A novel model system to address the relevance of aggregation in animal origins

This is the authors' abstract. We don't add key points for this paper.

The origin of animals from unicellular ancestors remains a fundamental biological question. Cell aggregation, a widespread eukaryotic behaviour, has been underappreciated as a potential pathway to multicellularity. Here, we establish Capsaspora owczarzaki , a close unicellular relative of animals, as a model system to investigate this process. We demonstrate C. owzarzaki aggregates dynamically deploying key metazoan-related genes such as integrins, tyrosine kinases, and Hippo pathway components. Moreover, we further model mathematically the aggregation process, revealing a threshold-like adhesion response to fetal bovine serum (FBS) and dynamic aggregation kinetics driven by cell-cell adhesion and access to FBS. Our findings suggest that cell aggregation could have played a pivotal role in the evolution of animal multicellularity, providing a context for the origin of genes now crucial for animal development. This work positions Capsaspora as a powerful model system for quantitatively studying the evolutionary transition to multicellularity through cell aggregation.