OCT4 immunohistochemistry may be necessary to identify the real risk of gonadal tumors in patients with Turner syndrome and Y chromosome sequences

BACKGROUND

The aim of this study was to investigate the frequency of gonadal tumors among patients with Turner syndrome (TS) carrying Y-derivative sequences in their chromosomal constitution.

METHODS

Six out of 260 patients with TS were selected based on mosaicism of the entire Y chromosome; 10 were included because Y-derivative sequences have been detected by PCR with specific oligonucleotides (sex-determining region on the Y, testis specific-protein, Y and DYZ3) and further confirmed by FISH. The 16 patients were subjected to bilateral gonadectomy at ages varying from 8.7 to 18.2 years. Both histopathological investigation with hematoxylin and eosin (H&E) and immunohistochemical analysis with anti-octamer-binding transcription factor 4 (OCT4) antibody were performed.

RESULTS

Gonadal neoplasia was not detected in any of the 32 gonads evaluated by H&E; however, four gonads (12%) from three patients (19%) had positive OCT4 staining in 50-80% of nuclei, suggesting the existence of germ cell tumors (gonadoblastoma or in situ carcinoma).

CONCLUSIONS

Evaluation of the real risk of development of gonadal tumors in TS patients with Y-derivative sequences in their chromosomal constitution may require a specific histopathological study, such as immunohistochemistry with OCT4.

A naturally occurring deletion in the SRY promoter region affecting the Sp1 binding site is associated with sex reversal

Male to female sex reversal results from failure of testis development. Mutations in the SRY gene or in other genes involved in the sexual differentiation pathway are considered to cause XY gonadal dysgenesis. The majority of the mutations in the SRY described so far are located within the SRY coding region, mainly in the HMG-box conserved domain. Comparison of 5' flanking SRY gene sequences among different species indicated the presence of several putative conserved consensus sequences for different transcription regulators. In this study, we investigated a 360 bp sequence encompassing the SRY putative core promoter, in 17 patients with variable degrees of 46,XY sex reversal, which have been previously shown not to bear mutations in the SRYcoding region. Sequencing analysis of the SRYpromoter in one patient with complete XY gonadal dysgenesis revealed a three base pair deletion in one of the Sp1 binding sites. The deletion abolished Sp1 binding in vitro. This is the first report on a naturally occurring mutation affecting the Sp1 regulatory element in the SRY promoter region, which is associated with sex reversal. Additionally, upon familial investigation the father, who had 18 genital surgeries due to severe hypospadia without cryptorchidism, was found to bear the same deletion and several relatives were referred to have sexual ambiguity.

Mutations in SRY and WT1 genes required for gonadal development are not responsible for XY partial gonadal dysgenesis

The WT1 transcription factor regulates SRY expression during the initial steps of the sex determination process in humans, activating a gene cascade leading to testis differentiation. In addition to causing Wilms' tumor, mutations in WT1 are often responsible for urogenital defects in men, while SRY mutations are mainly related to 46,XY pure gonadal dysgenesis. In order to evaluate their role in abnormal testicular organogenesis, we screened for SRY and WT1 gene mutations in 10 children with XY partial gonadal dysgenesis, 2 of whom with a history of Wilms' tumor. The open reading frame and 360 bp of the 5' flanking sequence of the SRY gene, and the ten exons and intron boundaries of the WT1 gene were amplified by PCR of genomic DNA. Single-strand conformation polymorphism was initially used for WT1 mutation screening. Since shifts in fragment migration were only observed for intron/exon 4, the ten WT1 exons from all patients were sequenced manually. No mutations were detected in the SRY 5' untranslated region or within SRY open-reading frame sequences. WT1 sequencing revealed one missense mutation (D396N) in the ninth exon of a patient who also had Wilms' tumor. In addition, two silent point mutations were found in the first exon including one described here for the first time. Some non-coding sequence variations were detected, representing one new (IVS4+85A>G) and two already described (-7ATG T>G, IVS9-49 T>C) single nucleotide polymorphisms. Therefore, mutations in two major genes required for gonadal development, SRY and WT1, are not responsible for XY partial gonadal dysgenesis.

Novel mutations affecting SRY DNA-binding activity: the HMG box N65H associated with 46,XY pure gonadal dysgenesis and the familial non-HMG box R30I associated with variable phenotypes

The SRY gene (sex-determining region of the Y chromosome) initiates the process of male sex differentiation in mammalians. In humans mutations in the SRY gene have been reported to account for 10-15% of the XY sex reversal cases. We describe here two novel missense mutations in the SRY gene after the screening of 17 patients, including 3 siblings, with 46,XY gonadal dysgenesis and 4 true hermaphrodites. One of the mutations, an A to C transversion within the HMG box, causes the N65H substitution and it was found in a patient presenting 46,XY pure gonadal dysgenesis. The Escherichia coli expressed SRY(N65H) protein did not present DNA-binding activity in vitro. The other mutation, a G to T transversion, causes the R30I substitution. This mutation was found in affected and nonaffected members of a family, including the father, two siblings with partial gonadal dysgenesis, a phenotypic female with pure gonadal dysgenesis, and three nonaffected male siblings. The G to T base change was not found in the SRY sequence of 100 normal males screened by ASO-PCR. The R30I mutation is located upstream to the HMG box, within the (29)RRSSS(33) phosphorylation site. The E. coli expressed SRY(R30I) protein was poorly phosphorylated and consequently showed reduced DNA-binding capacity in vitro.

Recurrence of a nonsense mutation in the conserved domain of SRY in a Brazilian patient with 46,XY gonadal dysgenesis

We tested a female patient with 46,XY karyotype and pure gonadal dysgenesis for the presence of the SRY gene and for mutations within the SRY conserved domain. A point mutation was identified at nucleotide position 209 with respect to the first ATG. The base substitution is a G-->A transition in the first nucleotide of codon 70 which changes a tryptophan (TGG) to a stop codon (TAG). Even though the father was not available for investigation we assumed that it is a de novo mutation, since it probably generates a nonfunctional truncated protein.

True hermaphrodites in the southeastern region of Brazil: a different cytogenetic and gonadal profile

Sex ambiguity may be due to several disorders of gonadal differentiation, including true hermaphroditism (TH), as well as male and female pseudohermaphroditism. Although TH is a rare cause of intersex in Europe and North America, in Africa it presents one of the highest frequencies. The 46,XX karyotype has been found in the majority of the reported patients (70.6%), and aberrations in the sex chromosomes have been observed in about 22% of the cases. The 46,XY karyotype has been described as less frequent. Herein we describe ten cases of TH which have been diagnosed over the last 7 years, six lateral TH, two unilateral TH, and two cases of ovotestes with absent contralateral gonad. From a total of 18 gonads analyzed, there were 8 testes, 6 ovaries and 4 ovotestes. Nine subjects had originally a male sex assignment, and in three cases this was reverted to female. Four cases had a 46,XY karyotype. Additional sex chromosome aberrations had been found in four different cases [two 46,XX/46,XY, one 45,X/47,XYY, one 46,X,del(Yq)]. A 46,XX karyotype was found in only two individuals, and both were SRY negative. Our preliminary data, especially on the constitution of chromosomes and gonads, indicate marked differences from those in the literature.