My PhD project focused on the identification of components and the architecture of the gene regulatory network that controls the formation of the segment addition zone (SAZ) and posterior segments in the spider Parasteatoda tepidariorum. Analysis of the formation and function of the SAZ among arthropods suggests that Wnt and Delta-Notch signaling regulated this process ancestrally in an analogous mechanism to that regulating somitogenesis in vertebrates. However, it remained unknown how the two major signaling pathways interact during the formation of the SAZ and regulate other putatively downstream segmentation genes, such as evenskipped (Pt-eve) and runt (Pt-run-1). Therefore, I studied the interactions between Delta (Pt-Dl) and its receptor Notch (Pt-N) and the Wnt ligand gene Wnt8 (Pt-Wnt8). I showed that Pt-Dl initially activates Pt-Wnt8 in the posterior SAZ, but conversely inhibits Pt-Wnt8 expression in the anterior SAZ. Furthermore, I observed the dynamic expression of Pt-eve and Pt-run-1 in the SAZ and the forming segments, suggesting an important role in posterior development. Moreover my results show that the expression of Pt-eve and Ptrun-1 is regulated by the read out of Delta-Notch and Wnt signaling via caudal (Pt-cad), which might be a mechanism ancestral to all arthropods. To investigate the function of Wnt signaling in more detail in spiders, I also studied the evolution and expression of Frizzled receptors (Fz) during spider embryogenesis. Four Fz genes (Pt-fz1, Pt-fz2, Pt-fz4a, Pt-fz4b) have been identified in Parasteatoda and analysis of the expression of the frizzled receptor genes throughout embryonic development suggests an involvement in neuroectoderm development, segmentation and development of anterior 5 structures. Moreover, the early ubiquitous and later segmental expression of Pt-fz1 shows that this gene is a good candidate receptor for Wnt8 in Parasteatoda.
Schönauer, A
Faculty of Health and Life SciencesDepartment of Biological and Medical Sciences
Year: 2016
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