|M.Sc Student||Shasha Yoav|
|Subject||The Role of the POU - Domain Transcription Factor VVL in|
Proprioceptor Development in Drosophila
|Department||Department of Medicine||Supervisor||Professor Adi Salzberg|
|Full Thesis text|
Most of the cells in the embryonic peripheral nervous system (PNS) of Drosophila are born in their final location. One known exception is the five lateral chordotonals organ (lch5), a proprioceptive organ whose precursors are born in the dorsal PNS cluster, while the mature organs reach a lateral position by a lateral localization process. Genetic screens had shown that mutation in the ventral - veinless (vvl) gene perturbs the localization of lch5 neurons resulting in a 'dorsal chordotonals' phenotype.
Ventral veinless (Vvl) is a class III POU domain transcription factor. In its absence cell fates within the lch5 lineage are determined properly, but the entire organ fails to migrate ventrally. Vvl is expressed throughout the ectoderm, in lch5 neurons and in the oenocytes, hepatocyte like cells that reside near the lch5 organs. Till today the mechanism and function of vvl in the process of lch5 lateral localization remained elusive.
The purpose of this work was to investigate the role of vvl in the process of lch5 lateral localization. In order to identify the factors through which vvl controls this process three different routes were taken:
1. We examined the effects of the guiding molecule Slit and its receptor Roundabout (Robo) on the correct localization process and tested for possible interaction with vvl. We found that Slit does affect lch5 localization. Both the absence of Slit and its ectopic expression lead to abnormal positioning of the lch5. In addition, in vvl mutant embryos the expressions of Robo1 in the lch5, and Slit in the oenocytes, was lost. This implies that vvl could affect lch5 localization by controlling the expression of Slit and its receptor Robo1.
2. We tested for possible interactions between Vvl and Spalt, a transcription factor which affects oenocyte formation and lch5 localization. The results showed that Spalt and Vvl mutually affect each other expression.
3. We tested whether vvl affects lch5 localization through the regulation of Stripe (Sr), a transcription factor that is important for the differentiation and formation of chordotonals attachment cells and tendon cells. We found that Vvl does not regulate Sr expression in the lch5 organs. On the other hand, this work shows that Vvl affects the organization of the lateral transverse muscles and the primary patterning of their Sr expressing tendon cells.