Specification of thermosensory neuron fate in C-elegans requires ttx-1, a homolog of otd/Otx

Temperature is a critical modulator of animal metabolism and behavior, yet the mechanisms underlying the development and function of thermosensory neu rons are poorly understood. C. elegans senses temperature using the AFD the rmosensory neurons. Mutations in the gene ttx-1 affect AFD neuron function. Here, we show that ttx-1 regulates all differentiated characteristics of t he AFD neurons. ttx-1 mutants are defective in a thermotactic behavior and exhibit deregulated thermosensory inputs into a neuroendocrine signaling pa thway. ttx-1 encodes a member of the conserved OTD/ OTX homeodomain protein family and is expressed in the AFD neurons. Misexpression of ttx-1 convert s other sensory neurons to an AFD-like fate. Our results extend a previousl y noted conservation of developmental mechanisms between the thermosensory circuit in C. elegans and the vertebrate photosensory circuit, suggesting a n evolutionary link between thermosensation and phototransduction.