Enhancers, development, and evolution.

A single-celled fertilized egg develops into a complex, multicellular animal through a series of selection processes of developmental pathways. During these processes, regulatory genes exhibit spatiotemporally restricted expression under the control of the species-specific genetic program, and dictate developmental processes from germ layer formation to cellular differentiation. Elucidation of molecular mechanisms underlying developmental processes and also of mechanistic bases for morphological diversification during evolution is one of the central issues in contemporary developmental biology. Progress has been made due to recent technological innovations, such as high-throughput nucleotide sequencing, live-cell imaging, efficient genetic manipulation, and establishment of the organoid system, opening new avenues to the above issues.