# in vivo imaging of circuit remodeling in mouse visual cortex

> **NIH NIH R01** · MASSACHUSETTS INSTITUTE OF TECHNOLOGY · 2021 · $387,750

## Abstract

Many brain disorders manifest impaired synaptic integrity, stability, and experience-dependent selection,
resulting in wiring deficits and perturbed function. Unfortunately, our ability to monitor synaptic or circuit failures
as they occur has been hindered by the difficulty of visualizing synapses in vivo. Here we propose in vivo
monitoring of the ‘order of operations’ in synapse formation and elimination, and identifying the steps and
molecules controlling experience-dependent synapse selection. We focus on the visual system, where there is
a well-characterized toolkit for manipulating experience. We hypothesize that the dynamics of a synapse's
assembly and disassembly, and its propensity to remodel, are intimately linked to its connection identity and
proteomic content. To test this, we propose the following aims: Aim1: To track the structural remodeling of
inhibitory synapses and how it relates to their afferent input specificity and proteomic content. We will
label Somatostatin and Parvalbumin inputs onto the full dendritic arbor of single L2/3 pyramidal neurons in mouse
visual cortex, track their daily dynamics and their response to monocular deprivation, and analyze their proteomic
content in relation to dynamic history and afferent identity. To this purpose, we will implement triple color two-
photon microscopy to simultaneously track, in vivo, both pre- and postsynaptic elements of inhibitory synapses,
followed by Magnified Analysis of Proteome (MAP), a combination of tissue clearing and expansion microscopy,
for super resolution analysis of synaptic protein content across the entire neuron. Aim 2: To track the structural
remodeling of excitatory synapses and how it relates to their afferent input specificity and proteomic
content. Using a similar strategy as in Aim 1, we will discriminate general thalamic, LGN, and LP inputs to
excitatory synapses across the arbor of L2/3 pyramidal neurons, track their daily dynamics and response to dark
adaptation, and analyze their proteomic content in relation to dynamic history and afferent identity. Aim 3: To
dissect, at a molecular level, experience-dependent selection and stabilization of excitatory synapses.
CPG15/neuritin is an activity-regulated gene product critical for synapse stabilization and maturation. In vivo
imaging in WT and CPG15 knockout mice revealed that while spine formation occurs normally in the absence of
visual experience or CPG15, in both cases PSD95 recruitment to nascent spines is deficient. CPG15 expression
in the absence of activity is sufficient to restore normal PSD95 recruitment and spine stabilization, suggesting it
acts as an activity-dependent synapse selector. We ask how CPG15 loss impacts molecular events in synapse
formation and maturation. Aim 4: To develop and implement spectrally resolved two-photon microscopy
for simultaneous tracking of four distinct genetically encoded fluorophores marking different cellular
proteins. We will develop new labeling and two-p...

## Key facts

- **NIH application ID:** 10207000
- **Project number:** 2R01EY025437-06A1
- **Recipient organization:** MASSACHUSETTS INSTITUTE OF TECHNOLOGY
- **Principal Investigator:** Elly Nedivi
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $387,750
- **Award type:** 2
- **Project period:** 2015-04-01 → 2023-09-29

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10207000

## Citation

> US National Institutes of Health, RePORTER application 10207000, in vivo imaging of circuit remodeling in mouse visual cortex (2R01EY025437-06A1). Retrieved via AI Analytics 2026-05-29 from https://api.ai-analytics.org/grant/nih/10207000. Licensed CC0.

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