Astrocytes Give Rise to New Neurons in the Adult Mammalian Hippocampus

TLDR

Neurogenesis in the adult hippocampal dentate gyrus continues throughout life, with progenitor cells residing in the subgranular layer, yet the in vivo primary precursors for new neurons had remained unidentified. We demonstrate that GFAP‑positive astrocyte‑like cells in the subgranular layer divide to produce new neurons, and that a distinct type D cell population derived from these astrocytes likely serves as a transient precursor in adult hippocampal neurogenesis.

Abstract

Neurogenesis in the dentate gyrus of the hippocampus persists throughout life in many vertebrates, including humans. The progenitors of these new neurons reside in the subgranular layer (SGL) of the dentate gyrus. Although stem cells that can self-renew and generate new neurons and glia have been cultured from the adult mammalian hippocampus, the <i>in vivo</i> primary precursors for the formation of new neurons have not been identified. Here we show that SGL cells, which express glial fibrillary acidic protein and have the characteristics of astrocytes, divide and generate new neurons under normal conditions or after the chemical removal of actively dividing cells. We also describe a population of small electron-dense SGL cells, which we call type D cells and are derived from the astrocytes and probably function as a transient precursor in the formation of new neurons. These results reveal the origins of new neurons in the adult hippocampus.