Reinnervation of stratum lucidum by hippocampal mossy fibers is developmentally regulated

Hippocampal mossy fiber axons simultaneously activate CA3 pyramidal cells and stratum lucidum interneurons (SLINs), the latter providing feedforward inhibition to control CA3 pyramidal cell excitability. Filopodial extensions of giant boutons of mossy fibers provide excitatory synaptic input to the SLIN. These filopodia undergo extraordinary structural plasticity causally linked to execution of memory tasks, leading us to seek the mechanisms by which activity regulates these synapses. High-frequency stimulation of the mossy fibers induces long-term depression (LTD) of their calcium-permeable AMPA receptor synapses with SLINs; previous work localized the site of induction to be postsynaptic and the site of expression to be presynaptic. Yet, the underlying signaling events and the identity of the retrograde signal are incompletely understood. We used whole cell recordings of SLINs in hippocampal slices from wild-type and mutant mice to explore the mechanisms. Genetic and pharmacologic perturbations revealed a requirement for both the receptor tyrosine kinase TrkB and its agonist, brain-derived neurotrophic factor (BDNF), for induction of LTD. Inclusion of inhibitors of Trk receptor kinase and PLC in the patch pipette prevented LTD. Endocannabinoid receptor antagonists and genetic deletion of the CB1 receptor prevented LTD. We propose a model whereby release of BDNF from mossy fiber filopodia activates TrkB and PLCγ1 signaling postsynaptically within SLINs, triggering synthesis and release of an endocannabinoid that serves as a retrograde signal, culminating in reduced glutamate release. Insights into the signaling pathways by which activity modifies function of these synapses will facilitate an understanding of their contribution to the local circuit and behavioral consequences of hippocampal granule cell activity. NEW & NOTEWORTHY We investigated signaling mechanisms underlying plasticity of the hippocampal mossy fiber filopodial synapse with interneurons in stratum lucidum. High-frequency stimulation of the mossy fibers induces long-term depression of this synapse. Our findings are consistent with a model in which brain-derived neurotrophic factor released from filopodia activates TrkB of a stratum lucidum interneuron; the ensuing activation of PLCγ1 induces synthesis of an endocannabinoid, which provides a retrograde signal leading to reduced release of glutamate presynaptically.

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Layer-Specific Vesicular Glutamate Transporter 1 Immunofluorescence Levels Delineate All Layers of the Human Hippocampus Including the Stratum lucidum

Frontiers in Cellular Neuroscience ◽

10.3389/fncel.2021.789903 ◽

2021 ◽

Vol 15 ◽

Author(s):

Sarah Woelfle ◽

Tobias M. Boeckers

Keyword(s):

Pyramidal Neurons ◽

Hippocampal Formation ◽

Glutamate Transporter ◽

Mossy Fibers ◽

Vesicular Glutamate Transporter ◽

Nissl Staining ◽

Clear Cut ◽

Human Hippocampus ◽

Stratum Lucidum ◽

Glutamate Transporter 1

The hippocampal formation consists of the Ammon’s horn (cornu Ammonis with its regions CA1-4), dentate gyrus, subiculum, and the entorhinal cortex. The rough extension of the regions CA1-3 is typically defined based on the density and size of the pyramidal neurons without clear-cut boundaries. Here, we propose the vesicular glutamate transporter 1 (VGLUT1) as a molecular marker for the CA3 region. This is based on its strong labeling of the stratum lucidum (SL) in fluorescently stained human hippocampus sections. VGLUT1 puncta of the intense SL band co-localize with synaptoporin (SPO), a protein enriched in mossy fibers (MFs). Owing to its specific intensity profile throughout all hippocampal layers, VGLUT1 could be implemented as a pendant to Nissl-staining in fluorescent approaches with the additional demarcation of the SL. Furthermore, by high-resolution confocal microscopy, we detected VGLUT2 in the human hippocampus, thus reconciling two previous studies. Finally, by VGLUT1/SPO co-staining, we provide evidence for the existence of infrapyramidal MFs in the human hippocampus and we show that SPO expression is not restricted to MF synapses as demonstrated for rodent tissue.

