The region on 9p associated with 46,XY sex reversal contains several transcripts expressed in the urogenital system and a novel doublesex-related domain.

Deletions of 9p have been associated with 46,XY gonadal dysgenesis, and the smallest region of overlap has been mapped to the tip of chromosome 9. Two candidate genes (DMRT1 and 2) have been found in the region. Despite intensive mutation searches, no mutations have been detected in these genes. To gain insights into the genomics of the region and to isolate other candidate genes for the phenotype, we have constructed a P1 artificial chromosome (PAC)/bacterial artificial chromosome (BAC) contig spanning over 500 kb and covering the consensus critical region. We have analyzed the expression pattern of several ESTs mapped or sublocalized within the framework of the contig. In addition, a sample shotgun sequencing of a PAC containing the mentioned DM genes led to the detection of novel transcripts displaying an expression pattern specific to testis and kidney, consistent with a role in the development of the urogenital system. One of them, expressed in adult testis and human embryos aged 4-5 weeks, encodes a potential polypeptide and is located immediately downstream of a sequence capable of encoding a novel DM domain. The region was partially screened for mutations in sex-reversed patients by Southern blot, sequencing, and FISH. No mutations were found. Our results suggest that the critical region on 9p involved in male-to-female sex reversal displays greater gene density and genomic complexity than previously anticipated. Future investigations will include functional and mutational studies of the novel transcripts mapped or sublocalized within the critical region by this study as well as cloning efforts to isolate additional candidate genes.

A high frequency of Y chromosome deletions in males with nonidiopathic infertility.

Microdeletions of the long arm of the human Y chromosome are associated with spermatogenic failure and have been used to define three regions of Yq (AZFa, AZFb, and AZFc) that are recurrently deleted in infertile males. In a blind study we screened 131 infertile males (46 idiopathic and 85 nonidiopathic) for Y chromosome microdeletions. Nineteen percent of idiopathic males, with an apparently normal 46,XY chromosome complement had microdeletions of either the AZFa, AZFb, or AZFc region. There was no strict correlation between the extent or location of the deletion and the phenotype. The AZFb deletions did not include the active RBM gene. Significantly, a high frequency of microdeletions (7%) was found in patients with known causes of infertility and a 46,XY chromosome complement. These included deletions of the AZFb and AZFc regions, with no significant difference in the location or extent of the deletion compared with the former group. It is recommended that all males with reduced or absence sperm counts seeking assisted reproductive technologies be screened for deletions of the Y chromosome.

Donor splice-site mutations in WT1 are responsible for Frasier syndrome.

Frasier syndrome (FS) is a rare disease defined by male pseudo-hermaphroditism and progressive glomerulopathy. Patients present with normal female external genitalia, streak gonads and XY karyotype and frequently develop gonadoblastoma. Glomerular symptoms consist of childhood proteinuria and nephrotic syndrome, characterized by unspecific focal and segmental glomerular sclerosis, progressing to end-stage renal failure in adolescence or early adulthood. No case of Wilms' tumour has been reported, even in patients with extended follow-up. In contrast with FS patients, most individuals with Denys-Drash syndrome (DDS; refs 6,7) have ambiguous genitalia or a female phenotype, an XY karyotype and dysgenetic gonads. Renal symptoms are characterized by diffuse mesangial sclerosis, usually before the age of one year, and patients frequently develop Wilms' tumour. Mutations of the Wilms'-tumour gene, WT1, cause different pathologies of the urogenital system, including DDS. WT1 is composed of ten exons and encodes a protein with four zinc-finger motifs and transcriptional and tumour-suppressor activities. Alternative splicing generates four isoforms: the fifth exon may or may not be present, and an alternative splice site in intron 9 allows the addition of three amino acids (KTS) between the third and fourth zinc fingers of WT1 (ref. 17). Here we demonstrate that FS is caused by mutations in the donor splice site in intron 9 of WT1, with the predicted loss of the +KTS isoform. Examination of WT1 transcripts indeed showed a diminution of the +KTS/-KTS isoform ratio in patients with FS.