The Story of C. Elegans
If you have read Dr. Seung’s book – “The Connectome: How the Brain’s Wiring Makes Us Who We Are”, you probably know that our story begins with a little worm – C. Elegans. It was the first organism to have its connectome mapped. Mapping the connectome of this simple worm was, understandably, a much less daunting task than mapping the connectome of human. This hermaphrodite creature is much simpler than we are and was the starting point for much of neuroscience research!
Why would we start with a worm? Imagine playing EyeWire for C. Elegans. The worm is much smaller than the human brain so our goal of “mapping the brain” would be a considerably easier – or at least faster – achievement. We also have to consider that these worms are less biologically complex than we are. They have one linear body with no legs or arms, so they don’t need to have neuronal activity to account for limb movement; their digestive systems is considerably simpler than ours … the list could go on for hours!
Let’s say that you are an ambitious five year old who terribly wishes to be an architect. Unfortunately for you, building a massive structure like the Empire State Building is a bit hard for a five year old – it would take a long time and lots of help to be able to construct it for a person of any age! In order to assuage your architectural fever, you might get Lego blocks to practice with. Perhaps you build a miniature version of the Empire State Building. It would certainly give you the confidence and practice to create the larger one in the future.
Let’s introduce our worm slightly more formally: it is called Caenorhabditis elegans which is its binomial naming classification, just as we are Homo Sapiens. Binomial naming classifies by genus and species and it is obvious that we do not share either with C. Elegans. “Elegans” is actually Latin for elegant – in kind of an obvious way it looks a bit like a ribbon. I’m not sure what people would describe humans as but … probably not elegant from first look! If an alien came down to observe us we would most likely get a Latin phrase for “gangly” or “clumsy”. Although they are elegant, their senses are limited to to taste, smell, and light sensitivity. The worms are ideal for lab research because they are easily adaptable to any new environments that provide them with bacterial food.
C. Elegans makes for a very good lego block in neuroscience. It about 1 mm in diameter and transparent which makes it easy to image. C. Elegans also has a constant amount of cells which allows for mutations to be easily tracked. The first claim to fame that CE had was that it was the first creature to have it’s entire genome sequenced. About 50 years ago there was a massive development in science – the discovery of the molecular structure of DNA by Watson and Crick who won a Nobel Prize. This breakthrough led to a mini-science revolution of organizing specific organism’s DNA structures – their genomes. The word connectome is a play on genome. DNA (so, genes) creates a systems of information that we named the genome. Similarly, neurons (which are the basis for neuronal connections) creates the connectome. It seems natural then that the C. Elegans was the starting point for the connectome too! And especially helpful because we had worked so hard on mapping its biological information beforehand.
In fact, a quick Google search reveals that there’s an entire database to organize information about the worm. It all started in the 70s when biologist and Nobel Prize winning scientist Sydney Brenner started to map the connectome of C. Elegans. The method was similar to how we are mapping the human brain – using electron microscopy and drafting a diagram. With C. Elegan’s 302 neurons this was possible, much like the miniature Empire State Building. The human brain , though, has 100 billion neurons – around 300 million times as many. It could take quite some time to map! Thankfully, that’s what citizen scientists are for.