Project description:Snakes possess a unique sensory system for detecting infrared radiation, enabling them to generate a ‘thermal image’ of predators or prey. Infrared signals are initially received by the pit organ, a highly specialized facial structure that is innervated by nerve fibers of the somatosensory system. How this organ detects and transduces infrared signals into nerve impulses is not known. Here we use an unbiased transcriptional profiling approach to identify TRPA1 as the infrared receptor on sensory neurons that innervate the pit organ. TRPA1 from pit bearing snakes (rattlesnakes and pythons) are the most heat sensitive vertebrate ion channels thus far identified, consistent with their role as primary transducers of infrared stimuli in these animals. Thus, snakes detect infrared signals through a mechanism involving radiant heating of the pit organ, rather than photochemical transduction. These findings illustrate the broad evolutionary tuning of TRP channels as thermosensors in the vertebrate nervous system.
Project description:Snakes possess a unique sensory system for detecting infrared radiation, enabling them to generate a ‘thermal image’ of predators or prey. Infrared signals are initially received by the pit organ, a highly specialized facial structure that is innervated by nerve fibers of the somatosensory system. How this organ detects and transduces infrared signals into nerve impulses is not known. Here we use an unbiased transcriptional profiling approach to identify TRPA1 as the infrared receptor on sensory neurons that innervate the pit organ. TRPA1 from pit bearing snakes (rattlesnakes and pythons) are the most heat sensitive vertebrate ion channels thus far identified, consistent with their role as primary transducers of infrared stimuli in these animals. Thus, snakes detect infrared signals through a mechanism involving radiant heating of the pit organ, rather than photochemical transduction. These findings illustrate the broad evolutionary tuning of TRP channels as thermosensors in the vertebrate nervous system. Gene expression measurements implicate TRPA1 as the heat-sensitive channel in diverse pit snakes
Project description:Vampire bats and snakes have taken thermosensation to the extreme by developing specialized systems for detecting infrared radiation. As such, these creatures provide a window into the molecular and genetic mechanisms underlying evolutionary tuning of thermoreceptors in a species or cell type specific manner. In each case, robust thermal sensitivity likely reflects specialized anatomical features of infrared sensing pit organs, as well as intrinsic heat sensitivity of trigeminal nerve fibers that innervate these structures. Here we show that vampire bats use a molecular strategy involving alternative splicing of the TRPV1 gene to generate a channel specifically within trigeminal ganglia that has a reduced thermal activation threshold. Selective expression of splicing factors in trigeminal, but not dorsal root ganglia, together with unique organization of the vampire bat TRPV1 gene underlies this mechanism of sensory adaptation. Comparative genomic analysis of the TRPV1 locus supports phylogenetic relationships within the proposed Pegasoferae clade of mammals. Gene expression measurements implicate a TRPV1 splice isoform as the heat-sensitive channel in vampire bats