To confirm that candidate enhancers can drive tissue-specific gene expression in vivo, five evolutionarily conserved CAGE-defined human enhancers (including the POU3F2 and MEF2C-proximal enhancers identified above) were tested via Tol2-mediated transgenesis in zebrafish embryos. We observed tissue-specific enhancer activity with 3 of 5 fragments, which corresponded to the human enhancer tissue expression (Fig. 4). None of three control fragments without CAGE signal activated the gata2 promoter (Supplementary Table 9). While the sample size is not high enough to reliably estimate the validation rates in zebrafish, the correlation between the enhancer usage profiles in zebrafish to those defined in human by CAGE is notable.
