H-Y antigen in Swyer syndrome and the genetics of XY gonadal dysgenesis

Genomics of the human Y-chromosome. 1. Association with male infertility

The human Y chromosome contains over 60 million nucleotides, but least number of genes compared to any other chromosome and acts as a genetic determinant of the male characteristic features. The male specific region, MSY, comprising 95% of the Y chromosome represents a mosaic of heterochromatic and three classes of euchromatic (X-transposed, X-degenerate and ampliconic) sequences. Thus far, 156 transcription units, 78 protein-coding genes and 27 distinct proteins of the Y chromosome have been identified. The MSY euchromatic sequences show frequent gene conversion. Of the eight massive palindromes identified on the human Y chromosome, six harbor vital testis specific genes. The human male infertility has been attributed to mutations in the genes on Y chromosome and autosomes and failures of several physical and physiological attributes including paracrine controls. In addition, deletion of any one or all the three azoospermia (AZFa, AZFb or AZFc) factor(s) and some still unidentified regulatory elements located elsewhere in the genome result in infertility. Characterization of palindromic complexes on the long arm of Y chromosome encompassing AZFb and AZFc regions and identification of HERV15 class of endogenous retroviruses close to AZFa region have facilitated our understanding on the organization of azoospermia factors. Considerable overlap of the AZFb and AZFc regions encompassing a number of genes and transcripts has been shown to exist. However, barring details on AZF, information on the exact number of genes or the types of mutations prevalent in the infertile male is not available. Similarly, roles of sizable body of repetitive DNA present in close association with transcribing sequences on the Y chromosome are yet not clear. In a clinical setting with known cases of infertility, systematic search for loss or gain of these repeat elements would help understand their biological role(s). We present a brief overview on the genetic complexity of the human Y chromosome in the context of human male infertility.

Gonadal agenesis in XX and XY sisters: evidence for the involvement of an autosomal gene

Two agonadic sisters, one with a 46,XY and the other with a 46,XX karyotype, both with normal female external genitalia and hypoplastic Müllerian derivatives, born to a consanguineous marriage, were studied from a clinical, endocrinological, histological, and genetic perspective. Using PCR amplification, Southern hybridization, and DGGE analysis, it was found that the XY patient had no mutations in the conserved sequence of the SRY gene, the putative testis-determining gene in mammals, whereas her XX affected sister is SRY-negative. To our knowledge, this is the first report of XY and XX sibs in familial gonadal agenesis without other somatic abnormalities. The involvement of an autosomal locus impeding gonadal development in both sexes is discussed.

Comparison of adult height between patients with XX and XY gonadal dysgenesis: support for a Y specific growth gene(s)

Adult height was compared between published cases of patients with XX gonadal dysgenesis (XXGD) and those with XY gonadal dysgenesis (XYGD). The mean adult height of XYGD patients (171.0 cm (SD 7.8), n = 27) was significantly greater than that of XXGD patients (164.4 cm (7.7), n = 27) (p less than 0.01). This finding supports the existence of a Y specific growth gene(s) which promotes statural growth independently of the effects of gonadal sex steroids.

In-vivo and in-vitro endocrine investigation of pure gonadal dysgenesis

Diagnosis of XY pure gonadal dysgenesis was established in a patient of female phenotype, with female internal genitalia, but with a chromosomal constitution of 46 XY. Streak gonads had undergone neoplastic transformation--gonadoblastoma and dysgerminoma. Before operation the concentrations of gonadotrophins in plasma were high and of oestradiol was low. Administration of oestradiol benzoate initially suppressed and then stimulated an increase in the plasma concentration of LH. These changes were not accompanied by changes in blood levels of endogenous sex steroids. A single injection of hCG failed to stimulate steroid secretion. The activities in vitro of steroid-metabolizing enzymes in the dysgenetic gonadal tissue more closely resembled those of ovarian tissue from a premenopausal and from a postmenopausal women than those in testes from two androgen-insensitive patients. However, aromatase activity was higher in the dysgenetic gonads than in the pre or post-menopausal ovaries. Examination of enzymes in genital skin fibroblasts demonstrated normal activities of 3 alpha/beta-beta-hydroxysteroid dehydrogenase and 17 beta-hydroxysteroid dehydrogenase (oxidative and reductive directions). However, 5 alpha-reductase activity was low in minces and fibroblasts of genital skin from the patient. Androgen binding was within the range for male controls.

