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Identifier

uch.biology.phd//2001apidianakis

Title

Μελέτη των γονιδίων m4, mα & Tom κατά τη διαδικασία της νευρογένεσης και του γονιδίου gro κατά την ανάπτυξη των άκρων στη D. melanogaster

Alternative Title

Study of m4, mα and Tom genes, with respect to neurogenesis and of groucho gene, in regard to limb development of D. melanogaster

Author

Απιδιανάκης, Γιώργος

Thesis advisor

Δελιδάκης, Χρήστος

Abstract

(I) The m4 and mα genes belong to the Enchancer of split gene complex [(Espl)-C], which contains, among others, seven bHLH genes (Espl-bHLH). The latter are the immediate targets of Notch signalling and their induction results in the repression of proneural genes. High proneural gene activity is necessary for neural determination. Notch is implicated also in other processes such as eye development, leg junction formation and wing disc dorsoventral boundary determination. Although they are activated by Notch, the m4 and mα genes seem to inhibit signal transmission (our study). Overexpression of one or both of these genes, causes multiplication of sensory organ precursors (SOPs). This is due to downregulation of Espl-bHLH, which in turn results in high proneural gene activity in more cells than in the wild type. Based on sequence homology we cloned Tom, which has a similar mode of action when overexpressed. In either wing disc overexpression or in S2 cell transient transfection experiments, all three genes (m4, mα or Tom), downregulate Notch dependent induction of Espl-bHLH. Their action seems very specific in downregulating Notch signalling during determination of SOPs, but not in other instances of the signal. (II) Although groucho (gro) belongs to the E(spl)-C and interacts physically with the Espl-bHLH proteins, its biological role goes beyond neurogenesis. Gro interacts with many transcription factors and is involved in many instances of gene regulation in development and in well conserved signalling pathways of the whole evolutionary spectrum. It is a corepressor, due to its inability to bind DNA, that is, it requires protein interaction with specific DNA binding transcription factors, in order to achieve its transcriptional repression. In this study we analysed a heretofore overlooked genetic interaction with the hedgehog (hh) gene. Initially, it was noticed that gro affects hh and engrailed (en) expression in the anterior wing disc. Studing further this effect, we come to the conclusion that gro downregulates hh transcription, independently of the known repression activity of cubitus interruptus (ci). Furthermore, we did a functional domain analysis of gro taking into account the repressive activity and the subcellular localization of gro mutants. In these assays the CKII and cdc2 putative phosphorylation sites are dispensable for gro function. On the other hand, the GCS domain, which contains the whole NLS signal, and the WD40 domain and Q domain are necessary for gro function.

Language

Greek

Subject

Γονίδια; Νευρογένεση; Ανάπτυξη άκρων; Δροσόφιλα; Πλευρική αναστολή; Καταστολέας

Issue date

2001-12-20

Collection

School/Department--School of Sciences and Engineering--Department of Biology--Doctoral theses

Type of Work--Doctoral theses

Permanent Link

https://elocus.lib.uoc.gr//dlib/e/2/6/metadata-dlib-2001apidianakis.tkl