Models of Segmentation

The formation of segmented structures is a very important step during development of higher organisms. With the formation of somites in vertebrates or the segments in insects the primary anteroposterior pattern of the organisms is laid down. Segmentation is the result of the superposition of two pattern formation processes. One generates a periodic pattern, i.e. a repetition of homologous structures. It consists in vertebrates of somites and somitic clefts and in insects of segments and segment borders. Superimposed on this periodic pattern is a sequential pattern which makes the repetitive subunits different from each other. In recent years, we have proposed molecularly feasible models which are able to generate periodic and sequential structures precisely superimposed on each other (Meinhardt, 1982a,b). For insect development more detailed experimental and genetic data are available. For that reason the model of insect segmentation is more advanced. At the beginning of this paper a short overview of the model proposed for insect segmentation will be provided. I will show that, with some adaptations, the basic mechanism is also able to account for somite formation.