Abnormal sexual differentiation and neoplasia

The prevalence of neoplasia is increased in individuals with certain disorders of sexual differentiation. Etiology and frequency of neoplasia vary with the particular disorder. In uncomplicated cryptorchidism, the testis is at least 10 times more likely to undergo neoplastic transformation than a normal scrotal testis. Neoplasia probably is a function of both testicular location (intraabdominal) and underlying dysgenetic structure. If cryptorchidism is unilateral, and if orchiopexy has not been performed prior to age 6-10 years, orchiectomy should be encouraged. In those forms of gonadal dysgenesis not associated with a Y chromosome (e.g., 45,X; 45,X/46,XX; 46,XX) there is no definite increase in neoplasia, suggesting that elevated gonadotropin levels per se are not carcinogenic. Gonadal tumors are found in at least 30% of individuals with XY gonadal dysgenesis and are particularly frequent (55%) in H-Y antigen-positive patients. These tumors are almost always gonadoblastomas or dysgerminomas. Similar tumors are found in 15%-20% of 45,X/46,XY individuals. In either situation the neoplastic transformation could be a) secondary to the existence of XY gonadal tissue in an inhospitable environment, or b) integrally related to that process--genetic or cytogenetic--producing the dysgenetic gonads. The risk of neoplasia is sufficiently high that most of these patients should be offered early gonadal extirpation. The prevalence of gonadal tumors is not increased in Klinefelter's syndrome, further indicating that gonadotropins are not carcinogenic per se. However, Klinefelter patients are 20 times more likely to develop a carcinoma of the breast than are 46,XY males. Extragonadal germ cell tumors also are more common. In female pseudohermaphrodites there is probably no increased risk of neoplasia, whereas, in true hermaphrodites neoplasia is unusual but does occur. Neoplasia occurs in patients with complete testicular feminization (complete androgen insensitivity) but rarely in those with incomplete testicular feminization/Reifenstein's syndrome, 5 alpha-reductase deficiency, anorchia, agonadia, or testosterone biosynthetic defects. In complete testicular feminization the risk of malignant tumors is small prior to age 25. After age 25, it is about 2%-5%. Orchiectomy is recommended after pubertal feminization.

Gonadal tumor and H-Y antigen in 46,XY pure gonadal dysgenesis

Six cases of Swyer's syndrome (46,XY pure gonadal dysgenesis) are reported. Three patients, without gonadal tumor, had female H-Y antigen. Three patients, after gonadal tumor ablation, had intermediate H-Y antigen levels. Repeated blood samples were obtained from two siblings. H-Y antigen level in the first sibling, who presented with a gonadoblastoma and underwent a gonadectomy before the H-Y assays, was intermediate, and did not show any significant variation for 21 months. H-Y antigen level in the second sibling showed an increase in the male range, presumably due to the presence of gonadoblastomas. After resection of the tumors, H-Y antigen level became intermediate. These findings suggest a relation between the tumorization potentiality of the gonadal remnants and the H-Y antigen levels in 46,XY pure gonadal dysgenesis.

Study of H-Y antigen in abnormal sex determination with monoclonal antibody and an ELISA

A newly developed enzyme-linked immunosorbent assay (ELISA) has been applied to the study of H-Y antigen in cases of XY, XYY, and X,dicY gonadal dysgenesis, testicular feminization syndrome, XXXXY syndrome, and XX true hermaphroditism. Monoclonal H-Y antibody was absorbed with cells from each of eight patients and from normal male and female controls, and then reacted with a plated antigen source in a system subsuming the addition of biotinylated secondary antibody, avidin-biotin-enzyme complex and substrate, and thereby the generation of a color. Positive absorption decreased the reaction, and this allowed sensitive measurement of H-Y phenotype in an electronic optical density reader. The ELISA obviates many of the technical difficulties encountered in complement-mediated cytotoxicity systems and can be used in the study of clinical cases of aberrant sex determination and in the evaluation of current models of the genetics of sex determination.

46,XY gonadal dysgenesis: is oncogenesis related to H-Y phenotype or breast development?

Among women with 46,XY gonadal dysgenesis, there is a high incidence of gonadal tumors. Because of evidence of a connection between occurrence of those tumors, H-Y phenotype, and breast development, we surveyed 55 cases of 46,XY gonadal dysgenesis and 12 related cases involving chromosomal and/or skeletal abnormalities. Our survey, including three new cases presented here, indicates that H-Y phenotype but not breast development may be related to the development of the gonadoblastoma-dysgerminoma. Thus among women with 46,XY gonadal dysgenesis, there are H-Y- and H-Y+ classes, but gonadal tumors are found almost exclusively in the H-Y+ class. Yet one of our patients may represent an exception to the association of H-Y+ phenotype and gonadal tumors in this syndrome.

Testicular regression in a patient with virilized female phenotype

The 16-year old girl studied here had ambiguous external genitalia, ie, enlarged clitoris, pseudo vagina, and rudiments of Wolffian tubes. Her karyotype was 46,XY and she was H-Y antigen-positive. In spite of absence of gonadal tissue, genital virilization suggests presence of testes during embryogenesis. This patient is compared to 20 others with testicular regression from the literature. Autosomal-recessive inheritance of this condition is proposed.

Absence of H-Y antigen in a case of sporadic pure gonadal dysgenesis

H-Y activity, endocrine function and gonadal histology were studied in a phenotypic female presenting with features of sporadic 46,XY pure gonadal dysgenesis. H-Y activity was absent, hormonal data revealed a primary ovarian failure with a blunted response of FSH to LHRH; there was no testicular tissue nor microscopic evidence of gonadal tumor in the gonads. The current view on the role of H-Y antigen in the differentiation of the gonads and in the occurrence of gonocytoma is discussed.

