Figure 5.

Expression of the NEM-linked I64N- and N115S-actin mutants. EGFP-tagged I64N- (A, B) and N115S- (C, D) actin mutantswere expressed in C2C12 myoblasts (A, C) and differentiated myotubes (B, D). Both mutants showed poor integration in undifferentiated cells: EGFP fluorescence revealed delocalization in many myoblasts (A, C; short arrows). I64N-actin also produced large rods (A; long arrow), whereas N115S-actin formed smaller, punctuate aggregates in the cytoplasm of some cells (C; long arrow), in both cases not co-staining with phalloidin or alpha-actinin (A', A"; C', C"; long arrows). After differentiation both mutants incorporated into actin structures such as stress fibres (D-D"; long arrows) and sarcomeric thin filament bundles (B, B', inset). (Scale bars: 5 μm)