Evaluating the functional state of adult-born neurons in the adult dentate gyrus of the hippocampus: from birth to functional integration

2015 ◽  
Vol 26 (3) ◽  
Author(s):  
Andrea Aguilar-Arredondo ◽  
Clorinda Arias ◽  
Angélica Zepeda
Keyword(s):  
Dentate Gyrus ◽  
Functional State ◽  
Functional Integration ◽  
Critical Time ◽  
Hippocampal Neurogenesis ◽  
Adult Brain ◽  
Maturation Stage ◽  
Methodological Approaches ◽  
Adult Born Neurons ◽  
Newborn Neurons

AbstractHippocampal neurogenesis occurs in the adult brain in various species, including humans. A compelling question that arose when neurogenesis was accepted to occur in the adult dentate gyrus (DG) is whether new neurons become functionally relevant over time, which is key for interpreting their potential contributions to synaptic circuitry. The functional state of adult-born neurons has been evaluated using various methodological approaches, which have, in turn, yielded seemingly conflicting results regarding the timing of maturation and functional integration. Here, we review the contributions of different methodological approaches to addressing the maturation process of adult-born neurons and their functional state, discussing the contributions and limitations of each method. We aim to provide a framework for interpreting results based on the approaches currently used in neuroscience for evaluating functional integration. As shown by the experimental evidence, adult-born neurons are prone to respond from early stages, even when they are not yet fully integrated into circuits. The ongoing integration process for the newborn neurons is characterised by different features. However, they may contribute differently to the network depending on their maturation stage. When combined, the strategies used to date convey a comprehensive view of the functional development of newly born neurons while providing a framework for approaching the critical time at which new neurons become functionally integrated and influence brain function.

scholarly journals Androgens Increase Survival of Adult-Born Neurons in the Dentate Gyrus by an Androgen Receptor-Dependent Mechanism in Male Rats

Endocrinology ◽  
2013 ◽  
Vol 154 (9) ◽  
pp. 3294-3304 ◽  
Author(s):  
D. K. Hamson ◽  
S. R. Wainwright ◽  
J. R. Taylor ◽  
B. A. Jones ◽  
N. V. Watson ◽  
...  
Keyword(s):  
Androgen Receptor ◽  
Dentate Gyrus ◽  
Adult Neurogenesis ◽  
Hippocampal Neurogenesis ◽  
Adult Brain ◽  
Male Rats ◽  
Male Rat ◽  
Testicular Feminization ◽  
Wild Type ◽  
Adult Born Neurons

Gonadal steroids are potent regulators of adult neurogenesis. We previously reported that androgens, such as testosterone (T) and dihydrotestosterone (DHT), but not estradiol, increased the survival of new neurons in the dentate gyrus of the male rat. These results suggest androgens regulate hippocampal neurogenesis via the androgen receptor (AR). To test this supposition, we examined the role of ARs in hippocampal neurogenesis using 2 different approaches. In experiment 1, we examined neurogenesis in male rats insensitive to androgens due to a naturally occurring mutation in the gene encoding the AR (termed testicular feminization mutation) compared with wild-type males. In experiment 2, we injected the AR antagonist, flutamide, into castrated male rats and compared neurogenesis levels in the dentate gyrus of DHT and oil-treated controls. In experiment 1, chronic T increased hippocampal neurogenesis in wild-type males but not in androgen-insensitive testicular feminization mutation males. In experiment 2, DHT increased hippocampal neurogenesis via cell survival, an effect that was blocked by concurrent treatment with flutamide. DHT, however, did not affect cell proliferation. Interestingly, cells expressing doublecortin, a marker of immature neurons, did not colabel with ARs in the dentate gyrus, but ARs were robustly expressed in other regions of the hippocampus. Together these studies provide complementary evidence that androgens regulate adult neurogenesis in the hippocampus via the AR but at a site other than the dentate gyrus. Understanding where in the brain androgens act to increase the survival of new neurons in the adult brain may have implications for neurodegenerative disorders.

