Research Spotlight: Leon Xuanyu Min, MD, PhD

What began as a technician position in the Xin Zhang Lab in 2019 has evolved into a promising career as a physician-scientist for Leon Xuanyu Min, now an MD-PhD candidate in the Medical Scientist Training Program (MSTP) at the University of Pittsburgh School of Medicine and a third-year PhD student in Bioengineering. Recently, Leon reached a major milestone as first author of the Nature Communications paper, “Wnt signaling regulates passive cell competition in the retina by inducing differential cell adhesion.” His study uncovers a new mechanism that helps shape the developing retina, offering insights into how cells compete and organize during development. In this interview, Leon reflects on the journey behind the discovery, the challenges and excitement of leading a research project, and how his experiences continue to shape his path toward a career at the intersection of medicine and science.

How did you become interested in research? Tell us about how your scientific career started.
 

As an undergraduate, I investigated biomaterials designed to improve endovascular coiling outcomes in the treatment of intracranial aneurysms. That experience gave me a strong foundation in bioengineering and showed me how engineering principles could be translated into clinically relevant solutions.

I recognized that a deeper understanding of basic science would broaden my engineering perspective and strengthen my ability to conduct impactful biomedical research. I was drawn to Dr. Zhang’s lab because he was willing to train someone without prior experience in mouse genetics or developmental signaling, which was not an opportunity offered by many laboratories. I initially joined the lab as a research technician, maintaining mouse lines through PCR genotyping, preparing reagents, and assisting postdoctoral researchers with immunofluorescence staining. As I became proficient in these techniques, I was given increasing independence and eventually began working on my own projects. What started as a technical position developed into an intensive three-year research experience at Columbia University.

What is the focus on your research now? What kind of medicine do you hope to practice?
 

My current research focuses on tissue-engineered vascular grafts in the context of bypass procedures, particularly how biological and mechanical cues can be used to improve graft integration and remodeling. I am investigating how bioactive extracellular-matrix materials can regulate the immune response and how matching a graft’s mechanical loading to that of the native artery may promote more constructive remodeling. I plan to pursue vascular surgery, so my research directly aligns with the diseases and procedures I hope to address clinically.

What was the original question that motivated your paper “Wnt signaling regulates passive cell competition in the retina by inducing differential cell adhesion”?

The project was motivated by the broader question of how Wnt signaling coordinates cell-fate specification with the spatial organization of progenitor cells during retinal development. The unexpected observation that ciliary margin-derived structures still formed after mosaic β-catenin ablation became a major turning point rather than the original question itself. It led us to investigate the biophysical sorting mechanism that connects Wnt signaling to the establishment of the ciliary margin niche.

What did you and your co-authors each contribute to this paper?

I generated the mouse models and performed the detailed phenotypic characterization that provided the foundational data for this study and helped establish the biological phenomenon investigated in the paper. As the project developed, many colleagues contributed their expertise and effort to bring the work to completion. Yingyu (Doris) Mao performed the elegant in vitro cell-sorting experiments that provided important mechanistic insights. Hao Wu generated an independent mosaic deletion model that helped confirm our findings, and Neoklis Makrides, another postdoctoral fellow, generously provided critical experimental support. Josh Bock contributed detailed histological analyses, while Chenqi Tao provided valuable mentoring and technical guidance throughout the study.

I would also like to give special recognition to Alyssa Chow and Yelenia Almonte, two fellow technicians who generated crucial additional data needed to address reviewers’ concerns during the long and demanding revision process. I am particularly proud that the three of us technicians worked with persistence and determination to carry this project through to publication. The final paper truly reflects a collaborative effort, with each co-author contributing complementary expertise at different stages of the study.

What were the main outcomes of your paper? What do the findings of this paper suggest for congenital eye disorders?

Using genetic ablation of β-catenin, a Wnt signaling effector, in the peripheral optic cup, we unexpectedly found that the ciliary body and iris still formed in adult mice. Further investigation showed that β-catenin-deficient cells were excluded from the developing ciliary margin (CM) and displaced into the neural retina, whereas the remaining wild-type cells in the CM continued to respond to Wnt signaling, and contributed to formation of the ciliary body and iris.

This segregation of wild-type and mutant cells was partly due to the loss of β-catenin-dependent adherens junctions, but more importantly, it was driven by a switch in cadherin expressions that was sufficient to segregate cells. The study therefore demonstrates that Wnt signaling establishes retinal compartments through passive cell competition driven by differential adhesion. Conceptually, the segregation resembles an oil-and-water phenomenon: cells sort passively due to differences in their adhesive properties rather than through an instructive signal sent from wild-type cells to actively change the fate of mutant cells.

Broadly speaking, understanding how signaling pathways regulate cell segregation may inform strategies for tissue regeneration, including efforts to control the organization and integration of stem-cell-derived tissues. Additional studies will be necessary to determine how this mechanism contributes to specific congenital eye disorders.

Were there any results that were particularly surprising or were a turning point for the project? Is there a particular aspect of the paper you are most proud of?

The major turning point was the finding that CM-derived structures (ciliary body, iris) still formed despite loss of Wnt signaling during embryonic development. This was unexpected because CM specification requires canonical Wnt signaling. That observation prompted us to look more closely at the mosaic distribution of mutant and wild-type cells, which eventually led to the mechanistic findings.

Scientifically, I am most impressed by how the paper addresses each question sequentially through experiments that are both rigorous and logically connected. I am also proud of the quality of the immunofluorescence images and their importance in communicating the findings.

How does this paper and research tie into your current medical and research interests?

Although my current work is in vascular tissue engineering rather than developmental ophthalmology, the conceptual connection is strong. Both fields examine how cell-cell interactions, and the mechanical or biochemical microenvironment regulate tissue organization and remodeling. During my time as a research technician, I learned immunofluorescence staining, PCR genotyping, cell culture, and western blot. Just as importantly, I learned how to interpret results, develop follow-up questions, and connect experimental observations into a mechanistic scientific narrative. The analytical and technical skills I developed in Dr. Zhang’s lab continue to shape how I approach questions.

The mentorship I received from Dr. Zhang was invaluable in shaping my scientific thinking. He taught me how to approach research with curiosity, formulate meaningful questions, and design rigorous experiments that build upon one another to produce a cohesive scientific narrative. He also gave me opportunities despite my limited initial experience in mouse genetics and signaling pathways, maintained an open-door policy, and mentored me with exceptional patience. I am deeply grateful for his support, and his example will continue to influence both how I conduct research and how I mentor trainees as I pursue a career in academic medicine.