This caused the tail region to relax and lose its curvature.

A second more telling experiment used the genetically encoded calcium reporter GCaMP3 to show that the body wall muscles are more active on the inside of the curve than on the outside of the curve. They then did something rather clever. They used a pneumatic microfluidic device to change the curvature of the trapped worm and examine what happens to more posterior segments. Rapidly changing the channel curvature from a dorsal to ventral bias, or vice versa, resulted in a corresponding change in the curvature of the posterior body ( Figure 1B). From these experiments, they concluded that the body of the worm senses curvature and is able to relay this information to more posterior segments, which then follow suit. What is the cellular mechanism that allows worms to sense body curvature and propagate the bending movement to more posterior segments? Doxorubicin manufacturer Could the body wall muscles themselves propagate this proprioceptive signal,

given that they are coupled by gap junctions? A combination of classical genetics and optogenetic manipulation was employed to rule this possibility out. Mutant worms that lack functional gap junctions between muscle cells were still able to sense and propagate bending. There Cytoskeletal Signaling inhibitor was also no change in the curvature of the posterior body when muscles located within the channel were hyperpolarized with NpHR, nor did localized channelrhodopsin-induced contraction of these muscles cause the flanking body segments to bend either ventrally or dorsally. This makes it highly unlikely that the

muscle cells themselves signal stretch or curvature to each other. What about motor neurons, as these cells have elongated cellular processes that could potentially function as a stretch organ? Not surprisingly, expression of NpHR in all cholinergic neurons (A- and B-type) abolished the bending of the body, while mutations that alter the dorsal B-type motor neurons caused the ventral bias in the bending. Most tellingly, inactivation of B-type motor neurons as opposed to A-type or D-type motor neurons disrupted the correlation between the curvature of the trapped region and more posterior segments, indicating that the worms can no longer sense curvature. Montelukast Sodium Using calcium imaging, they observed a very close correlation between bending and the activation of the B-type motor neurons. The evidence, while largely correlative, clearly points to B-type motor neurons being the cellular substrate for this proprioceptive signal. A number of questions still remain. Is the proprioceptive signal transferred directly from motor neuron to motor neuron? One way of testing this might be to inactivate or ablate a single B-type motor neuron in the chain and ask if posterior propagation of the signal is disrupted.