Is adult hippocampal neurogenesis really relevant for the treatment of psychiatric disorders?

2020 ◽  
Vol 18 ◽  
Author(s):  
Marco Carli ◽  
Stefano Aringhieri ◽  
Shivakumar Kolachalam ◽  
Biancamaria Longoni ◽  
Giovanna Grenno ◽  
...  
Keyword(s):  
Psychiatric Disorders ◽  
Emotional Processing ◽  
Imaging Techniques ◽  
Hippocampal Neurogenesis ◽  
Adult Brain ◽  
Adult Hippocampal Neurogenesis ◽  
Mood Stabilizers ◽  
Post Traumatic Stress ◽  
Newborn Neurons ◽  
Hippocampal Circuitry

: Adult neurogenesis consists in the generation of newborn neurons from neural stem cells taking place in the adult brain. In mammals, this process is limited to very few areas of the brain, and one of these neurogenic niches is the subgranular layer of the dentate gyrus (DG) of the hippocampus. Adult newborn neurons are generated from quiescent neural progenitors (QNPs), which differentiate through different steps into mature granule cells (GCs), to be finally integrated into the existing hippocampal circuitry. In animal models, adult hippocampal neurogenesis (AHN) is relevant for pattern discrimination, cognitive flexibility, emotional processing and resilience to stressful situations. Imaging techniques allow to visualize newborn neurons within the hippocampus through all their stages of development and differentiation. In humans, the evidence of AHN is more challenging, and, based on recent findings, it persists through the adulthood, even if it declines with age. Whether this process has an important role in human brain function and how it integrates into the existing hippocampal circuitry is still a matter of exciting debate. Importantly, AHN deficiency has been proposed to be relevant in many psychiatric disorders, including mood disorders, anxiety, post-traumatic stress disorder and schizophrenia. This review aims to investigate how AHN is altered in different psychiatric conditions and how pharmacological treatments can rescue this process. In fact, many psychoactive drugs, such as antidepressants, mood stabilizers and atypical antipsychotics (AAPs), can boost AHN with different results. In addition, some non-pharmacological approaches are discussed as well.

scholarly journals Canonical Wnt-signaling modulates the tempo of dendritic growth of adult-born hippocampal neurons

2020 ◽  
Author(s):  
Jana Heppt ◽  
Marie-Theres Wittmann ◽  
Jingzhong Zhang ◽  
Daniela Vogt-Weisenhorn ◽  
Nilima Prakash ◽  
...  
Keyword(s):  
Young Adult ◽  
Wnt Signaling ◽  
Progenitor Cells ◽  
Dendritic Growth ◽  
Functional Integration ◽  
Hippocampal Neurogenesis ◽  
Adult Hippocampal Neurogenesis ◽  
Canonical Wnt Signaling ◽  
Adult Born Neurons ◽  
Canonical Wnt

AbstractIn adult hippocampal neurogenesis neural stem/progenitor cells generate new dentate granule neurons that contribute to hippocampal plasticity. The establishment of a morphologically defined dendritic arbor is central to the functional integration of adult-born neurons. Here, we investigated the role of canonical Wnt/β-catenin-signaling in dendritogenesis of adult-born neurons. We show that canonical Wnt-signaling follows a biphasic pattern, with high activity in stem/progenitor cells, attenuation in early immature neurons, and re-activation during maturation, and demonstrate that the biphasic activity pattern is required for proper dendrite development. Increasing β-catenin-signaling in maturing neurons of young adult mice transiently accelerated dendritic growth, but eventually resulted in dendritic defects and excessive spine numbers. In middle-aged mice, in which protracted dendrite and spine development was paralleled by lower canonical Wnt-signaling activity, enhancement of β-catenin-signaling restored dendritic growth and spine formation to levels observed in young adult animals. Our data indicate that precise timing and strength of β-catenin-signaling is essential for the correct functional integration of adult-born neurons and suggest Wnt/β-catenin-signaling as a pathway to ameliorate deficits in adult neurogenesis during aging.

