Molecular and anatomical organization of the dorsal raphe nucleus

The dorsal raphe nucleus (DRN) is an important source of neuromodulators in the brain and has been implicated in a wide variety of behavioral and neurological disorders. Although mostly studied as a source of serotonin, the DRN is comprised of multiple cell types that are subdivided into distinct anatomical subregions. However, the complex and incompletely characterized cellular organization of the DRN has impeded efforts to investigate the distinct circuit and behavioral functions of its subdomains. Here we used high-throughput single-cell RNA sequencing with in situ hybridization and viral tracing to develop a map of transcriptional and spatial profiles of cells in and around the mouse DRN. Our studies reveal the molecular and spatial organization of multiple neuron subtypes that are the cellular bases of functionally and anatomically distinct serotonergic subsystems, and provide a resource for the design of strategies for further dissection of these subsystems and their diverse functions.