Sally Johnson


 Paul Mellon Distinguished Professor of Agriculture – School of Animal Sciences

What are you working on now?
My research group studies structural repair and metabolic recovery of skeletal muscle following strenuous exercise and muscle damage. The process is intimately linked to muscle stem cell activity. This group of cells, conventionally referred to as satellite cells, is heterogeneous and contains classic stem cells, progenitor cells and rapid-responder fusogenic cells. We use mouse and horse models to identify the systemic and fiber-associated signals that allow satellite cells to incorporate into muscle. Our current efforts are exploring how the intracellular mediators, SMAD2 and SMAD3, control satellite cell identity and bioactivity in exercising mice. And, using diet supplements to enhance satellite cell activity during the post-exercise recovery period in horses.

What’s the most inspiring or enjoyable part of your work?
Discovering new ways to engage stem cells to promote tissue repair.  Controlling the actions of muscle stem cells has numerous applications that include reducing the time needed to recover from strenuous exercise, improving muscle mass in older people and horses, and accelerating muscle growth in livestock.  

Eight people standing side by side in a grassy pasture, smiling at the camera, with horse facilities and rolling hills behind them.
The Crew celebrating the completion of the Summer Project. Pictured (L-to-R): Madison Barshick, Sally Johnson, and Keely Mogge (Virginia Tech). Emily Jolley (Middle Tennessee State University) and Brooke Williams, Adrianna DiSilvestro, Lauren Wesolowski and Sarah White-Springer (Texas A&M University). Photo courtesy of TAMU.
Microscope image showing satellite cells (indicated by white arrows) positioned next to muscle fibers, which appear as large hexagonal structures.

Muscle satellite cells are located on the exterior of the contracting muscle fibers.  In response to exercise or other forms of muscle damage, these cells fuse into the adjacent fiber, contributing their nucleus and assisting with the repair process.  This photo depicts satellite cells (white arrows) lying adjacent to muscle fibers, the large hexagonal structures.  Fibers that have incorporated a satellite cell are red.  Note that satellite cells represent a small percentage of the nuclei (blue) found in muscle and not all fibers have added a satellite cell.  The Johnson lab examines the means by which dietary supplements accelerate muscle repair following intense exercise by increasing the numbers of satellite cells and their fusion to the injured fiber. Photo courtesy of the Johnson lab.

Dark mare standing beside a young foal in a grassy field at sunset, with warm light and clouds in the background.
Mouse and Eddie enjoying the evening at the MARE Center. Photo courtesy of Sally Johnson.

How did your undergraduate or early academic experiences shape your current research interests?
I went to Michigan State to study animal science with no interests in going to vet school. During my sophomore year, my advisor mentioned he was doing a small research project and asked if I could give him a hand.  I learned rumen canulation, fluid collection and basic general chemistry. From that point forward, I was hooked on research. My mentor was wonderful and allowed me to stay in his lab for 3 years. After graduation, I pursued a M.S. in growth biology which led to my long-term interests in stem cells. I have stayed in the topic area for my entire career.





"The most rewarding aspect of my career is seeing former students succeed."

What do you love about teaching or sharing your field with students?
Horses have always had a special place in my personal life but only over the past few years have they become my research focus as well.  My interests in how muscle stem cells participate in post-exercise muscle repair has created opportunities for numerous undergraduates. The studies are labor intensive because of the daily feeding and exercise schedule for 18-24 horses. I gain the most satisfaction from working with the summer interns on our exercise projects. It gives me a chance to work directly with the students, share experiences, and learn more about them as people while helping them reach their career goals. Because most wish to become equine vets, I can introduce them to my vet collaborators and colleagues and facilitate experiential learning opportunities for them. Four former interns are now practicing vets in NOVA, expanding the lab network and providing additional mentorship to undergraduates. The most rewarding aspect of my career is seeing former students succeed.

If you could go back in time and tell your younger self something about this field, what would it be?
You chose a career that encourages intellectual freedom. Let your creative juices flow!

Lara Chance galloping a research gelding at the Treadmill Barn with the assistance of Kristine Ely.
Two horses in a round, fenced hotwalker with sandy ground, with a barn and pasture visible in the background.
Research geldings performing daily exercise on the hotwalker at the MARE Center. Photos courtesy of Sally Johnson.

Several horses grazing on a sloped grassy hillside bordered by a wooden fence, with trees and a mountain in the background.
Group of grazing horses owned and managed by Dr. Johnson. 

    Contact:  Laura Coffey

                                     540-231-6870