Molecular profiling and targeting of brain cells and circuits related to energy balance and food reward

Abstract

In this thesis, we investigated neurons in the brain that are involved in energy balance and motivation using two approaches. With the first approach we used RNA sequencing in order to sequence the transcriptome of cells in the hypothalamus that respond to leptin. Leptin is a satiety hormone secreted by fat tissue that signals to the brain to increase energy expenditure and reduce feeding. With TRAP-Seq, we revealed the transcriptome of leptin-responsive neurons in the lateral hypothalamus, an understudied cell population that is involved in motivation for food and energy expenditure. With single-cell RNA sequencing we studied leptin-responsive cells in the whole hypothalamus, revealing the presence of leptin receptor in cell clusters of neuronal and non-neuronal cells which signifies the importance and diversity of leptin’s actions. Thus, we provided insight into molecular mechanisms of this rare cell population, which will guide future studies. With the second approach we developed and optimized viral vector tools for gene delivery in the brain. While using promoter-driven viral constructs in order to achieve expression in specific neuropeptide cell populations in the hypothalamus, we found that the amount of genomic copies used influences specificity and efficiency, which has implications for the use of this type of constructs in translational neuroscience as well as gene therapy. Finally, we developed a novel viral vector which facilitates the transient activation of specific cells within a neuronal pathway and confirmed its efficacy on driving hyperactivity when activating mesolimbic dopamine neurons.