Narcolepsy type 1 is a sleep-wake disorder characterized by hypocretin deficiency. It has been considered an autoimmune disorder for decades due to the strong associating with the HLA-DQB1*06:02 allele and possible relations to the H1N1 pandemic in 2009. However, the pathophysiological mechanisms underlying the loss of hypocretin neurons is not understood. We hypothesize that a hypocretin neuron-specific antigen, other than hypocretin itself but sharing an expression pattern, may be the target of the autoimmune response leading to the development in individuals with narcolepsy type 1. In this study, we employed an in silico method to identify novel candidate antigens for an autoimmune response leading to the destruction of hypocretin cells. A combination of multiple publicly available datasets, based on human brain tissue from healthy individuals, was used to map the expression profile of hypocretin. Genes were categorized based on their expression pattern and its association with hypocretin expression. 15 candidate genes were identified as potentially relevant targets in the development of NT1, with varying degrees of confidence regarding the likelihood of their involvement. Six candidate genes also showed higher expression within hypocretin cells compared to other cells in the hypothalamus of which NPVF seems most promising. This study provides important new directions and potential targets for investigating and understanding the pathophysiology of narcolepsy type 1.

Hypothalamic arginine vasopressin (AVP) and oxytocin (OXT) magnocellular neurons (MCNs), share a developmental lineage. The transcription factors driving specification are yet unknown. Using gene regulatory network analysis on published single-cell RNA-sequencing data of the developing mouse hypothalamus, we identified RORA, EBF3, FOXP1, FOXP2, and BCL11B as candidate transcription factors for differential MCN specification. We modeled developmental gene expression dynamics using computational cell fate mapping, revealing enrichment of EBF3 and BCL11B in the Avp lineage, and FOXP1 and FOXP2 in the Oxt lineage. In silico analysis of Avp and Oxt promoters predicted a binding site for FOXP1 and FOXP2, and an in vitro reporter assay identified regulation on both Avp and Oxt genomic promoters. Finally, heterozygous FOXP1 knockout mice exhibited a significant reduction in AVP and OXT neuron abundance, with OXT neurons disproportionally affected. We conclude that FOXP1 participates in MCN development, while being differentially active in OXT MCNs relative to AVP MCNs.

The hypothalamic suprachiasmatic nucleus (SCN) hosts the central circadian pacemaker and regulates daily rhythms in physiology and behavior. The SCN is composed of peptidergic neuron populations expressing arginine vasopressin (AVP) and vasoactive intestinal polypeptide (VIP), as well as glial cells. Patients with Prader–Willi Syndrome (PWS) commonly experience circadian disturbances, which are particularly evident in their sleep/wake patterns. Using publicly available single-cell RNA sequencing data, we assessed the cell-type specificity of PWS-causative genes in murine SCN, which revealed the differential presence of PWS-related genes in glial and neural subpopulations. We then investigated neurons and glial cells in the SCN using immunohistochemistry in the postmortem hypothalami of PWS subjects and matched controls. We profiled neural populations characterized by AVP and VIP, astroglia characterized by glial fibrillary acid protein (GFAP), and microglia marked by ionized calcium-binding adapter molecule 1 (Iba1) and NADPH oxidase 2 (NOX2). Our analysis revealed an increased total number, neuronal density, and relative staining intensity of AVP-containing neurons in the PWS compared to controls while VIP-containing cells were unaltered. In contrast, GFAP-expressing astroglial cells were significantly lower in PWS subjects. Moreover, we did not detect any differences in microglia between PWS subjects and controls. Collectively, our findings show that PWS selectively affects AVP-containing neurons and GFAP-expressing astrocytes in the SCN. As each of these cell populations can affect the daily rhythmicity of the SCN biological clock machinery, the disruption of these cells may contribute to the circadian disturbances in patients with PWS.

Glucocorticoid stress hormones are powerful modulators of brain function and can affect mood and cognitive processes. The hippocampus is a prominent glucocorticoid target and expresses both the glucocorticoid receptor (GR: Nr3c1) and the mineralocorticoid receptor (MR: Nr3c2). These nuclear steroid receptors act as ligand-dependent transcription factors. Transcriptional effects of glucocorticoids have often been deduced from bulk mRNA measurements or spatially informed individual gene expression. However, only sparse data exists allowing insights on glucocorticoid-driven gene transcription at the cell type level. Here, we used publicly available single-cell RNA sequencing data to assess the cell-type specificity of GR and MR signaling in the adult mouse hippocampus. The data confirmed that Nr3c1 and Nr3c2 expression differs across neuronal and non-neuronal cell populations. We analyzed co-expression with sex hormones receptors, transcriptional coregulators, and receptors for neurotransmitters and neuropeptides. Our results provide insights in the cellular basis of previous bulk mRNA results and allow the formulation of more defined hypotheses on the effects of glucocorticoids on hippocampal function.