Drosophila segmentation is a well-established paradigm for developmental pattern formation. However, the later stages of segment patterning, regulated by the “pair-rule” genes, are still not well understood at the system level. Building on established genetic interactions, I construct a logical model of the Drosophila pair-rule system that takes into account the demonstrated stage-specific architecture of the pair-rule gene network. Simulation of this model can accurately recapitulate the observed spatiotemporal expression of the pair-rule genes, but only when the system is provided with dynamic “gap” inputs. This result suggests that dynamic shifts of pair-rule stripes are essential for segment patterning in the trunk and provides a functional role for observed posterior-to-anterior gap domain shifts that occur during cellularisation. The model also suggests revised patterning mechanisms for the parasegment boundaries and explains the aetiology of the even-skipped null mutant phenotype. Strikingly, a slightly modified version of the model is able to pattern segments in either simultaneous or sequential modes, depending only on initial conditions. This suggests that fundamentally similar mechanisms may underlie segmentation in short-germ and long-germ arthropods.

果蝇分割是发育模式形成的成熟范例。然而，由“配对规则”基因调控的片段模式的后期阶段在系统水平上仍然没有得到很好的理解。在已建立的遗传相互作用的基础上，我构建了果蝇配对规则系统的逻辑模型，该模型考虑了已证明的配对规则基因网络的阶段特定架构。该模型的模拟可以准确地概括观察到的成对规则基因的时空表达，但前提是系统提供动态“间隙”输入。这一结果表明，成对规则条纹的动态变化对于躯干的节段图案化至关重要，并且为观察到的细胞化过程中发生的从后到前的间隙域变化提供了功能性作用。该模型还建议修改副节段边界的模式机制，并解释偶数跳跃无效突变体表型的病因学。引人注目的是，该模型的稍微修改版本能够以同时或顺序模式对片段进行模式化，仅取决于初始条件。这表明根本上相似的机制可能是短胚节肢动物和长胚节肢动物的分割的基础。