Enhancer identification through comparative genomics.

With the availability of genomic sequence from numerous vertebrates, a paradigm shift has occurred in the identification of distant-acting gene regulatory elements. In contrast to traditional gene-centric studies in which investigators randomly scanned genomic fragments that flank genes of interest in functional assays, the modern approach begins electronically with publicly available comparative sequence datasets that provide investigators with prioritized lists of putative functional sequences based on their evolutionary conservation. However, although a large number of tools and resources are now available, application of comparative genomic approaches remains far from trivial. In particular, it requires users to dynamically consider the species and methods for comparison depending on the specific biological question under investigation. While there is currently no single general rule to this end, it is clear that when applied appropriately, comparative genomic approaches exponentially increase our power in generating biological hypotheses for subsequent experimental testing. It is anticipated that cardiac-related genes and the identification of their distant-acting transcriptional enhancers are particularly poised to benefit from these modern capabilities.