The evolutionary origin of developmental enhancers in vertebrates: Insights from non-model species.

How random DNA mutations have established the diverse morphology of extant vertebrates is one of the major challenges in evolutionary biology. Thanks to the recent advancement in DNA sequencing technologies, the genome sequences of many non-model species have been determined, which allows us to address previously inaccessible questions about gene regulatory evolution in vertebrates. In particular, the genome sequences of non-teleost ray-finned fishes and cartilaginous fishes offer clues about when and how vertebrates gained developmental enhancers related to morphological traits that were required for the water-to-land transition. In this review, I examine the evolutionary origin of conserved non-coding elements (CNEs), which often function as tissue-specific developmental enhancers, and discuss how CNEs are related to gene regulatory changes that caused the major morphological transitions of vertebrates.