# Molecular Mechanisms of Visual Circuit Formation between Superior Colliculus and Thalamus

> **NIH NIH R21** · YALE UNIVERSITY · 2020 · $209,375

## Abstract

Orderly and specific patterns of neural wiring are critical for proper behavioral outcomes. Most studies on long-
range neuronal connections have utilized invertebrate models or analyzed periphery-to-brain connectivity.
Those studies have uncovered the basic mechanisms responsible for establishing long-range neuronal
connections, such as axon pathfinding, topographic mapping and laminar-specific connectivity. However, our
understanding of the other connectivity-based phenomena, e.g., axon-target nuclei selection, remains rather
limited. Axon-target nuclei selection is the process, by which growing axons choose their final targets while
avoiding the adjacent ones. However, how such selection is achieved within complex mammalian brain, is not
well understood. In this application, we propose to examine mechanisms of axon-target matching, focusing on
connections between superior colliculus (SC) and thalamus in the mammalian brain. SC is a midbrain center
controlling head and eye movements in response to a sensory stimulation. SC also mediates visual cue-
triggered defense responses, such as freezing and escaping. The superficial layer of SC (sSC) receives visual
inputs from the retina and cortex and contains neurons that project to the deep layers of the SC and to the
other subcortical areas. The sSC projections to thalamus modulate visual information to elicit appropriate
behavioral responses to specific stimuli. Moreover, some studies have reported that projections to a specific
thalamic nucleus comprise the second visual pathway that responds to sensory cues in the absence of the
primary visual cortex. However, little is known about the molecular mechanisms that regulate the development
of neuronal connections between sSC and thalamus. Recently, we discovered that expression of retinoid-
related orphan receptor β (Rorβ) is highly enriched within sSC. Based on the layer-restricted expression of
Rorβ, we hypothesize that Rorβ+ sSC neurons project axons to distinct thalamic nuclei. Using innovative
genetic strategies, we will examine the role of Rorβ in the development of specific sSC circuits. We will also
define underlying molecular mechanisms that regulate axonal projections of Rorβ+ neurons to distinct thalamic
nuclei. This project will help us understand molecular basis of neuronal connections between sSC and
thalamus that are involved in specific visual responses and fear-related behaviors. Proposed studies will also
improve our understaninding of how long-range axon-target nuclei selection is regulated in mammalian brain.
The novel genetic approach employed in this proposal should be broadly applicable for studying long-range
projections throughout mammalian nervous system.

## Key facts

- **NIH application ID:** 9986809
- **Project number:** 5R21EY029820-02
- **Recipient organization:** YALE UNIVERSITY
- **Principal Investigator:** In-Jung Kim
- **Activity code:** R21 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $209,375
- **Award type:** 5
- **Project period:** 2019-08-01 → 2022-07-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9986809

## Citation

> US National Institutes of Health, RePORTER application 9986809, Molecular Mechanisms of Visual Circuit Formation between Superior Colliculus and Thalamus (5R21EY029820-02). Retrieved via AI Analytics 2026-05-21 from https://api.ai-analytics.org/grant/nih/9986809. Licensed CC0.

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