Subcellular Molecular Profiling of Midbrain Dopamine Neurons

Midbrain dopamine neurons play a critical role in motor function, motivation, reward, and cognition by providing modulatory input to cortical and basal ganglia circuits. Given the importance of dopamine neurotransmission and its dysregulation in disease, mechanistic insight into the molecular underpinnings of dopaminergic neuronal function is needed. This thesis seeks to advance our understanding of dopamine neuronal cell biology by developing and applying cutting edge molecular profiling methods to study the subcellular translatome and proteome of dopamine neurons in mice. Chapter 1 provides an overview of the anatomy and cell biology of midbrain dopamine systems, with a particular emphasis on dopamine neurotransmission, neuronal heterogeneity, and selective vulnerability in Parkinson’s disease. Chapter 2 focuses on methods for studying local translation in neurons and describes newly discovered artifacts associated with two of these methods. Chapter 3 describes a global analysis of ribosome and mRNA localization in dopamine neurons; the results suggest that local translation in dopaminergic dendrites, but not axons, regulates dopamine release. Chapter 4 presents a method for subcellular proteomic profiling of dopamine neurons in the mouse brain, revealing the somatodendritic and axonal polarization of proteins encoded by Parkinson’s disease-linked genes. Emerging data are presented on Synaptotagmin 17, a novel axonal protein identified in midbrain dopamine neurons. Finally, I synthesize key findings regarding the molecular organization underlying dopamine neuronal cell biology and highlight promising areas for future investigation.