Screening of patients with Turner syndrome for "hidden" Y-mosaicism

Genomics and genetics of human and primate y chromosomes

In mammals, the Y chromosome plays the pivotal role in male sex determination and is essential for normal sperm production. Yet only three Y chromosomes have been completely sequenced to date--those of human, chimpanzee, and rhesus macaque. While Y chromosomes are notoriously difficult to sequence owing to their highly repetitive genomic landscapes, these dedicated sequencing efforts have generated tremendous yields in medical, biological, and evolutionary insight. Knowledge of the complex structural organization of the human Y chromosome and a complete catalog of its gene content have provided a deeper understanding of the mechanisms that generate disease-causing mutations and large-scale rearrangements. Variation among human Y-chromosome sequences has been an invaluable tool for understanding relationships among human populations. Comprehensive comparisons of the human Y-chromosome sequence with those of other primates have illuminated aspects of Y-chromosome evolutionary dynamics over much longer timescales (>25 million years compared with 100,000 years). The future sequencing of additional Y chromosomes will provide a basis for a more comprehensive understanding of the evolution of Y chromosomes and their roles in reproductive biology.

Molecular identification of chromosome Y sequences in Brazilian patients with Turner syndrome

The investigation of Y-specific sequences in patients with Turner Syndrome (TS) with karyotype 45,X or mosaic, has a fundamental role in the clinical management of these patients. The relationship between the presence of Y chromosome fragments and a higher risk of gonadoblastoma in TS has already been established. The aim of the study was to investigate the presence of Y-chromosome fragments in a population of 42 female Brazilian patients with TS from Mato Grosso state. Cytogenetic analysis has shown the karyotypes 45,X in 27 of them (64.3%) and mosaic in 15 (35.7%). The presence of the Y-primers SRY, DYZ3, ZFY, DYZ1, DYS1 and PABY was investigated in all patients. These markers were amplified by polymerase chain reaction (PCR) technique, using DNA genomic from peripheral blood lymphocytes. None of these patients had shown any Y-chromosome fragments when they were analysed only by the classic cytogenetic technique. The PCR analysis with the Y-specific sequences ZFY and DYZ3 were identified in two different patients (4.8%), both with karyotype 45,X. It was concluded that PCR is efficient in the investigation of hidden Y-fragments in TS patients. Therefore, this method should be included in the routine assistance of these patients.

Participation of OCT3/4 and beta-catenin during dysgenetic gonadal malignant transformation

Gonadoblastoma (GB) is an in situ tumor consisting of a heterogeneous population of mature and immature germ cells, other cells resembling immature Sertoli/granulosa cells, and Leydig/lutein-like cells, may also be present. GB almost exclusively affects a subset of patients with intersex disorders and in 30% of them overgrowth of the germinal component of the tumor is observed and the lesion is term dysgerminoma/seminoma. Several pathways have been proposed to explain the malignant process, and abnormal OCT3/4 expression is the most robust risk factor for malignant transformation. Some authors have suggested that OCT3/4 and beta-catenin might both be involved in the same oncogenic pathway, as both genes are master regulators of cell differentiation and, overexpression of either gene may result in cancer development. The mechanism by which beta-catenin participates in GB transformation is not completely clear and exploration of the E-cadherin pathway did not conclusively show that this pathway participated in the molecular pathogenesis of GB. Here we analyze seven patients with mixed gonadal dysgenesis and GB, in an effort to elucidate the participation of beta-catenin and E-cadherin, as well as OCT3/4, in the oncogenic pathways involved in the transformation of GB into seminoma/dysgerminoma. We conclude that the proliferation of immature germ cells in GB may be due to an interaction between OCT3/4 and accumulated beta-catenin in the nuclei of the immature germ cells.

Clinical implications of the detection of Y-chromosome mosaicism in Turner's syndrome: report of 3 cases

OBJECTIVE

To determine the clinical implications of the presence of a Y chromosome in Turner's syndrome patients with karyotype abnormalities.

DESIGN

To investigate the presence of Y-chromosome sequences in different tissue samples.

SETTING

Endocrinology outpatient clinic of a federal university in Brazil.

PATIENT(S)

Five Turner's syndrome patients with karyotype abnormalities such as marker chromosomes, additional material, or ring chromosomes.

INTERVENTION(S)

Peripheral blood, oral epithelial cells, and hair root samples were collected.

MAIN OUTCOME MEASURE(S)

The SRY gene and the DYZ3 repeat region were amplified by polymerase chain reaction followed by gel electrophoresis mobility of amplified genomic DNA, and ultraviolet visualization. Prophylactic gonadectomy was offered to the Y-positive patients.

RESULT(S)

The analysis of the different tissues revealed that three of the five patients studied presented Y-chromosome mosaicism. These three patients underwent prophylactic gonadectomy, and in one of them, the histopathologic study of the gonads disclosed hilus cell hyperplasia and stromal luteoma with contralateral nodular hyperthecosis.

CONCLUSION(S)

A systematic search for Y-chromosome mosaicism in Turner's syndrome patients is justified by the risk of developing gonadal tumors or androgen-producing lesions.

Detection of hidden Y mosaicism in Turner's syndrome: importance in the prevention of gonadoblastoma

The presence of Y chromosome fragments in patients with Turner's syndrome (TS) is known to increase the risk of gonadoblastoma. The investigation of Y sequences is usually performed only in the presence of marker chromosomes and therefore does not rule out the presence of hidden mosaicism in patients with 45,X TS without any marker.

AIMS

1. To investigate the presence of hidden Y mosaicism in non-mosaic 45,X patients with TS, using samples from different tissues, and its association with the development of gonadoblastoma.

