2D and 3D Stem Cell Models of Primate Cortical Development Identify Species-Specific Differences in Progenitor Behavior Contributing to Brain Size

TLDR

Variation in cerebral cortex size and complexity is thought to contribute to differences in cognitive ability between humans and other animals. The study compares cortical progenitor cell output in humans and three nonhuman primates. This comparison is performed by directed differentiation of pluripotent stem cells in adherent two-dimensional and organoid three-dimensional culture systems. Clonal lineage analysis showed that primate cortical progenitors proliferate for a protracted period, generating early-born neurons, and that the extent of this additional expansion differs among primates, resulting in varying numbers of neurons per progenitor and indicating a cell-autonomous mechanism that partly regulates cortical size.

Abstract

Variation in cerebral cortex size and complexity is thought to contribute to differences in cognitive ability between humans and other animals. Here we compare cortical progenitor cell output in humans and three nonhuman primates using directed differentiation of pluripotent stem cells (PSCs) in adherent two-dimensional (2D) and organoid three-dimensional (3D) culture systems. Clonal lineage analysis showed that primate cortical progenitors proliferate for a protracted period of time, during which they generate early-born neurons, in contrast to rodents, where this expansion phase largely ceases before neurogenesis begins. The extent of this additional cortical progenitor expansion differs among primates, leading to differences in the number of neurons generated by each progenitor cell. We found that this mechanism for controlling cortical size is regulated cell autonomously in culture, suggesting that primate cerebral cortex size is regulated at least in part at the level of individual cortical progenitor cell clonal output.