The interest of our lab is to investigate the role of RhoGTPase family in neuronal development. RhoGTPases are involved in modulating the actin cytoskeleton and promoting polarity in a number of different cells. The three mostly studied RhoGTPases are Rho, Rac and Cdc-42. Neuronal Wiskott-Aldrich syndrome protein (N-WASP) is a downstream effector of CDC-42 in central nervous system and a key regulator of actin reorganization. It has been reported that in human intractable epilepsy patients, both N-WASP and CDC-42 are significantly upregulated, which indicates either a cause or consequence (1). We have determined that CDC-42 appears to regulate synaptic transmission based on the uncoordinated phenotype of
cdc-42 mutant and the fact that
cdc-42 homozygous worms showed hypersensitivity to acetylcholine esterase inhibitor : aldicarb and furthermore, an "epileptic like" behavior on plates containing PTZ, a GABA receptor antagonist (2). C. elegans
wsp-1 has two splicing transcripts, a major transcript which is the homologue of mammalian N-Wasp, and a minor transcript containing a region unique to C. elegans
wsp-1 (3). To study the role of
wsp-1 in neuronal development, we obtained a strain named NG324, which has a portion of the major transcript deleted. We found that this
wsp-1 mutant is also hypersensitive to aldicarb and were able to rescue this phenotype with somatically expressed transgene
wsp-1. We propose that WSP-1 is also a synaptic regulator at the neuromuscular junction. But
wsp-1mutant did not show obvious phenotype on PTZ plates, which suggests that the interaction of WSP-1 to CDC-42 may not be essential for CDC-42 function in GABAnergic synaptic transmission. To better understand the role of
wsp-1, we are generating double mutants with known roles in synaptic transmission, one we have made is
unc13(e51 );
wsp-1(
gm324). We found that deletion of the major transcript of
wsp-1 in
unc13 mutant can switch its aldicarb sensitivity from resistant to sensitive, which indicates that WSP-1 may negatively regulate the neurotransmitter release. We are currently performing transgene rescue experiment to understand the exact function site of
wsp-1 in synaptic transmission. References 1.Xiao F, Wang XF, Li JM et al. (2008) Overexpression of N-WASP in the brain of human epilepsy Brains Research 1233:168-175 2.Locke C, Berry K et al. (2008) Paradigms for pharmacological characterization of C. elegans synaptic transmission mutants J Vis Exp 18: 837 3.Sawa M, Suetsugu S et al. (2003) Essential roles of the C. elegans Arp2/4 complex in cell migration during ventral enclosure Journal of Cell Science 116:1505-1518.