Marielle Valdez’s Life-Long Quest for Answers

Why do our bodies sometimes fail us, and what can we do about it? These questions drive PhD candidate Marielle Valdez and her genomics research in search of targeted therapies that promote health and well-being.

Marielle Valdez was drawn to the field of medicine at a very young age. When she was just five, the tragic death of her 13-year-old cousin from a severely virulent infection of Rickettsia rickettsii sparked an insatiable fascination with how we fight infection and disease.

“That experience of loss and bereavement planted a deep need in me to understand how the body works, why it fails and what we can do about it,” says Marielle. As a PhD candidate studying genomics in the UC Irvine School of Medicine, she is dedicated to finding new, targeted therapies that promote health and well-being.

“What continues to amaze me is that every living organism carries an almost incomprehensible archive of information, encoded in DNA and RNA, that has been refined over generations to help us survive, fight disease and adapt,” says Marielle. “And yet, even with all that stored knowledge, we still get sick. That tension, that question of why, is what drives me every single day.”

Hooked on a Molecular Messenger

Marielle was attending an undergraduate lecture when she first learned about Yongsheng Shi, PhD, a professor of microbiology and molecular genetics. “I was in a virology class and the professor, Dr. Jo Ellen Brunner, talked about the work happening in Dr. Shi’s lab at UC Irvine in a way that lit something within me,” she says.

Marielle started researching the Shi Lab and its focus on the molecular mechanisms that govern messenger RNA (mRNA) processing. “For mRNA to function correctly, it has to go through a series of tightly controlled steps,” says Marielle, “and disruptions to any one of them can have serious downstream consequences.”

Fascinated by this work, Marielle reached out to Shi, even though she was years away from grad school. “I had my eye on his lab,” she says. “UC Irvine and the Shi Lab were always where I wanted to be.”

By the time Marielle began her PhD, the world was in the middle of the COVID-19 pandemic. “Suddenly, mRNA was everywhere,” she says. “Here was this molecule, a messenger, carrying instructions that could change outcomes at a biological level. I was completely hooked.”

Building Knowledge for New Therapies

Aberrant mRNA processing is now recognized as a significant driver of diseases like cancer and neurological disorders. The dysregulation can come from alternative splicing errors, RNA editing changes, or modifications that affect mRNA stability and translation efficiency.

“What makes this particularly challenging, and fascinating, is that these are not always catastrophic mutations,” explains Marielle. “Sometimes it is a subtle shift in how a transcript is processed that tips the balance toward disease.”

For her dissertation, Marielle is focused on Symplekin, a core factor of the mRNA 3′ end processing machinery. “What makes my work especially exciting is emerging evidence that Symplekin’s influence extends beyond the nucleus, suggesting previously unrecognized regulatory roles in other cellular compartments,” she says. Using brain tissue data, she and Shi have identified that Symplekin is dysregulated in the neurodegenerative disorder Huntington’s Disease.

“I am investigating the additional roles of Symplekin to understand how to fix this dysregulation,” says Marielle. “The possibility that a protein long understood within one context may have additional, unexplored functions associated with neurological health is what motivates much of my research.”

Her broader goal is to build the type of foundational knowledge needed to develop new targeted therapies. “It’s not just knowing that something goes wrong,” she says, “but understanding exactly where, when and why.”

In recognition of this work, and of her scientific promise more generally, Marielle received the School of Medicine’s 2025 Outstanding Graduate Research & Service Award. “I was genuinely astonished,” says Marielle. “I never expected to be seen in that way, and I am deeply grateful.”

Building Community

The award also honored Marielle for her commitment to leadership and mentorship. As a co-president of the Association of Women in Science, she is helping others follow in her footsteps.

“What I love most is that it’s not just a social group but also a network that helps you figure out what comes next,” says Marielle. “All students, at every level, have doubts about the road ahead, and this community helps you navigate those moments with guidance, support and the comfort of knowing others have been exactly where you are.”

Marielle has had plenty of doubts along the way. “I have made mistakes, taken detours and had to rebuild my confidence more than once,” she says. “When you have had to push hard without a clear roadmap, you naturally want to be that roadmap for someone else.”

Finding her footing under Shi’s mentorship has also been a journey. “Early on, his style felt intense. I used to joke that it felt like being on a Gordon Ramsay cooking show!” she says. “But the pressure always came from a place of genuine investment, and it pushed me to grow.” She genuinely loves her research and her collaborators. “I would not trade these experiences for anything.”

She is also proud to be the first in her family to pursue a doctoral degree. “I come from a large, close-knit family, and this achievement carries a weight that is genuinely hard to put into words,” she says, referring to her family as the “pit crew” that fuels her work. “They do not wear lab coats or publish papers, but they are as much a part of this journey as any experiment I have ever run.”

Beyond the Bench

While most of her time is spent in the lab, Marielle loves getting boba tea with her family, decompressing in the home gym her brother built, going to concerts and discovering new restaurants.

She is also a passionate cyclist and recalls participating in the UCI Anti-Cancer Challenge. “I signed up for the 60-mile route, but somewhere along the way, I started following another group,” she says. Only later did she realize she ended up on the 100-mile route. “I just kept going,” she says, laughing. “Accidentally completing a century ride might be the most on-brand thing I have ever done!”

As she prepares to graduate and start her postdoctoral training, she plans to advance science through not only discovery but also community and collaboration.

“I want to keep deepening our understanding of mRNA processing and its role in disease, hopefully contributing to work that moves us closer to meaningful therapies for neurodegenerative disease,” she says. “Beyond the bench, I want to keep investing in the people around me and mentoring the next generation of scientists.”

— Shani Murray