Molecular analysis of 46,XY females and regional assignment of a new Y-chromosome-specific probe

The Biology and Evolution of Mammalian Y Chromosomes

Mammals have the oldest sex chromosome system known: the mammalian X and Y chromosomes evolved from ordinary autosomes beginning at least 180 million years ago. Despite their shared ancestry, mammalian Y chromosomes display enormous variation among species in size, gene content, and structural complexity. Several unique features of the Y chromosome--its lack of a homologous partner for crossing over, its functional specialization for spermatogenesis, and its high degree of sequence amplification--contribute to this extreme variation. However, amid this evolutionary turmoil many commonalities have been revealed that have contributed to our understanding of the selective pressures driving the evolution and biology of the Y chromosome. Two biological themes have defined Y-chromosome research over the past six decades: testis determination and spermatogenesis. A third biological theme begins to emerge from recent insights into the Y chromosome's roles beyond the reproductive tract--a theme that promises to broaden the reach of Y-chromosome research by shedding light on fundamental sex differences in human health and disease.

In situ hybridization analysis of the Y chromosome in gonadoblastoma

Gonadoblastoma is a rare tumor arising in the streak gonads of about 30% of 46,XY sex-reversed females. Because gonadoblastoma develops only in patients who have Y-chromosome material and dysgenetic gonads, it has been hypothesized that positive expression of a gene (or genes) on the Y chromosome (GBY) is involved in the etiology of the tumor. To examine the Y chromosome directly in tumors, we performed nonisotopic in situ hybridization of a biotin-labeled Y-specific probe for the DYZI locus on formalin-fixed, paraffin-embedded sections of tumor samples from four different patients. After hybridization to DYZI, the Y chromosome was found to be present in all gonadoblastoma foci in the four patients studied, and the gonadoblastoma foci showed an average of 85% cell nuclei positive for the Y chromosome on tissue sections. Normal male and female control tissues showed an average of 78% and 0% positive nuclei, respectively. One patient with bilateral gonadoblastoma had previously been shown to be mosaic, with a 45,X/46,XY karyotype in lymphocytes, skin fibroblasts, and cultures from both gonads. Examination of sections of this patient's gonads showed 79% positive nuclei within the gonadoblastoma foci, whereas the nontumor stromal tissue had 19% positive nuclei. These results indicate that, in this mosaic gonad, tumor foci developed only from cells that had a Y chromosome. Our results support the hypothesis that there is a GBY locus on the Y chromosome and that the Y chromosome is retained in the gonadoblastoma foci during the development of the tumor.

Phenotype/karyotype correlations of Y chromosome aneuploidy with emphasis on structural aberrations in postnatally diagnosed cases

Over 600 cases with a Y aneuploidy (other than non-mosaic 47,XYY) were reviewed for phenotype/karyotype correlations. Except for 93 prenatally diagnosed cases of mosaicism 45,X/46,XY (79 cases), 45,X/47,XYY (8 cases), and 45,X/46,XY/47,XYY (6 cases), all other cases were ascertained postnatally. Special emphasis was placed on structural abnormalities. This review includes 11 cases of 46,XYp-; 90 cases of 46,XYq- (52 cases non-mosaic; 38 cases 45,X mosaic); 34 cases of 46,X,r(Y) (9 cases non-mosaic and 25 cases 45,X mosaic); 8 cases of 46,X,i(Yp) (4 non-mosaic and 4 mosaic with 45,X); 12 cases of 46,X,i(Yq) (7 non-mosaic and 5 mosaic); 44 cases of 46,X,idic(Yq); 80 cases of 46,X, idic(Yp) (74 cases had breakpoints at Yq11 and 6 cases had breakpoints at Yq12); 130 cases of Y/autosome translocations (50 cases with a Y/A reciprocal translocation, 20 cases of Y/A translocation in 45,X males, 60 cases of Y/DP or Y/Gp translocations); 52 cases of Y/X translocations [47 cases with der(X); 4 cases with der(Y), and 1 case with 45,X with a der(X)], 7 cases of Y/Y translocations; 151 postnatally diagnosed cases of 45,X/46,XY; 14 postnatally diagnosed cases of 45,X/47,XYY; 18 cases of 45,X/46,XY/47,XYY; and 93 aforementioned prenatally diagnosed cases with a 45,X cell line. It is clear that in the absence of a 45,X cell line, the presence of an entire Yp or a region of it including SRY would lead to a male phenotype in an individual with a Y aneuploidy, whereas the lack of Yp invariably leads to a female phenotype with typical or atypical Ullrich-Turner syndrome (UTS). Once there is a 45,X cell line, regardless of whether there is Yp, Yq, or both Yp and Yq, or even a free Y chromosome in other cell line, there is an increased chance for that individual to be a phenotypic female with UTS manifestations or to have ambiguous external genitalia. This review once again shows a major difference in reported phenotypes between postnatally and prenatally diagnosed cases of 45,X/46,XY, 45,X/47,XYY, and 45,X/46,XY/47,XYY mosaicism. It appears that ascertainment bias can explain the fact that all known patients with postnatal diagnosis are phenotypically abnormal, while over 90% of prenatally diagnosed cases are reported to have a normal male phenotype. Further elucidation of major Y genes and their clinical significance can be expected in the rapidly expanding gene mapping projects. More, consequently better, phenotype/karyotype correlations can be anticipated at both the cytogenetic and the molecular level.

