Speaker
Description
Studying the origin and evolution of tissues is a main interest in comparative biology. However, a core challenge lies in the approach employed for distinguishing homology from convergence, and innovation. In recent years, the advent and development of cell type-focused technologies have allowed the use of cell type composition comparisons between organs of different species. This strategy has yielded valuable insights into the evolution of complex structures with heterogeneous cell compositions, such as brains and gonads. However, this approach is not without complications because cells, like other biological units, evolve and are influenced by selective pressures. The challenge is further intensified by the difficulty in identifying and classifying cells with comparative value, given that historically cell identity has been determined based on morphology and function, mostly in a handful of model organisms.
To accurately identify and compare cells across species, we need an evolutionary approach to cell identification, ideally nested within a phylogenetic framework. The evolutionary concept of cell type, which focuses on the mechanisms underlying the origin and evolution of cell types across species, allows us to understand how cell types originate and diversify, which has significant implications for addressing cell type evolution across phylogenetic lineages. Nonetheless, applying this concept presents numerous challenges, including comparing transcriptomic data from diverse cells across evolutionarily distant species and reconciling cell evolution with the broader evolution of organs.
By employing a cell type evolution framework, we address the origins and evolution of the brain and gonads across vertebrates. To accomplish this, we are generating a comprehensive and spatially resolved transcriptomic cell type atlas for these organs from different species whose phylogenetic positions enable trait reconstruction within the vertebrate clade. By comparing broad cell type classes and families between these species, we have discovered conserved expression profiles, indicating that these families and classes are homologous across vertebrates.
Collectively, this research identifies ancestral cellular configurations and their diversification across vertebrate clades. Notably, these findings not only address unresolved questions in comparative biology but also point to new directions concerning the temporal and mechanistic dynamics behind the evolution of cells and organs. Additionally, this research proposes ideas on new directions regarding cell type evolution studies, addressing the need for multidisciplinary approaches akin to "integrative taxonomy", that help further understand cell identity and evolution and its interplay with the evolution of organs and species.
