Fig. S6

Isl1 mutants and morphants form secondary sprouts but they do not turn to form a parachordal chain. (A-H) Lateral views of 48 hpf isl1^+/?; fli1a:egfp^y1 or isl1^-/-; fli1a:egfp^y1 embryos injected with plcg1 morpholino and stained with znp-1 antibody. Confocal projections. (D,H) Volume renderings of a single hemisegment, transverse view. (A-D) In plcg1 morpholino-injected isl1^+/? sibs, motoneuron axons form (A), secondary sprouts grow from the posterior cardinal vein (PCV) (B) and turn at the HMS (filled star, D) to form the PAC (parachordal chain, solid yellow arrowheads, B). (E-H) In plcg1 morpholino-injected isl1^-/- mutants, secondary sprouts form and extend dorsally (F) but fail to turn (star, H) and form the PAC (arrowheads, F). (I) Quantitation of PAC formation in 4-5 somites per embryo of plcg1 morpholino-injected isl1 mutants and siblings. plcg1/isl1^+/?: complete, 60±16%; partial, 15±8%; absent, 25±13%. plcg1/isl1^-/-: complete, 25±15%; partial, 42±4%; absent, 71±14%. (J-L) Lateral views of 48 hpf fli1a:egfp^y1 embryos injected with isl1 morpholino and stained with znp-1 antibody. Confocal projections. In isl1 morphants, motoneuron axons form (J) and the PAC does not form (arrowheads, K). (M) Quantitation of PAC formation in 4-5 somites per embryo. Uninjected control embryos: complete, 91±4%; partial, 9±4%; absent, 0±0%. isl1 morphants: complete, 26±6%; partial, 32±8%; absent, 42±10%. All values are mean±s.e.m.; P-values by Mann-Whitney U test. n, number of hemisegments (number of embryos). A, anterior; D, dorsal; L, lateral. Scale bars: 50 μm.