Fig. 1

(A) Transmitted DIC image (top) and confocal image (bottom) of a 5 dpf Tg(gata3:loxP-dsRed-loxP:GFP) animal. Scale bars = 0.5 mm. (B) Lateral view of a midbody spinal cord hemisegment; dashed lines mark muscle segments. In this and all subsequent figures, rostral is to the left and dorsal is to the top. Purple triangles mark CSF-cN neurons and orange stars mark ISN. Scale bar = 20 μm. (C) V2b cell counts per hemisegment quantified along the rostrocaudal body axis, n = 7 fish from three clutches. (D) Example cell morphology using two techniques to label single V2b axons: single-cell dye electroporation (top) and Kaede photoconversion (bottom). Scale bar = 20 μm. (E) Midbody V2b neurons extend axons through more segments than V2b neurons in other rostrocaudal locations. *p<0.01 (p=3.17×10⁻³); **p<0.001 (p=4.44×10⁻⁴). (F) Ball and stick plots indicate soma position and axon extension along the body axis for 35 V2b neurons in 12 animals from two clutches.