Fig. 7. A point-mutant form of GFPactin79B, actin79B^R291H, is specifically incorporated only into Z-lines. (A) In the process of cloning actin79B we also recovered and expressed a point-mutant version of the protein that leads to an R-H amino acid exchange in position 291 of the protein. (B-F) This single amino acid change had striking consequences on the localization of actin79B^R291H in muscles: the protein is nearly exclusively incorporated into Z-lines (most dramatically seen in the indirect flight muscles; E,F). (B-F) Incorporation into (B) larval visceral muscles, (C,D) third instar larval body wall muscles (D shows the modified Z-line at the tendon ends of the muscles) and (E-F) indirect flight muscles (F shows the modified Z-line at the muscle end). Analysis in epithelial tissues showed that actin79B^R291H is not enriched in the filopodia of the leading edge or the amnioserosa in embryos (G shows GFPactin; G', phalloidin). (H-I') Within the follicle epithelium, actin79B^R291H was only weakly found in the cell cortex (H,H'), but was incorporated into apical microvilli and the basal actin bundles (I,I'). In all colour panels GFPactins is shown in green, labelling with phalloidin is in red. All black and white panels show either GFPactin or phalloidin single channels as indicated on each panel.