Get out that disco ball—it seems mutant worms have some brand new moves to show us. New research, led by Kenneth Miller (Oklahoma Medical Research Foundation, Oklahoma City), looked at phototaxia in Caenorhabditis elegans, which lack eyes as well as any of the proteins known to transduce light signals. The group used C. elegans mutants engineered to lack the synaptic signaling molecules cyclic adenosine monophosphate (cAMP) and diacylglycerol (DAG), resulting in paralysis and lack of response to harsh physical stimuli.

When they exposed these paralyzed C. elegans mutants to ultraviolet (UV) light, they observed a strong locomotive response (PLoS Biol. 6, e198; 2008). In fact, UV light rescued the paralysis and restored locomotion to normal levels. The UV response had not been noted previously, despite decades of research using the nematodes, because wild-type C. elegans can move freely. Miller and colleagues then traced the locomotion response to a new UV-sensitive light receptor that they called LITE-1. “This sensor doesn't resemble any other light sensors previously discovered,” noted Miller.

The scientists then expressed the sensor in muscle cells that are not normally responsive to light. LITE-1 expression in these cells resulted in light sensitivity. They also found that exposing only the tails of the mutant worms to UV light rescued the paralysis as effectively as did whole-body exposure. In addition, they observed that the light-driven locomotion is directionally oriented toward the UV light.

Miller's group believes that the UV-induced phototaxia is consistent with recent indications that C. elegans may spend substantial amounts of time above ground, despite previous notions that the species was primarily subterranean. If they do remain above ground for any length of time, they would require a sensory mechanism for detecting and avoiding harmful exposure to sunlight.

LITE-1 is not found in humans, but research into its mode of function may shed light on the molecular mechanisms of neuronal communication, which underlies perception, behavior, learning and memory in humans and other organisms. “It gives us a tool that we can use to solve the mysteries of nerve cell communication and could ultimately help us understand the biology of everything from sleep and memory to depression,” said Miller. But there is much work to be done before this discovery could lead to treatments for any human disorders.