Fig. 7. The inappropriate defasciculation observed in mutants with reduced MMP activity is suppressed by increasing interaxonal adhesion. 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) Wild-type embryo exhibiting normal ISNb morphology. (B,E) elav>Fas2 mutant embryos have increased motor axon adhesion. (C,F) elav>Fas2, Timp embryos exhibit phenotypes consistent with weakened interaxonal adhesion relative to elav>Fas2 embryos. (G,J) Mmp2^W307*/Mmp2^Df mutant embryos have loosely bundled ISNb axons and ectopic branching. (H,K) The ISNb of Sema-1a^P1/Sema-1a^P1 mutant embryos exhibits hyperfasciculation and does not properly innervate its muscle targets. (I,L) In Sema-1a^P1 Mmp2^W307*/+ Mmp2^Df mutant embryos, ISNb morphology resembles that of wild-type embryos. Note that these embryos have more tightly bundled nerves than do the Mmp2 homozygous mutants shown in G. Scale bar: 15 µm.