Chromosomal localisation of a gene(s) for Turner stigmata on Yp

Although recent cytogenetic and molecular studies in patients with Turner stigmata are consistent with a gene(s) for Turner stigmata being present on both Xp and Yp, the precise location has not been determined. In this report, we describe a phenotypically female infant with Turner stigmata and a partial Yp deletion and review genotype-phenotype correlations of the putative Turner gene(s) in non-mosaic patients with Y chromosome rearrangements resulting from chromosomal breakage at Yp or Yc (pericentromeric region). The results indicate that the putative Turner gene(s) on Yp is located in the Y specific region from interval 1A1A to interval 2B. In addition, assessment of ZFX/ZFY and RPS4X/RPS4Y in the context of the Turner gene(s) suggests that ZFX/ZFY rather than RPS4X/RPS4Y could be a candidate gene for the Turner stigmata.

Deletion mapping of H-Y antigen to the long arm of the human Y chromosome

A gene encoding or controlling the expression of the H-Y transplantation antigen was previously mapped to the human Y chromosome. We now report the sublocalization of this gene on the long arm of the human Y chromosome. Eight patients with Y-chromosomal abnormalities were examined with a series of existing and new DNA markers for the Y chromosome. The resulting deletion map was correlated with H-Y antigen expression. We conclude that the H-Y antigen gene maps to a portion of deletion interval 6 that is identified by specific DNA markers.

DNA analysis of two patients with a non-fluorescent Y chromosome

Results of DNA study on two patients of gonadal dysgenesis with a 45,X/46,X,Ynf (non-fluorescent Y chromosome) karyotype are described. In one patient who developed gonadoblastoma, all 12 loci on the non-fluorescent part of Yq were detected. Another patient did not have gonadoblastoma at 20 years, and only the proximal 6 loci out of 12 were detected.

Partial gonadal dysgenesis in a patient with a marker Y chromosome

We evaluated a patient with partial gonadal dysgenesis including a right dysgenetic testis and a left streak gonad with rudimentary fallopian tube and uterus. She had ambiguous external genitalia and was raised female. Although her height is normal (25th centile at age 12 years), she has some findings of Ullrich-Turner syndrome. Her karyotype was reported to be 46,X,+marker; subsequent molecular investigations showed the marker to be the short arm of the Y chromosome. Genomic DNA, isolated from leukocytes of the patient and her father, was digested with a variety of restriction endonucleases and subjected to Southern blot analysis. A positive hybridization signal was obtained with probes for the short arm of the Y chromosome (pRsY0.55, SRY, ZFY, 47Z, pY-190, and YC-2) in DNA from the patient, indicating the presence of most if not all of the short arm, while long arm probes (HinfA and pY3.4) indicated that at least 75% of the long arm of the Y chromosome was missing. The gene responsible for testicular determination (TDF) is on the distal portion of the short arm of the Y chromosome; Yq has no known influence on sex determination. Hence, the deletion of the long arm of the Y chromosome cannot explain the gonadal dysgenesis in this patient. One explanation for the gonadal dysgenesis and Ullrich-Turner phenotype in the patient could be undetected 45,X/46,X,+marY mosaicism but no such mosaicism was observed in peripheral lymphocytes. Several investigators have suggested the presence of an "anti-Turner" gene near TDF. Hence it is possible that the clinical phenotype in our patient results from a Y chromosomal defect in sequences flanking TDF, which reduces the function of both TDF and the "anti-Turner" genes.

Deletion mapping of interval 6 of the human Y chromosome

DNAs of four individuals demonstrating abnormalities in sexual development and mosaic 45,XO/46,XY karyotypes with terminal deletions of Yq were studied using a number of Y-specific probes. The results of these analyses allowed us to map several known DNA fragments within deletion interval 6 in the following order: Ycen-pDP105B/52dA, 50f2E, Fr25-II/Fr15-II, 50f2C, 49f-Yqter (groups of fragments in undetermined order separated by diagonal lines).

Homologous ribosomal protein genes on the human X and Y chromosomes: escape from X inactivation and possible implications for Turner syndrome

We have isolated two genes on the human sex chromosomes, one on the Y and one on the X, that appear to encode isoforms of ribosomal protein S4. These predicted RPS4Y and RPS4X proteins differ at 19 of 263 amino acids. Both genes are widely transcribed in human tissues, suggesting that the ribosomes of human males and females are structurally distinct. Transcription analysis revealed that, unlike most genes on the X chromosome, RPS4X is not dosage compensated. RPS4X maps to the long arm of the X chromosome (Xq), where no other genes are known to escape X inactivation. Curiously, RPS4X maps near the site from which the X-inactivating signal is thought to emanate. On the Y chromosome, RPS4Y maps to a 90 kb segment that has been implicated in Turner syndrome. We consider the possible role of RPS4 haploinsufficiency in the etiology of the Turner phenotype.

Correlation of the testicular determinant factor sequence zinc finger Y with varying gonadal phenotypes in a series of 13 subjects with gonadal dysgenesis due to Y aneuploidy

Deoxyribonucleic acid samples from a series of 13 subjects with 45,X/46,X,altered Y, and varying gonadal phenotypes (streak-streak, n = 9; streak-testis, n = 2; testis-testis, n = 2) were analyzed for the presence of the candidate testicular determinant factor sequence zinc finger Y. The Y-specific probes Y97 mapped to Y centromere, pDP105 A,B mapped to Yp and distal Yq11, respectively, hybridized with the deoxyribonucleic acid from all the 13 study subjects. The same deoxyribonucleic acid samples were analyzed for the presence of the zinc finger Y sequence. Eleven of the 13 subjects were positive for the zinc finger Y sequence. Four zinc finger Y-positive subjects had unilateral (n = 2) or bilateral (n = 2) testicular differentiation. Among the nine subjects with bilateral streak gonads, seven showed the presence of this sequence. The lack of testicular differentiation in the presence of quantitatively normal or almost normal zinc finger Y bands could not be explained by mosaicism alone. Mutations not detectable by analysis with the method of Southern with pDP1007, may occur in the testicular determinant factor gene vitiating testicular development.