Recent work suggests that microRNAs might have been important in the evolution of complexity in multicellular animals. Here it is shown that the most ancient known microRNA, miR–100, was initially active in neurosecretory cells around the mouth. Other highly conserved varieties were first present in specific tissues and organ systems. Thus, microRNA expression was initially restricted to an ancient set of ancient animal cell types and tissues.
- Foteini Christodoulou
- Florian Raible
- Detlev Arendt
