Abstract
The STS (steroid sulfatase) gene which has been assigned to the short arm of human X chromosome (band p22) is thought to have escaped from Lyon's inactivation. For that reason, the STS enzyme activities differ between male and female according to the number of X chromosomes in cells. In this report, the STS enzyme activities were studied in different human tissues such as placentas, lymphocytes, and cultured fibroblasts of normal individuals and sex anomaly patients. Tritium labelled dehydroepiandrosterone sulfate (DHA-S) was used as the reaction substrate.
The placental STS activities between normal male and female subjects showed a significant difference in spite of wide variences that were ascertained not to be the effects of methodological alterations involving enzyme purification, substrate concentration, and activity calculation (units per mg of protein or DNA). Further, in lymphocytes and fibroblasts which had low levels of enzyme concentration compared with placentas, the STS enzyme activities were also significantly different between both sexes. These results confirmed that the STS gene in cells of tissues tested here seemed to be inactive at the gene level and followed the gene dosage effect to some extent.
The enzyme activity was also studied in 17 patients with sex anomalies using lymphocytes and cultured fibroblasts. The cells of 45, X Turner syndrome and of Klinefelter syndrome with 47, XXY or other karyotypes, showed slightly lower levels of enzyme activity when compared with control values of normal males or females. The enzyme activity in intersexual disturbances, especially XX male and XX true hermaphrodites, showed intermediate levels between normal male and female values. This result may give support to the concept that at least one X chromosome in these diseases is genetically abnormal due to X-Y interchanges, something that has been partly proved recently by analysis of H-Y antigen and Y-specific DNA probes.
The present study on the STS enzyme activity revealed the presence of a gene dosage effect of STS gene between males and females not precise but rather rough in quantity, and it pointed out problems, some of which were related to genetic and environmental factors modifying the STS gene expression in normal individuals as well as sex anomaly patients.
