Role of neural stem cell behavior in neocortical expansion across species
|Title||Role of neural stem cell behavior in neocortical expansion across species|
|Sponsor||Marie Skłodowska-Curie Action (MSCA)|
|Institution||Institute of Science and Technology Austria|
Associated cell lines
The neocortex regulates higher-level brain functions and behaviors, and is composed of heterogeneous populations of neurons and glia. Throughout mammalian evolution and especially in the human lineage, the neocortex in particular has expanded, accompanied by the generation of folds and fissures1. Although the mechanisms underlying neocortical expansion are not well understood, regulation of neural stem cell dynamics during embryonic development has been shown to be a critical process1. Radial glial progenitors (RGPs) constitute the major neural stem cell population in the developing neocortex1, producing nearly all neocortical neurons and a fraction of glial cells. Hippenmeyer and colleagues were instrumental in developing the MADM (Mosaic Analysis with Double Markers) technique, allowing unprecedented insight into the precise patterns of RGP division, and neuron and glia production. Quantitative assessment of the neurogenic potential of individual RGPs using MADM in mice suggest that the behavior of RGPs is remarkably coherent and predictable across all developmental stages in the mouse neocortex. How RGP behavior at the single progenitor level changes in different species with larger and more complex brains is unknown. By establishing the MADM technique for the first time in rat and in rodent cortical organoids, this research proposal will contribute to answering this complex question, and is highly complementary to ongoing experiments with human cortical organoids in the Hippenmeyer lab. Objectives 1. Generate MADM transgenic rats in order to assess the proliferative neurogenic and gliogenic potential and level of stochasticity of RGP behavior in a rodent with a larger brain. 2. Determine the recapitulation of RGP behavior in situ in cortical organoids derived from MADM mouse and rat embryonic stem cells (ESCs). 3. Compare RGP behavior at specific developmental time points in cortical organoids from mouse, rat and human, in collaboration with ERC-funded work with human embryonic stem cells performed by other members of the Hippenmeyer lab. This research proposal will extend MADM technology used in the Hippenmeyer lab to rats and to rodent cortical organoids, which will not only complement ongoing work in the Hippenmeyer lab, but will also address aspects of neurodevelopment that are currently unexplored. Experiments establishing MADM in rats in objective 1 will help elucidate mechanisms of neocortical expansion in rodents. Experiments in objective 2 will determine to what extent principles of RGP behavior in vivo are recapitulated in organoids, which are increasingly used to study fundamental mechanisms of human brain development and disease (Suzuki and Vanderhaeghen, 2015). Rather than analyzing complete lineage trees to determine the neurogenic and gliogenic potential of RGPs as in objectives 1 and 2, the recently added objective 3 will include human organoids to comparatively study RGP behavior during precise time windows across three species. Establishment of reproducible and rigorous assays using MADM in rodent organoids, in addition to human organoids, may provide in the future a potential intersectorial experimental platform for CRISPR and or chemical screening to assess neurodevelopmental outcomes across species.