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Origin of the Apparent Asynchronous Activity of Hippocampal Mossy Fibers

Journal of Neurophysiology ◽

10.1152/jn.1997.78.1.24 ◽

1997 ◽

Vol 78 (1) ◽

pp. 24-30 ◽

Cited By ~ 12

Author(s):

Darrell A. Henze ◽

Nathaniel N. Urban ◽

German Barrionuevo

Keyword(s):

Mossy Fiber ◽

Molecular Layer ◽

Mossy Fibers ◽

Pyramidal Cells ◽

Antidromic Activation ◽

Stratum Lucidum ◽

Hippocampal Area ◽

Ca3 Pyramidal Cells ◽

Area Ca3

Henze, Darrell A., Nathaniel N. Urban, and German Barrionuevo. Origin of the apparent asynchronous activity of hippocampal mossy fibers. J. Neurophysiol. 78: 24–30, 1997. Fiber volleys (FVs) from the stratum lucidum of rat hippocampal area CA3 were recorded extracellularly from in vitro slices in the presence of 10 mM kynurenic acid. In agreement with previous work, bulk stimulation of the dentate gyrus (DG) near the hilar border leads to an asynchronous FV. Transection of the stratum lucidum between the DG stimulation site and the CA3 recording site reduced or eliminated the early components of the asynchronous FV, indicating that they are of mossy fiber (MF) origin. In contrast, moving the stimulating electrode away from the hilus toward the hippocampal fissure reduced or eliminated the late components of the FV. Subsequently, we found that bulk stimulation on the DG/hilar border induces an antidromic population spike in CA3 pyramidal cells. Finally, the MFs and associational collaterals have differentconduction velocities (0.51 and 0.37 m/s, respectively; temperature =33°C). From these data, we conclude that the late components of the asynchronous FV are due to antidromic activation of CA3 collaterals that have been shown to be present in the DG and hilus. A corollary of these findings is that bulk stimulation on the DG/hilar border can lead to at least two different monosynaptic inputs to CA3 pyramidal cells: the MFs and the antidromically activated associational collaterals. We suggest that when MF synaptic responses are being evoked with the use of bulk stimulation, stimulating electrodes should be placed in the outer molecular layer of the DG to prevent the activation of hilar-projecting associational collaterals. This procedure should be added to the previously proposed criteria for preventing polysynaptic contamination of the intracellularly recorded evoked MF synaptic response.

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Involvement of pontocerebellar mossy fibers in the development of cerebellar cortex revealed by analyzing weaver mutant mouse

Neuroscience Research ◽

10.1016/s0168-0102(00)81668-5 ◽

2000 ◽

Vol 38 ◽

pp. S137

Author(s):

R Yano

Keyword(s):

Cerebellar Cortex ◽

Mutant Mouse ◽

Mossy Fibers ◽

Weaver Mutant Mouse

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Identification of Differentially Expressed Genes Using cDNA-AFLP During Six Days In Vitro Tuberization of Potato

Zuriat ◽

10.24198/zuriat.v14i1.6751 ◽

2015 ◽

Vol 14 (1) ◽

Author(s):

Nono Carsono ◽

Christian Bachem

Keyword(s):

Gene Expression ◽

Developmental Process ◽

Expression Patterns ◽

Induction Medium ◽

In Vitro Tuberization ◽

Storage Organ ◽

Developmentally Regulated ◽

Study Gene Expression ◽

Differential Pattern

Tuberization in potato is a complex developmental process resulting in the differentiation of stolon into the storage organ, tuber. During tuberization, change in gene expression has been known to occur. To study gene expression during tuberization over the time, in vitro tuberization system provides a suitable tool, due to its synchronous in tuber formation. An early six days axillary bud growing on tuber induction medium is a crucial development since a large number of genes change in their expression patterns during this period. In order to identify, isolate and sequencing the genes which displaying differential pattern between tuberizing and non-tuberizing potato explants during six days in vitro tuberization, cDNA-AFLP fingerprint, method for the visualization of gene expression using cDNA as template which is amplified to generate an RNA-fingerprinting, was used in this experiment. Seventeen primer combinations were chosen based on their expression profile from cDNA-AFLP fingerprint. Forty five TDFs (transcript derived fragment), which displayed differential expressions, were obtained. Tuberizing explants had much more TDFs, which developmentally regulated, than those from non tuberizing explants. Seven TDFs were isolated, cloned and then sequenced. One TDF did not find similarity in the current databases. The nucleotide sequence of TDF F showed best similarity to invertase ezymes from the databases. The homology of six TDFs with known sequences is discussed in this paper.

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