Figure 6.

In situ hybridization (ISH) illustrates that Bmp6 expression shifts mirror enhancer activity differences in marine and freshwater backgrounds. ISH of Bmp6 expression on thin sections of marine (left column) and freshwater (right column) fish suggest that marine fish exhibit expanded mesenchymal expression at early and late bell stages (white arrowheads in middle and bottom rows, respectively), while freshwater fish exhibit relatively broader expression in the inner dental epithelium of late bell stage teeth (black arrowheads in bottom row). No expression domain differences were observed in cap stage tooth germs (top row). Marine and freshwater strains are derived from population in Rabbit Slough, AK, USA (RABS), and Paxton Lake, BC, Canada (PAXB), respectively. Black dotted lines demarcate the basalmost layer of epithelium, adjacent to the basement membrane, which includes the inner and outer dental epithelium. See Supplementary Figure S6 for DAPI counterstains and ISH images without markup. Scale bar=20 µm and applies to all panels. n=6 fish per population, >10 teeth per fish.