Developmental pattern formation: insights from physics and biology.

The spatial organization of cell fates during development involves the interpretation of morphogen gradients by cellular signaling cascades and transcriptional networks. Recent studies use biophysical models, genetics, and quantitative imaging to unravel how tissue-level morphogen behavior arises from subcellular events. Moreover, data from several systems show that morphogen gradients, downstream signaling, and the activity of cell-intrinsic transcriptional networks change dynamically during pattern formation. Studies from Drosophila and now also vertebrates suggest that transcriptional network dynamics are central to the generation of gene expression patterns. Together, this leads to the view that pattern formation is an emergent behavior that results from the coordination of events occurring across molecular, cellular, and tissue scales. The development of novel approaches to study this complex process remains a challenge.