6533b7ddfe1ef96bd127474c

RESEARCH PRODUCT

Neurobiology

subject

description

In the adult mammalian brain, neurogenesis occurs in the dentate gyrus (DG) of the hippocampus throughout the life span. Neurogenesis has been extensively characterized in rodents and to a lesser extent in primates. Within the hippocampus, the adult neurogenic niche is specifically located in the subgranular zone of the DG, where neural stem/progenitor cells (NSPCs) reside. It has been confirmed that these stem cells, which possess astrocytic features, give rise to intermediate progenitors, immature neurons, and neurons. The NSPCs have radial glia-like morphology and electrolucid cytoplasm, in contrast to the immature neurons whose cytoplasm is electrodense, containing abundant polyribosomes and microtubules. The newly born neurons are known to migrate to the granule cell layer of the DG where they mature and integrate into the existing hippocampal circuitry. Here we review the ultrastructure of the NSPCs as revealed by intrinsic and extrinsic markers characteristic of stem cells, proliferating cells, or immature neurons. Further, we discuss the morphological characteristics of the NSPCs and the immature neurons in both rodents and primates. We also highlight some of the future challenges that lie ahead in this field, including the characterization of the ultrastructural properties of the NSPCs in humans and their behavior throughout human life.