Sex Chromosome Mosaicism Research Articles

P-576: Sex chromosome micromosaicism in infertile men with normal karyotypes

Peripheral blood lymphocytes are commonly analyzed for karyotypes among infertile men, especially with azoospermia. These men commonly have sex chromosome anamolies in number or morphology. Recently, fluorescence in-situ hybridization has been applied using sex-chromosome specific probes to investigate more subtle defects in chromosome structure. Our study sought to define the prevalence of low-level sex chromosome mosaicism among a consecutive series of infertile men.

Detection of low level sex chromosome mosaicism in Ullrich–Turner syndrome patients

Ullrich-Turner syndrome (UTS) is most commonly due to a 45,X chromosome defect, but is also seen in patients with a variety of X-chromosome abnormalities or 45,X/46,XY mosaicism. The phenotype of UTS patients is highly variable, and depends largely on the karyotype. Patients are at an increased risk of gonadoblastoma when a Y-derived chromosome or chromosome fragment is present. Since constitutional mosaicism is present in approximately 50% of UTS patients, the identification of minor cell populations is clinically important and a challenge to laboratories. We identified 50 females with a 45,X karyotype as the sole abnormality or as part of a more complex karyotype. Twenty two (44%) had a 45,X karyotype; mosaicism for a second normal or structurally abnormal X was observed in 24 (48%) samples, and mosaicism for Y chromosomal material in 4 (8%) cases. To further investigate the possibility of mosaicism in the 22 patients with an apparently non-mosaic 45,X karyotype, we performed FISH using centromere probes for the X and Y chromosomes. A minor XX cell line was identified in 3 patients, and the 45,X result was confirmed in 19 samples. No samples with XY mosaicism were identified. We describe our validation process for a FISH assay to be used in clinical practice to identify XX or XY mosaicism. FISH as an adjunct to karyotype analysis provides a sensitive and cost-effective technique to identify sex chromosome mosaicism in UTS patients.

Ovarian Transplantation In A Series Of Identical Twins Discordant For Ovarian Failure

To investigate the prospects for restoring spontaneous menstrual cycles and fertility by ovarian isotransplantation between monozygotic twin sisters. A series of 4 otherwise healthy monozygotic twins, where 1 had idiopathic premature menopause & the other had normal ovarian function. 4 pairs of monozygotic twins (aged 24, 25 and 38[n=2] years of age) requested ovarian transplantation from the fertile sister to their sibling who had premature ovarian failure (POF). 3 of the donor sisters had normal menstrual cycles and had completed their target family sizes of 2 or 3 children; a 25 y.o. twin donor had no children and was on oral contraception. All 4 prospective recipients had FSH levels > 90 mIU/ml, no menses for ≥10 years, and complete absence of ovarian follicles in ovarian biopsies. They were menopausal from ages 14, 15, 16, and 22 years. 2 of the twins underwent transplantation at age 24 and 38, and 2 are awaiting. One ovary was removed from the donor and cortical tissue was dissected ex vivo in Leibovitz-L15 medium at 4°C. Donor ovarian cortex was then sutured microsurgically into the recipient’s medulla via a mini-laparotomy. This procedure was outpatient, with prompt & uneventful recovery. Surplus tissue from the youngest twin-pair was cryopreserved for future use with a slow-freezing protocol using 1,2-propanediol & sucrose as cryoprotective agents. Ovarian tissues & peripheral blood from both women was cultured for analysis by karyotyping and analyzed by FISH for sex chromosome mosaicism. All twin-pairs were genetically fingerprinted, and DNA from the sterile sisters was tested for fragile X mutation. All the twin-pairs were confirmed by genetic fingerprinting to be homozygous, implying that immunosuppression was unnecessary for transplant survival. Histology confirmed that the recipient ovaries were sterile, whereas the donor ovaries contained numerous primordial and small growing follicles, consistent with the antral follicle counts obtained preoperatively by transvaginal ultrasound. Karyotypes were normal 46,XX and there was no expansion of CCG repeats in the FMR-1 gene. The first of the ovary transplant recipients menstruated lightly at 12 weeks postoperatively and conceived naturally with an intrauterine pregnancy at the next cycle (∼20 weeks postoperatively). At 22 weeks of pregnancy, ultrasound revealed a normal girl and, at the time of writing, the pregnancy is proceeding uneventfully at the 33rd week. The 2nd twin-pair has also undergone transplantation with similar genetic and histologic findings, and 2 additional pairs are awaiting the same procedure. Evidence we present elsewhere indicates that POF within discordant twin-pairs is less rare than expected. These first cases of ovarian tissue transplantation between women are made possible by virtue of a genetically identical twin willing to be a donor. There is a latent period of several months before ovulation is restored & the endocrine profile is normalized, but in our first case, conception occurred promptly thereafter & pregnancy was normal. If this success can be repeated, ovarian transplantation may provide an alternative to conventional egg donation for comparable patients, and it confirms the feasibility of natural conception after transplanting thawed ovarian tissue in cancer patients. Finally, ongoing molecular study of such twin-pairs may eventually shed light on the causes of premature ovarian failure.%3:45 p.m.

