Alyssa Brunal's Dissertation Defense (10/15/2020): Effects of Constitutive and Acute Connexin 36 Deficiency On Brain-wide Susceptibility to PTZ-induced Neuronal Hyperactivity
Dissertation Defense: Effects of Constitutive and Acute Connexin 36 Deficiency On Brain-wide Susceptibility to PTZ-induced Neuronal Hyperactivity
Alyssa Brunal
Graduate Student, Virginia Tech Translational Biology, Medicine, and Health
Graduate Research Assistant, Pan Lab, Fralin Biomedical Research Institute at VTC
Oct. 15, 2020 at 9:00 a.m.
About this Dissertation
Connexins are transmembrane proteins that form hemichannels allowing the exchange of molecules between the extracellular space and cell interior. Two hemichannels from adjacent cells dock and form a continuous gap junction pore, thereby permitting direct intercellular communication. Connexin 36 (Cx36), expressed primarily in neurons, is involved in the synchronous activity of neurons and may play a role in aberrant synchronous firing, as seen in seizures. To understand the reciprocal interactions between Cx36 and seizure-like neural activity, we examined three questions: a) does Cx36 deficiency affect seizure susceptibility, b) does seizure-like activity affect Cx36 expression patterns, and c) does acute blockade of Cx36 conductance increase seizure susceptibility. We utilize the zebrafish pentylenetetrazol (PTZ; a GABA(A) receptor antagonist) induced seizure model, taking advantage of the compact size and optical translucency of the larval zebrafish brain to assess how PTZ affects brain-wide neuronal activity and Cx36 protein expression. We exposed wild-type and genetic Cx36-deficient (cx35.5-/-) zebrafish larvae to PTZ and subsequently mapped neuronal activity across the whole brain, using phosphorylated extracellular-signal-regulated kinase (pERK) as a proxy for neuronal activity. We found that cx35.5-/- fish exhibited region-specific susceptibility and resistance to PTZ-induced hyperactivity compared to wild-type controls, suggesting that genetic Cx36 deficiency may affect seizure susceptibility in a region-specific manner. Regions that showed increased PTZ sensitivity include the dorsal telencephalon, which is implicated in human epilepsy, and the lateral hypothalamus, which has been underexplored. We also found that PTZ-induced neuronal hyperactivity resulted in a rapid reduction of Cx36 protein levels. 30 minutes and one-hour exposure to 20 mM PTZ significantly reduced the expression of Cx36. This Cx36 reduction persists after one-hour of recovery but recovered after 3-6 hours. This acute downregulation of Cx36 by PTZ is likely maladaptive, as acute pharmacological blockade of Cx36 by mefloquine results in increased susceptibility to PTZ-induced neuronal hyperactivity. Together, these results demonstrate a reciprocal relationship between Cx36 and seizure-associated neuronal hyperactivity: Cx36 deficiency contributes region-specific susceptibility to neuronal hyperactivity, while neuronal hyperactivity-induced downregulation of Cx36 may increase the risk of future epileptic events.
More About the Candidate and Project
Education
Virginia Tech Translational Biology, Medicine, and Health, Ph.D. Candidate
Virginia Tech, B.S., Psychology
Training
Graduate Research Assistant, Pan Lab, Fralin Biomedical Research Institute at VTC
Mentor
Yuchin Albert Pan, Ph.D., Associate Professor, Commonwealth Research Commercialization Fund Eminent Research Scholar in Developmental Neuroscience, Fralin Biomedical Research Institute at VTC
Committee Members
- Susan Campell, Ph.D., Assistant Professor, Department of Animal and Poultry Sciences, College of Agriculture and Life Sciences, Virginia Tech
- Michelle Olsen, Ph.D., Associate Professor and Director of Graduate Studies, School of Neuroscience, College of Science, Virginia Tech
- James Smyth, Ph.D., Associate Professor, Fralin Biomedical Research Institute at VTC
Ex Officio Committee Members
- Michael J. Friedlander, Ph.D., Executive Director, Fralin Biomedical Research Institute at VTC, and Virginia Tech Vice President for Health Sciences and Technology
- Michelle Theus, Ph.D., Associate Professor, Department of Biomedical Sciences and Pathobiology, Virginia-Maryland College of Veterinary Medicine
- Steven Poelzing, Ph.D., Associate Professor, Fralin Biomedical Research Institute at VTC, and Co-Director, Translational Biology, Medicine and Health Graduate Program.
Honors
- Graduate Student Commitment to Diversity and Inclusion, Honorable Mention, Virginia Tech Office of Student Engagement and Campus Life, April 2020
- Neuroscience Scholars Program Associate, Society for Neuroscience, May 2019- May 2021
Presentations
Brunal-Brown, A., Pan, Y. Albert. Neuronal Connexin 36 in Seizure-like Activity, poster presented at the Diversity poster session at the 2019 Society for Neuroscience Annual Conference, Chicago, IL. (October 2019)
Brunal-Brown, A., Pan, Y. Albert. Neuronal Connexin 36 is regulated by and contributes to the susceptibility of PTZ-induced seizures, poster presented at the 2019 Triangle Zebrafish Research Symposium, Duke University, Durham, NC. (April 2019)
Brunal-Brown, A. Building a Brain: How your neurons make you, public oral presentation as part of the Science Museum of Western Virginia’s STEM Tavern series. (August 2018)
Scientific Publications
Brunal, A. A., Clark, K. C., Ma. M., Pan, Y. A. (October/November 2020) Effects of constitutive and acute Connexin 36 deficiency on brain-wide susceptibility to PTZ-induced neuronal hyperactivity
Newspaper Op-Eds
Brunal, A., (August 2020) Diets and weight loss: What new insights do we have?, The Roanoke Times, Roanoke, VA
- Collaborative Conversations: Empowering a Culture of Respect: Organized and planned a full day workshop surrounding the issue and providing access to resources for sexual harassment and implicit bias in STEM. Conducted pre- and post-workshop evaluative measures. August 2019-March 2020
- Annual Biomedical Research Conference for Minority Students (ABRCMS): Panelist “Putting Your Best Foot Forward in Graduate School Inter views” Webinar, February 2019
- West Salem Elementary STEM Night: Had a Zebrafish booth and spoke to ~300-400 elementary school students, November 2018 and March 2018
- STEAM Day at the Taubman Museum of Art: Had a Zebrafish booth and spoke to ~ 300 elementary school students, September 2018, had a booth titled “How scientists use light!” and spoke to ~900 elementary school students, October 2017
- Public lecture as a part of the Science Museum of Western Virginia’s STEM Tavern Series titled “Building a Brain: How your neurons make you," August 2018