What Comes First: Phrenic Motor Neuron Loss or Neuromuscular Junction Dysfunction?
Ann Mary Wilfred
Fourth Year
Health sciences major with biomedical specialization
McMaster University

My Research Project

Drawing of the chest cavity with the diaphragm colored in red.

As we age, there are many changes that happen in our body. One of these changes is the loss of phrenic motor neurons (PhMNs), a specific type of neuron that controls the diaphragm, the main muscle we use for breathing.

In older adults, the consequence of this loss of neurons is the inability to clear the airways through high-force behaviors like coughing and sneezing. Not being able to clear the airways may lead to infection and sometimes, death. With aging, the connection between these PhMNs and the muscle fibers it innervates—called the neuromuscular junction (NMJ)—breaks down because the PhMNs withdraw their connection from these muscles in a process called pre-synaptic withdrawal. The problem is that we do not know which event happens first: PhMN loss or pre-synaptic withdrawal.

My project aimed to chronicle a timeline of these events using a specific type of imaging technique called confocal microscopy. Being able to identify the sequence of events may help us pinpoint areas of therapeutic intervention in order to prevent or delay PhMN loss and NMJ dysfunction.

Realities of Research

Although I have participated in previous research activities, this summer fellowship was my first experience in a wet lab. It was a very valuable opportunity because I learned a wide variety of wet lab techniques, such as immunohistochemistry staining and how to handle rodents. What surprised me most was how much trouble-shooting was required— there are so many things that can go wrong! My project was mainly focused on imaging PhMNs. The biggest learning highlight of this project was learning how to use a confocal microscope and quantitatively analyzing the images. Initially, I felt intimidated because the process seemed so complex, and this was a very advanced and expensive piece of equipment. However, after imaging and analyzing so many samples, I am proud to say that I feel comfortable using this type of technique. I was happy to see that the experiments worked and the results were what I expected:that pre-synaptic withdrawal precedes PhMN loss in the NMJ and that large PhMNs seem to be more vulnerable to this loss.

Life as a Scientist

Working in the lab was an amazing experience! There were moments where it was very hectic, days when I had to go home later than usual or even times when I felt very frustrated because the work was tedious and laborious. Despite all of this, the experience was very rewarding because of the friends I made in the lab, the valuable networking opportunities I was engaged in, the important connections I made and most of all, the unique satisfaction I experienced when the experiments worked properly. In the end, I had really good data that I can contribute to a paper or publication.

I am grateful to have had the opportunity to work in a very supportive and welcoming lab environment; my lab mates, research mentor and principal investigator were always so receptive to my questions and concerns and helped mold me into the scientist and researcher that I am today.

It feels amazing to know that my research is contributing in a meaningful way to the larger goal of improving age-related respiratory dysfunction in hopes of someday helping so many people.

Ann Mary Wilfred is a senior in the Bachelor of Health Sciences (biomedical sciences specialization) at McMaster University in Hamilton, Ontario, Canada. She is a 2019 Undergraduate Student Research Fellow (UGSRF) working under the mentorship of Dr. Gary C. Sieck at Mayo Clinic in Rochester, Minn. Ann’s fellowship is funded by the American Physiological Society. After graduation, Ann plans to pursue a career in medicine, specializing to become a pediatric neurosurgeon, while also continuing her involvement in neuroscience and physiology research.

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