21-P014 Sequential roles for Wnt signalling in the skull

main transcription factors, Sox10 and Mifta (microphthalmiaassociated transcription factor), are already known to be involved in this process [Dutton et al., 2001; Elworthy et al., 2003]. Fate specification of melanocytes depends upon Sox10, and on Wnt signalling, to mediate regulation of Mitfa transcription. In contrast, the precise mechanism resulting in stable melanocyte differentiation remains unclear. In order to better define the genetic regulatory network (GRN) underlying melanocyte differentiation, I am testing different aspects of an initial GRN derived from a combination of our recent experimental data and mathematical modelling. Our invivo data suggests that Sox10 forms part of a Feed-Forward Loop repressing melanocyte differentiation that is relieved by Mitfa-dependent repression of Sox10. Our modelling predicts that a Factor Y is then required for maintenance of Mitfa expression. First, in order to establish the timecourse of expression of Sox10 and Mitfa during melanocytes differentiation, we are developing quantitative RT-PCR for single melanocytes. Second, we are testing two candidates for Factor Y. (A) Wnt signalling has been proven to be regulating Mitfa expression during fate specification in both mouse and zebrafish [e.g. Dorsky et al., 2000]. (B) Mc1R signalling. We are using morpholinos to explore the precise roles of this pathway in melanocyte differentiation. Together, our data will provide experimental constraints on the mathematical model of the GRN.