Searching for missing pieces of the sex determination puzzle

Little is known of the mechanisms whereby the mammalian indifferent gonad d evelops into a testis or ovary. In XY individuals, Sry, the mammalian testi s-determining gene, is expressed in the pre-Sertoli cells, which then diffe rentiate into Sertoli cells. Other cell types, which include the germ cells , the steroidogenic cells and the connective tissue cells, must then be ins tructed to develop in a male-specific manner. Although some genes involved in sex-determination and differentiation processes have been identified, we know little of how they interact and cooperate to orchestrate the developm ent of a testis or ovary. We have initiated an expression-screening program designed to identify additional genes, known or novel, which play a role i n these processes. This approach is based on our belief that many of the ge nes we seek will be expressed in a sex-specific manner during the period of sex-determination and differentiation. Most of the genes identified previo usly are transcription factors and so we aim, in particular, to find genes involved in cell-to-cell communication, signal transduction, and transcript ional regulation, downstream of the differentiation of Sertoli cells. We ha ve used a suppression subtractive-hybridization method to generate male- an d female-enriched probes and libraries. Clones are validated as being sex-s pecific in their expression patterns by array screening and in situ hybridi zation. Here we report on our progress to date and the general applicabilit y of the approach for studies in other systems. J. Exp. Zool. 290:517-522, 2001. (C) 2001 Wiley-Liss, Inc.