The evolution of cell types and neural circuits in the cerebral cortex
Maria Antonietta Tosches
Department of Biological Sciences, Columbia University, New York City
The long-term vision of the Tosches lab is to unravel fundamental principles underlying the evolution of vertebrate brains, using neuron types as the primary units of analysis and comparison across species. Questions addressed in the lab include: (1) Evo-devo: how does variation of developmental processes fuel the evolution of neuronal diversity? (2) Cell types: how do neuron types in the same brain areas compare across species? (3) Circuits and behavior: do conserved neuron types and circuits have similar functions in distantly related species?
In this talk, I will describe recent insights emerging from the analysis of the salamander telencephalon. Our transcriptomic comparison of neuron types sampled from salamanders and other vertebrate species clarifies the evolutionary origins of cortical cell types: while GABAergic interneurons belong to ancient cell classes, glutamatergic pyramidal neurons have diversified extensively in vertebrate evolution. Furthermore, the analysis of salamander brain development reveals conserved principles for the assembly of a layered cerebral cortex. In the amphibian pallium, which is layered, multipotent progenitors generate sequentially neurons with distinct identities in an outside-in sequence. These findings indicate that in mammalian ancestors, the number and diversity of cortical layers expanded concomitantly with the inversion of corticogenesis from outside-in to inside-out.