The transcription factor Escargot is involved in neuronal differentiation. Anne Ramat, Michel Gho. Laboratory of Developmental Biology CNRS/UPMC, Paris, France.

   The properties of the nervous system rely on the quality of its neuronal network. How the complex arborization of axons and dendrites is determined, is still poorly understood. Cues provided by neurons themselves play a crucial role for neuronal projections. Indeed, each type of neuron has its own shape. In order to analyze how neuronal morphogenesis is intrinsically controlled, we have focused our attention on the evolutionarily conserved transcription factor Escargot (Esg) that is widely expressed in neural precursor cells in diverse model systems. In order to analyze the role of Esg in neuronal differentiation, we studied neuronal processes in the embryonic and adult Drosophila peripheral nervous system under esg mutant conditions. Using clonal analysis, our study revealed that neurons inside esg clones present thinner axons than normal and frequently harbour altered projection trajectories. Interestingly, these defects were also observed when we expressed, an RNAi directed against esg transcript exclusively in neurons. These data show that esg is involved, cell autonomously, in neuronal differentiation in both embryonic and adult PNS. In addition, these defects were correlated with a reduction in the expression of several identity factors such as those encoded by elav and prospero genes. Since it is known that axonogenesis is impaired in elav and prospero mutants, we are currently studying whether esg acts through these factors to control axonogenesis. We anticipate that this study will shed light on the mechanism by which esg regulates neuronal differentiation and axonogenesis.