Expression profiles of Dax1, Dmrt1, and Sox9 during temperature sex determination in gonads of the sea turtle Lepidochelys olivacea.

Sex determination is controlled either by genetic or environmental factors. In mammals Sry initiates determination but no homologue of this gene exists in non-mammalian species. Other genes of the mammalian sex-determining pathway have been identified in gonads of different vertebrates. Sox9, Dax1, and Dmrt1 are expressed at the onset of gonadal development in birds and reptiles. In the sea turtle Lepidochelys olivacea, a species with temperature sex determination (TSD), Sox9 is expressed in undifferentiated gonads at male- (MPT) or female-promoting temperatures (FPT). At MPT, Sox9 remains expressed in male gonads, but at FPT it is downregulated coinciding with the onset of the ovarian morphologic differentiation and female sex determination. At MPT however, male sex is determined early than at FPT in still undifferentiated gonads suggesting that other genes maintain Sox9 expression in testis. Here we used RT-PCR to study the expression profiles of Dax1, Dmrt1, and Sox9 in gonads of embryos of L. olivacea incubated at MPT or at FPT. The profiles were correlated with sex determination during and after the temperature-sensitive period (TSP). Dax1 maintained similar levels at both temperatures during the TSP. The Dax1 expression level increased significantly in ovaries compared to testes at stage 27, once they were morphologically distinct. The expression levels of Dmrt1 were higher at MPT than at FPT at all stages, in contrast with Sox9 levels which were similar at both temperatures at stages 23-25. Together, current results suggest that, whereas Dax1 is not involved in TSD in L. olivacea, upregulation of Dmrt1 and downregulation of Sox9 may play a role in male and female sex determination, respectively.

[Molecular detection of chromosome Y DNA sequences in patients with Turner's syndrome]. / Detección molecular de secuencias de ADN derivadas del cromosoma Y en pacientes con síndrome de Turner.

The presence of Y-chromosome material in the genome of phenotypic females has been associated with an increased risk of developing gonadal tumors. To assess whether DNA sequences of the Y-chromosome are present in the genome of individuals with gonadal dysgenesis and clinical features of Turner's syndrome, we have studied three patients with 45, X/46, X, + mar chromosome complement, and two Turner patients with 45, X/46, XY and 45, X karyotypes who served as positive and negative controls, respectively. Molecular detection of Y-DNA sequences was done by DNA-DNA hybridization using the specific probes pY97 and pDP1007 as well as by polimerase chain reaction. The results revealed that the marker chromosome of one of the patients contained DNA sequences from the centromeric region of the Y-chromosome in a manner similar to that found in the 45, X/46, XY patient and in the male control; the gene ZFY was negative in this patient, and was probably lost when the ring chromosome was formed. In contrast, the ring chromosomes of the other two patients did not exhibit the presence of Y-chromosome material. The results were interpreted as demonstrating the Y-chromosome origin of the ring marker in one patient with gonadal dysgenesis, and suggest an X-chromosome origin of the ring markers in the other two patients. These data further underline the relevance of practicing molecular studies in these disorders which may help to determine appropriate therapeutic strategies.