The interest of our lab is on the signaling events involving the Rho-GTPase family. These membrane associated proteins play a critical role in receptor-mediated signaling cascades that regulate transcription, cell division, vesicle transport and actin dynamics in a way that provides the cell with polarity, force for motility during movement and determining the morphology of the cell. The three most studied Rho-GTPases are Rho, Rac and Cdc42 and they are key regulators of actin cytoskeleton organization and cellular morphogenesis. The purpose of this project is to further investigate the biological role of
cdc-42 using C.elegans as a model organism. It is well established that
cdc-42 is essential in early embryonic development, but many details of its role later in development still need to be determined. Previous studies have shown that the
rho-1 gene is a pre-synaptic activator of neurotransmitter release in C.elegans (1) and a genome wide RNAi screen for genes required in membrane traffic links
cdc-42 to endocytosis (2). We hypothesize that the presence or absence of
cdc-42 may affect the synaptic transmission at the neuromuscular junction by regulating either exocytosis in nerve cells and/or endocytosis in muscle cells. To test this hypothesis, we have obtained a strain from the Caenorhabditis Genetics Center that contains a balanced deletion in the
cdc-42 gene (VC898). We have determined that the VC898 strain, which is heterozygous for the
cdc-42 deletion, is sensitive to the acetylcholine esterase inhibitor aldicarb when compared to worms containing the balancer (mIn1) and wild-type
cdc-42 gene. This phenotype is rescued by a transgene that expresses wild-type
cdc-42 in all somatic cells in the VC898 background. We are currently determining the site of CDC-42 action by creating transgenes for specific expression of
cdc-42 in neurons and in muscle cells. We will also investigate the developmental timing required for
cdc-42 expression by creating a transgene that contains the
cdc-42 gene under control of the heat-shock promoter and expressing
cdc-42 early in development (during synapse formation) or later in the adult. Progress of these experiments will be reported at this meeting.