REGULATION AND FUNCTION OF THE TRANSLATIONAL REPRESSOR NANOS IN DROSOPHILA MELANOGASTER PERIPHERAL NERVOUS SYSTEM DEVELOPMENT

Abstract

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.