|CHORDOTONAL ORGAN; DENDRITE MORPHOGENESIS; NANOS; RNA PARTICLE; Molecular biology; Neurosciences; Developmental biology
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Nanos (Nos) and Pumilio (Pum) are well-known translational repressors required in Drosophila early embryogenesis for anterior-posterior body axis determination and germline development. nos mRNA is localized to the posterior of the embryo and is translated there to form a Nos protein gradient. The unlocalized nos mRNA, in contrast, is translationally repressed to avoid ectopic Nos expression. More recently, nos and pum were found to play a role in neuronal morphogenesis and function in the Drosophila larval nervous system. In class IV dendritic arborization (da) neurons, nos and pum regulate dendrite morphology and nos mRNA localization to the dendrites is essential for this function. However, the mechanism underlying nos RNA transport in the dendrites was unknown. In this thesis, we first explored this mechanism by analyzing factors required for nos mRNA localization in da neuron dendrites through living imaging of fluorescently labeled nos mRNA. We found that nos mRNA particle transport depends on the dynein motor machinery, as well as factors used in early development including the RNA binding protein Rumpelstiltskin and germ plasm protein Oskar. Additionally, we uncovered a role for nos and pum in class IV da neuron function, which is most likely independent of nos mRNA localization and function in dendrite morphogenesis. The pleiotropic roles of nos indicate that Nos might function by regulating different downstream target mRNAs. I explored several approaches to investigate potential targets for the Nos/Pum translation repression complex, including a candidate-based method and unbiased high throughput methods. I have identified a few promising targets and optimized methods for the high throughput analysis. In addition, I showed that nos is expressed in Drosophila chordotonal neurons and that nos and pum play a role in lateral chordotonal organ development and oenocyte specification. Further investigation of Nos and Pum function in these two events identified hunchback mRNA and the EGFR signaling pathway as potential targets for the Nos/Pum complex.