Identification of high frequency of Y chromosome deletions in patients with sex chromosome mosaicism and correlation with the clinical phenotype and Y‐chromosome instability

A mosaic karyotype consisting of a 45,X cell line and a second cell line containing a normal or an abnormal Y chromosome is relatively common and is associated with a wide spectrum of clinical phenotypes. The aim of this study was to investigate patients with such a mosaic karyotype for Y chromosome material loss and then study the possible association of the absence of these regions with the phenotype, diagnosis, and Y-chromosome instability. We studied 17 clinically well-characterized mosaic patients whose karyotype consisted of a 45,X cell line and a second cell line containing a normal or an abnormal Y chromosome. The presence of the Y chromosome centromere was verified by fluorescence in situ hybridization (FISH) and was then characterized by 44 Y-chromosome specific-sequence tagged site (STS) markers. This study identifies a high frequency of Yq chromosome deletions (47%). The deletions extend from interval 5 to 7 sharing a common deleted interval (6F), which overlaps with the azoospermia factor region (AZF) region. This study finds no association between Y-chromosome loci hosting genes other than SRY, and the phenotypic sex, the diagnosis, and the phenotype of the patients. Furthermore, this study shows a possible association of these deletions with Y-chromosome instability.

Mosaic status in lymphocytes of infertile men with or without Klinefelter syndrome

Gonosomal aneuploidies such as Klinefelter syndrome (47,XXY) are the most frequent chromosomal aberration in infertile men. Normally the chromosomal status of patients is detected by karyotyping of up to 20 metaphase spreads of lymphocyte nuclei, whereby low grade mosaicism may be overlooked. To test whether Klinefelter patients with 47,XXY karyotype or infertile men with 46,XY karyotype represent gonosomal mosaicisms, we performed meta- and interphase fluorescence in situ hybridization (FISH) on 45 men. A total of 400 interphase and 40 metaphase lymphocyte nuclei per patient were scored after hybridization with DNA probes specific for chromosomes X and Y, and chromosome 9 as a control. On the basis of conventional karyotype, hormone levels and clinical appearance, patients were subdivided into 18 Klinefelter syndrome patients with 47,XXY (group I), 11 Klinefelter syndrome-like patients with normal karyotype, 46,XY (group II) and six non-Klinefelter-like infertile patients with normal 46,XY karyotype (group III). Ten normal men (group IV) served as controls. Testicular volume in the Klinefelter group I was smaller compared with group II (P = 0.016), group III (P < 0.001) and group IV (P < 0.001). In addition, testicular volumes in group II were lower compared with group III and group IV (P < 0.004). No significant differences between the aneuploidy rate analysed by FISH in interphase nuclei and metaphases were found in either single patients or groups. Patients with Klinefelter syndrome, 47,XXY (group I) or with symptoms similar to those in Klinefelter patients 46,XY (group II) showed a similar aneuploidy rate (group I 7.1 +/- 4.0% and group II 4.6 +/- 3.4%) and two 47,XXY patients with a high prevalence for normal 46,XY lymphocytes had sperm in their ejaculate. However, in general, no correlations between FISH mosaic status and serum hormone parameters, nor with ejaculate parameters were found. The results suggest that 47,XXY patients with an increased incidence of XY cells (average of 4.2 +/- 2.3) may have a higher probability of germ cells as we found sperm only in the ejaculate of Klinefelter syndrome patients with mosaic 46,XY cells (6.0 and 7.0%). On the other hand, 46,XY patients with mosaic sex chromosome aneuploidies detected by FISH analysis more often show symptoms of hypogonadism phenotypically resembling Klinefelter syndrome.

