A diverse population of pericoerulear neurons controls arousal and exploratory behaviors

Abstract

As the primary source of norepinephrine (NE) in the brain, the locus coeruleus (LC) regulates both arousal and stress responses. However, how local neuromodulatory inputs contribute to LC function remains unresolved. Here we identify a network of transcriptionally and functionally diverse GABAergic neurons in the LC dendritic field that integrate distant inputs and modulate modes of LC firing to control arousal. We define peri-LC anatomy using viral tracing and combine single-cell RNA sequencing and spatial transcriptomics to molecularly define both LC and peri-LC cell types. We identify several cell types which underlie peri-LC functional diversity using a series of complementary approaches in behaving mice. Our findings indicate that LC and peri-LC neurons comprise transcriptionally and functionally heterogenous neuronal populations, alongside anatomically segregated features which coordinate specific influences on behavioral arousal and avoidance states. Defining the molecular, cellular and functional diversity in the LC provides a road map for understanding the neurobiological basis of arousal alongside hyperarousal-related neuropsychiatric phenotypes.

The gene expression landscape of the human locus coeruleus revealed by single-nucleus and spatially-resolved transcriptomics

“…This identified 14 clusters representing inhibitory neuronal subpopulations, which varied in their expression of several inhibitory neuronal marker genes including CALB1, CALB2, TAC1, CNR1 , and VIP (additional marker genes shown in Supplementary Figures 13, 16 ). In addition, similar to recently published results from mice [27], we found that expression of neuropeptides PNOC, TAC1 , and PENK varied across the individual inhibitory neuronal populations ( Supplementary Figure 13) .…”

“…We note that a recent publication using snRNA-seq in mice found that LC-NE neurons were highly enriched for Calca, Cartpt, Gal , and Calcr in addition to canonical NE neuron marker genes [27]. In the human data, we noted significant enrichment of GAL and CARTPT in DE testing between the manually annotated LC and non-LC regions in the SRT samples ( Supplementary Table 2) .…”

“…However, compared to the SRT samples, we observed relatively higher expression of the conserved genes within the NE neuron cluster, which is expected since the NE neuron cluster contains reads from individual nuclei from this population only. We note that a recent publication using snRNA-seq in mice found that LC-NE neurons were highly enriched for Calca, Cartpt, Gal, and Calcr in addition to canonical NE neuron marker genes [27]. In the human data, we noted significant enrichment of GAL and CARTPT in DE testing between the manually annotated LC and non-LC regions in the SRT samples (Supplementary Table 2).…”

“…We observe expression of cholinergic marker genes within NE neurons, and confirm that this is due to co-expression within individual cells using fluorescent labeling with high-resolution imaging. We compare our findings from the human LC and adjacent region to molecular profiles of LC and peri-LC neurons that were previously characterized in rodents using alternative technological platforms [25–27], and observe partial conservation of LC-associated genes across these species.…”

“…The integrated measurements were subsequently used as the input for spatially-aware clustering using BayesSpace [35]. including neuropeptides and receptors included for comparison with [27] (dark blue-purple), and cholinergic marker genes (yellow). We observed diversity in expression of inhibitory neuronal marker genes across inhibitory neuronal subpopulations (additional results in Supplementary Figure 16), and we observed expression of cholinergic marker genes within NE neurons (additional results in Supplementary Figure 18).…”