Tag Archives: Nematode

Talk at Institute of Molecular Pathology, Vienna

WP_20130129_001

On Wednesday I was at the IMP in vienna to deliver a talk about my recent paper.Manuel Zimmer, my host, put together a great schedule of people to meet with and I had a great time delivering the talk .. the audience was highly engaged and asked a lot of very good questions. I spent the rest of the day having some great discussions with members of top-notch labs Continue reading

Advertisements

Comparative Connectomics paper is out!

papertitleFinally, after years of blood sweat and tears our comparative connectomics paper has been published. This represents a huge victory for myself and all of the people who have helped me along the way. It is rather humbling to have this work get the kind of exposure it gets by being published in Cell. It is the culmination of years of work, complete with with heart-breaking failures, long grinding hours on the microscope and in front  of the computer, and the occasional adrenaline-inducing discovery. In the paper, we compare a wiring diagram(or connectome) of the pharyngeal nervous system of the nematode Pristionchus pacificus to that of the well-known model organism C. elegans. The data are obtained by Continue reading

Pristionchus pacificus predatory feeding video

One of the things that interests me about the nematode Pristionchus pacificus is that it is capable of taking advantage of many different food sources. Like it’s cousin and well known model organism Caenorhabditis elegans, this nematode can be raised on agar plates seeded with bacteria. Pristionchus can additionally feed on other sources, including other nematodes! These predatory feeding behaviors are quite distinct from bacterial feeding. For instance, Pristionchus has tooth-like denticles in its mouth opening that are highly active during predatory but not bacterial feeding. This increase in the complexity of the P. pacificus
behavioral palette is most interesting when you consider that the nervous systems are composed of a nearly identical set of neurons. So how do you teach an old nervous system to do new tricks? This is one of my primary motivations for comparing networks of synaptic connectivity between these two species.

Amphid commissure

We are continuing to experience great success in acquiring data for our Prisitonchus connectome project. Here’s an image showing how far into the worm we are with our current dataset. In it you can see the terminal bulb of the pharynx, and if you look very closely you can see the amphid commissures, which contain most of the nose sensory organs. The image is taken very close to the duct for the secretory/excretory system, which can also be seen very nicely in the image. It looks like we should be able to switch to worrying about the tremendous task of describing all of the synaptic connectivity in January. Metta and I have been working very hard to collect these data as fast as we can.. in fact I’m sitting at the electron microscope while typing this post! I’ve added a couple of images to my Pristionchus Flickr album HERE.

Nematode Brain!

Metta and I are still in the process of collecting images of a serial section dataset through the front end of our nematode. I am hoping it will eventually become the second species for which we have a complete connectome, or “wiring” diagram of all the synaptic connections in the nervous system. We have now imaged everything from the tip of the nose to the brain of the animal, which is called the nerve ring as it wraps around the pharynx making a ring shape. Everything is going exceptionally well, and we only need a few hundred more images to have a very complete and useful dataset showing all of the connections. The above image is a cross section of the nematode. The pharynx is in the middle, and you can see the neuropil wrapping around in a circle, forming synapses as they pass each other. All of these images are taken at much higher resolution than is shown here. Click HERE for a Flickr gallery showing the same image at different magnifications.

Synapses at last.

Finally, after years of tedious work, we have our first very high quality thin section series through synapses in Pristionchus pacificus. This image is of the nerve ring in the pharynx, which controls many aspects of feeding behavior in the nematode and is like a mini-brain. It is very difficult to obtain such data and few groups have done it, so this is no small victory for me. We have a long way to go though, as the “real” brain of the animal is still hundreds of sections away, but if things continue to go well we could finish this in January or early February. The triangular white structure you see in the middle is the lumen of the pharynx, through which all of the food passes. In fact, there is rather conveniently a bacteria in the center in the process of being swallowed by the worm. Clusters of black spheres in the smaller cells are synaptic vesicles, and the black blotches on the cell membrane adjacent to the synaptic vesicles are pre-synaptic densities.. on the other side of each synaptic density is the cell each neuron is “talking” to. The two irregularly shaped holes near the pharynx lumen are gland cell ducts, that fuse with the lumen a few microns from this image and likely secrete digestive enzymes. Filamentous structures radiating out from the lumen are muscle cell filaments, used to open and close the lumen. Beautiful, isn’t it?