Neuronal dendrites and synapses are structurally distorted in individuals with mental retardation and other neurological disorders. Dendrites and synapses also differ greatly in their appearance in normal brains. Hence, variability in structure-function relationships must be understood in the normal brain to be able to draw conclusions about the distortions. A rigorous plan is proposed to identify structure- function relationships along dendrites in the mature hippocampus, a brain region long known to be involved in learning and memory. Six core subcellular structures will be investigated along dendrites and into dendritic spines that host excitory synapses, including microtubules for transport, polyribosomes for protein synthesis, Golgi apparatus for posttranslational modifications, endosomes for membrane recycling, and smooth endoplasmic reticulum (SER) and mitochondria for calcium regulation. Connectivity relationships among dendrites, axons and perisynaptic astroglia will also be discerned. Several recent findings from this laboratory reveal the power of serial section transmission electron microscopy (ssTEM) to investigate these relationships. Dendrites containing more microtubules had more synapses. Dendritic spines with polyribosomes or perisynaptic astroglia had larger synapses. Different spines contained endosomes from those containing SER. Only large, mature spines contained a spine apparatus, which is similar to the Golgi apparatus. A cellular memory mechanism, known as long-term potentiation (LTP), enhanced several of these relationships in both mature and immature hippocampus. New dendritic spines formed and existing spine synapses enlarged by 5-30 minutes after the induction of LTP. Spine membrane was supplied from local recycling endosomes. Only spines that acquired polyribosomes had enlarged synapses two hours later. Here it is proposed to determine whether this structural plasticity relates to recognized distance- dependent changes in dendritic function and caliber among dendrites in the mature hippocampal area CA1. We will assess whether or not dendrites of varying caliber have different levels of structural plasticity after the induction of LTP. We will ascertain whether dendrites with more or larger synapses connect with more of the axons surrounding them after the induction of LTP. We will determine distance-dependent differences in dendrite structure, composition, and connectivity throughout the CA1 apical and basilar dendritic arbors. We will enhance and develop new Neuroinformatics tools to collect and share these content-rich data. We predict greater understanding will emerge about distance dependent dendritic and synaptic structure and function.

Public Health Relevance

Neuronal dendrites and synapses appear structurally distorted in individuals with mental retardation and other neurological disorders. Dendrites and synapses are also structurally diverse in normal brains; hence the variability in structure-function relationships must be understood to draw meaningful conclusions about these distortions. A rigorous plan is proposed to use neuroinformatics tools and three-dimensional reconstruction to identify important structure-function relationships along the length of dendrites, at their synapses, and with their neighboring axons and astroglia during long-term potentiation, a well-studied cellular mechanism of learning and memory. ? ?

Agency
National Institute of Health (NIH)
Institute
National Institute of Biomedical Imaging and Bioengineering (NIBIB)
Type
Research Project (R01)
Project #
2R01EB002170-14
Application #
7380246
Study Section
Special Emphasis Panel (ZRG1-MDCN-K (51))
Program Officer
Cohen, Zohara
Project Start
1997-09-30
Project End
2011-06-30
Budget Start
2007-09-01
Budget End
2008-06-30
Support Year
14
Fiscal Year
2007
Total Cost
$334,125
Indirect Cost
Name
University of Texas Austin
Department
Type
Organized Research Units
DUNS #
170230239
City
Austin
State
TX
Country
United States
Zip Code
78712
Bell, Maria Elizabeth; Bourne, Jennifer N; Chirillo, Michael A et al. (2014) Dynamics of nascent and active zone ultrastructure as synapses enlarge during long-term potentiation in mature hippocampus. J Comp Neurol 522:3861-84
Edwards, John; Daniel, Eric; Kinney, Justin et al. (2014) VolRoverN: enhancing surface and volumetric reconstruction for realistic dynamical simulation of cellular and subcellular function. Neuroinformatics 12:277-89
Kuwajima, Masaaki; Mendenhall, John M; Harris, Kristen M (2013) Large-volume reconstruction of brain tissue from high-resolution serial section images acquired by SEM-based scanning transmission electron microscopy. Methods Mol Biol 950:253-73
Kinney, Justin P; Spacek, Josef; Bartol, Thomas M et al. (2013) Extracellular sheets and tunnels modulate glutamate diffusion in hippocampal neuropil. J Comp Neurol 521:448-64
Kuwajima, M; Spacek, J; Harris, K M (2013) Beyond counts and shapes: studying pathology of dendritic spines in the context of the surrounding neuropil through serial section electron microscopy. Neuroscience 251:75-89
Cui-Wang, Tingting; Hanus, Cyril; Cui, Tao et al. (2012) Local zones of endoplasmic reticulum complexity confine cargo in neuronal dendrites. Cell 148:309-21
Cao, Guan; Harris, Kristen M (2012) Developmental regulation of the late phase of long-term potentiation (L-LTP) and metaplasticity in hippocampal area CA1 of the rat. J Neurophysiol 107:902-12
Bowden, Jared B; Abraham, Wickliffe C; Harris, Kristen M (2012) Differential effects of strain, circadian cycle, and stimulation pattern on LTP and concurrent LTD in the dentate gyrus of freely moving rats. Hippocampus 22:1363-70
Bourne, Jennifer N; Harris, Kristen M (2012) Nanoscale analysis of structural synaptic plasticity. Curr Opin Neurobiol 22:372-82
Shi, Bitao; Bourne, Jennifer; Harris, Kristen M (2011) SynapticDB, effective web-based management and sharing of data from serial section electron microscopy. Neuroinformatics 9:39-57

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