F-Spondin Expression in Zebrafish Figure 11. Spon1b expression in peripheral tissues of Tg(spon1b:GFP). A. Spon1b expression in pharyngeal teeth of zebrafish larvae at 3dpf (arrow). Asterisk: eye. B-C. Pharyngeal teeth in adult zebrafish with spon1b:GFP expressed in newly developing teeth. Asterisk: old mineralized teeth. Green signal: spon1b-positive soft tissue. In C, soft tissue is moved off the hard tissue. D. Spon1b:GFP positive enteric neurons in intestine of developing larva, 72hpf (sagittal view of live specimen). E. Spon1b:GFP positive enteric neurons in adult zebrafish (confocal z-stack). F-H. Progression of spon1b expression in larval tail. Expression in larval fin rays at 5 dpf (F). Development of the adult tail primordium (arrow) by 8 dpf (G). Subsequent splitting into 2 domains (arrows in H, 15 dpf) that will give rise to the two adult caudal fin lobes. I. Spon1b expression in the endoskeleton of the adult zebrafish caudal fin. Note spon1b-positive axons of the motor neurons traversing the trunk and musculature (arrow). J. Dissected endoskeleton in (I), showing a thin sheet of spon1b-positive tissue covering the bone. K. Spon1b signal at the distal end of the growing adult tail 4 days post caudal fin amputation. Blue line shows the level of amputation and yellow line marks a growing lepidotrichium. L. High magnification image of region in (K) showing the two spon1b-positive domains of blastema, patterning each growing lepidotrichium (yellow line). White line: distal edge of regenerating caudal fin. Scale bars: 20 mm. doi:10.1371/journal.pone.0037593.g011 PLoS ONE | www.plosone.org 16 June 2012 | Volume 7 | Issue 6 | e37593