Fig. 5. Activin signaling pathway components have similar expression and mutant phenotypes. (A,B) babo mRNA is enriched in the VNC and brain in stage 13 (A, lateral view), and stage 15 (B, ventral view) embryos. (C) Incidence of total pathfinding defects in babo, put and Smad2 mutants, as compared with daw^- and Oregon R. MN refers to maternal/zygotic nulls. Hemisegments scored: babo³²/babo³² n=187/120, babo MN n=211/116, put⁸⁸/put⁸⁸ n=208/174, Smad2³⁸⁸/Y n=137/138. (D-F) ISNb and (G-I) SNa guidance defects. Motoneuron projections in late stage 16/17 filleted embryos stained with 1D4. Arrowheads in D-G indicate stalled axons. Arrow in D marks ISNb axons that extend to muscle 12 but fail to form a synapse. In G-I, arrows indicate defasciculation failures and loss of SNa branches.