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Fig. 6
Axons of isl2b+ Rohon-Beard project onto dorsalmost chx10+ V2a interneurons in the spinal cord.
(A) Z-projection stack of the spinal cord imaged from the lateral side in a 4 dpf Tg(isl2b:gal4,cmcl2:eGFP;UAS:GFP-aequorin;chx10:DsRed) triple transgenic larva. White dashed lines delineate ventral and dorsal limits of the spinal cord; these limits define the dorso-ventral (D/V) axis from 0 to 1. The axon bundle from isl2b+ Dorsal Root Ganglia (DRG) and Rohon-Beard (RB) neurons contact the soma of dorsal chx10+ V2a interneurons. The white square is enlarged in the right panel to stress the anatomical connections (arrow). (B) Dendrites of dorsal V2a interneurons are targeted by axonal processes from isl2b+ sensory neurons (arrows). (C) D/V positions of V2a neurons receiving putative inputs from isl2b+ cells (mean D/V position = 0.72 ± 0.04. N = 12 cells in n = 4 larvae). (D) Profile of expression of 4 dpf Tg(isl2b:gal4,cmcl2:eGFP;chx10:DsRed) injected with the Tg(UAS:CoChR-tdTomato) construct reveals projections from single Rohon Beard cells onto chx10+ dorsal V2a interneurons. Scale bars in (A) and (D) are 50 µm and is 10 µm in (B). For each panel rostral side (R) is on the left and ventral side (V) is at the bottom.