Logically defining Neurons in the Cell Ontology

The Cell Ontology (CL) is a candidate OBO Foundry ontology for the representation of cell types and is under revision to better represent neuronal cell types. As the CL grows in complexity, logical definitions are used to ensure neuron types are mutually independent from each other. For successful implementation of logical definitions, the differentiae used by a biologist to distinguish a neuron from other cell-types must be established. At a recent joint CL-INCF workshop*, ontology editors and neurobiologists discussed the differentiae that are necessary and sufficient to distinguish a neuron. The concept of a “neuron” was found to have different meanings among neurobiologists, with a hierarchy established for three definitions of “neuron” that are increasingly stringent in the number of cell types they include. The most permissive neuron type includes cell types that detect stimulus involved in sensory perception (“olfactory receptor cell’) while the most conservative neuron cell-type only includes those cells that carry out voltage-dependent release of cell signaling molecules and have the ability to maintain a voltage gradient or propagate an action potential along a cell process. With either a permissive or stringent definition of neuron, there was an agreed upon set of necessary and sufficient differentiae to define sub-types of neurons.  These differentiae fall along axes of anatomy, cell morphology, neurotransmitter release, electrophysiology, developmental lineage, and the biological processes a neuron type participates in.  We are currently in the process of generating logical definitions for retinal neurons based on these differentiae and will use this as a model for how we define all neuron types in the CL. (Work supported by INCF and an ARRA administrative supplement grant HG002273-09Z to the parent grant, HG002273).

* Participants of the Cell Ontology-INCF Neuron Workshop, Atlanta, GA (April, 2011)