Research Interests

Dissection of the Wnt/Wingless signaling pathway
using functional genomic approaches

The Wnt/Wingless (Wg) pathway is one of a core set of evolutionarily conserved signaling pathways that regulates many aspects of animal development. Aberrant Wnt signaling has been linked to human disease, such as cancers of the intestine, stomach, breast, liver, and skin. Mutations in the Wnt genes or in those that encode regulators of this pathway can cause devastating birth defects, including debilitating abnormalities of the central nervous system, axial skeleton, limbs, and occasionally other organs.

The focus of my laboratory is to integrate a variety of functional genomic and proteomic high-throughput screens to generate a global picture of how the Wnt signaling pathway is regulated at a molecular level. We are also interested in understanding how components of the Wnt pathway may interact with other signal transduction cascades during development and disease. We are using a newly developed technology, called RNA interference (RNAi) to systematically knockdown gene function on a genome scale and testing the effects (phenotype) of reduced gene function on cells and in the developing embryo. The RNAi screens are used to assign new function to genes in the context of the Wnt pathway. We have also initiated screens to identify key micro RNA (miR) regulators of the Wnt/wg pathway, both in Drosophila as well as mammalian cells.

We have performed a genome-wide RNAi screen in Drosophila cells to screen for new regulators of the Wnt pathway. We identified several potential regulators, which include known pathway components, genes with functions not previously linked to this pathway, and genes with no previously assigned functions. Functional assays of selected genes from the cell-based screen in Drosophila, mammalian cells, and zebrafish embryos demonstrated that these genes have evolutionarily conserved functions in Wnt signaling. High throughput RNAi screens in cultured cells, followed by functional analyses in model organisms, thus proved to be a rapid means of identifying regulators of signaling pathways implicated in development and disease.

We are continuing the use of functional genomic and proteomic approaches to further investigate the molecular mechanisms of these potential regulators. Our initial studies have launched several areas of investigation that include, 1) Validation of the candidate genes identified in the RNAi screen by defining their role(s)/molecular mechanisms in the regulation of the Wnt/Wg signaling pathway in vivo using the power of Drosophila genetics. We are also investigating the function of mammalian orthologs of candidate genes (identified in the Drosophila RNAi screen) in mammalian cells, using siRNA technology and a variety of biochemical assays. 2) Investigating the role of micro-RNAs (miRs) in the regulation of the Wnt/wg pathway, both in Drosophila and mammalian cell culture models, including embryonic stem cells (ESCs). We are interested in developing miR-based molecular tools to modulate the activity of the Wnt pathway in stem cells and in cancer. 3) Determination of the function of the Wnt/wg and other cell signaling pathways in ESC homeostasis/differentiation using RNAi/miR-based functional genomic screens. 4) Conduct a small molecule chemical-genetic screen to identify potential drug targets of the molecules involved in modulating Wnt/Wg signaling activity using a variety of cell-based assays.