Fig. 6. MMP catalytic activity is required for motor axon pathfinding. In each micrograph, two abdominal hemisegments of Stage 17 dissected embryos stained with -FasII to label the motor projections are shown with anterior left and dorsal up. Below each image are schematics of the observed phenotypes with motor axons in brown and muscles represented by gray boxes. (A,D) In wild type, the ISNb exhibits a highly stereotyped morphology as its axons innervate their muscle targets. (B,E) In elav>Timp embryos, ISNb axons appear loosely bundled. (C,F) In repo>Timp embryos, ISNb axons are loosely bundled and project ectopically. (G,I) elav>Mmp2^E258A embryos exhibit aberrant ISNb projections with axons failing to innervate their appropriate targets. (H,J) In repo>Mmp2^E258A embryos, ISNb axons are loosely bundled and often branch ectopically. Scale bar: 15 µm.