Modeling of the Drosophila gap-gene network with the variation of the Bcd morphogen

Abstract

Expression patterns of segmentation genes form under the influence of gradients of maternal transcription factors, which initiate spatially local expression in the segmentation gene cascade. Bcd acts as one of these activators. A model of the regulation in the gap-gene network was studied by varying the Bcd concentration. The topology that is known for the gap-gene network was found to be insufficient for explaining the experimental finding that the hb anterior expression domain shifts when the Bcd concentration changes in the embryo. Modeling that was performed to comply with this experimental finding yielded a new topology, which determined the proper shifts of the hb expression domain. The result indicates that interactions of hb, Kr, and gt act as key regulatory factors to ensure the correct behavior of the hb expression pattern upon changes in Bcd concentration. This study made it possible to specify the limits of the validity of phenomenological models of gene networks.