Understand how epithelial sheets move and what regulates their movement is fundamental for understanding many events impacting human health, including fetal development and the control of metastatic growth in cancer. The embryonic hypodermis of the nematode, C. elegans, is a powerful model system for studying epithelial morphogenesis. We have carried out a screen for mutations which affect hypodermal enclosure in specific ways, and we propose to analyze genes we have cloned to gain a greater understanding of how specific molecular lesions in identified proteins affect epithelial morphogenesis at single-cell resolution. This proposal has four major aims: (1) Defining the role of catenin/cadherin homologues during enclosure. We will analyze the specific defects in embryos mutant for hmp-1 (an alpha- catenin), hmp-2 (a beta-catenin), and hmr-1 (a cadherin) in multiple mutants, mosaics, and germline mosaics. We will also test the morphogenetic role of hmp-2 by creating several transgenic lines containing various chimeric constructs that cannot perform the signaling functions associated with beta-catenins. (2) Defining the role of the kinesin-like protein ZEN-4 during enclosure. zen-4 encodes a kinesin-like protein similar to the vertebrate CHO1 antigen. We will analyze enclosure defects in zen-4 homozygotes. Finally, we will test whether the ZEN-4 protein functions in a manner similar to the CHO1 KRP by generating transgenic lines carrying heat-shock constructs and by performing transfection experiments using cultured cells. (3) Defining the role of the partially penetrant mutation vab-9 during enclosure. We have obtained cosmid rescue of vab-9, which shows consistent enclosure defects and other morphogenetic abnormalities in embryos and larvae. We will narrow the rescuing region to identify the gene encoded by vab-9 protein, by generating reagents to characterize its location, and by examining genetic interactions with other vabs. (4) Defining the role of novel mutations during enclosure. We have partially characterized additional mutations that show completely penetrant enclosure defects (zygotic, lethal, enclosure, defective, or zen mutants) as well as mutations that show incompletely penetrant enclosure defects, and defects in other morphogenetic processes (morphogenesis of epithelial defective, or med). As a long-term goal, we will continue initial characterization of several novel zen and med loci. As a result of these studies, we expect to gain a greater understanding of how specific lesions in identified molecules give rise to specific cellular defects during epithelial morphogenesis.
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