Deletion mapping of DNA segments from the Y chromosome long arm and their analysis in an XX male

Y Chromosome deletions and male infertility

Approximately one in ten couples experience infertility, and in about 40% of these infertile unions there are abnormalities in the fertility of the male partner. The clinical management of these infertile men is less than satisfactory because in 40% of such patients the cause of the abnormalities of sperm production and quality is unknown. The possibility that genetic disorders may account for a proportion of these disturbances of sperm production has been raised. It is well recognized that chromosomal abnormalities such as Klinefelter's syndrome cause azoospermia and that gene defects are the basis of testicular feminization, Kallman's syndrome and Reifenstein's syndrome. With the explosion in our knowledge of the human genome, the possibility exists that other genetic disorders may form the basis of other sperma-togenic abnormalities. The past decade has witnessed the accumulation of evidence linking abnormalities of the Y chromosome with disturbances in sperm production and these observations form the basis of this review.

Phenotypical expression in XX males correlates with testicular response to exogenous choriogonadotropin in early infancy: does a variable degree of testicular failure determine the degree of genital ambiguity?

The 46,XX male syndrome is characterized by the presence of testicular development in subjects who lack a Y chromosome. The majority of patients have male external genitalia without ambiguity; however, 10-15% show diverse degrees of hypospadias. Testicular function is normal at birth but deteriorates thereafter. However, it has not been clarified why some cases exhibit genital ambiguity. This study examined 10 affected patients, including 4 prepubertal (< 1 year old) with hypospadias (1 glandular, 1 penile, and 2 penoscrotal). In all subjects, testicular function was evaluated by performing a stimulation with choriogonadotropin. In the postpubertal individuals, basal and poststimuli testosterone were below the reference values. Prepubertal patients had age-appropriate basal test-osterone concentrations. All responded to the choriogonadotropin challenge; however, the most significant response was observed in the patient with the glandular hypospadias, the second highest response was presented by the patient with the penile hypospadias, while both patients with the penoscrotal hypospadias had the poorest responses. These results suggest that the degree of genital ambiguity is correlated with the impairment in testosterone response to choriogonadotropin in early infancy, indicating a defect in testosterone production in XX males with genital ambiguity.

Clinical traits and molecular findings in 46,XX males

46,XX maleness is characterized by the presence of testicular development in subjects who lack a Y chromosome. The majority of affected persons have normal external genitalia, but 10-15% show various degrees of hypospadias. Several hypotheses have been proposed to explain the etiology of this constitution: translocation of the testis-determining factor (TDF) from the Y to the X chromosome, mutation in an autosomal or X chromosomal gene which permits testicular determination in the absence of TDF, and undetected mosaicism with a Y-bearing cell line. We report the phenotypic data and results of molecular analyses performed in six sporadic Mexican males with 46,XX karyotype. Molecular studies revealed Yp sequences in two individuals (ZFY+ SRY+) with different phenotypes, a third one presented with a smaller segment of Yp (ZFY- SRY+) and complete virilization, while the remaining three were Y-negative and showed hypospadias. In all subjects a hidden mosaicism with a Y-bearing cell line was ruled out due to the absence of Y-centromeric sequences. Our data demonstrate that the phenotype does not always correlate with the presence or absence of Y-sequences in the genome, and confirm that 46,XX maleness is a genetically heterogeneous condition.

Molecular analysis of aberrations of Xp and Yq

Three cases of Y chromosomal aberrations were studied using a panel of Y-specific DNA sequences from both Yp and euchromatic Yq. One case was a phenotypic male fetus with a Y-derived marker chromosome. The short arm of this chromosome was intact, but most of its long arm was missing. The second case had a 46,XYq- karyotype with portions of euchromatic Yq, including the spermatogenesis region, missing. The third case was a phenotypic female with a 46,XXp+ karyotype. The extra material on the Xp+ chromosome was derived from the heterochromatic, and part of the euchromatic, portion of Yq. Application of X-specific DNA sequences demonstrated that the distal portion of the short arm of the translocation X chromosome was deleted (Xpter-p22.3). The three examples demonstrate the importance of diagnostic DNA analysis in cases of marker chromosomes, and X and Y chromosomal aberrations. In addition, the findings in the patients facilitate further deletion mapping of euchromatic Yq.