Supplemental Figure 1
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Fig. S1. Mutations
in fra, Abl, trio, ena and
the Netrins affect the
organization of longitudinal axon pathways. A subset of longitudinally
projecting axons in stage 17 embryos was labeled with mAb 1D4 (anti-Fas2).
Genotypes are indicated. (A) In wild-type embryos, axons course in three
distinct bundles on either side of the CNS midline. (B-N) In mutant embryos,
two distinct phenotypes were observed, breaks in longitudinal pathways in which
longitudinal fascicles were discontinuous between segments, and fascicle
fusions in which two or more fascicles merged. Small arrows in B, D and H
indicate mild breaks in which only the lateral pathway is discontinuous. Large
arrows in K and N indicate severe breaks in which none of the three
longitudinal pathways projects into the next segment. Small arrowheads in G, I
and L indicate mild fusions in which two fascicles have collapsed onto each
other. Large arrowheads in J and N indicate severe fusions in which it appears
that most longitudinal axons are present, but individual fascicles are
indistinguishable. Severe breaks in all three fascicles were rarely observed,
even in trio,Abl mutants. Severe
fusions were observed most frequently in fra;Abl, fra;trio and trio,Abl double mutants.
