R.C. elegans

One diagnostic tool which has received a lot of attention recently are the channelrhodopsins, which were isolated from the green algae Chlamydomonas reinhardtii, and serve as light-activated nonspecific cation channels which can cause nerve cells to depolarise in response to certain wavelengths of light. These have been used extensively in research biology to interrogate the roles of the neurons in C. elegans and other species, allowing researchers to, for example, cause nematodes to contract all of their muscles at once and seize up in response to specific wavelengths of light.¹

Acting as counterpart to the channelrhodopsins is a channel called halorhodopsin, isolated from halophilic archaeans, which causes the cell to uptake chloride anions, and thus can be used to hyperpolarise a neuron and prevent it from firing. Importantly, the halorhodopsin excitation frequency is well-separated from the excitation frequency of channelrhodopsin-2, and so they can be used in the same organism, or even the same cell, without significant cross-talk.

By combining these proteins in a single transgenic organism, behind specifically-chosen promoters which target only certain neurons, we hope to make a "remote control" worm, which can be instructed to move either forward or backward by exposing it to the appropriate wavelengths of light.