Identification of candidate Notch targets in Hydra vulgaris

Moneer, Jasmin (2022): Identification of candidate Notch targets in Hydra vulgaris. Dissertation, LMU München: Faculty of Biology

Abstract

The Notch signalling pathway plays major roles in several developmental processes including embryogenesis and maintenance of adult tissue homeostasis. Conserved core components of the Notch pathway have been identified in the simple cnidarian Hydra vulgaris. Previous experiments have shown the successful application of the chemical DAPT in Hydra, which blocks the Notch signaling pathway by preventing the translocation of the intracellular domain of the Notch receptor (NICD) into the nucleus. This inhibition resulted in several severe phenotypical changes in Hydra polyps. This study focused on the identification of candidate Notch targets in order to unravel the molecular mechanism underlying the observed phenotypes. A comparative transcriptome analysis was performed and the data of the RefSeq experiment of DAPT-treated and control animals were mapped to data from the recent Hydra single cell analysis. Differential expression analysis showed that especially cells of the nematoblast lineage were affected by Notch inhibition. About 50% of the identified Notch-responsive genes were found to be expressed in nematoblasts or nematocytes including HyPOU4, NOWA, Spinalin, CnASH and several nematoblast-specific genes. The analysis emphasized that for nematoblast development, Notch signaling becomes important when nematoblasts undergo the final mitosis to differentiate into nematocytes. Known genes specific for proliferating nematoblasts, were not affected by Notch inhibition. Since the majority of the Notch-responsive nematoblast genes were down-regulated upon Notch inhibition, it can be concluded that Notch drives nematoblast differentiation. In addition, cluster analysis showed several small clusters of Notch-responsive genes, that were specifically expressed in distinct cell types, including endodermal or ectodermal epithelial cells or both, tentacle genes, both ectodermal like battery cells and endodermal, head cells and foot cells. Notch-affected head specific genes included HyAlx, CnOtx, Cngoosecoid and HyWnt7. Interestingly, Notch-responsive head genes were mainly down-regulated whereas Notch-responsive genes in the foot and basal disc were mainly up-regulated, suggesting that Notch plays opposing roles in these two Hydra extremities.

• Item Type: Theses (Dissertation, LMU Munich)
• Keywords: Notch pathway, Hydra, NGS
• Subjects: 500 Natural sciences and mathematics; 500 Natural sciences and mathematics > 570 Life sciences
• Faculties: Faculty of Biology
• Language: English
• Date of oral examination: 28. November 2022
• 1. Referee: Böttger, Angelika
• Signature of the printed copy: 0001/UMC 29399