Penn-Led International Research Team Builds Single-Cell Kidney Atlas to Advance Precision Medicine
Nature Genetics study connects Penn researchers with international collaborators, including Charité–Universitätsmedizin Berlin, to reveal how biological pathways vary across individual patients.
A Penn-led international research team has developed a cross-species single-cell kidney atlas that offers a new way to understand how molecular pathways differ among individual patients—and how findings from experimental models can be translated more effectively into precision medicine.
Published in Nature Genetics on August 7, 2025, the study integrates more than one million cells from 140 human and animal samples, defining more than 70 conserved cell states across human and rodent kidneys. The researchers also developed CellSpectra, a computational method for measuring how coordinated patterns of gene activity within biological pathways vary among individual patients and across species.
The research brings together expertise in nephrology, genetics, computational biology, and single-cell science across Penn and an international network of collaborators, including researchers at Charité–Universitätsmedizin Berlin.
Katalin Susztak, MD, Ph.D.
Willard and Rhoda Ware Professor of Diabetes and Metabolic Diseases IV
Department of Medicine, Perelman School of Medicine
Co-Chair, Penn/CHOP Kidney Innovation Center
Member, Institute for Diabetes, Obesity and Metabolism
Member, Institute for Translational Medicine and Therapeutics Graduate Group in Cell and Molecular Biology
Graduate Group in Genomics and Computational Biology
Susztak conceptualized the study and jointly supervised the research with Nancy R. Zhang, Professor of Statistics and Data Science in the Wharton School. The interdisciplinary team brought together expertise in nephrology, genetics, computational biology, clinical research, and single-cell science.
Single-cell technologies allow scientists to measure gene activity within individual cells, generating extraordinarily detailed maps of healthy and diseased tissue. Translating these enormous datasets into information that can guide treatment for individual patients, however, remains a significant challenge. Differences between human disease and experimental animal models create an additional barrier.
The researchers developed a computational approach called CellSpectra to examine coordinated patterns of gene activity within specific cell types and compare those pathways across individual patients and species. This approach can help researchers identify biological processes associated with disease and determine which experimental models most closely reflect the molecular features found in human patients.
The study demonstrates how large-scale single-cell data can move beyond cataloging cell types toward understanding the biological pathways that distinguish one patient from another—an important step toward applying genomic research more directly to precision medicine.
From Penn to Berlin: Building a Transatlantic Kidney Research Network
The study also illustrates how international scientific collaborations can grow through the movement of researchers and the relationships established during training. Michael S. Balzer, MD, a co-author of the study, conducted postdoctoral research in Penn’s Renal-Electrolyte and Hypertension Division, establishing an early connection with Penn’s kidney research community and its work in molecular nephrology and single-cell science.
Balzer subsequently continued his physician-scientist career in Germany, developing a research program focused on translational molecular nephrology and single-cell phenotyping. His participation in the Nature Genetics study demonstrates how relationships formed through research training can develop into longer-term international collaborations, allowing expertise, methods, and scientific questions to continue moving between institutions.
The German component of the research also received support from organizations including the German Research Foundation (DFG) and the Berlin Institute of Health at Charité Clinician Scientist Program, further connecting the project to Germany’s biomedical research infrastructure.
Balzer now leads the Balzer Lab, where his team applies single-cell and related molecular approaches to questions in kidney disease. His trajectory from postdoctoral research at Penn to an independent research program in Europe demonstrates one way that researcher mobility can create durable scientific networks extending well beyond an individual appointment.
International partnerships such as this expand the expertise, data, and research infrastructure available to investigators while creating pathways for discoveries and methodologies developed at one institution to evolve through sustained collaboration elsewhere. Through support for interdisciplinary research, researcher development, and international engagement, the Office of the Vice Provost for Research (OVPR) helps strengthen relationships connecting Penn investigators and trainees with leading research communities around the world.
Read the study in Nature Genetics:
Analysis of individual patient pathway coordination in a cross-species single-cell kidney atlas