Evolution of genetic mechanisms regulating cortical neurogenesis

Abstract

The size of the cerebral cortex increases dramatically across amniotes, from reptiles to great apes. This is primarily due to different numbers of neurons and glial cells produced during embryonic development. The evolutionary expansion of cortical neurogenesis was linked to changes in neural stem and progenitor cells, which acquired increased capacity of self-amplification and neuron production. Evolution works via changes in the genome, and recent studies have identified a small number of new genes that emerged in the recent human and primate lineages, promoting cortical progenitor proliferation and increased neurogenesis. However, most of the mammalian genome corresponds to noncoding DNA that contains gene-regulatory elements, and recent evidence precisely points at changes in expression levels of conserved genes as key in the evolution of cortical neurogenesis. Here, we provide an overview of basic cellular mechanisms involved in cortical neurogenesis across amniotes, and discuss recent progress on genetic mechanisms that may have changed during evolution, including gene expression regulation, leading to the expansion of the cerebral cortex.

Conservation and Diversification of Pallial Cell Types across Vertebrates: An Evo-Devo Perspective

“…Our focus here will be on the pallium or the dorsal telencephalon, which is a major subdivision of the vertebrate embryonic telencephalon. It is characterized by the presence of a larger proportion of glutamatergic neurons and a subpopulation of interneurons derived from subpallial progenitor domains, populated via tangential migration to their pallial destinations [Medina and Abellán, 2009;Montiel and Aboitiz, 2015;Espinós et al, 2022]. This higher proportion of excitatory neurons (ENs) is recognized across most vertebrates [Markram et al, 2004;Suryanarayana et al, 2017;Tosches et al, 2018;Huang and Paul, 2019].…”

“…They consist of many cytoarchitectural variants in different vertebrate clades including laminated and nuclear structures, with their corresponding developmental domains yet unclear. Reconciling the variance in the adult derivatives vis-à-vis their developmental origins and lineages has been anything but straightforward [García- Moreno and Molnár, 2020;Espinós et al, 2022]. In mammals, the developing pallium can be divided, as proposed by the "tetrapartite model" [Puelles, 2017], into four domainsthe medial, dorsal, lateral, and ventral pallia (Fig.…”

Evolution of cortical neurons supporting human cognition

“…We also acknowledge that evolutionary changes in the developmental timing of cortical neurons and synapses play an important role in the evolution of human cognition. Although this topic falls outside the scope of this review, we would like to point the reader to excellent recent reviews [24][25][26]. Finally, the focus of our review is on the pyramidal neurons of supragranular layers, as the morpho-electric properties of these neurons are more extensively studied in human cortex compared with deeper layers.…”

Keeping the balance: Trade-offs between human brain evolution, autism, and schizophrenia

“…Evolutionary changes in gene activity may emerge from alterations in the sequence of the gene (for review see Espinós et al (2022) ) or of the DNA regulatory elements including promoters, enhancers, silencers or insulators (for reviews see Bae et al (2015) ; Silver, (2016) ; Liu et al (2021) ). As a result, genes which are similarly expressed across species may still differ in function due to divergence in coding sequences ( Staes et al, 2017 ), while genes with conserved coding sequence may vary in expression level between species due to alterations in regulatory program ( Prescott et al, 2015 ; Kanton et al, 2019 ; Wang et al, 2020 ).…”