A survey of the mouse hindbrain in the fed and fasted states using single-nucleus RNA sequencing

Abstract

Objective The area postrema (AP) and nucleus tractus solitarius (NTS) located in the hindbrain are key nuclei that sense and integrate peripheral nutritional signals and consequently regulate feeding behaviour. While single-cell transcriptomics have been used in mice to reveal the gene expression profile and heterogeneity of key hypothalamic populations, similar in-depth studies have not yet been performed in the hindbrain. Methods Using single-nucleus RNA sequencing, we provide a detailed survey of 16,034 cells within the AP and NTS of mice in the fed and fasted states. Results Of these, 8,910 were neurons that group into 30 clusters, with 4,289 from mice fed ad libitum and 4,621 from overnight fasted mice. A total of 7,124 nuclei were from non-neuronal cells, including oligodendrocytes, astrocytes, and microglia. Interestingly, we identified that the oligodendrocyte population was particularly transcriptionally sensitive to an overnight fast. The receptors GLP1R, GIPR, GFRAL, and CALCR, which bind GLP1, GIP, GDF15, and amylin, respectively, are all expressed in the hindbrain and are major targets for anti-obesity therapeutics. We characterise the transcriptomes of these four populations and show that their gene expression profiles are not dramatically altered by an overnight fast. Notably, we find that roughly half of cells that express GIPR are oligodendrocytes. Additionally, we profile POMC-expressing neurons within the hindbrain and demonstrate that 84% of POMC neurons express either PCSK1, PSCK2, or both, implying that melanocortin peptides are likely produced by these neurons. Conclusion We provide a detailed single-cell level characterisation of AP and NTS cells expressing receptors for key anti-obesity drugs that are either already approved for human use or in clinical trials. This resource will help delineate the mechanisms underlying the effectiveness of these compounds and also prove useful in the continued search for other novel therapeutic targets.

Anti-obesity drug discovery: advances and challenges

“…However, long-acting (acyl) GIPR agonists decrease body weight in obese wild-type and GLP1R knockout mice 184 , 185 and GIP affects body weight through signalling via the GIPR in the CNS. In line with this notion, GIPR is expressed in neurons of the hypothalamus and the hindbrain 186 , 187 and DREADD-mediated activation of hypothalamic GIPR cells decreases food intake 186 . Consistent with this, single central administration of a fatty acyl-GIP decreases body weight and food intake in DIO mice and increases cFOS neuronal activity in the hypothalamus 185 .…”

Glial Modulation of Energy Balance: The Dorsal Vagal Complex Is No Exception

“…We cannot exclude that these effects are indirectly induced by the activation of GLP-1R expressed in neuronal cells; indeed, the question of GLP-1R expression in glial cells is still debated. GLP-1R expression in DVC astrocytes was not detected using snRNA sequencing methods [34,97,98]. Nonetheless, it is important to note that while snRNA sequencing is effective at detecting the presence of transcripts, it is not designed to demonstrate the absence of a transcript [98].…”

Sensory Circumventricular Organs, Neuroendocrine Control, and Metabolic Regulation

“…Further characterization of receptor expression in specific cell types has revealed that amylin, leptin, Ang-II, GLP-1, adiponectin 1/2, CCK, and ghrelin receptors are expressed in AP neurons [ 89 , 90 , 91 , 92 , 93 , 94 , 95 , 96 ]. Leptin, TLR-4, glial-cell derived neurotrophic factor receptor -like (GFRAL) and complement type 3 (a receptor linked to hypoxia-induced emesis) receptors are also localized on glial cells in this brain region [ 97 , 98 , 99 , 100 ]. mRNA expression of AVP V 1 a and PYY Y 1 receptors have been detected in the AP; however, the specific AP cell types expressing these receptors is currently unclear [ 101 , 102 ].…”