CBCB Seminar. Friday 8th Nov. 2002, 12:00.

We are using gene circuits to construct a physiological theory of segment determination in the early embryo of the fruit fly Drosophila melanogaster. The gene circuit approach uses systems of coarse-grained kinetic equations which describe changes in concentration over time for the protein products of the Drosophila segmentation genes. A gene circuit is defined by its model parameters, which determine gene interactions, rates of protein synthesis and transport, and protein half-lives. Model parameters are not fixed a priori but rather obtained using numerical optimization by simulated annealing to find the gene circuit with a minimal least-square difference to gene expression data. Thus, the quality of the model produced is dependent on the accuracy of the data we use for fitting. Previous work with relatively crude data yielded a number of interesting biological results. We are currently fitting the model to data from a new high-resolution database of gene expression (http://urchin.spbcas.ru/flyex). Since this data is of much higher precision and temporal resolution than the previously used data, we expect this work to yield important novel insights into the dynamics and biological functions of the Drosophila segmentation gene network. In this talk, gene circuits of the gap gene system obtained using the new dataset and preliminary analysis of these circuits will be presented.