This Essay explores the notion that specialized cells have unique vulnerabilities to environmental contingencies that microRNAs help to counteract. Given the ease with which new microRNAs evolve, they may serve as ideal facilitators for the emergence of new cell types.
Neuroscience Research Institute, Department of Molecular Cellular Developmental Biology, University of California, Santa Barbara, Santa Barbara, CA 93106, USA. kenneth.kosik@lifesci.ucsb.edu
