A (Y;17) translocation in a fibroblast culture from a female with 46 chromosomes. Repository identification No. GM-2598

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.

Dicentric Y chromosome and mixed dysgenesis

We report 4 cases of mixed gonadal dysgenesis with a karyotype containing a dicentric Y chromosome. All cases were mosaic with 45X and 46X, dic(Y) cell lines. Of the patients 1 had ambiguous genitalia and some features of Turner's syndrome, 2 had classical features of Turner's syndrome with normal female external genitalia and 1 had no features of Turner's syndrome but he presented with penoscrotal hypospadias, inguinal hernia and cryptorchidism. Female gender assignment and early total gonadectomy should be considered when a dicentric Y chromosome is present in cases of mixed gonadal dysgenesis.

Y-derived sequences detected in a 45,X male by in situ hybridization

A two-month-old boy with normal genitalia and descended testes was referred for a suspected hematological disorder. Cytogenetic analysis showed a 45,X chromosome constitution. In situ hybridization with the Y-derived probe 50f (provided by Professor Marc Fellous) was performed utilizing metaphase chromosomes to determine whether Y material could be detected. A significant amount of label (17 of 150 cells) was found on chromosome 5p suggesting a 5;Y translocation. This translocation was verified by high-resolution G-banded and G-11-stained chromosomes.

Localisation of male determining factors in man: a thorough review of structural anomalies of the Y chromosome

It is widely accepted that male determination in man depends on the presence of a factor or factors on the Y chromosome. These factors may be localised within the Y chromosome through the study of structural anomalies of the Y. A thorough review of seven different structural anomalies of the Y is presented: dicentric Y chromosomes, Y isochromosomes, ring Y chromosomes, Y; autosome, Y;X, and Y;Y translocations, and Y deletions. The evidence from these studies indicates that a gene or genes on the short arm or the Y near the centromere play a crucial role in the development of the testes. A few studies indicate that one or more factors on the long arm of the Y may also influence testicular development. If such a factor is present on the long arm, then it too must be very near the centromere. The theory that separate genes independently control the initial development and maturation of the tests (on the long and short arms of the Y, respectively) may be premature. Recently proposed arguments in its favour are examined. Some evidence also indicates the presence of a fertility factor on the non-fluorescent segment of the long arm. Relevant information on the H-Y antigen is discussed.