Abstract
Comparing single-cell transcriptomic atlases from diverse organisms can provide evolutionary definition of cell types, elucidate the origins of cellular diversity, and transfer cell type knowledge between species. Yet, comparison among distant relatives, especially beyond a single phylum, is hindered by complex gene histories, lineage-specific inventions, and cell type evolutionary diversifications. Here, we develop a method to enable mapping cell atlases throughout Metazoa spanning sponge to mouse. Within phyla, we identify homologous cell types, even between distant species, with some even emerging from distinct germ layers. Across phyla, we find ancient cell type families that form densely interconnected groups, including contractile and stem cells, indicating they likely arose early in animal evolution through hierarchical diversifications. These homologous cell types often substitute paralog expressions at surprising prevalence. Our findings advance the understanding of cell type diversity across the tree of life and the evolution of associated gene expression programs.
Competing Interest Statement
The authors have declared no competing interest.
