The ancestral vertebrate brain and its cellular diversification during evolution

The question of how new organs originate and evolve is fundamental to understanding the evolution of complex animals.

Recent single-cell genomics technologies permit detailed investigations of the evolutionary ""birth"" of organs and constituent cell types.

Here, we will scrutinize the origins and cellular evolution of the vertebrate brain by generating and analyzing extensive single-cell transcriptomic, epigenomic, and spatial transcriptomic data across species representing all major vertebrate lineages.

The project has three interlaced aims:In Aim 1, we will infer the cell type repertoire of the ancestral vertebrate brain and its regulatory and molecular foundations, by comparing single-cell data across the most diverged vertebrate species.

In Aim 2, we will trace the cell type diversification of the ancestral brain during evolution and underlying regulatory and molecular changes.

We will first investigate the origination of two key cell types (oligodendrocytes and Purkinje cells) that underlie the emergence of neuron insulation and the cerebellum, respectively, thus facilitating functional elaborations of the jawed vertebrate brain.

We will then compare rates of cellular evolution across brain structures and test the hypothesis that cell type innovation was most frequent in the pallium, which affords advanced cognitive functions and experienced massive structural changes during evolution.In Aim 3, we will focus on the amniote pallium, a preeminent model for understanding neural tissue diversification.

We will scrutinize the origins, development, and evolutionary relationships of cell types in three new structures: neocortex, dorsal ventricular ridge, and Wulst.

Two of these structures the neocortex in mammals and Wulst in birds facilitated the convergent evolution of advanced cognitive abilities.Overall, our work will provide an overview of the cellular evolution of the vertebrate brain and, more generally, illuminate principles of cell type evolution.