During embryogenesis, epithelial cells migrate and change shape in order to generate three dimensional structure. How these cells move,and the signals that cause their movement is the focus of our research. During the process known as ventral enclosure epithelial cells that originate on the dorsal surface of the embryo migrate to the ventral midline, forming adhesive junctions.
jc5 is a cold sensitive mutant that is defective in ventral enclosure and was identified in an EMS mutagenesis screen performed in the Hardin laboratory. Phenotypically,
jc5 mutants show defects during varying stages of embryogenesis. Approximately 20% of embryos die because migration of epithelial cells from the dorsal side never occurs. Another 20% die during enclosure, predominantly displaying dorsal retraction or partial enclosure phenotypes. 40% of dead embryos that enclose properly, but develop severe body shape defects as they try to elongate into a worm. In addition, another 20% of embryos may display cytokinesis defects leading to too few hypodermal cells. These phenotypes have been observed using 4D Normarski microscopy, as well as with multiphoton microscopy with the Junction Associated Molecule-1 (JAM-1) GFP. We have mapped the gene to a small region of approximately 80KB on LG IV. One candidate gene in the region is an inositol 1,4,5-triphosphate receptor (ITR-1). In RNA interference experiments using
itr-1, we have been able to phenocopy the
jc5 phenotypes. Preliminary evidence with individual cosmids that break within
itr-1 is consistent with the hypothesis that the
jc5 mutation is caused by a lesion in the
itr-1 gene. In order to test whether
itr-1is jc5, we will try to rescue the
jc5 phenotype by injection using a cosmid that spans the
itr-1region. ITR-1 has already been found to act in behavioral rhythms in C. elegans larva and adults (Dal Santo, P. et al, 1999. Cell 98, 757), and can act as a Ras-independent effector of the LET-23 epidermal growth factor receptor (Clandinin, T. et al, 1998. Cell 92, 523). However, no one has characterized the role of this protein in embryonic development. It is known that ITR-1 controls intracellular calcium levels; recent papers in other systems have implicated calcium in the regulation of actin during cell migration (Gallo, G. and Letourneau, P.C., Current Biology 9, 490). This may indicate a role for ITR-1 in cytoskeletal rearrangement during ventral enclosure.