Fig. 3. GFP::RAC-2 is anchored to the plasma membrane. (A) A diagram of the unc-115::gfp::rac-2 transgene and the putative GFP::RAC-2 molecule produced from this transgene are shown. The neuron-specific unc-115 promoter was used to drive expression of gfp fused in-frame to the entire wild-type rac-2-coding region, including introns. This transgene is predicted to produce a RAC-2 molecule with an N-terminal GFP tag. The CAAX motif at the C terminus of RAC-2 might direct covalent addition of a prenyl group and subsequent anchorage of the molecule to the plasma membrane. The position of the frame shift mutation in unc-115::gfp::(FS)::rac-2 is indicated. (B,D) Wild-type animals harboring the unc-115::gfp::rac-2 transgene. GFP::RAC-2 accumulated at the cell margins of neuroblasts of the 1.5-fold embryo in (B) and of neurons in the L1 larva in C. The animal in C displayed strong GFP::RAC-2 accumulation in the nerve ring. (D) A magnified image of the area around the nerve ring of the animal in (C). Neuron cell bodies with GFP::RAC-2 at their periphery are evident. (E,G) Wild-type animals of the same age as those in B,C harboring the unc-115::gfp::(FS)rac-2 transgene that contains a frameshift mutation between gfp and rac-2 sequences. This transgene is predicted to encode a full-length GFP without RAC-2 sequences. GFP accumulation was no longer observed at cell margins of neuroblasts and neurons and was observed throughout the cytoplasm, and nerve ring accumulation was abolished. (G) A magnified view of the area around the nerve ring of the animal in F. Scale bars: in B 10 µm for B,C,E,F; in D 2 µm for D,G.