The presence of SRY gene during embryogenesis determines the initial events in the fetal gonad to differentiate into testis. This single exon gene belongs to the family of HMG proteins (high mobility group) which are transcription factors that bind to DNA and bend it. We studied SRY gene in 26 patients with gonadal differentiation disorders through PCR using the primers XES10 f and XES11r which cover the whole gene. In SRY positive patients with gonadal dysgenesis, mutations on SRY gene were screened through DGGE (denaturing gradient gel electrophoresis). Table

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XXM-male XX; TH-true hemaphrodite; CGD-complete gonadal dysgenesis: PGD-partial gonadal dysgenesis; A-agonadism) Results: 1) Out of 10 patients with 46,XX karyotype and testicular tissue only one was positive for SRY gene. 2) All 46,XY patients without testicular tissue were SRY positive. 3) DGGE disclosed a mutation in SRY gene, also present in the paternal DNA, in a PGD patient. The sequencing of these samples revealed a mutation out of the HMG box. Conclusions: Most cases of gonadal differentiation disorders cannot be explained only through the SRY gene. Data about the control mechanisms of this gene (enhancing and suppressing elements) as well as the identification of other genes that interact with SRY gene will certainly elucidate many of these cases. Conversely, the finding of mutant SRY proteins in affected patients' relatives with normal phenotypes, allows the analysis of the functional consequences of these mutations and their real outcomes in gonadal differentiation.