PhD Thesis Defense

Title: Multimodal analysis of cell types in a hypothalamic node controlling social behavior in mice.

Abstract: The advent and recent advances of single-cell RNA sequencing (scRNA-seq) have yielded transformative insights into our understanding of cellular diversity in the central nervous system (CNS) with unprecedented detail. However, due to current experimental and computational limitations on defining transcriptomic cell types (T-types) and the multiple phenotypic features of cell types in the CNS, an integrative and multimodal approach should be required for the comprehensive classification of cell types. To this end, my thesis works have been mainly focused on performing scRNA-seq in the ventrolateral subdivision of the ventromedial hypothalamus (VMHvl), which only contains ~4,000 neurons per hemisphere in mice but known to be behaviorally, anatomically, and molecularly heterogeneous, by using two independent platforms: SMART-seq2 (~4,500 neurons sequenced) and 10x (~78,000 neurons sequenced). Specifically, 17 joint VMHvl T-types including several sexually dimorphic clusters were identified by canonical correlation analysis (CCA) in Seurat, and the majority of them were validated by multiplexed single-molecule FISH (seqFISH). Correspondence between transcriptomic identity, and axonal projections or behavioral activation, respectively, was also investigated. Immediate early gene analysis identified T-types exhibiting preferential responses to intruder males versus females but only rare examples of behavior-specific activation. Unexpectedly, many VMHvl T-types comprise a mixed population of neurons with different projection target preferences. Overall our analysis revealed that, surprisingly, few VMHvl T-types exhibit a clear correspondence with behavior-specific activation and connectivity. Based on expanding the results from the first part and my other preliminary data, the second part of my thesis will discuss about future directions for a deeper and better understanding of VMHvl cell types.