Function (biology)

Cell type

Caenorhabditis elegans

Neuron

Homeobox

Cell

Neuroscience

Biology

Gene

Gene expression

Homeobox A1

EMX2

Computational biology

Homeobox protein Nkx-2.5

Genetics

Nature

It is not known at present&nbsp;whether neuronal cell-type diversity—defined by cell-type-specific anatomical, biophysical, functional and molecular signatures—can be reduced to relatively simple molecular descriptors of neuronal identity1. Here we show, through examination of the expression of all of the conserved homeodomain proteins encoded by the Caenorhabditis elegans genome2, that the complete set of 118&nbsp;neuron classes of C.&nbsp;elegans can be described individually by unique combinations of the expression of homeodomain proteins, thereby providing—to our knowledge—the simplest currently known descriptor of neuronal diversity. Computational and genetic loss-of-function analyses corroborate the&nbsp;notion that homeodomain proteins not only provide unique descriptors of neuron type, but also have a critical role in specifying neuronal identity. We speculate that the pervasive use of homeobox genes in defining unique neuronal identities reflects the evolutionary history of neuronal cell-type specification. Each one of the complete set of 118&nbsp;neuron classes in Caenorhabditis elegans can be specified individually by the expression of unique combinations of&nbsp;homeodomain proteins.

Unique homeobox codes delineate all the neuron classes of C. elegans