Author: Garrett Jones
C. elegans is a great model organism for neural processes for a couple reasons. C. elegans (in its hermaphroditic stage) has a total of 959 cells and will have no more than 959 cells. This is a great quality because as a scientist you have consistency among the organism being studied. Also, C. elegans has about 302 neurons and 8,000 synaptic connections. Now you might think this is a lot to focus on when studying the functions of neurons, but compared to the 80 – 100 billion neurons and 100 trillion synaptic connections in humans, C. elegans has a very small amount of neural circuitry. This is excellent because C. elegans exhibits the same 3 behaviors all organisms exhibit, so if these behaviors are related to neural circuitry it will be easier to observe a correlation between the two with fewer neurons to look at.
Even though C. elegans has a small neural circuit, it still has the same basic functions that the neural circuit has in any organism. These three functions are finding food (sensory), evading threats, and reproduction. Without these three vital functions organisms would die and its lineage would not be carried on. These functions can be traced to certain nerve cells and when obliterated by laser oblation the nerve cells cease to function. By doing this the function of specific nerve cells can be determined and mapped out.
Dr. Cornelia Bargmann identified that soil dwelling C. elegans can smell strong odors by ablating neurons until the organism could no long detect pungent odors. She identified a specific receptor molecule (odr-10) in a pair of olfactory neurons that can detect diacetyl, a chemical released from decaying food. C. elegans can use this diacetyl gradient released by decaying food to locate it for consumption.
While feeding, C. elegans either behave on their own, or in clumps/groups as foragers. The behavioral feeding is specific to each organism and is consistent for the duration of its life. Dr. Bargmann’s lab discovered that solitary foragers could be transformed into group foragers by inserting a gene (npr-1) into the organism’s genome. Npr-1 can be compared to neuropeptide Y in other animal systems. Neuropeptide Y regulates food consumption, mood, and anxiety. From this Dr. Bargmann concluded that the behavior could be altered by altering the genome of C. elegans.
Dr. Bargmann’s lab isolated a gene from C. elegans that effects the function of several neurons. This gene was later named nematocin because of its functional similarities to oxytocin and vasopressin. Normally C. elegans must complete behavioral steps to successfully mate. The steps are searching for a mate, contact, reverse turns, producing the vulva, insertion of the spicule, and transfer of sperm. Dr. Bergmann and her team realized that if C. elegans does not have the nematocin gene active all of the steps still occur. However, the steps do not occur at the correct time or order for fertilization to occur.
These are just a few examples of how the animal nervous system can translate sensory information into fundamental behaviors. This research is so important because it is linking biochemicals, neurons, and receptors in C. elegans to functional behaviors the organism has. If this can be linked in one organism it is possible that they can be linked in humans. If specific neuron functions, and receptor functions can be understood we can better understand the behavioral characteristics we have as humans.
https://www.nature.com/news/neuroscience-as-the-worm-turns-1.12461 (link to article)
http://www.quickmeme.com/meme/3sq99t (laser meme)