Fig. 1.

Sox9b is expressed in the zebrafish larval heart. Wild-type AB zebrafish carrying sox9b:EGFP were collected at the indicated times for either in situ hybridization with a sox9b probe (A and B) or confocal microscopy (C and D). Lateral views are shown in all images, with head extending leftward, and the yolk sac to the right, with n = 6 fish examined per group. For the in situ images, the arrowheads point to the heart. For the confocal images, the white outline indicates the border of the atrium, indicated as A; the ventricle is indicated as V. The sox9b-GFP signal is shown in green. Blue indicates immunostaining for activated leukocyte cell adhesion molecule (ALCAM).