Fig. 4. De novo filament assembly in transfected keratin-free SW13 epithelial cells. At 24 hours after transfection, most cells coexpressing K8 (wild type) and K18 (wild type) contained extended filament networks (A), whereas most cells coexpressing K8(G62C) and K18 (wild type) contained short lengths of disorganized filaments and aggregates (B). By 120 hours after tranfection with wild-type K8 and K18, most transfected cells contained extended arrays of ordered keratin filaments (C). However, cells expressing the K8(G62C) mutant contained predominantly disordered filament fragments (D). Bar, 20 µm.