scholarly journals Haploinsufficiency of the psychiatric risk gene Cyfip1 causes abnormal postnatal hippocampal neurogenesis through microglial and Arp2/3 mediated actin dependent mechanisms

2018 ◽  
Author(s):  
Niels Haan ◽  
Laura J Westacott ◽  
Jenny Carter ◽  
Michael J Owen ◽  
William P Gray ◽  
...  
Keyword(s):  
Genetic Risk ◽  
Hippocampal Neurons ◽  
Hippocampal Neurogenesis ◽  
Actin Dynamics ◽  
Biological Processes ◽  
Risk Gene ◽  
A Cell ◽  
Adult Born Neurons ◽  
Newborn Neurons ◽  
And Migration

AbstractGenetic risk factors can significantly increase chances of developing psychiatric disorders, but the underlying biological processes through which this risk is effected remain largely unknown. Here we show that haploinsufficiency of Cyfip1, a candidate risk gene present in the pathogenic 15q11.2(BP1-BP2) deletion may impact on psychopathology via abnormalities in cell survival and migration of newborn neurons during postnatal hippocampal neurogenesis. We demonstrate that haploinsufficiency of Cyfip1 leads to increased numbers of adult born hippocampal neurons due to reduced apoptosis, without altering proliferation. We confirm this is due to a cell autonomous failure of microglia to induce apoptosis through the secretion of the appropriate factors. Furthermore, we show an abnormal migration of adult-born neurons due to altered Arp2/3 mediated actin dynamics. Together, our findings throw new light on how the genetic risk candidate Cyfip1 may influence the hippocampus, a brain region with strong evidence for involvement in psychopathology.

scholarly journals Metabolic tuning of inhibition regulates hippocampal neurogenesis in the adult brain

2020 ◽  
Vol 117 (41) ◽  
pp. 25818-25829
Author(s):  
Xinxing Wang ◽  
Hanxiao Liu ◽  
Johannes Morstein ◽  
Alexander J. E. Novak ◽  
Dirk Trauner ◽  
...  
Keyword(s):  
Dentate Gyrus ◽  
Energy Homeostasis ◽  
Inhibitory Neuron ◽  
Hippocampal Neurogenesis ◽  
Adult Brain ◽  
Adult Hippocampal Neurogenesis ◽  
Neuron Activity ◽  
Adult Mice ◽  
Sphingosine 1 Phosphate ◽  
Underlying Mechanisms

Hippocampus-engaged behaviors stimulate neurogenesis in the adult dentate gyrus by largely unknown means. To explore the underlying mechanisms, we used tetrode recording to analyze neuronal activity in the dentate gyrus of freely moving adult mice during hippocampus-engaged contextual exploration. We found that exploration induced an overall sustained increase in inhibitory neuron activity that was concomitant with decreased excitatory neuron activity. A mathematical model based on energy homeostasis in the dentate gyrus showed that enhanced inhibition and decreased excitation resulted in a similar increase in neurogenesis to that observed experimentally. To mechanistically investigate this sustained inhibitory regulation, we performed metabolomic and lipidomic profiling of the hippocampus during exploration. We found sustainably increased signaling of sphingosine-1-phosphate, a bioactive metabolite, during exploration. Furthermore, we found that sphingosine-1-phosphate signaling through its receptor 2 increased interneuron activity and thus mediated exploration-induced neurogenesis. Taken together, our findings point to a behavior-metabolism circuit pathway through which experience regulates adult hippocampal neurogenesis.

