The environment has a profound impact on animal behavior. The ability to sense environmental cues and to adjust behavior in response is essential for an animal’s life. Molecular sensors are a central player in sensory perception. These sensory receptors, which are expressed in sensory neurons/cells, detect sensory inputs and transduce them into electrical and/or chemical outputs to trigger behavioral responses. In some cases, sensory receptors are also ion channels (ionotropic) that are directly activated by sensory stimuli, leading to the excitation of sensory neurons/cells. In many other cases, sensory receptors are metabotropic and require downstream signaling molecules to transduce sensory signals. Identifying sensory receptors/channels and understanding how they detect and transduce sensory information represent a major task in sensory biology research.
C. elegans worms are a powerful genetic model for the study of various questions in neuroscience, particularly sensory neuroscience. To survive their harsh environment, worms have evolved complex sensory systems to sense and react to sensory cues, such as temperature, touch and chemicals. Recent work has greatly expanded the repertoire of sensory modalities in C. elegans. For example, we demonstrated that, despite the lack of eyes, worms can sense light and engage in phototaxis behavior mediated by photoreceptor neurons, enabling them to avoid lethal doses of ultraviolet light. We also showed that worms possess the sense of proprioception mediated by stretch-sensitive proprioceptor neurons, which allows these animals to control body posture during locomotion. Apparently, worms have evolved most, if not all, of the sensory modalities found in mammals. Importantly, the genes encoding sensory receptors and channels in worms, which detect sensory stimuli, tend to be evolutionarily conserved in other species. This, together with its short generation time (~3 days) and facile genetic tools, makes C. elegans an excellent model system for identifying novel sensory receptors/channels and signal transduction mechanisms.
Over the years, we have identified and characterized a number of sensory receptors/channels, including, among others, a mechanosensitive channel (TRP-4/TRPN1), an alkali-sensing receptor (TMC-1) and a cold-sensing receptor (GLR-3/GluK2). We have also demonstrated that the taste receptor homolog LITE-1 is a bona fide light receptor with an exceptionally high efficiency in photon capturing. Current work involves identifying novel types of sensory receptors/channels through genetic screens in C. elegans, and investigating how these sensory receptors/channels detect and transduce different sensory cues to generate behavioral outputs. Because many of these sensory receptors/channels are evolutionarily conserved, we also explore their roles in somatosensation and pain sensation in mammals using mouse models.