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Fig. 8 Tenascin-C immunoreactivity is absent from the region of the horizontal myoseptum in unp mutants. A-L: Double immunolabeling of axons (A,D,G,J) and tenascin-C (B,E,H,K, overlays in C,F,I,L) in the trunk at 22 hours postfertilization (hpf); orientation as in Figure 1A. A-C: In a nonhomozygous unp clutch mate, ventral motor nerves are unbranched (arrow in A) and tenascin-C immunoreactivity in the region of the horizontal myoseptum (arrow in B) and in vertical myosepta (asterisk in B) is similar to that in wild-type embryos. D-I: In two unp mutants, motor nerves are stalled and slightly branched (arrows in D,G). E,H: Tenascin-C immunoreactivity is absent from the region of the horizontal myoseptum (arrows) and reduced in vertical myosepta (asterisks) in these embryos. J-L: In a sty mutant, axons stall at the horizontal myoseptum (arrow in J) but tenascin-C immunoreactivity around the horizontal myoseptum (arrow in K) and in vertical myosepta (asterisk in K) is indistinguishable from wild-types. In the image stack in K, the upper surface of the notochord (arrowhead) is included because the embryo is slightly tilted. Scale bar = 50 μm in L (applies to A-L).