STUDY DESIGN

Twenty patients with a 45,X karyotype were studied. The SRY and DYZ3 sequences were amplified by PCR, using genomic DNA from peripheral blood, oral epithelial cells and hair roots. Prophylactic gonadectomy was offered to the Y-positive patients.

RESULTS

The analysis of the different tissues revealed that seven (35%) out of the 20 patients studied presented hidden chromosome Y mosaicism. Four of these patients underwent prophylactic gonadectomy, and bilateral gonadoblastoma was found in one of them.

CONCLUSIONS

A systematic search for hidden Y chromosome mosaicism in patients with TS and 45,X karyotype is justified by the possibility of developing gonadoblastoma.

Distribution of Y-chromosome-bearing cells in gonadoblastoma and dysgenetic testis in 45,X/46,XY infants

Gonadoblastoma is an unusual mixed germ cell-sex cord-stromal tumor that has the potential for malignant transformation and 30% of all patients with gonadoblastoma develop germ cell tumors mainly dysgerminoma/seminoma. An additional 10% gives rise to other malignant germ cell neoplasms. This tumor affects a subset of patients with intersex disorders. The age at diagnosis is variable ranging from birth to the fourth decade, but around 94% of cases are diagnosed during the first three decades of life and there are few cases with gonadoblastoma diagnosed in infants. In this paper, we present the histological and molecular findings of four patients with gonadal dysgenesis who developed gonadoblastoma in the first 2 years of life and one case with bilateral dysgerminoma diagnosed at 15 years of age. The sex chromosomes of mosaic patients do not distribute homogenously in dysgenetic gonads; however, statistical analysis of FISH results revealed significant differences between the XY cell line in the gonadoblastoma compared with the dysgenetic testis. Our cases demonstrate that tumors could be present at a very early age, so the prophylactic removal of the gonads is advised.

Refined quantitative fluorescent PCR of Y-chromosome DNA sequences mosaics in Turner's syndrome patients—alternative to real-time PCR

BACKGROUND

Real-time polymerase chain reactions (PCRs) are the most frequently used techniques for gonosomal mosaics quantification. The primary aim of this work is to assess and optimize the refined technique of quantitative fluorescent polymerase chain reaction (RQF PCR) in the quantification of Y-chromosome sequences in gonosomal mosaics. The method was applied to the analysis of Y-chromosome sequences (amelogenin gene, AMELX/Y-loci) in peripheral lymphocytes and gonadal tissues in Y-positive Turner's syndrome (TS) patients.

METHODS

RQF PCR was used for molecular quantification, and fluorescent in situ hybridization (FISH) technique was used for comparison.

RESULTS

Based on a formulated calibration curve, DNA mosaics from six Y-positive patients and gonads from one patient were deducted. For calculation of rare mosaics, it is possible to take advantage of a new empirical formula. FISH results were comparable to RQF PCR.

CONCLUSION

The sensitivity of RQF PCR brings significant progress in the analysis of gonosomal aberrations. RQF PCR also finds applications in prenatal diagnostics of maternal contaminations of amniotic fluid and foetal DNA in maternal blood and analysis of chimerism in patients after bone marrow transplantation. The method is very convenient for determining the number of testis-specific protein, Y-linked (TSPY) gene repetitions.

Genetic analysis of mosaicism in 53 women with Turner syndrome

Mosaicism involving the sex chromosomes is a common finding in women with Turner syndrome (TS). It is especially important to detect Y-chromosomal material, since this is a risk factor for the development of gonadoblastoma. Recent studies have also indicated that the frequency of 45,X cells may be used to predict prognosis. As part of an ongoing multi-disciplinary study, we have examined the extent of Y-chromosomal material and sex chromosomal mosaicism and its tissue specificity in 53 women with TS. The results of lymphocyte karyotyping were compared with the use of interphase X/Y fluorescence in situ hybridisation (FISH) analysis of lymphocytes and buccal mucosal cells. As could be expected, an extended FISH analysis detected more Y-chromosomal material than karyotyping (in 15% vs. 11% of the women, respectively) and also detected more X-chromosomal mosaicism among the TS women (in 70% vs. 45 % of the women, respectively). In half of the women, tissue-specific differences between lymphocytes and buccal mucosal cells were found. Based on these results, we suggest the use of X/Y interphase FISH as a complement to karyotyping in order to obtain a more complete knowledge of the chromosome constitution of each individual with TS.

Tumors of the testis in intersex syndromes

Patients with intersex syndrome are rare in the general population. In these patients, cryptorchid gonads that have an Y chromosome or Y chromosomal material are at risk for development of germinal and non-germinal neoplasm and non-neoplastic masses. Diagnosis of individual patients should be accurate for optimal care and risk assessment.

Insights into causes of sexual ambiguity

Our understanding of the causes of sexual ambiguity has progressed from the determination of the hormonal etiologies to defining the genetic basis of intersex disorders. The localization of specific genes involved in the process of sexual differentiation has made it possible to determine the mutations and other molecular events that result in sexual ambiguity. With this information, some disorders can now be diagnosed before birth and possibly even treated in utero.

Recognition and management of childhood cancer syndromes: a systems approach

Recognition of congenital anomalies that predispose to childhood cancer allows for the institution of a cancer surveillance program, identification of relatives with increased cancer risk, and recurrence risk counseling. In this article, a systems approach to the diagnosis of 21 childhood cancer syndromes is set forth in the format of the pediatric physical examination. In the second part of this article, guidelines are presented for genetic testing, cancer screening, and genetic counseling for the 21 cancer syndromes.