weeks of pregnancy) was 1.69% in the ICSI group and 1.31% in the IVF group. Total malformation rate taking into account major malformations in stillborns, in terminations and in liveborns was 4.2% in ICSI and 4.6% in IVF (P = 0.482).

CONCLUSIONS

The comparison of ICSI and IVF children taking part in an identical follow-up study did not show any increased risk of major malformations and neonatal complications in the ICSI group.

Is intracytoplasmic sperm injection safe? Current status and future concerns

In vitro fertilization with intracytoplasmic sperm injection (ICSI) has revolutionized the treatment of patients with severe forms of male infertility. However, because ICSI has been performed for only 10 years, long-term outcomes and risks to offspring remain largely unknown. The fact that ICSI can potentially bypass natural selection barriers to genetic disease transmission has brought a sobering but important impetus to recent research on the risks and outcomes of ICSI. Several studies were done recently to examine specific risks to children born following ICSI. Because of rapid advances in the ICSI procedure itself, studies evaluating the safety of using immature sperm forms from the testis (spermatids, spermatocytes) also have been undertaken. This review summarizes recent studies examining the risks and long-term outcomes to date of in vitro fertilization with ICSI.

[Genetic male infertility and medically assisted reproduction]

About half the cases of infertility have their origin in the male partner. Infertility due to males has several possible aetiologies. In about 30% of cases, genetic disorders are suspected of being the main cause. They could interfere with the development of the male gonads, the urogenital tract or the hypothalamo-hypophyseal axes. Such disorders could also stop germ cell generation and maturation or lead to the production of non-functional spermatozoa. Genetic disorders of chromosomal origin could give rise to abnormal karyotypes or germinal mosic figure. They could involve gene abnormalities affecting numerous genes localized on several chromosomes, in particular the Y chromosome. The physiopathologic identification of male infertility is interesting because of the risk of the genetic factors involved being transmitted to the offspring. The subject is of importance, specially because of the increasing use of intracytoplasmic sperm injections. Couples should therefore be precisely counselled to enable them to make a well-informed choice among various solutions, e.g. ART, with or without sperm donation, or adoption.

Chromosomal abnormalities and polymorphisms in infertile men

The aim of this study was to determine the prevalence of alterations and normal variable chromosome features in males from infertile couples. Karyotyping was performed to 84 men attending the infertility clinic at the Hospital Clinic i Provincial of Barcelona (Spain). Sex chromosome abnormalities were detected in 19 patients (26.62%): 14 (16.67%) aneuploidies 47,XXY and 47,XYY, 3 (3.57%) Y-chromosome long arm deletions; 1 (1.19%) mosaic 45,x/46,XY and 1 (1.19%) Robertsonian translocation (45.X-15-Y+t(15p: Yq). Chromosomal polymorphisms were observed in 29 patients. Yqh+ was the most frequent variant in sex chromosomes and increased length in heterochromatin and satellites were present in autosomal chromosomes. The high prevalence of chromosomal abnormalities observed in infertile men justify the use of karyotyping to evaluate males enrolled in new assisted reproductive technologies programs.

Chromosomal factors of infertility in candidate couples for ICSI: an equal risk of constitutional aberrations in women and men

To assess the frequency of chromosomal aberrations in French candidates for intracytoplasmic sperm injection (ICSI), and to explore the existence of a female chromosomal factor in some cases of couple infertility, a collaborative retrospective clinical and cytogenetic study was performed, launched by the Association des Cytogénéticiens de Langue Franciaise (ACLF). The karyotypes of 3208 patients [2196 men (68.4%), 1012 (31.6%) women] included in ICSI programmes over a 3-year period in France were collected. A total of 183 aberrant karyotypes was diagnosed, corresponding to an abnormality frequency of 6.1% (134/2196) for men and 4.84% (49/1012) for women. The following frequencies of abnormalities were observed respectively for men and women: 1.23% (n = 27) and 0.69% (n = 7) for reciprocal translocations, 0.82% (n = 18) and 0.69% (n = 7) for Robertsonian translocations, 0.13% (n = 3) and 0.69% (n = 7) for inversions, 3.32% (n = 73) and 2.77% (n = 28) for numerical sex chromosome aberrations, and 0.59% (n = 13) and 0% for other structural aberrations. Among the male patients of this latter group, 0.40% (n = 9) had a Y chromosome abnormality. Among the male patients with numerical sex chromosome abnormalities, 2.23% (n = 49) were 47,XXY, 0.32% (n = 7) were 47,XYY, and 0.77% (n = 17) had a mosaicism for numerical sex chromosome anomalies. All the female patients with sex chromosome abnormalities (2.77%, n = 28) had mosaicism for numerical sex chromosome anomalies. Even if these cases-the significance of which was sometimes questioned-were disregarded in the analysis, 2.08% (21/1012) of abnormal karyotypes remained in women. An overall increased frequency of chromosomal aberrations was found, and this confirmed that in some cases of poor reproductive outcome there may be a contribution of maternal chromosome aberrations. Indeed, the existence of a chromosome abnormality in the female partner was associated with the group of infertile men in which there was no apparent cause of infertility.

Genetic causes of male infertility: current concepts

Infertile men with severe spermatogenic defects and low or no sperm counts have a significantly higher rate of genetic abnormalities than fertile men. The fact that intracytoplasmic sperm injection can potentially bypass natural selection barriers to genetic disease transmission has brought a sobering but important impetus to recent research in the area of genetic infertility. Recent studies have focused on examining the prevalence of certain genetic defects in infertile men, analyzing the molecular basis of infertility in genetic disorders, and detecting new causes of genetic infertility. Several novel research findings deserve mention for their potential impact on genetic infertility. It has been demonstrated that elongated and round spermatids can be successfully injected into human oocytes and viable births obtained. Likewise, significant advances have been made in the arena of interspecies germ cell transplantation. Of some concern is the finding of a relationship between faulty DNA repair and infertility in men with severe testis failure. This review summarizes the recent genetic advances in these areas of male genetic infertility.

Genetically determined male infertility and assisted reproduction techniques

This is a review of the common chromosome and genetic disorders associated with male infertility that need to be considered by the clinician and the couple in the context of treatment. Until recently the most relevant disorders have been those inherited from parents, however, with the advent of technologies enabling recovery of sperm from the testicle in men with severely damaged spermatogenesis there is increased interest in those genetic abnormalities that may occur in mitosis and meioses. It is likely that over the next ten years there will be increasing focus on this aspect of male fertility genetic disorders. This article needs to be read in conjunction with the specific in depth reviews in this journal edition.

Genetics and male infertility

This article reviews chromosomal and genetic disorders in the context of male fertility. Particular emphasis is on those disorders, which are encountered, in clinical practice including Klinefelter's syndrome, Kallman's syndrome, Androgen insensitivity, Y microdeletions, Y fertility gene deletions, and cystic fibrosis gene mutations. These disorders are discussed in relation to the aetiology of male fertility and also risks to children who are born of fathers with these disorders. A list of fathers' categories is proposed for outcome studies for children born after IVF-ICSI. Finally a question is proposed to catalyse debate about germ line therapy.