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Our goal this summer was to build a toolkit for the nematode Caenorhabditis elegans to facilitate its future use as a synthetic biology chassis. Our focus was on finding and selecting viable promoters, protein domains, and other key components for use by future teams.

The motivation for our project is simple enough: to date, there has been little interest in using complex eukaryotic and multicellular organisms in iGEM, and we feel that the advantages of multicellular organisms outweigh the challenges involved in working with them. With the benefit of the documentation and components we hope that most of these issues.

The jump from working with E. coli to C. elegans not an insurmountable one; the worm has a short generation time, is grown at room temperature on agar plates, can be frozen, and it can be transformed using standard BioBrick plasmids assembled in E. coli.

Through WormGuide, future teams will be able to easily and quickly learn all about the worm and the possibilities that it holds. The parts that we have submitted will then provide them with a solid base from which they can build their projects.

The benefits of working in a complicated organism like C. elegans are significant. It has been extensively studied as a model organism for developmental biology and was the first multicellular organism sequenced. As such, the worm represents one of the best and most accessible opportunities for iGEM-style synthetic biology to make inroads into higher forms of life.

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.

Footnotes and Citations

1: Nagel G et al., 2003 Channelrhodopsin-2, a directly light-gated cation-selective membrane channel. PNAS 100(24). doi:10.1073/pnas.1936192100

2: Han X, Boyden ES, 2007 Multiple-Color Optical Activation, Silencing, and Desynchronization of Neural Activity, with Single-Spike Temporal Resolution. PLoS ONE 2(3): e299. doi:10.1371/journal.pone.0000299