Figure 7.—

SH3-domain binding motifs in the SNS cytodomain are required for proper myoblast fusion. (A) Schematic of the transgenes, with the positions of the SH3 binding motifs and their amino acid substitutions indicated. (B and E–G) Stage 16 embryos in which the musculature has been visualized by immunostaining with an antibody to muscle myosin. Rescued embryos are representative of results obtained using two independent transgenic lines. (B–D) Expression of the transgene was directed to sns^Zf1.4/sns^XB3 mutant embryos using mef2Gal4 at 25°, using the transgenic lines (B and D) UAS-sns2xPXXP and (C) UAS-snsHA. (C and D) Embryos express sns-LacZ and are stained fluorescently for β-galactosidase to highlight the unfused myoblasts. (E–G) Dorsal, lateral, and ventral views, in which the UAS-sns2xPXXP transgene was directed to sns^Zf1.4/sns^zf1.4 mutant embryos using snsGal4 at 18°. Arrows mark unfused myoblasts in D and asterisks mark regions of missing muscles in E–G. Bar, 20 μm.