The Impacts of Downregulation of mam-RC on the Wingless Pathway in Drosophila melanogaster
Leyao Shen, Vassar College ’16 and Prof. Jennifer KennellWnt signaling is significant to human development and related to a variety of diseases including cancers and Type 2 Diabetes. The regulation of gene expression by Wnt signaling has been studied via researching the homologous Wingless (Wg) pathway in Drosophila melanogaster. Previous studies have shown that an isoform of the gene Mastermind (mam), mam-RC, is able to negatively regulate Armadillo (Arm), a coactivator of Wg signaling. In order to study the inhibitory effect on Wg signaling by mam-RC, we proposed to see whether Wg signaling was increased when mam-RC was downregulated. Two primary methods of mam-RC under-expression were designed: deletion of mam-RC using imprecise excision of a transposable element and knockdown of gene expression using RNA interference (RNAi). Our previous studies showed that duplicate sensory organ precursor cells were found on the imaginal wing discs and additional thoracic sensory bristles were observed in fly lines with RNAi knockdown. This suggests that RNAi is off-targeting and affecting the full-length isoforms of Mastermind, which are positive regulators of Notch signaling. In our study, we found significant morphological changes on vein patterning, especially characterized by a lack of posterior crossveins (pcv) when mam-RC expression was inhibited in the posterior portion of the developing wing by RNAi. This change might be caused by the overexpression of Decapentaplegic (dpp) as a result of downregulation of Notch signaling, which further confirms that RNAi knockdown lines are not reliable. Furthermore, the number of thoracic sensory bristles and pcv in deletion mutants were normal, suggesting that mam-RC deletion lines should be the focus of future research rather than the RNAi lines. In the future, mitotic clones, generated using a FLP-FRT recombination system, will be applied to study the effect of mam-RC deletion on Wg signaling.