The sry gene and sex determination in mammals
With the isolation and characterization of Sry, a gene with a critical role in development has been defined. Sry can be described as a master regulatory gene in that it has a pivotal role in the sex determination pathway. However, much work must be done to discover how the gene fits into such a pathway, both at the level of molecular cascades and their integration with morphogenic events during organogenesis. First, the precise pattern of expression of Sry suggests that it must be regulated by tissue-specific transcription factors, or a unique combination of factors present within the supporting cell precursor lineage. These factors are clearly not sex-specific. Second, there are likely to be gene products that interact with the Sry protein and contribute to the specificity of its interaction with target genes. Third, the downstream target genes need to be defined. Sry must initiate (or repress) the expression of some critical genes. Sry appears to act only for a very brief period just before testis cord formation; therefore, it is not required for any long-term maintenance of gene activity. How does the expression of Sry lead to the changes in cellular properties which result in organization into testis cords? Determining the nature of the interaction of Sry with DNA, and the definition of target genes will clearly be required before the role of Sry in sex determination can be understood at the cellular and molecular levels.