The Glorious Glia
As promised, I am here to debrief my thesis meeting.
But first, I guess I should explain why I've chosen to study the Glymphatic system. I love and appreciate the glia because they are the bearers of balance and moderation. Essentially, they keep the entire brain in check, making sure there is just enough of each substance and getting rid of anything that's not supposed to be there. Maybe it has something to do with the way glial cells' homeostatic characteristics contrast with my own erratic conduct, but even though I can't exactly put my finger on the reason for my weird obsession, I can tell you that I've never experienced such curiosity and awe until I started studying the glia.
Perhaps also, it is because of the way the Glymphatic system, and its components, the glial cells, have confounded neuroscientists to a degree like nothing else. The mystery lies in a multitude of questions such as, why do the glia only exist in the brain? Can their function be fulfilled by any other part of the brain? In C. Elegans it isn't exactly clear whether or not the glia are actually necessary to maintain the life of the nematode. On a human level, up until very recently, people used to study a brain by initially removing any visible glia. This shows that there is something to be said about the controversy but not what that something actually is. But I think we also cannot disregard the limitations present in studying worms to understand humans.
For starters, while the glia in humans are basically a cushion for neurons to sit in, glia in C. Elegans form a sheet-like coating around the nerve ring (comparable to a humans brain). This coating as a whole functions in a similar way to the Blood Brain Barrier in humans but each individual glia has a life cycle of purposes. At first, when the worm is very young, the glia are responsible for specializing each neuron to its specific location and process. Then, when the worm reaches the L2/L3 stages, the glia begin to act as moderators of substance and keep the system in balance. Lastly, as the worm arrives at full adulthood (L4 stage), the glia combine to form that sheet-like coating around the nerve ring. Within this sheet however, there are still multiple types of glia, synaptic, CEP sheath glia, socket glia, among others. Although there is not as much confirmed about human glia, they are likely not involved in neuronal specialization and are definitely not involved in constituting the Blood Brain Barrier. Their most prominent known purpose is to regulate substances inside and outside the neuron membrane and throughout the entire brain. An additional limit to this worm-human interface is the surface area/space/number of neurons. If you look at Beta-Amyloid or Tau plaques in the worms, they are presented at a humanly unrealistic level because the substance is so concentrated in the sole 302 neurons. Regardless of these flaws in the comparison, however, most scientists have chosen C. Elegans as the prime measure for understanding the human brain due to its simplicity and the fact that although very far, is the closest thing to a human nervous system.
So I hope I haven't completely lost your trust (however much I previously had) but my goal in laying out all of these limitations and circumstances was to simply provide some context as we encounter various stages of experimentation and neuroscience literature. I guess that's all the background information I believe to be necessary at this point, so now we can get to discussing the actual content of my meeting with Dr. Norman.
At the beginning, I had an idea but it quickly changed into something else as we discussed the possibilities. Just like usual, I initially overestimated my own and the lab's capabilities. Worms that have a dangerous build up of proteins often show different phenotypes than humans, locomotive for the most part. Humans, on the other hand, see deficits physiologically, cognitively as well as locomotively. So my original idea was to see if the reason that the C. Elegans had different symptoms could be attributed to the differences between human and nematode glia (see above). This way, I would possibly gain insight into what exactly the glia are responsible for doing. The problem here, firstly for myself, is that glia in C. Elegans has been virtually an untouched topic in the research realm and I know that this project is supposed to be an original thesis, but it really doesn't seem logical for me to do so without any baseline or background literature. The other problem, is that the most preferred process available in the lab for studying the insides of the worms is microscopy - which just basically means that we inject a certain fluorescent molecule into the worm and it then adheres to a specific substance to show us its quantity and location. Anything beyond this would require much training and some very expensive equipment.
Of course, I was a little disappointed to hear this but not so much as last year because, well, let me put things into a little bit of perspective - every time I walk into the lab, I am intimidated and essentially blown away by the amount of knowledge and brain power that I am surrounded by. This sentiment kind of makes me unnecessarily nervous/jittery but also instills a great sense of trust for the people in there. So when Dr. Norman told me that my idea was a little bit too ambitious, I trusted that we would find something I could do. And this is one of the big differences that I've noticed between last year and this year. I think I panicked so intensely after realizing that I was conducting a largely aimless project last year mostly because I didn't know what to do next. I had many problems, but also what seemed like absolutely no solutions and that really frightened me. That's a deficiency in myself, I realize that I probably should have been more independent and self-reliant but I believe that there is also something to be said about not trusting yourself because you honestly have no idea what you're doing. But that's a whole other story.
Anyway, after Dr. Norman told me that my idea was not realistic, we proceeded to brainstorm other ideas that still allowed me to study the glia. And I won't chronicle every idea that was set forth because that would simply be a waste of yours and my own time but what follows is the idea we are going with. Although, please forgive me as the rest of this post will be rather technical in nature and I'm not sure there is any way to get around that. Consider yourself warned...
Okay, so here's the deal. First of all, I've found that it is proving difficult to escape studying Alzheimer's as it is most accessible to simulate in the worms so I guess I'll just have to go along with it and see what happens. One of the genetic precursors for Alzheimer's is presenilin precursor proteins 1 and 2. In worms, we can express this as a sel-12 background which is pro-aggregate simply meaning that any large amount of substance has an 85% chance of forming a plaque. Theoretically, the glial cells form a coating around the nerve ring and dually function as a counter to the effects of sel-12 by moderating the amount of protein and at the same time simulating something similar to the Blood Brain Barrier.
So what I would do is cross worm strains of sel-12 with tau protein fluorescence and observe the longitudinal functioning of sel-12 versus glial function. The question I am asking is whether or not this sel-12 background in the worms impairs or lessens the function of glial cells (glymphatic system) with respect to plaques in the nervous system.
Practically, I would have to study three sections of the worm population that I produce. One would be a control, observing levels of tau and glial function without manipulation. Then I would use one group to study tau amounts with yellow fluorescence and the other group to study glial function with green fluorescence. The trick here is that green and yellow fluorescence often can get confused because they are both just different degrees of green fluorescence so I have to make sure that I am studying each component in a separate group but do it all at the same time so that the worms are controlled in terms of developmental state. Dr. Norman and I took some strains of bacteria and worms out of this crazy cool freezer room to thaw and he's going to order some glial cell fluorescence molecules from a worm world storage house in Minnesota (wild stuff, I know).
On an application/planning level, I think I'm okay with this. But I am a little concerned as to what unexpected things may come up in the process. I feel like I have to give ample time for things to go wrong and include that in the official plan but I am struggling to find space for it. I don't know what will happen but if I learn anything, I hope that this teaches me to move with the tides of change a bit more efficiently.