The function of Notch signalling in segment formation in the crustacean Daphnia magna (Branchiopoda).
Ten years ago we showed for the first time that Notch signalling is required in segmentation in spiders, indicating the existence of similar mechanisms in arthropod and vertebrate segmentation. However, conflicting results in various arthropod groups hampered our understanding of the ancestral function of Notch in arthropod segmentation. Here we fill a crucial data gap in arthropods and analyse segmentation in a crustacean embryo. We analyse the expression of homologues of the Drosophila and vertebrate segmentation genes and show that members of the Notch signalling pathway are expressed at the same time as the pair-rule genes. Furthermore, inactivation of Notch signalling results in irregular boundaries of the odd-skipped-like expression domains and affects the formation of segments. In severe cases embryos appear unsegmented. We suggest two scenarios for the function of Notch signalling in segmentation. The first scenario agrees with a segmentation clock involving Notch signalling, while the second scenario discusses an alternative mechanism of Notch function which is integrated into a hierarchical segmentation cascade.
School of Biological and Chemical Sciences, Queen Mary University of London, Mile End Road, London E1 4NS, UK; Department of Neurobiology, University of Vienna, Althanstrasse 14, 1090 Vienna, Austria.
Bo Joakim
BJ
Eriksson
Petra
P
Ungerer
Angelika
A
Stollewerk
D000818:Animals; D019521:Body Patterning / Q000235:genetics; D003621:Daphnia / Q000196:embryology* / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000196:embryology; D004625:Embryo, Nonmammalian / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D008954:Models, Biological; D051880:Receptors, Notch / Q000235:genetics / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction / Q000235:genetics; D062211:Spatio-Temporal Analysis
D051880:Receptors, Notch
Delta-Notch signalling; Hes; Pair-rule genes; Segmentation cascade; odd-skipped; snail