Single-cell data for heart and lung tissues of the Eurasian Tree Sparrow

Birds' specialized cardiac (four-chamber heart) and lung systems (parabronchial lung/air sac) are critical for the evolution of their flight lifestyle. Here, we construct single-cell atlases for heart and lung tissues of a wild bird (Eurasian Tree Sparrow) from two different elevational environments and life stages. We found a substantial difference in cell abundance and transcriptional divergence between neonatal and adult birds. Additionally, adult and neonatal birds exhibited different cellular and regulatory responses to a high-elevation environment. By comparing birds' data with the corresponding published data for mice and humans, we found that cell types exhibited different extents of transcriptomic divergence across species. The cardiomyocytes show the most conserved expression profiles, and the alveolar cells exhibit the most divergent expression profiles across species. We further demonstrate the tissue and cell-type specific conserved and divergent transcriptional profiles across species and their relevance to heart diseases and respiratory virus-mediated diseases. Overall, our study sheds light on the cellular heterogeneity and regulatory mechanisms of birds' hearts and lungs, providing information for the evolution of the hearts and lungs of endothermic animals.