Neurogenesis in the Adult Hippocampus

Abstract

Of the neurogenic zones in the adult brain, adult hippocampal neurogenesis attracts the most attention, because it is involved in higher cognitive function, most notably memory processes, and certain affective behaviors. Adult hippocampal neurogenesis is also found in humans at a considerable level and appears to contribute significantly to hippocampal plasticity across the life span, because it is regulated by activity. Adult hippocampal neurogenesis generates new excitatory granule cells in the dentate gyrus, whose axons form the mossy fiber tract that links the dentate gyrus to CA3. It originates from a population of radial glia-like precursor cells (type 1 cells) that have astrocytic properties, express markers of neural stem cells and divide rarely. They give rise to intermediate progenitor cells with first glial (type 2a) and then neuronal (type 2b) phenotype. Through a migratory neuroblast-like stage (type 3), the newborn, lineage-committed cells exit the cell cycle and enter a maturation stage, during which they extend their dendrites into a the molecular layer and their axon to CA3. They go through a period of several weeks, during which they show increased synaptic plasticity, before finally becoming indistinguishable from the older granule cells.

Distinct capacity for differentiation to inner ear cell types by progenitor cells of the cochlea and vestibular organs

“…Some of the neural progenitors in the embryo are restricted to playing a developmental role only. Stem cells remain, however, in the dentate gyrus and the subventricular zone, where they give rise to the rostral migratory stream and hippocampal neurons (Kempermann et al, 2015;Kriegstein and Alvarez-Buylla, 2009;Zhao et al, 2008). The capacity of neural stem cells to differentiate to single or multiple cell types has been difficult to assess without sufficient markers for both the progenitors and their cellular progeny.…”

Buttressing a balanced brain: Target-derived FGF signaling regulates excitatory/inhibitory tone and adult neurogenesis within the maturating hippocampal network

“…3 Another important and unique feature of hippocampal circuitry is that the subgranular zone (SGZ) in the dentate gyrus is one of at least 2 areas in the brain where neurogenesis continues into adulthood. 4 The rate at which new neurons are born depends on many factors, including exercise, stress, hormones, network activity; 5,6 and the DGCs that arise through adult neurogenesis are important in aspects of memory formation. 7,8 Disruption of either excitatory/ inhibitory balance or rates of adult neurogenesis causes neuropsychiatric disease: abnormal excitatory/inhibitory balance can lead to epilepsy, autism spectrum disorders, schizophrenia, cognitive processing, and anxiety disorders; 9,10,11,12 and abnormal neurogenesis is seen in depression, cognitive impairment, and epilepsy.…”

Selective transduction of astrocytic and neuronal CNS subpopulations by lentiviral vectors pseudotyped with Chikungunya virus envelope

“…In the adult DG DCX is only expressed in cells contributing to adult neurogenesis and therefore the transduction of such cells by this vector can be used as evidence of newborn adult generated neurons [52,53]. The stem cells behind this process are astrocytic in nature [54] raising the intriguing possibility of a common receptor-bearing progenitor for both striatal astrocytes and dentate granule neurons. The spatial distribution within the DG where transduction was most prominent in layers GCL1 less in 2 and absent in GLC3 is most intriguing and is similar to what was observed in the hippocampus with CMV-egfp VSV-G LVs [55].…”