Sex determination in mammals: state of this art

Sex determination relies on the translation of chromosomal sex established at fertilisation into gonadal sex (testis or ovary), and later into somatic sex (male or female) under the control of gonadal hormone secretions. The aim of the current review will be to highlight our knowledge of the key eve nts which, in the presence of a Y chromosome, induce the organisation of th e developing epithelial cells located inside the genital ridges into testic ular cords. Many groups have tried to define the molecules relevant to this process, with a double goal: unravelling a molecular pathway which leads to cell fate decision (Sertoli cell in this particular case) during development; improving the establishment of a diagnosis and subsequent medical managemen t in cases where chromosomal, gonadal and then somatic sexes are discordant . Recent progress made in this area will be depicted with the introduction of several pieces to this developmental jigsaw puzzle.