scholarly journals Adult dentate gyrus neurogenesis: a functional model

2019 ◽  
Author(s):  
Olivia Gozel ◽  
Wulfram Gerstner
Keyword(s):  
Theoretical Model ◽  
Dentate Gyrus ◽  
Granule Cells ◽  
Functional Integration ◽  
Functional Model ◽  
Behavioral Pattern ◽  
Pattern Separation ◽  
Cell Maturation ◽  
Newborn Cell ◽  
Newborn Neurons

SummaryIn adult dentate gyrus neurogenesis, the link between maturation of newborn neurons and their function, such as behavioral pattern separation, has remained puzzling. By analyzing a theoretical model, we show that the switch from excitation to inhibition of the GABAergic input onto maturing newborn cells is crucial for their proper functional integration. When the GABAergic input is excitatory, cooperativity drives the growth of synapses such that newborn cells become sensitive to stimuli similar to those that activate mature cells. When GABAergic input switches to inhibitory, competition pushes the configuration of synapses onto newborn cells towards stimuli that are different from previously stored ones. This enables the maturing newborn cells to code for concepts that are novel, yet similar to familiar ones. Our theory of newborn cell maturation explains both how adult-born dentate granule cells integrate into the preexisting network and why they promote separation of similar but not distinct patterns.

Postnatal Neurogenesis in the Olfactory Bulb

2016 ◽  
Author(s):  
Aleksandra Polosukhina ◽  
Pierre-Marie Lledo
Keyword(s):  
Olfactory Bulb ◽  
Granule Cells ◽  
Sensory Information ◽  
Adult Brain ◽  
Sensory Function ◽  
The Other ◽  
Forthcoming Article ◽  
Adult Born Neurons ◽  
Newborn Neurons ◽  
The Brain

This is an advance summary of a forthcoming article in the Oxford Research Encyclopedia of Neuroscience. Please check back later for the full article. In adult mammals, the olfactory bulb and the hippocampus are the regions in the brain that undergo continuous neurogenesis (production and recruitment of newborn neurons). While the other regions of the brain still retain a certain degree of plasticity after birth, they no longer can integrate new neurons. In rodents, thousands of adult-born neurons integrate into the bulb each day, and this process has been found to contribute not only to sensory function, but also to olfactory memory. This was a surprising finding, since historically the adult-brain has been viewed as a static organ. Understanding the process of regeneration of mature neurons in the brain has great potential for therapeutic applications. Consequently, this process of adult-neurogenesis has received widespread attention from clinicians and scientists. Neuroblasts bound for the olfactory bulb are produced in the subventricular zone of the lateral ventricle. Once they reach the olfactory bulb, they mostly develop into inhibitory interneurons called granule cells. Just after one month, about half of the adult-born neurons are eliminated, and the other half fully integrate and function in the olfactory bulb. These cells not only process information from the sensory neurons in the bulb, but also receive massive innervation from various regions of the brain, including the olfactory cortex, locus coeruleus, the horizontal limb of diagonal band of Broca, and the dorsal raphe nucleus. The sensory (bottom-up) and cortical (top-down) activity has been found to play a vital role in the adult-born granule cell survival. Though the exact purpose of these newborn neurons has not been identified, some emerging functions include maintenance of olfactory bulb circuitry, modulating sensory information, modulating olfactory learning, and memory.

scholarly journals Sonic Hedgehog is expressed by hilar mossy cells and regulates cellular survival and neurogenesis in the adult hippocampus

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Luis E. Gonzalez-Reyes ◽  
Chia-Chu Chiang ◽  
Mingming Zhang ◽  
Joshua Johnson ◽  
Manuel Arrillaga-Tamez ◽  
...  
Keyword(s):  
Dentate Gyrus ◽  
Sonic Hedgehog ◽  
Hippocampal Neurons ◽  
Hippocampal Neurogenesis ◽  
Adult Brain ◽  
Cellular Survival ◽  
Mossy Cells ◽  
Cellular Source ◽  
Dynamic Source ◽  
Hilar Neurons

