Article Impact Level: HIGH Data Quality: STRONG Summary of Circulation https://doi.org/10.1161/CIRCULATIONAHA.125.074959 Dr. Timothy Pan et al.
Points
- The study used long-read single-nucleus RNA sequencing and computational analysis to map isoform heterogeneity in the human left ventricle.
- Isoform heterogeneity is widespread in the cardiac system, acting as a posttranscriptional buffer that calibrates molecular reservoirs.
- In healthy hearts, around 30% of cell type–specific genes were polyform, utilizing multiple isoforms tailored to specific programs.
- Heart failure in cardiomyocytes showed marked isoform usage shifts in 379 genes, affecting protein coding outcomes and biotypes.
- The data present a comprehensive atlas, suggesting crucial roles for isoforms in buffering core cellular programs and disease states.
Summary
This research utilized long-read single-nucleus RNA sequencing and advanced computational analysis to comprehensively map the full-length isoform heterogeneities, expression patterns, and usage shifts across various cell types, cell states, and cardiac conditions within the adult human left ventricle. This detailed characterization aimed to fill gaps in understanding the human heart isoform landscape, recognizing alternative splicing’s critical role in normal heart development and cardiac disease progression by influencing protein-coding sequences, functional domains, and molecular networks. The methodology included in silico functional assessments, validation via RT-qPCR and targeted amplicon sequencing, and the development of an interactive web server for data exploration.
The findings reveal widespread isoform heterogeneity within the cardiac cellular system, indicating its function as a posttranscriptional buffer that finely calibrates molecular reservoirs in human hearts. Specifically, in healthy left ventricles, approximately 30% of cell type–specific genes were identified as “polyform,” utilizing multiple isoforms adapted to distinct cellular programs. Among genes expressed ubiquitously, over 300 displayed differential isoform usage with clear cell type specificity, highlighting a sophisticated layer of gene regulation.
Comparing healthy hearts with those in heart failure, 379 genes in cardiomyocytes exhibited significant isoform usage shifts. The majority of these shifts are predicted to alter protein coding outcomes through direct changes in protein coding sequences and transitions between intron retention and non–protein-coding biotypes. In contrast, cell state–specific programs were observed to predominantly operate on “monoform” genes, which are associated with changes across different cell states. Furthermore, the data uncovered heart failure–associated differential isoform usage events within the stromal and immune cell types of the cardiac microenvironment, underscoring the broad impact of splicing alterations in cardiac disease.
Link to the article: https://www.ahajournals.org/doi/10.1161/CIRCULATIONAHA.125.074959
References
Pan, T., Lu, L., Youker, K., Shiau, C.-K., Wang, M., Lin, H.-Y., Nguyen, A., He, Y., Tong, E., Zhu, P., Ranka, R., Yan, Y., Sinha, A., Bharat, A., Eagar, T., Wilcox, J., Bhimaraj, A., & Gao, R. (2025). Single-cell splicing isoform atlas of the adult human heart and heart failure. Circulation, CIRCULATIONAHA.125.074959. https://doi.org/10.1161/CIRCULATIONAHA.125.074959
