A single-cell transcriptomic and anatomic atlas of mouse dorsal raphe Pet1 neurons

Abstract

Among the brainstem raphe nuclei, the dorsal raphe nucleus (DR) contains the greatest number of Pet1-lineage neurons, a predominantly serotonergic group distributed throughout DR subdomains. These neurons collectively regulate diverse physiology and behavior and are often therapeutically targeted to treat affective disorders. Characterizing Pet1 neuron molecular heterogeneity and relating it to anatomy is vital for understanding DR functional organization, with potential to inform therapeutic separability. Here we use high-throughput and DR subdomain-targeted single-cell transcriptomics and intersectional genetic tools to map molecular and anatomical diversity of DR-Pet1 neurons. We describe up to fourteen neuron subtypes, many showing biased cell body distributions across the DR. We further show that P2ry1-Pet1 DR neurons – the most molecularly distinct subtype – possess unique efferent projections and electrophysiological properties. These data complement and extend previous DR characterizations, combining intersectional genetics with multiple transcriptomic modalities to achieve fine-scale molecular and anatomic identification of Pet1 neuron subtypes.

Serotonergic Modulation of Locomotor Activity From Basal Vertebrates to Mammals

“…Context-dependent modulation of locomotor output by the same 5-HT nucleus suggests that different 5-HT cell subtypes in the dorsal raphe nucleus are recruited in a behavior-dependent manner (Correia et al, 2017;Seo et al, 2019). Such different cell subtypes likely exist in this nucleus, as recently uncovered by single-cell transcriptomics, anatomical and electrophysiological properties (Ren et al, 2018;Cardozo Pinto et al, 2019;Huang et al, 2019;Okaty et al, 2020). These likely project to different brain regions involved in modulating the locomotor circuitry.…”

“…that selectively innervates the basal ganglia in mice (Ren et al, 2018;Cardozo Pinto et al, 2019;Huang et al, 2019;Okaty et al, 2020).…”

“…In recent years, the use of genetic tools has allowed researchers to refine the characterization of 5-HT nuclei. In the dorsal raphe nucleus (the largest 5-HT nucleus), subtypes of 5-HT neurons with distinct molecular, electrophysiological, and anatomical signatures have been identified, with e.g., one cell type that selectively innervates the basal ganglia in mice (Ren et al, 2018 ; Cardozo Pinto et al, 2019 ; Huang et al, 2019 ; Okaty et al, 2020 ).…”

Three-Week Treadmill Exercise Enhances Persistent Inward Currents, Facilitates Dendritic Plasticity, and Upregulates the Excitability of Dorsal Raphe Serotonin Neurons in ePet-EYFP Mice

“…In addition, 5-HT neurons in lwDR are predominately recruited with panicogenic stimuli and participate in controlling the expression of panic-associated escape behaviors (Johnson et al, 2005 ; Vilela-Costa et al, 2019 ). Recently, the more complex molecular and anatomical diversity of DRN is revealed with single-cell transcriptomics and intersectional genetic tools (Ren et al, 2019 ; Okaty et al, 2020 ). In addition to the anatomical diversity of DRN, Calizo et al ( 2011 ) reveal that electrophysiological properties of 5-HT neurons in different subregions of DRN are significantly different.…”

Neuron-type specificity of dorsal raphe projections to ventral tegmental area

“…In particular, subsets of serotonin neurons project to subsets of their forebrain targets (Kiyasova et al, 2011;Commons, 2015;Kast et al, 2017;Petersen et al, 2020). These anatomical data, together with single-cell RNA sequencing experiments (Okaty et al, 2015;Huang et al, 2019;Ren et al, 2019;Okaty et al, 2020), support the hypothesis that this system may be usefully subdivided into different types (Okaty et al, 2019). In addition, electrophysiological recordings during behavioral tasks demonstrate substantial heterogeneity in the response properties of serotonin neurons and their neighbors (Nakamura et al, 2008;Ranade and Mainen, 2009;Cohen et al, 2015;Hayashi et al, 2015;Grossman et al, 2020).…”