Recent work in our laboratory has uncovered a novel wingless (Wg) signaling pathway that is required for synaptic outgrowth at the Drosophila neuromuscular junction (NMJ). Initial studies have demonstrated that Wg is secreted from the presynaptic motor neuron and that this secretion is required for translocation of a Cterminal fragment of dFrizzled 2 (DFz2), a Wg receptor, into the nucleus. Once translocated into the postsynaptic muscle nuclei, DFz2(C) forms distinct foci. The cleavage of DFz2 to generate the C-terminal fragment and the nuclear import are required for proper synaptic outgrowth. The goal of this proposal is to begin to elucidate how DFz2(C) functions in the nucleus to regulate synapse development. Preliminary microarray experiments indicate the DFz2(C) may regulate synaptic outgrowth by regulating gene expression. In order to uncover the role of DFz2(C) in the nucleus, the first aim will include: 1) Verification of the genes uncovered in the microarray via quantitative PCR 2) Testing if verified genes physically associate with DFz2(C) foci in the nucleus and 3) Determining if DFz2(C) can interact with promoters of genes by performing chromatin immunoprecipitation (ChIP) assays. Additional preliminary data demonstrate that Lamin C (LamC), an A-type lamin, localizes to the DFz2(C) foci. Moreover, lamC null mutants display similar phenotypes to dfz2 mutants and expression of a LamCGFP fusion protein results in changes in the morphology of DFz2(C) foci and specifically disrupts synaptic outgrowth, suggesting that DFz2(C) and LamC may function together in the nucleus to regulate synaptic development. Mutations in A-type lamins in humans lead to a myriad of neuromuscular diseases called laminopathies. The goal of the second aim is to 1) Further test lamC and dfz2 mutants for overlapping phenotypes 2) Look for genetic and biochemical interactions between DFz2(C) and LamC and 3) Determine the function of LamC at DFz2(C) foci.
Misregulation of the Wnt/Wg signaling pathways in humans can lead to a myriad of different cancers and neural diseases. Therefore this study is expected to significantly contribute to our understanding of a novel Wg signaling pathway, and in the development of new strategies to prevent or cure diseases caused by disruptions in this pathway. Preliminary data also suggest that this pathway may interact with A-type lamins, which are mutated in host of muscular dystrophies called laminopathies. Therefore, understanding lamins'role in this signaling will be essential to our understanding of laminopathies.
