Poster abstracts
Poster number 6 submitted by Marcos Corchado
The role of lpr-3 as a cell non-autonomous regulator of activated let-60/Ras in C. elegans
Marcos Corchado (Department of Molecular Genetics, The Ohio State University), Dr. Helen Chamberlin (Department of Molecular Genetics, The Ohio State University), Dr. Komal Rombani (Biomedical Sciences Program, The Ohio State University), Dr. Gustavo Leone (Department of Biochemistry and Molecular Biology, Medical University of South Carolina)
Abstract:
Tissue signaling is required for organogenesis across a wide array of organisms. More specifically, mesoderm-to-epithelium signaling regulates epithelial cell proliferation during various developmental processes such as lung branching and ureteric branching in kidneys. Tissue signaling is also important in cancer as extracellular signals from the stroma (mesoderm) are required for the maintenance and progression of cancer cells (epithelium). However, identifying such factors is particularly challenging due to the complexity of stromal cell types in mammals. A recent screen performed in a simpler organism, the nematode C. elegans, identified lipocalin-related 3 (lpr-3) as a candidate for such a signal. lpr-3 is expressed in mesodermal tissue but is required for hyperproliferation of a set of epithelial cells, known as the vulva precursor cells (VPCs), under the presence of a gain-of-function mutation of let-60/Ras. In mammals, lipocalins transport hydrophobic ligands to initiate cellular processes by binding to specific membrane receptors. Furthermore, it is known that human lipocalins are endocytosed upon binding to a membrane receptor. The aim of my research is to determine if LPR-3 functions similarly by binding to a receptor in the VPCs to promote let-60/Ras(gf)-mediated hyperproliferation. To test this hypothesis, I inhibited receptor-mediated endocytosis in the VPCs by performing a VPC-specific RNAi knockdown of clathrin on let-60/Ras(gf) animals. Results show a significant suppression of hyperproliferation, which supports the hypothesis that an LPR-3 receptor is present. Currently, I am performing a genome-wide VPC-specific RNAi screen on let-60/Ras(gf) animals to identify potential membrane receptors and downstream effectors of LPR-3. Thus far, 4 out of the 6 C. elegans chromosomes have been completed and 193 candidates have been identified. In particular, 15 candidate genes show high suppression of let-60/Ras(gf) upon RNAi knockdown (>50% suppression). 8 of these genes have human orthologs which regulate cell proliferation or exhibit overexpression in tumors, and 2 nematode-specific genes encode receptors. Together, these results validate the effectiveness of the screen.
Keywords: Ras, C elegans, lpr-3