Historical Perspectives

Fifty years ago, Professor Paul Polani and colleagues described young women who had Turner syndrome and were found to have apparently male “chromosomal sex.” (1) At that time, the generally accepted number of chromosomes in humans was 48. Five years earlier, Barr and Bertram described the presence of a prominent mass of chromatin lying close to the nucleolar membrane in neurons of some female cats. (2) This “sex-chromatin” was not found in the males. These “Barr bodies” later were detected in cells grown from skin biopsies. (3) Then, in 1956, Tjio and Levan reported that the number of diploid chromosomes was 46, (4) which rapidly was confirmed by others. (5) From this ripple, a wave soon developed. Three years later, the first association of a clinical syndrome with an abnormal number of chromosomes was reported from France (6) and quickly confirmed in Scotland. (7) This was the association of Down syndrome (mongolism) with an extra chromosome number 21 (trisomy 21), although this was called chromosome number 22 at the time. Not long afterward, translocation was noted in a girl who had Down syndrome born to a 21-year-old mother, (8) and translocation was described as a cause of familial mongolism. (9) Other trisomies soon were described. (10)(11) Based on the realization that the number of sex-chromatin bodies was one less than the number of X chromosomes present, the chromosomes of women who had Turner syndrome and appeared to be chromosomally “male” were investigated. They were found to have 45 chromosomes, with the sex chromosomes being XO. (12) Many of these exciting chromosomal discoveries were made by Professor Polani and his colleagues. Elsewhere, Professor Polani (now 90 years old) has described in detail the origins and evolution of clinical cytogenetics. (13) In this issue of NeoReviews , …

The Results of Cytogenetic Analysis with Regard to Intracytoplasmic Sperm Injection in Males, Females and Fetuses

Objectives: To determine the incidence of chromosome abnormalities among couples for whom intracytoplasmic sperm injection (ICSI) treatment was indicated and fetuses conceived through the ICSI procedure. Methods: All cytogenetic results were evaluated retrospectively. Patients undergoing ICSI (n = 508) were classified according to the referring indications as: (1) males with severe infertility (87 azoospermia and 34 oligoasthenoteratozoospermia, OAT), (2) prior to ICSI (56 males and 61 females), and (3) following an unsuccessful ICSI procedure (132 males and 138 females). Fetuses conceived through ICSI (n = 475) were also classified into 4 groups according to the additional risk factors for chromosome abnormalities: ICSI (n = 185), ICSI + advanced maternal age (AMA, n = 215), ICSI + positive triple test result (TT, n = 50), and ICSI + abnormal ultrasound findings (USG, n = 25). Results: An abnormal karyotype was found in 31.03% of males with azoospermia and 14.71% of males with OAT, in 3.57% of males and 1.64% of females in the group prior to ICSI, and in 5.30 and 5.07%, respectively, in the group following unsuccessful ICSI treatment. Gonosomal aneuploidies were predominant in males with azoospermia and autosomal rearrangements in males with OAT, while low-level sex chromosome mosaicism was found in females. The overall frequency of chromosome abnormalities in fetuses was 4.42% and varied in the different groups from 1.62% in ICSI, 2.79% in ICSI + AMA, 10.0% in ICSI + TT to 28.0% in ICSI + USG. The frequencies of the different types of chromosome abnormalities were as follows: balanced 1.05%, unbalanced 3.37%, familial 0.84%, de novo 3.37%, autosomal 3.58%, gonosomal 0.84%, numerical 1.89%, structural abnormalities 2.53%, and mosaicism 1.26%. Conclusion: Our results indicate that cytogenetic investigations of the ICSI parents and fetuses are essential for the families, genetic counselors and also reproductive centers. In fetal karyotyping, de novo structural chromosome abnormalities and mosaicism should be taken into consideration.

FISH analysis helps identify low-level mosaicism in Ullrich-Turner syndrome patients

Purpose: To search for X or Y chromosome mosaicism in 45,X individuals using fluorescent in situ hybridization (FISH).Methods: From our series of 53 Ullrich-Turner syndrome patients, we used interphase FISH to evaluate the 19 who had an apparently nonmosaic 45,X karyotype with G-banding.Results: Of those 19 patients, mosaicism was detected in seven (37%), five patients had an XX line, one had a monocentric isochromosome X, and one had a dicentric isochromosome X. No Y chromosome mosaic was identified.Conclusion: FISH analysis is a sensitive and cost-effective adjunct to karyotype analysis to identify sex chromosome mosaicism in UTS.

