Abstract
BackgroundAdult neurogenesis occurs in specific regions of the mammalian brain such as the dentate gyrus of the hippocampus. In the neurogenic region, neural progenitor cells continuously divide and give birth to new neurons. Although biological properties of neurons and glia in the hippocampus have been demonstrated to fluctuate depending on specific times of the day, it is unclear if neural progenitors and neurogenesis in the adult brain are temporally controlled within the day.Methodology/Principal FindingsHere we demonstrate that in the dentate gyrus of the adult mouse hippocampus, the number of M-phase cells shows a day/night variation throughout the day, with a significant increase during the nighttime. The M-phase cell number is constant throughout the day in the subventricular zone of the forebrain, another site of adult neurogenesis, indicating the daily rhythm of progenitor mitosis is region-specific. Importantly, the nighttime enhancement of hippocampal progenitor mitosis is accompanied by a nighttime increase of newborn neurons.Conclusions/SignificanceThese results indicate that neurogenesis in the adult hippocampus occurs in a time-of-day-dependent fashion, which may dictate daily modifications of dentate gyrus physiology.
Highlights
Neurogenesis in the mammalian brain persists through adulthood mainly within the two neurogenic structures, the dentate gyrus of the hippocampus and the subventricular zone of the forebrain [1,2]
Glial proliferation seems to depend on the time of the day in the hilus. These observations suggest an intimate connection between the temporal information and hippocampal neurons/glia, it is unclear whether neural progenitor cells and neurogenesis in the dentate gyrus of the hippocampus are modulated in a time-ofday-dependent fashion
We examined the number of dividing cells in the subgranular zone (SGZ) of the dentate gyrus by immunostaining with an antibody against phospho-histone H3 (PH3), a marker for M-phase cells
Summary
Neurogenesis in the mammalian brain persists through adulthood mainly within the two neurogenic structures, the dentate gyrus of the hippocampus and the subventricular zone of the forebrain [1,2] In these areas neural progenitor cells continuously divide and give birth to new neurons [1]. Glial proliferation seems to depend on the time of the day in the hilus These observations suggest an intimate connection between the temporal information and hippocampal neurons/glia, it is unclear whether neural progenitor cells and neurogenesis in the dentate gyrus of the hippocampus are modulated in a time-ofday-dependent fashion. Biological properties of neurons and glia in the hippocampus have been demonstrated to fluctuate depending on specific times of the day, it is unclear if neural progenitors and neurogenesis in the adult brain are temporally controlled within the day
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