A RHO GTPase-mediated pathway is required during P cell migration in Caenorhabditis elegans

Abstract

The Rho family of guanine triphosphate hydrolases controls various cellular processes, including cell migration. We describe here the demonstration of a role for a RhoA GTPase homologue during cell migration in Caenorhabditis elegans. We show that eliminating or reducing rho-1 gene function by using a dominant-negative transgene or dsRNA interference results in a severe defect in migration of hypodermal P cells to a ventral position. Biochemical and genetic data also suggest that unc-73, which encodes a Trio-like guanine nucleotide exchange factor, may act as an activator of rho-1 in the migration process. Mutations in let-502 ROCK, a homologue of a RhoA effector in mammals, also cause defects in P cell migration, suggesting that it may be one of several effectors acting downstream of rho-1 during P cell migration. Finally, we provide evidence to support the idea that other small Rac subfamily small GTPases act redundantly and in parallel to RHO-1 in this specific cell migration event.rho-1 ͉ rac ͉ unc-73

Guanine Nucleotide Exchange Factor OSG-1 Confers Functional Aging via Dysregulated Rho Signaling in Caenorhabditis elegans Neurons

“…Therefore, to determine whether OSG-1 can interact with Rho GTPases, as predicted by sequence analysis, we individually knocked down these genes by bacterial RNAi. The ability to turn ON/OFF RNAi at any desired age by feeding C. elegans with RNAi-producing bacteria was a crucial asset to these experiments, because eliminating GTPase activities too early disrupts embryogenesis (Spencer et al 2001). Indeed, RHO-1 or CED42 RNAi treatment from day 0 was lethal (data not shown).…”

toca-1 Is in a Novel Pathway That Functions in Parallel with a SUN-KASH Nuclear Envelope Bridge to Move Nuclei in Caenorhabditis elegans

“…migration, were previously shown to lead to 60% of L2 larvae with lateral P-cell derivatives (Spencer et al 2001). In our observations of GABA neurons in L2 larvae, we very rarely (eight neurons in 149 L2 toca-1 unc-84 double-mutant animals) observed misplaced neurons at the lateral sides, suggesting we are not studying a general defect in cell migration and can genetically separate nuclear migration from cell migration.…”

“…Next, 3.4 kb of the promoter for hlh-3, which is expressed specifically in embryonic and larval P cells, was obtained from pRD1 (Doonan et al 2008) and cloned into the SmaI site of pSL614 to make p hlh-3 ::toca-1::gfp (pSL626). Alternatively, 1.2 kb of the promoter for col-10, which is expressed in embryonic and larval hypodermal cells, was obtained from pOS12 (Spencer et al 2001) and cloned into the SphI and SmaI sites of pSL614 to make p col-10 ::toca-1::gfp (pSL627). p hlh-3 ::toca-1::gfp (2 ng/ml) or p col-10 ::toca-1::gfp (5 ng/ml) was microinjected with odr-1::gfp (100 ng/ml) as a marker into the gonads of young adult hermaphrodites (Mello and Fire 1995).…”

“…Second, we tested whether wild-type toca-1 could rescue the nuclear migration defect of the yc20 mutation. Wild-type toca-1 was expressed in P cells prior to nuclear migration from two independent promoters: the pan-hypodermal promoter of col-10 ( Spencer et al 2001) and the P-cell-specific promoter of hlh-3 (Doonan et al 2008). The yc20 unc-84(n369) nuclear migration defect was rescued in transgenic animals expressing either p col-10 ::toca-1::gfp or p hlh-3 ::toca-1::gfp.…”

Caenorhabditis elegans CNK-1 promotes Raf activation but is not essential for Ras/Raf signaling

“…In particular, we do not observe embryonic-lethality or cell-migration defects indicative of defects in rho-1 signaling (46,47). It is possible that alternative roles for cnk-1 may be detectable only in the right genetically sensitized background.…”