What advice would you give to a young scientist?
“To identify what you like to do within the science realm… If you’re excited about doing science and you like asking questions then there’s always a place for you.“
The human brain is made up of hundreds of billions of cells, which make trillions of connections with one another. During development, each brain cell has to make decisions about where to grow, what cell type to become, and which other cells to connect with. Remarkably, this system—which is arguably the most complex system in the known world—assembles itself. How the brain assembles itself is the question that Carol Mason, PhD, a Professor of Pathology and Cell Biology, Neuroscience, and Ophthalmology, has devoted her life to studying.
Carol is the Principal Investigator for the Mason Lab at the Zuckerman Mind Brain Behavior Institute at Columbia University. Her lab overlooks Broadway from the third floor of the JL Greene Science Center, which houses the Zuckerman Institute in Harlem. Carol herself is easy to spot with her iconic curly gray hair, thick-rimmed glasses, and bold necklaces and earrings. Upon entering Carol’s office, one sees that she has decorated her walls with an abundance of science publications and cherished artwork. Above her desk hangs a large portrait of Santiago Ramon y Cajal, who is known as the “Father of Modern Neuroscience.” Like Cajal, Carol is both an artist and a scientist. In her time outside of the lab Carol paints and does photography, but her artistic eye is also at the root of her approach to doing science.
“I learned to explore and to persist in unraveling puzzles.”
When Carol began studying neuroscience in the 1970’s, scientists had limited knowledge of how the brain developed. Carol had obtained her Ph.D. in invertebrate zoology and endocrinology from the University of California, Berkeley and joined the Lab of Dr. Ray Guillery at the University of Wisconsin as a postdoctoral fellow. Dr. Guillery was interested in the visual system, and was trying to determine how connections were made as the brain ‘wired itself up’ during development. Carol’s role was to map out the connections between neurons, using various types of microscopy images. The process was exacting, but it resonated with Carol’s artistic inclination to draw the forms of brain cells, and she enjoyed using her keen eye to map the small developing structures. In remembrance of her time with Dr. Guillery, Carol wrote, “I learned to explore and to persist in unraveling puzzles.”
Upon finishing her postdoctoral fellowship with Dr. Guillery, Carol went on to start her own lab at New York University. While she wondered about the visual system, she instead dedicated her lab to studying the cerebellum, a brain system involved in coordinating fine movement. She made this decision in part because the cerebellum was more fertile ground for developmental research, with its known, regular structure and location of the cells. Over the next decade, Carol investigated how one of the most elaborately shaped brain cells, the Purkinje cells of the cerebellum, developed. She published papers describing how Purkinje cells interact with other cerebellar cellst, and these interactions appear to be critical for proper Purkinje maturation. Looking back on her work, she recollects that science at the time had no answers about the underlying factors that guide brain cell development. It was clear that cells were interacting and influencing one another, but no one could explain how this occurred. She sought to change that.
In 1987, Carol transitioned to the next chapter in her career: having started her own lab at NYU in 1980, she moved to Columbia University and returned to the questions and puzzles that had initially captivated her from her work with Dr. Guillery. She had always been fascinated with the unique architecture of the visual system. In particular, she was drawn to the type of cells that connect the eye and the brain, called retinal ganglion cells, or RGCs. During development, as RGCs build their connections between the eye and brain, something rather surprising happens: some growing RGC tips cross the midline and wire up to the opposite side of the brain, while others grow directly through to the same side of the brain. Carol had visualized and sketched the criss-crossing RGC fibers, and she wondered, “what endows cells that start at the same place, in the [eye], with the ability to end up in different places in the brain?” Then several years later, the fields of molecular biology and genetics were just starting to tackle these key questions of brain development. Carol put her ideas to work, creating mice with genetic mutations and seeing how these alterations affected the behavior of RGC growth, especially as these cells navigated in different directions. Through decades of experimenting, Carol and her team have revealed many of the key genes and molecules that orchestrate RGC growth. Carol’s seminal work in characterizing visual system development has helped to establish some of the core principles behind brain development. She continues in this line of inquiry, going back earlier in development to probe how RGCs are “endowed” with genes that enable them to grow to each side of the brain.
Carol’s contributions have made her a leader in the field of developmental neuroscience. In 2013, she served as the President of the Society for Neuroscience, which is the world’s largest organization of researchers and physicians dedicated to discovering how the brain works. She has also codirected Columbia’s graduate program in Neurobiology and Behavior, and was granted membership to the highly prestigious National Academy of Sciences in 2018. Despite her many titles and awards, Carol notes the importance of valuing your work first and foremost. “I just did science because I thought it was cool, and I liked doing the science,” she says. She encourages younger scientists to explore their unique interests as well, and to follow what they are most passionate about. “I say, what turns you on? If you’re excited about doing science and you like asking questions, then there’s always a place for you.”
“Science is constantly evolving and new things come along, new techniques and new ways of thinking and seeing.”
“We need the diversity of women and men in every layer and facet of our world of science.”
Carol is also an advocate for greater inclusion of women in science. When Carol attended college in the 1960’s, she felt burdened by double standards and cultural expectations for academic women of that time. “You have to understand, I went to a small all women’s college [the now coed Chatham University],” she says. She describes the culture of some professors as old-fashioned and strict. On the other hand she felt that her passions often confused people she met outside of school. She recalls, “When people found out I was a scientist, they backed off.” Carol has thought long and hard about why academia creates a crossroads so that men and women end up in different places. In particular, women are underrepresented in the upper ranks of academia where key decisions are being made. Several years ago, Carol wrote a Call to Action letter stating, “As president of the Society for Neuroscience, I speak to both the younger generation and those of us who have been around for a while. We need the diversity of women and men in every layer and facet of our world of science.” She also wrote on underlying factors that produce gender disparities in academia in her article titled, ‘A Tale of Two Sexes,’ which was published in the journal Neuron. Through her activism, she hopes to make science more inclusive than it was when she forged the path of her career.
As a Principal Investigator, Carol also offers mentorship to the next generation of men and women in science. “Science is constantly evolving and new things come along, new techniques and new ways of thinking and seeing,” she says. So, too, is the culture around science, and it is largely being shaped by people like Carol, who have been bold enough to stand out from the crowd. Where will Carol go from here? “People ask me when are you going to retire,” Carol says, “and I say never.” Once again Carol is looking towards a less-traversed path. “What I look forward to is to be at the [laboratory] bench. I want to encourage a model for senior scientists in which they can join a younger person’s lab and spend time at the bench,” she says. “That’s my dream.”
Carol Mason, PhD, is a Professor of Pathology and Cell Biology, Neuroscience, and Ophthalmology at Columbia University. Faculty profile
by Maia Weisenhaus
Scientist on the Subway 