Sex chromosomal mosaicism in the gonads of patients with gonadal dysgenesis, but normal female or male karyotypes in lymphocytes

ObjectivesIn most cases, XX or XY gonadal dysgenesis remains genetically unexplained. In this pilot study we searched for sex-chromosomal mosaicism in gonads of patients with XX or XY gonadal dysgenesis of undetermined origin. Study DesignGonadal tissues were analyzed by cytogenetic and interphase fluorescence in-situ hybridization (FISH) analyses in four patients with gonadal dysgenesis and normal female (46,XX) or male (46,XY) karyotypes in lymphocytes. ResultsCytogenetic and FISH analyses of the gonads demonstrated in three patients a sex-chromosomal mosaicism. Cytogenetic analysis of gonadal tissue of the fourth patient confirmed the result of the lymphocytes with 46,XX, but FISH analysis revealed in 17% of nuclei only one X-chromosome. ConclusionOur data indicate that sex-chromosomal mosaicism in gonads may be a frequent cause of gonadal dysgenesis despite of normal karyotypes in lymphocytes. Therefore, cytogenetic and FISH analyses of gonadal tissue can provide important information in unexplained cases of gonadal dysgenesis.

Cytogenetics and fluorescence in situ hybridization assessment of sex-chromosome mosaicism in Klinefelter’s syndrome

A retrospective study was carried out in 152 infertile men to determine the prevalence of sex chromosome abnormalities among non-obstructive azoospermic and severe oligospermic men ( n = 51) and to evaluate the feasibility of fluorescence in situ hybridization (FISH) techniques to assess mosaicism in Klinefelter’s patients in comparison with conventional cytogenetics. Cytogenetic analysis were performed for 51 infertile men and among 14 chromosomal abnormalities found, nine were compatible with Klinefelter’s syndrome. FISH staining with a CEP X/CEP Y probes were performed for Klinefelter’s patients and for five of them; testes were biopsied for histopathologic examination. Six Klinefelter’s patients showed a non-mosaic 47,XXY and three showed a 47,XXY/46,XY mosaic by G or R banding analysis of 20 cells with a ratio of 17%, 20% and 33%, respectively. FISH analysis confirmed mosaicism in only one patient (the first) in whom a third cells population was found. There was no relationship between the ratios of mosaicism by banding and FISH analysis. Conventional histopathologic findings in five non-mosaic Klinefelter’s patients confirm the diagnosis of Sertoli Only Cells syndrome. FISH is recommended in Klinefelter’s syndrome to define exactly the cytogenetic statute as mosaic or non-mosaic and then discussing prognosis and decision regarding fertility counseling.

Detection of embryo sex chromosome by dual color fluorescent in-situ hybridization.

In order to evaluate the effects of sex chromosomal mosaicism on the accuracy of single-cell gender diagnosis, sex chromosomes of 21 normal fertilized embryos were detected by dual color fluorescent in-situ hybridization (FISH). The results showed that 4 embryos had sex chromosomal mosaicism (19%) and the remaining 17 showed uniformly XX or XY signals in all blastomeres. In conclusion, identification of sex by dual color FISH analysis of a single cell was accurate and efficient, and sex chromosomal mosaicism would not affect preimplantation gender diagnosis.

Frequency of sex chromosomal mosaicism in bovine embryos and its effects on sexing using a single blastomere by PCR.

Assessment of nuclear status is important when a biopsied single blastomere is used for embryo sexing. In this study we investigated the nuclear status of blastomeres derived from 8- to 16-cell stage in vitro fertilised bovine embryos to determine the representativeness of a single blastomere for embryo sexing. In 24 embryos analysed, the agreement in sex determination between a biopsied single blastomere and a matched blastocyst by polymerase chain reaction (PCR) was 83.3%. To clarify the discrepancies, karyotypes of blastomeres in 8- to 16-cell stage bovine embryos were analysed. We applied vinblastine sulfate at various concentrations and for different exposure times for metaphase plate induction in 8- to 16-cell stage bovine embryos. The 1.0 mg/ml vinblastine sulfate treatment for 15 h was selected as the most effective condition for induction of a metaphase plate (> 45%). Among 22 embryos under these conditions, only 8 of 10 that had a normal diploid chromosome complement showed a sex chromosomal composition of XX or XY (36.4%) and 2 diploid embryos showed mosaicism of the opposite sex of XX and XY in blastomeres of the embryo (9.1%). One haploid embryo contained only one X-chromosome (4.5%). Four of another 11 embryos with a mixoploid chromosomal complement contained a haploid blastomere with a wrong sex chromosome (18.2%). In conclusion, assessment of nuclear status of 8- to 16-cell stage bovine embryos revealed that morphologically normal embryos had a considerable proportion of mixoploid blastomeres and sex chromosomal mosaicism; these could be the cause of discrepancies in the sex between biopsied single blastomeres and matched blastocysts by PCR.

