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Fig. 3
Mypt1 is required in the environment to restrict excessive axon branching.
(A, B) SV2 antibody labeling at 25 hpf reveals disorganized motor axon morphologies in mypt1p82emcf mutants (B) compared to wildtype siblings (A). Unlike wildtype CaP motoneurons (C), individually labeled mutant motor axons (using mnx1:mKate) project with frequent changes in projection direction (dots), and exhibit excessive branching (arrowheads). The gray dashed line marks the border of the spinal cord. (E, F) Transplantation of rhodamine-dextran labeled wildtype blastula stage cells into mypt1 mutants analyzed at 26–27 hpf exhibit mutant motor axon phenotypes (E). Conversely, transplantation of mutant motoneurons into a wildtype host results in wildtype-like motor axon projections (F).