Towards a Rational Terminology for Cell Types

Cell types are fundamental biological units and partially independent evolutionary units, shaped by individualised gene regulatory networks and developmental lineages. Despite the recent explosion in single-cell sequencing and increased attention on cell characterization, we still lack a unified and consistent naming system for cell types that works across species. Since cell types are the products of evolutionary diversification, we propose that cell-type names should explicitly reflect evolutionary history, and suggest a naming system with a phylogenetic representation prefix as a simple, informative and intuitive way to do this. The key to this is establishing the evolutionary/taxonomic level of comparison, coupled with understanding homology and innovation in cell-type evolution. Put simply, it can apply to both individual cell types and their clades. We illustrate this approach using two case studies: chordate macroglia and more explicitly on vertebrate photoreceptors. The long-term goal is to stimulate progress towards a more coherent and informative language for cell-type identity and comparative analyses that is evolutionarily extendable as single-cell research proliferates across the tree of life.