High-throughput mapping of synaptic connectivity between transcriptomically defined cell types

项目总结

PROJECT SUMMARY Identifying the cell types that make up each region of the brain and the patterns of synaptic connections through which they are linked is key to understanding how neural circuits give rise to all perception, cognition, and behavior. Rapid improvements in optical, molecular, and computational technologies are enabling large- scale projects aiming to comprehensively map the cell types that comprise the mammalian brain. Nevertheless, defining the microconnectivity of the thousands of cell types in the brain remains challenging due to a lack of scalable methods. This proposal describes the development of a technology for addressing this methodological gap. Using a novel combination of high-sensitivity fluorescence voltage imaging and single- neuron optogenetic photostimulation, we will map synaptic connectivity within – and between – brain regions. Using this approach, synaptic connectivity can be mapped with throughput two to three orders of magnitude higher than existing techniques. Importantly, leveraging an all-optical approach to mapping connectivity will allow us integrate synaptic connectivity measurements with emerging techniques for highly multiplexed fluorescence in situ hybridization. In this way, we can identify the molecular identities of large neuronal populations and their connectivity. We will demonstrate the technology developed in this proposal in the motor cortex, a region where knowledge of gene expression patterns has far outpaced our ability to identify connectivity motifs. Revealing both local connectivity motifs and the precise molecular identity of cells that receive long-range input from the thalamus – an important driver of cortical activity – will provide new insights into the circuit mechanisms supporting voluntary movements.