Epigenetically regulated RNA-binding proteins signify malaria hypnozoite dormancy

Abstract

Dormancy enables relapsing malaria parasites, such as Plasmodium vivax and cynomolgi, to survive unfavorable conditions. It is enabled by hypnozoites, parasites remaining quiescent inside hepatocytes before reactivating and establishing blood-stage infection. We integrate omics approaches to explore gene-regulatory mechanisms underlying hypnozoite dormancy. Genome-wide profiling of activating and repressing histone marks identifies a few genes that get silenced by heterochromatin during hepatic infection of relapsing parasites. By combining single-cell transcriptomics, chromatin accessibility profiling, and fluorescent in situ RNA hybridization, we show that these genes are expressed in hypnozoites and that their silencing precedes parasite development. Intriguingly, these hypnozoite-specific genes mainly encode proteins with RNA-binding domains. We hence hypothesize that these likely repressive RNA-binding proteins keep hypnozoites in a developmentally competent but dormant state and that heterochromatin-mediated silencing of the corresponding genes aids reactivation. Exploring the regulation and exact function of these proteins hence could provide clues for targeted reactivation and killing of these latent pathogens.

Keywords: CP: Cell biology; Plasmodium cynomolgi; RNA-binding protein; dormancy; epigenetic silencing; hypnozoite; liver stage infection; relapsing malaria.