Fig. 3.

β-Dystroglycan expression inhibits agrin-induced formation of clusters without altering formation of microclusters. Transfected myotubes were incubated with 250 pm agrin N2(4,8) for 5 hr and double-labeled for AChRs (Texas Red-conjugated α-bungarotoxin; B, D) and anti-HA immunoreactivity (FITC-conjugated anti-mouse; A, C). A, B, A CD8tm-transfected myotube. C, D, A myotube transfected with DGΔP. In B andD, carets indicate large clusters, whereas small arrows point to a subset of the quantified microclusters (see Materials and Methods). E, Quantification of agrin-induced clusters (left) and microclusters (right). Agrin-induced formation of clusters is inhibited by dystroglycan and DGΔP relative to control CD8tm (p < 0.005; Student'st test; n = 4). In contrast, the numbers of microclusters per myotube segment were not different between myotubes transfected with the dystroglycan variants and controls. Scale bar, 20 μm.