The short isoform of rapsyn cannot cluster AChRs. QT-6 cells were transiently transfected with an expression vector encoding the short form of rapsyn shown in Figure 2c, in addition to AChR α plus β plus γ plus δ (a), α3 plus β2 (b), or α4 plus β2 (c) subunits. Two days later, cells were permeabilized and stained with anti-AChR (a–c) plus anti-rapsyn (a′–c′). Antibodies to both the C terminus (a′–c′) and N terminus (data not shown) (Fig. 3) recognized the short isoform. Both AChRs and the short form of rapsyn were diffusely distributed. Scale bar, 10 μm.