RESUMO
Individuals affected with Swyer syndrome are phenotypic females with 46, XY karyotype, sexual infantilism, mullerina derivatives, and bilateral streak gonads that may undergo neoplastic transformation. The pathogenesis of this syndrome is uncertain, but may be related to a defect in the regulation or expression of the testicular determining factor which is believed to be located on the short arm of the Y chromosome. Recently, a region termed "SRY", a single copy gene of the Y chromosome was identified as belonging to a testis-determining gene. This gene is Y-specific, highly conserved among mammals, and transcribed only in testis. The predicted amino acid sequence of SRY shares homology with DNA-binding domains of transcription factors such as chromatinassociated, nonhistone proteins HMG 1 and HMG 2. Hence, it was thought that there may be some change in SRY gene of the patients with Swyer syndrome. And it was reported in some cases that there was deletion or mutation in the gene, but no abnormality of SRY gene was observed in other cases. So, it is a new approach to understand the mechanism of the human sexual differentiation to investigate this syndrome in terms of DNA sequence of SRY gene. To verify the presence or absence of SRY, or the change in SRY, we performed polymerase chain reaction and DNA sequencing of the conserved region of SRY gene from four patients with Swyer syndrome and their family members. The results are as follows. 1) Four patients with Swyer syndrome, their father, and two normal male control were positive whereas two female control were negative for the band that represents the coding sequence of SRY. 2) The DNA sequences of SRY gene from four patients with Swyer syndrome, their father, and two normal male control were the same, and there was no deletion or mutation in the gene. In conclusion, there may be complex sex determining cascade including other genes not only on the Y chromosome, but also on the X chromosome or even autosome in human sexual differentiation.