Variability in serologically detected male antigen titer and some resulting problems: a critical review

Seroologically detected male antigen" (also called H-Y antigen) was first described in normal male mammals but now appears to occur in normal female mammals as well. "Serologically detected male predominant" (SDMP) antigen is a more appropriate name since the titer in normal males usually exceeds that of normal females. As we show, in each sex there is a considerable inter-individual variability in SDMP antigen titer, and in moderate-to-large size samples the low end of the male range of titers usually coincides with the high end of the female range. Several major problems arise from failure to recognize and/or to deal adequately with this normal variation in SDMP antigen titer. The chief problem is that the "controls" used (often a single individual) may be inadequate and misleading, leading to unjustified designation of samples as "positive", "negative", or even "deviant" ("intermediate", "reduced") for SDMP antigen titer. Other problems include deficiencies in technique and lack of statistical control for test and sample variability. Adequate attention to these problems, especially to the normal variability in SDMP antigen titer, could reduce the contradictions and inconsistencies which have troubled this field.

Dysgerminoma of the ovary in association with XY gonadal dysgenesis

A case is reported of an adolescent presenting with primary amenorrhea. On pelvic examination a large unilateral ovarian tumor was palpated. Microscopic examination of the tumor removed at laparotomy revealed a pure dysgerminoma. Further gynecological-endocrinological investigations and chromosome analysis showed an XY gonadal dysgenesis. A review of current approaches to diagnosis, prognosis and especially to the controversial therapeutic modalities is presented.

Dysgerminoma--gonadoblastoma and familial 46XY pure gonadal dysgenesis: case report and review of the genetics and pathophysiology of gonadal dysgenesis and H-Y antigen

46XY gonadal dysgenesis is a rare condition of intersexuality first described in detail by Swyer in 1955. It is characterized by a phenotypic female who is tall, eunuchoid with normal female external genitalia, hypoplastic uterus and Fallopian tubes, streak ovaries and primary amenorrhoea. The patients exhibit none of the associated congenital defects such as webbing of the neck and genu valgum seen in Turner's syndrome. Although rare, this clinical entity is important to recognize because of the high incidence of gonadoblastomas and subsequent development of dysgerminoma. The condition may be familial and therefore siblings need to be screened. To the geneticists and scientists researching in the area of intersexuality, hermaphroditism and sexual determination, it has helped to unveil the mechanisms of gonadal and genital sexual development.

The evolution of XY females in mammals

Some lemmings have a large proportion of XY females in the population, as well as XX females and XY males. In this paper we first review the biological literature on XY females in mammals, with particular emphasis on the genetics and cytogenetics of this trait. We then consider population genetics models of the behaviour of this trait, and we show that there are serious discrepancies between predictions and observations regarding the sex ratio and the frequency of XY females; in several lemming populations the reported sex ratio is lower and XY females are more common than expected. Finally we consider evolutionary models to understand why XY females persist in these populations and how selection might act on other parts of the reproductive biology to modify the system.

H-Y antigen expression in a case of mixed gonadal dysgenesis

H-Y antigen expression was studied on leukocytes and gonad-derived fibroblasts from a patient affected by mixed gonadal dysgenesis. Blood leukocytes and fibroblasts derived from the testis were typed H-Y positive, but the fibroblasts derived from the streak gonad were H-Y negative. Although the patient's karyotype was a mosaic, 45,XO/46,X+mar, as detected in-peripheral blood cells and testis-derived fibroblasts, all the fibroblasts derived from the streak gonad were 45,XO. These data suggests that the marker chromosome was in fact a Y-derived chromosome. Moreover, they showed that, at the gonadal level, a minority of H-Y positive 46,X+mar cells were able to organize a testis. Nevertheless, a large number of XO cells probably did not receive the testicular forming influence of the H-Y antigen and of the other masculinizing factors.

H-Y antigen in transsexuality, and how to explain testis differentiation in H-Y antigen-negative males and ovary differentiation in H-Y antigen-positive females

H-Y antigen was determined in eight transsexual patients. Two of the four male-to-female transsexual patients typed as H-Y antigen-negative, while the other two typed as expected from their phenotypic and gonadal sex, namely H-Y antigen-positive. Of the four female-to-male transsexual patients, three typed as H-Y antigen-positive and one was H-Y antigen-negative, as expected. The presence of normal testes in H-Y antigen-negative males is assumed to result from a mutation of nucleotide sequences of the H-Y structural gene for antigenic determinants. Thus, an H-Y is produced with normal receptor-binding activity which can sustain the testis determination of the bipotent gonadal anlage. In the case of H-Y antigen-positive females with normal ovaries a deletion of the autosomally located H-Y structural gene is assumed. This deletion should affect sequences for repressor-binding (as was suggested for H-Y antigen-positive XX-males) and for receptor-binding activity of the H-Y antigen molecule. The resulting H-Y antigen is unable to bind to the gonadal receptor of the bipotent gonadal anlage. Thus an ovary is determined. The relevance of H-Y antigen for the aetiology of transsexualism is discussed.