NOTCH1 IS REQUIRED FOR THE COORDINATE SEGMENTATION OF SOMITES

Members of the Notch family of transmembrane receptors mediate a numbe r of developmental decisions in invertebrates. In order to study Notch function in a vertebrate organism, we have mutated the Notch1 gene of the mouse. Notch1 gene function is required for embryonic survival in the second half of gestation. In the first half of gestation, we have found no effect of the mutation on the normal programs of neurogenesi s, myogenesis or apoptosis. We conclude that Notch1 function is not es sential for these processes, at least in early postimplantation develo pment. However, we have found that somitogenesis is delayed and disorg anized in Notch1 mutant embryos. We propose that Notch1 normally coord inates the process of somitogenesis, and we provide a model of how thi s might occur.