Identification of thermosensory and olfactory neuron-specific genes via expression profiling of single neuron types.

Most C. elegans sensory neuron types consist of a single bilateral pair of neurons, and respond to a unique set of sensory stimuli. Although genes required for the development and function of individual sensory neuron types have been identified in forward genetic screens, these approaches are unlikely to identify genes that when mutated result in subtle or pleiotropic phenotypes. Here, we describe a complementary approach to identify sensory neuron type-specific genes via microarray analysis using RNA from sorted AWB olfactory and AFD thermosensory neurons. The expression patterns of subsets of these genes were further verified in vivo. Genes identified by this analysis encode 7-transmembrane receptors, kinases, and nuclear factors including dac-1, which encodes a homolog of the highly conserved Dachshund protein. dac-1 is expressed in a subset of sensory neurons including the AFD neurons and is regulated by the TTX-1 OTX homeodomain protein. On thermal gradients, dac-1 mutants fail to suppress a cryophilic drive but continue to track isotherms at the cultivation temperature, representing the first genetic separation of these AFD-mediated behaviors. Expression profiling of single neuron types provides a rapid, powerful, and unbiased method for identifying neuron-specific genes whose functions can then be investigated in vivo.