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EMT is thought to be the mechanism oRG cells are formed by kriegstein.
Epithelial and mesenchymal cells are two types of cells that show a transition between cell types during embryonic development. Epithelial cells belong to the epithelial tissue while mesenchymal cells belong to the connective tissue. During embryogenesis, mesenchymal-epithelial transition (MET) and epithelial-mesenchymal transition (EMT) occur between epithelial and mesenchymal cells. The main difference between epithelial cells and mesenchymal cells is that epithelial cells (specialized and destinated) (can derived from endoderm, ectoderm and mesoderm) line organs, vessels, and cavities, providing protection to the body whereas mesenchymal cells (unspecialized and undestinated) (most derived from mesoderm while some derived from neural crest cells and surface ectoderm) are capable of differentiating into any type of smooth muscle, vascular endothelium, connective tissue, supporting tissue or blood cells.
Epithelium always have apico-basal polarity (just as the neuroepithelium). During the EMT the first step is polarity loss.
Simple epithelium contains a single layer of cells. Stratified epithelium contains multiple layers of cells, and pseudostratified epithelium contains a single layer of cells where the nuclei are arranged in different levels.
The cortex emerges from an initially pseudostratified neuroepithelium that gives rise to radial glia, the neural stem cells of the cortex1.
The human cerebral cortex is more than three times expanded compared to our closest nonhuman primate relatives
Radial glia generate neurons, initially through direct neurogenesis and then indirectly through transit-amplifying IPCs5. A number of subtypes of radial glia have been identified as the cortex matures, and their primary role in neurogenesis declines late in the second trimester, at which point they generate the glial populations of the cortex6.
the first trimester (actually the time we are looking for,,) of cortical development has not been described at this level of molecular detail, and important questions remain about the timing of neurogenesis
