Analysis of a Non-Canonical Notch Signaling Pathway in the Developing Nervous System in Zebrafish

The Notch pathway is an evolutionary conserved signaling system that is required for embryonic development, tissue homeostasis, maintenance of stem cell identities and cancer formation. Previous studies have shown that the canonical ligands DSL (Delta, Serrate, Lag2) and the intracellular co-factors CSL (CBF1, Su(H), LAG1) are the core members to activate the Notch target genes such as Hairy/E(Spl). However, a growing number of molecules have also been shown to be required for non-canonical Notch signaling. In the present proposal, we are going to study a non-canonical Notch singling in neural development. DNER (Delta/Notch-like EGF-related receptor) was recently identified to be a novel ligand for Notch and its function so far is far from clear. By analyzing CGAP libraries, I found DNER is highly expressed in several brain tumor tissues and cell lines including glioblastoma and astrocytoma, suggests its role in tumor formation and neural development. In order to analyze the role of DNER in vivo, we have identified the zebrafish homologue and performed in situ hybridization on zebrafish embryos. The result showed distinct expression of zebrafish Dner in the developing nervous system especially in the pro-neuronal clusters, suggests its role in neurogeneis and gliogenesis. We will further dissect the molecular regulation of DNER/Dner in correlation to Notch signaling pathway and the role of DNER-dependent Notch signaling in the developing nervous system. In addition, previous studies suggested that DNER may activate Notch singling through the non-canonical co-factor Deltex instead of CSL. Therefore we have also identified and isolated the homologues of Deltex in zefrafish and will study their roles in the DNER-dependent Notch signaling in neural development. During the last NSC project we have also characterized several Hairy/E(Spl) homologues, the potential downstream targets of Notch signaling, and these molecules will be used as candidates to identify the downstream target for DNER-dependent Notch signaling. In general, we will thoroughly dissect the role of the DNER-Notch-Deltex signaling in the developing nervous system. The results will provide novel insights into the molecular regulation of developing nervous system and provide further understanding for the formation of brain tumors.

Project ID:PA9808-0188
External Project ID:NSC98-2311-B182-002-MY3