Single cell transcriptomics of cerebrospinal fluid cells from patients with recent-onset narcolepsy

Narcolepsy is a rare cause of excessive daytime sleepiness and may be associated or not with cataplexy, i.e. sudden muscle weakness. These forms are designated NAR-type 1 (NT1) and -type 2 (NT2), respectively. Notable characteristics of narcolepsy are that most patients carry the HLA-DQB1*06:02 allele and NT1-patients have highly decreased levels hypocretin-1 (synonym orexin-A) in the cerebrospinal fluid (CSF). The pathogenesis of narcolepsy is still enigmatic but the strung HLA-bias and increased frequencies of CD4+ T cells reactive to hypocretin in the peripheral blood suggest autoimmune processes in the hypothalamus. Here we analyzed the transcriptomes of single CSF-cells from 16 narcoleptic patients by mRNAseq. As controls, we used single cells from patients with multiple sclerosis, radiologically isolated syndrome, and idiopathic intracranial hypertension. We identified 20 clusters of different cell types and >1000 genes that were differentially regulated between the different diseases. Surprisingly, the strongest upregulation in narcolepsy patients as compared to controls were the genome-encoded MTRNR2L12 and MTRNR2L8 peptides, which are homologous to mitochondria-encoded HUMANIN peptide that is known playing a role in other neurological diseases.