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We previously reported a subject with 46,XX true hermaphroditism who had a 46,X,del(X) karyotype and Y-chromosomal sequences in genomic DNA. We hypothesized that the Y-chromosomal sequences were translocated to the deleted X chromosome and that the incomplete testis determination of this individual was the result of inactivation of the translocated X chromosome. In situ hybridization studies demonstrated that the Y-chromosomal sequences were located on the distal portion of the short arm of the deleted X chromosome. Investigation of the replication of the X chromosome, using a modified R-banding technique and localization of Y-chromosomal sequences by in situ hybridization, showed that the translocated X chromosome was late replicating in all 100 EBV-transformed lymphoblasts that were examined. By contrast, when cells from a subject with 46,XX maleness were studied, the translocated X chromosome was late replicating in only 21 of 47 cells. As the late-replicating X chromosome is presumed to be the inactive X chromosome, selection of cells in which the Y-bearing X chromosome has been inactivated may play a role in the incomplete testis determination in subjects with "Y-positive" 46,XX true hermaphroditism.

The condition termed 46,XY complete gonadal dysgenesis is characterized by the lack of testicular determination with resulting streak gonads, normal Mullerian structures, and female external genitalia. In the partial form, there is incomplete testicular determination with a wide range in the degree of ambiguous genitalia and sexual duct development. We evaluated a kindred in which a partial form of 46,XY gonadal dysgenesis occurred in four subjects from two generations. Pedigree analysis indicated an X-linked or possibly an autosomal sex-limited mode of inheritance. All affected subjects were ascertained because of ambiguous genitalia with minimal virilization. At 10 days of age, the proband had a subnormal plasma level of testosterone, and at 4 months, there was no rise in plasma T after stimulation with hCG. At laparotomy, a dysgenetic gonad was found on the right side, but no gonad was found on the left side. A vas deferens was present on the right, indicating the presence of functional Leydig cells early in fetal life. In the other affected subjects, gonadal tissue was also limited to one side of the abdomen and showed poorly developed seminiferous tubules. The sex-determining region Y gene, which encodes the testis-determining factor, was present and unaltered in the genomic DNA of all affected subjects. Duplication of the distal short arm of the X-chromosome has been associated with 46,XY complete gonadal dysgenesis in some patients. In our studies, Southern blot analysis revealed that sequences of the distal short arm of the X-chromosome (DXS9 to DXS84) were present in single copy, excluding a large duplication in this area of the X. Several kindreds with familial 46,XY complete gonadal dysgenesis have been reported; five of them had evidence of an X-linked mode of inheritance. Our study of a kindred with 46,XY partial gonadal dysgenesis further supports the role of an X chromosome gene in testicular determination. Evidence of some fetal Leydig cell function in the affected subjects of our report suggests that mutations of the putative X-chromosome gene can result in a partial as well as complete defect in testicular determination.

The condition of 46,XX maleness is characterized by testicular development in subjects who have two X chromosomes but who lack a normal Y chromosome. Several etiologies have been proposed to explain 46,XX maleness: 1) translocation of the testis-determining factor from the Y to the X chromosome, 2) mutation in an autosomal or X chromosome gene which permits testicular determination in the absence of TDF, and 3) undetected mosaicism with a Y-bearing cell line. We evaluated 10 affected subjects who were ascertained for different reasons and who had several distinct phenotypes. Six subjects had inherited sequences from the short arm of the Y chromosome including the sex-determining region Y gene (SRY). Five of the subjects were pubertal at the time of evaluation and had a phenotype similar to that of Klinefelter syndrome with evidence of Sertoli cell and Leydig cell dysfunction. One subject had evidence from Southern blot analysis and in situ hybridization for the presence of an intact Y chromosome in approximately 1% of cells. Three subjects lacked Y sequences by Southern blot analysis and by polymerase chain reaction amplification of SRY. These subjects were ascertained in the newborn period because of congenital anomalies. One had multiple anomalies including cardiac abnormalities; one had cardiac anomalies alone; and one had ambiguous genitalia. Our data confirm the genetic heterogeneity of 46,XX maleness, in which some subjects have SRY while other subjects lack it. In addition, there is phenotypic heterogeneity among subjects who lack SRY suggesting that there is also genetic heterogeneity within this subgroup.

The syndrome of 46,XX true hermaphroditism is a clinical condition in which both ovarian and testicular tissue are found in one individual. Both Mullerian and Wolffian structures are usually present, and external genitalia are often ambiguous. Two alternative mechanisms have been proposed to explain the development of testicular tissue in these subjects: (1) translocation of chromosomal material encoding the testicular determination factor (TDF) from the Y to the X chromosome or to an autosome, or (2) an autosomal dominant mutation that permits testicular determination in the absence of TDF. We have investigated five subjects with 46,XX true hermaphroditism. Four individuals had a normal 46,XX karyotype; one subject (307) had an apparent terminal deletion of the short arm of one X chromosome. Genomic DNA was isolated from these individuals and subjected to Southern blot analysis. Only subject 307 had Y chromosomal sequences that included the pseudoautosomal boundary, SRY (sex-determining region of Y), ZFY (Y gene encoding a zinc finger protein), and DXYS5 (an anonymous locus on the distal short arm of Y) but lacked sequences for DYZ5 (proximal short arm of Y) and for the long arm probes DYZ1 and DYZ2. The genomic DNA of the other four subjects lacked detectable Y chromosomal sequences when assayed either by Southern blotting or after polymerase chain reaction amplification. Our data demonstrate that 46,XX true hermaphroditism is a genetically heterogeneous condition, some subjects having TDF sequences but most not. The 46,XX subjects without SRY may have a mutation of an autosomal gene that permits testicular determination in the absence of TDF.