Dissertations, Theses, and Capstone Projects

Date of Degree

9-2025

Document Type

Master's Thesis

Degree Name

Master of Science

Program

Cognitive Neuroscience

Advisor

Andreas Kottmann

Subject Categories

Behavioral Neurobiology | Cognitive Neuroscience | Molecular and Cellular Neuroscience | Other Neuroscience and Neurobiology

Keywords

Sonic Hedgehog, Basal Ganglia, LacZ, B-galactosidase, Tissue Clearing, Locomotor Activity

Abstract

Sonic Hedgehog (Shh) is best known for its role in development, yet evidence supports Shh signaling plays a functional role in the adult brain. Previous work demonstrated that Shh is expressed by dopamine (DA) neurons in the ventral midbrain and that loss of Shh from these neurons leads to late-onset motor and structural abnormalities resembling Parkinson’s disease. However, the extent of Shh expression and its connectivity to the striatum in the adult mouse brain remain unclear due to the lack of reliable antibodies for Shh detection. To address this gap, the present study employed Shh L/L and DAT-Cre+/- mice to ablate Shh following a unilateral AAV-Cre injection with LacZ serving as a reporter to detect Shh expression.

To investigate the effects of Shh expression in the adult brain, three aims were pursued. First, coronal brain sections were analyzed to perform a cell-quantification of Shh expression in adult brain regions. Second, a tissue-clearing protocol was developed to produce transparent ‘glass brains’ that enabled three-dimensional visualization of Shh expression. Third, open-field testing was conducted to assess general locomotor activity and turning behavior following Shh ablation in the striatum. Immunohistochemistry confirmed LacZ expression in the midbrain, supporting the validity of the LacZ reporter system. Tissue clearing successfully rendered intact brains transparent, however there was no difference in Shh expression following ablation. Open-field test results revealed no significant differences between genetic condition and time effect for general locomotor activity and turning bias across groups following Shh ablation.

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