Cytogenetic studies in patients with reproductive failure.

Cytogenetic studies in patients with reproductive failure To investigate the contribution of chromosomal abnormalities in sub fertility and in couples with repeated abortions. Hundred and 13 couples who had at least two or more spontaneous abortions and 65 women and 63 men with infertility were analyzed cytogenetically. Major chromosomal rearrangements were found in 8% and minor variants in 6% in the study population. Major chromosomal aberrations were judged to explain 4.9% of recurrent abortions and 13% of infertility. Chromosomal abnormalities in infertile men occurred in 5% and in infertile women in 21.5%. The chromosomal abnormalities were structural (57%), numerical (18%) or mosaics (25%). Chromosomal aberrations in recurrent abortions are mostly structural ones and those in female infertility mosaicism of sex chromosomes. Turner's syndrome, Turner variants and XY females are detected as a cause of female infertility. The structural and numerical aberrations of either sex or autosomal chromosomes were found in infertile men.

Sex chromosome mosaicism in couples undergoing intracytoplasmic sperm injection.

Several studies have shown an increased frequency of constitutional chromosome aberrations in male and female partners of couples examined prior to ICSI. We conducted a cohort study to determine whether there was an increase in numerical sex chromosome mosaicism among couples undergoing ICSI compared with fertile couples. Cytogenetic investigations were performed in 228 females and 208 males seen for ICSI between January 1997 and March 2001. They were matched to control females and males. Sex chromosome loss or gain was observed in at least one cell from 24.1% of ICSI women in comparison with 22% of controls (not significant). A significant difference between these two groups was found when X chromosome loss in at least two cells was considered, 9.6% for ICSI females versus 4.8% for controls (P = 0.01). No significant difference was observed between male groups concerning loss or gain of the X or Y chromosome. Our results support previously published studies indicating that the loss of an X chromosome in a single cell in females undergoing ICSI is probably an artefact. However, they suggest that a woman could have true sex chromosome mosaicism when two 45,X0 cells are found.

High prevalence of low-level sex chromosome mosaicism in female partner in couples with male factor infertility

Objective: Intracytoplasmic sperm injection (ICSI) has become a well-accepted procedure to assist fertilization in couples with severe male factor infertility. It is known that ICSI itself has a potentially elevated genetic risk such as de novo karyotypic abnormalities in children as well as the perpetuation of chromosome aberration from the infertile couple. Our purpose in this study was to analyze whether abnormal chromosomal findings such as low-level sex chromosome mosaicism in female partner might influence the outcome of such therapy.

Absence of sperm sex chromosome aneuploidies in an X0/XYY man

Objective: To determine appropriate genetic counseling of patients with a mosaic karyotype who wished to undergo assisted reproduction technology. Design: Case report. Setting: A tertiary center for assisted reproduction technology. Patient(s): A male with a mosaic karyotype X0/XYY. Intervention(s): Analysis of ejaculated spermatozoa by using fluorescence in situ hybridisation with probes directed against chromosomes X, Y, and 18. Main Outcome Measure(s): Degree of sex chromosome aneuploidies in spermatozoa. Result(s): Levels of sex chromosome aneuploidies in spermatozoa were normal. On the basis of these findings, the couple proceeded to assisted reproduction technology without preimplantation genetic diagnosis and conceived a healthy male baby. Conclusion(s): Sex chromosome mosaicism in men does not necessarily lead to high levels of abnormal spermatozoa. Sex chromosome aneuploidies may be eliminated in the testes through the selective degeneration of abnormal spermatogenic cells.

Impact of parental gonosomal mosaicism detected in peripheral blood on preimplantation embryos

This study evaluated the chromosomal condition of embryos generated by patients with an altered karyotype due to gonosomal mosaicism and the clinical outcome after preimplantation genetic diagnosis (PGD) for aneuploidy. Thirty-six patients aged 34.6 ± 3.6 years performed 54 treatment cycles and had 295 embryos diagnosed by fluorescence in-situ hybridization (FISH). Thirty-seven per cent of the embryos were chromosomally normal and generated 19 clinical pregnancies after replacement in 39 cycles. Only one pregnancy miscarried, yielding a take-home baby rate of 33.3%. Autosomal monosomy and trisomy contributed 36.1% of total abnormalities and gonosomal aneuploidy 5.9%, similar to the results detected in patients who undergo PGD for increased maternal age. Reanalysis was performed on 114 non-transferrable embryos: 41 were found to be mosaics, which were grouped in three different types, chaotic mosaics (56%), aneuploid mosaics (29%) and diploid/haploid/polyploid mosaics (15%). The incidence of aneuploid mosaics was higher than expected compared with PGD patients of the same age and resembled the condition observed in patients of advanced maternal age. These findings suggest that constitutional carriers of sex chromosome mosaicism are predisposed to autosomal mosaicism of embryos, possibly due to errors of cell division. There is an indication that this tendency is higher in female than male carriers.

