Acceleration in the dispersal of pre-patterned AChR clusters resulting from exogenous wild-type or constitutively active Shp2 expression. R-BTX labeled muscle cells expressing GFP only (A-C), or GFP plus Shp2 WT (D-F), Shp2 E76A (E-G) or Shp2 deltaP (not shown) were stimulated overnight with HB-GAM beads. In a fraction of bead-stimulated cells expressing GFP alone, pre-patterned AChR clusters were still present, but the fraction of such cells expressing wild-type or active Shp2 that retained pre-patterned clusters was significantly lower. To quantify these results, the number of pre-patterned clusters counted in bead-stimulated cells was divided by the number obtained from muscle cells that had not been exposed to beads (to offset differences in pre-patterned cluster formation; see text). Results normalized relative to GFP-cells are shown in panel J. GFP-cells, n = 212; Shp2 WT, n = 60; Shp2 E76A, n = 138; Shp2 deltaP, n = 127; *p < 0.01; **p < 0.05. Panel K shows that the expression of Shp2 proteins did not affect bead-induced AChR clustering.