The ARSs are associated with Nrg-containing membrane loops. (A–O) Nerve cords dissected from third instar larvae carrying Nrg-GFP (A–F), Nrx-GFP (G–L), or Scribble-GFP (M–O). GFP labeling is shown in A, D, G, J, and M, and the corresponding phalloidin staining is shown in B, E, H, K, and N. The corresponding merged images are shown in C, F, I, L, and O. D–F and J–L show high magnifications of the corresponding area marked with a white rectangle in C and I. Note that the ARSs often overlap the Nrg-GFP labeling (white arrowheads in D–F). In rare cases, we detected an ARS distal from the SPG border that does not overlap Nrg-GFP (open arrowheads in D–F). NrxIV does not overlap the ARSs (white and open arrowheads in J–L). Partial overlap is also noted between Scribble and phalloidin staining (arrowheads in M–O).