Fluorescence In Situ Hybridization Analysis of Sex‐Chromosome Mosaicism in Azoospermic Men

A retrospective study was carried out to determine the prevalence of sex-chromosome mosaicism among azoospermic men and to evaluate the feasibility of using fluorescence in situ hybridization (FISH) technique to assess mosaicism and the origin of marker chromosomes. Nine hundred eighty patients with azoospermia who were referred to a male infertility clinic at a university hospital were karyotyped by G-banding using peripheral blood lymphocyte (PBL) metaphase spreads. When sex chromosome mosaic karyotype was detected, FISH analyses using sex chromosome-specific probes were performed. Seventeen of 980 patients showed evidence of sex chromosomal mosaic karyotype or mosaicism with marker chromosomes by G-banding studies of PBLs. Ten patients showed mosaicism in the number of sex chromosomes and 7 showed mosaicism with marker chromosomes. All 17 patients agreed to undergo FISH analysis. FISH confirmed mosaicism in 88.2% of these patients (15 of 17). Low-frequency mosaicism showing a frequency of less than 10% by G-banding was proved to be nonmosaicism by FISH. Marker chromosomes detected in 7 patients were proved to be derived from the Y chromosome by FISH analyses. From these data the prevalence of sex chromosome mosaicism confirmed by FISH analysis is 1.5% (15 of 980 patients). FISH analysis should be applied when mosaicism shows a frequency of less than 10% by the G-banding technique. Also, FISH analysis is indicated when a marker chromosome is detected by G-banding.

Low-level sex chromosome mosaicism in female partners of couples undergoing ICSI therapy does not significantly affect treatment outcome.

There is an increased rate of chromosomal anomalies, in particular low-level sex chromosome mosaicism, in the female partners of couples undergoing intracytoplasmic sperm injection (ICSI). Among 811 consecutive couples presenting for pre-ICSI chromosome analysis, chromosomal abnormalities were detected in 54 individuals, of which 26 were low-level sex chromosome mosaicism in the females. Attention was focused on the treatment course and outcome of ICSI in 20 couples with low-level sex chromosome mosaicism in the females actually embarking on ICSI treatment (group I, n = 38 ICSI treatment cycles). Applying a case-control design, each of the 20 couples was matched according to female age and source of spermatozoa to couples without a chromosomal abnormality in either of the partners (group II, n = 38 ICSI treatment cycles). No significant differences were found between the groups in ovarian response, fertilization rate and number of embryos transferred. Pregnancy rates, as well as implantation and abortion rates did not differ significantly between the groups. The data suggest that low-level sex chromosome mosaicism in females has no major effect on the course and outcome of ICSI.

Sex chromosome mosaicism in males carrying Y chromosome long arm deletions

Microdeletions of the long arm of the Y chromosome (Yq) are a common cause of male infertility. Since large structural rearrangements of the Y chromosome are commonly associated with a 45,XO/46,XY chromosomal mosaicism, we studied whether submicroscopic Yq deletions could also be associated with the development of 45,XO cell lines. We studied blood samples from 14 infertile men carrying a Yq microdeletion as revealed by polymerase chain reaction (PCR). Patients were divided into two groups: group 1 (n = 6), in which karyotype analysis demonstrated a 45,X/46,XY mosaicism, and group 2 (n = 8) with apparently a normal 46,XY karyotype. 45,XO cells were identified by fluorescence in-situ hybridization (FISH) using X and Y centromeric probes. Lymphocytes from 11 fertile men were studied as controls. In addition, sperm cells were studied in three oligozoospermic patients in group 2. Our results showed that large and submicroscopic Yq deletions were associated with significantly increased percentages of 45,XO cells in lymphocytes and of sperm cells nullisomic for gonosomes, especially for the Y chromosome. Moreover, two isodicentric Y chromosomes, classified as normal by cytogenetic methods, were detected. Therefore, Yq microdeletions may be associated with Y chromosomal instability leading to the formation of 45,XO cell lines.