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theses

From an RNAi lines screen, our lab found the Drosophila Zyxin family gene, Zyx102 (Zyx) as a negative regulator of Fat-Hippo signaling. Epistasis analysis put Zyx between Dachs and Warts (Wts) in the Fat-branch, and Zyx-RNAi suppresses the reduction of Wts level by fat RNAi. Zyx partially co-localizes with Dachs, and its localization was not altered by manipulating other Fat-branch component. Zyx protein binds to Dachs, and Dachs stimulates binding of Zyx to Wts, suggesting a molecular mechanism for how Fat signaling regulates Wts through Dachs. Our results identified a new component of Fat signaling, and investigated possible molecular mechanism for signal transduction from Fat to Wts. Among the vast amount of genes involved in organ morphogenesis, Fat gene stands out as it transduces both growth cue and planar cell polarity (PCP). But the molecular mechanism underlying is unknown. A structure-function approach is recruited to figure out the motifs in Fat that are required for signal transduction mechanism. By a fat genomic Bac Clone, which is expressed under endogenous condition, activities that could be missed by over-expression can be revealed. We find out the PCP activity is evolutionarily conserved from Drosophila to mammals. And the Hippo and PCP activity can be largely separated at the level of the Fat receptor. A specific motif was identified to mainly impair Fat-Hippo activity and reduce Fat phosphorylation. Manipulating the potential phosphorylation sites in this motif gives similar phenotypes, implicating phosphorylation as an essential factor in Fat-Hippo signal transduction. This motif overlaps with the previously identified Dco binding site, but retains normal binding affinity. Another conserved four amino acid motif is crucial for Fat-PCP, while the Fat-Hippo activity is almost normal. And this motif contributes differently to multiple PCP assays, suggesting there are different kinds of PCP in Drosophila. Different Fat activity leads to distinctive Dachs localization pattern, and directly manipulating Dachs localization could phenocopy loss of Fat activity. Thus Dachs localization influences both Hippo and PCP phenotypes. Our results identify a conserved mechanism of Fat signaling, establish functional significances for Fat ICD motif, phosphorylation sites, and Dachs membrane localization to downstream pathways.

ETD_4686

Ph.D.

Includes bibliographical references

Includes vita

by Guohui Pan

http://hdl.rutgers.edu/1782.1/rucore10001600001.ETD.000068931

doi:10.7282/T38914FJ

ETD doctoral

The author owns the copyright to this work.