AbstractSonic hedgehog (Shh) is a multifunctional signaling protein governing pattern formation, proliferation and cell survival during embryogenesis. In the adult brain, Shh has neurotrophic function and is implicated in hippocampal neurogenesis but the cellular source of Shh in the hippocampus remains ill defined. Here, we utilize a gene expression tracer allele of Shh (Shh-nlacZ) which allowed the identification of a subpopulation of hilar neurons known as mossy cells (MCs) as a prominent and dynamic source of Shh within the dentate gyrus. AAV-Cre mediated ablation of Shh in the adult dentate gyrus led to a marked degeneration of MCs. Conversely, chemical stimulation of hippocampal neurons using the epileptogenic agent kainic acid (KA) increased the number of Shh+ MCs indicating that the expression of Shh by MCs confers a survival advantage during the response to excitotoxic insults. In addition, ablation of Shh in the adult dentate gyrus led to increased neural precursor cell proliferation and their migration into the subgranular cell layer demonstrating that MCs-generated Shh is a key modulator of hippocampal neurogenesis.

scholarly journals Haploinsufficiency of the schizophrenia and autism risk gene Cyfip1 causes abnormal postnatal hippocampal neurogenesis through microglial and Arp2/3 mediated actin dependent mechanisms

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Niels Haan ◽  
Laura J. Westacott ◽  
Jenny Carter ◽  
Michael J. Owen ◽  
William P. Gray ◽  
...  
Keyword(s):  
Genetic Risk ◽  
Hippocampal Neurons ◽  
Hippocampal Neurogenesis ◽  
Actin Dynamics ◽  
Biological Processes ◽  
Risk Gene ◽  
A Cell ◽  
Adult Born Neurons ◽  
Newborn Neurons ◽  
And Migration

AbstractGenetic risk factors can significantly increase chances of developing psychiatric disorders, but the underlying biological processes through which this risk is effected remain largely unknown. Here we show that haploinsufficiency of Cyfip1, a candidate risk gene present in the pathogenic 15q11.2(BP1–BP2) deletion may impact on psychopathology via abnormalities in cell survival and migration of newborn neurons during postnatal hippocampal neurogenesis. We demonstrate that haploinsufficiency of Cyfip1 leads to increased numbers of adult-born hippocampal neurons due to reduced apoptosis, without altering proliferation. We show this is due to a cell autonomous failure of microglia to induce apoptosis through the secretion of the appropriate factors, a previously undescribed mechanism. Furthermore, we show an abnormal migration of adult-born neurons due to altered Arp2/3 mediated actin dynamics. Together, our findings throw new light on how the genetic risk candidate Cyfip1 may influence the hippocampus, a brain region with strong evidence for involvement in psychopathology.

scholarly journals A functional model of adult dentate gyrus neurogenesis

eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Olivia Gozel ◽  
Wulfram Gerstner
Keyword(s):  
Theoretical Model ◽  
Dentate Gyrus ◽  
Granule Cells ◽  
Functional Integration ◽  
Functional Model ◽  
Behavioral Pattern ◽  
Pattern Separation ◽  
Cell Maturation ◽  
Newborn Cell ◽  
Newborn Neurons

In adult dentate gyrus neurogenesis, the link between maturation of newborn neurons and their function, such as behavioral pattern separation, has remained puzzling. By analyzing a theoretical model, we show that the switch from excitation to inhibition of the GABAergic input onto maturing newborn cells is crucial for their proper functional integration. When the GABAergic input is excitatory, cooperativity drives the growth of synapses such that newborn cells become sensitive to stimuli similar to those that activate mature cells. When GABAergic input switches to inhibitory, competition pushes the configuration of synapses onto newborn cells towards stimuli that are different from previously stored ones. This enables the maturing newborn cells to code for concepts that are novel, yet similar to familiar ones. Our theory of newborn cell maturation explains both how adult-born dentate granule cells integrate into the preexisting network and why they promote separation of similar but not distinct patterns.

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