My Summer Experience Observing Changes to Sarcomeres with Titin Regulation

Muscles are comprised of repeating units called sarcomeres, which can be seen as bands in myofibrils. Prior research has shown that the consistency of the lengths of these bands correlates to muscle strength – the more consistent the bands, the stronger the muscle. My project focuses on the relationship between the consistency of these sarcomeres and titin, the longest known protein which is proposed to maintain sarcomere length. Our lab developed an inducible skeletal muscle specific Bmal1 knockout mouse that demonstrates a to a longer titin isoform. By altering titin and comparing the variance of lengths of these sarcomeres to a control group, I hope to demonstrate a correlation between sarcomere length and the expression of titin. My project takes a histological approach to study changes in sarcomere length and A-band centrality in the skeletal muscle by staining for alpha actinin and myosin. These images are overlaid and peak fluorescence is measured. Knowledge from this experiment would contribute to knowledge about titin and could eventually lead to more targeted drugs or therapies. Results of my experiment thus far indicate that there is a trend toward a longer sarcomere length and no significant change in variance, but there are still other stains and trials I would like to do to strengthen my findings. If my hypothesis is supported then my project would support the assertion that titin has a structural role in the sarcomere.

The myosin stain allowed me to see if there were any differences in the location in the A-band in relation to the Z-line.

The alpha actinin stain labels the z-lines, allowing the sarcomere to be visualized and measured.

Realities of Research

Research in Dr. Esser’s lab was very different from what I had anticipated. Generally, people think of scientific research as solitary, but what I have found is there is a lot of collaboration in academic research. When we encountered an error in the RNA sequencing program of the model, and we reached out to other people at the university in order to help understand and correct this error. Additionally, we borrowed equipment such as the cryostat (a machine used to cut muscle at cold temperatures) and microscopes from other labs. Lab meetings were also a useful part of my experience because they allowed for brainstorming when I faced challenges. In addition to the RNA sequencing obstacle, there was also a problem with a control antibody stain because there was fluorescence in an unexpected region. After discussing the problem, we came up with the hypothesis that the secondary stain for one of the regions was attaching to the conjugated antibody of another region, which was why we were seeing the unexpected fluorescence. To correct this, I applied the antibodies in two steps instead of combining them. All of these obstacles were easier to overcome because I had people around to assist me, an invaluable asset that I did not expect.

Day-to-Day of a Scientist

I look forward to coming in to the lab because I like the challenge of overcoming the unforeseen obstacles. Designing ways to solve problems is definitely my favorite part of working in a lab. The production of ideas about how an experiment or procedure should work and testing the methods is exciting. While these obstacles can be a nice challenge, they can also become tedious. The problem with the RNA sequencing was especially frustrating because it was out of our hands. Despite these complications, my research was overall very enjoyable. I am very appreciative of the APS for allowing me to pursue my interests this summer, and would encourage others to do a program because the experience was very rewarding.

Joseph Mijares, also known as Robby, is a junior at the University of Florida in Gainesville, FL. He is grateful to be a 2017 Undergraduate Summer Research Fellow in Dr. Karyn Esser’s Lab at the University of Florida.  Robby plans on applying to several MD and MD-PhD programs after his junior year, with hopes of attending after graduation.

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