Fuente: Edinburgh Research Explorer RSS
Expuesto el: viernes, 03 de agosto de 2012 14:08
Autor: Edinburgh Research Explorer RSS
Asunto: Cell autonomous sexual development in birds: Mechanisms of Development
Our understanding of sexual development in mammals is largely based on the paradigm established by the pioneering work of Alfred Jost and others in the mid-20th century. This established that, at a specific point in development, the sexually dimorphic expression of a sex-chromosome gene induces the indifferent genital ridge to initiate gonadal development and that all other sexual development is a result of somatic cells responding to specific hormones. This principle is still widely accepted today and assumed to apply across vertebrates, although for many species the exact nature of the sex-determining mechanism and the identity of the sex-determining gene(s) have yet to be established. In birds, sex-determination is thought to be dependent on either a dominant ovary-determining gene on the W-chromosome or a dosage mechanism based on the Z-chromosome. To help resolve this issue, we analysed three gynandromorph chickens that display a bilateral male:female asymmetry. For the first time, we demonstrate that gynandromorph birds are genuine male:female chimaeras, with tissues comprised of normal male and female diploid cells. This finding demonstrated that the sexual phenotype in birds is not dependent on gonadal products, but is largely cell autonomous and suggests that the mechanism of sex determination in birds is different from that seen in mammals. To investigate this possibility, we carried out a series of transcriptomic screens and experiments in which we generated embryos containing male:female chimeric gonads. Our analyses provide conclusive evidence that sexual development in birds does not follow the Jost principle. 6/09/09 → 10/09/09 Event: Conference ID: 4183638
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