Fig. 3.

A non-coding enhancer sequence recapitulates endogenous MSX2A expression patterns in developing spines and fins. a GFP expression in a 26-day-old transgenic stickleback larva driven by the stickleback MSX2A-CNE enhancer and zebrafish hsp70 promoter. Structures showing expression include dorsal spines, pectoral and median fin rays, cloaca, anal spine, pelvic spines, median fin fold, jaws, teeth, nostrils, eye, and lateral line neuromasts. Eye (lens) expression is a regular background pattern of the hsp70 promoter. The image is horizontally reversed from the original. b RNA in situ hybridization in a 20-day-old marine stickleback larva, showing labeling in presumptive dorsal spines forming within the fin fold, as well as pelvis, cloaca, nostrils, gills, median fins, and pectoral fins. c, d Closer view of dorsal spines in the GFP and in situ larvae. In both the GFP transgenics and the in situ larvae, expression in spines is stronger near the distal ends. GFP fluorescence is strong in the fin fold surrounding the dorsal spines, with lighter signal in the spines themselves. In the GFP panel, the pectoral fin and three of the neuromasts (*) are also indicated. C cloaca, DS dorsal spines, GFP green fluorescent protein, PF pectoral fin, PS pelvic spine