Depolymerization of SUMO chains induces slender to stumpy differentiation in T. brucei bloodstream parasites

Trypanosoma brucei are protozoan parasites that cause sleeping sickness in humans and nagana in cattle. Inside the mammalian host, a quorum sensing-like mechanism coordinates its differentiation from a slender replicative form into a quiescent stumpy form, limiting growth and virulence. SUMOylation is a reversible post-translational modification that enables dynamic regulation of cellular metabolism by the attachment of SUMO monomer or SUMO polymeric chains. We have found that parasites able to conjugate only SUMO monomers are primed for differentiation. This was demonstrated for monomorphic lines that are normally unable to produce stumpy forms in response to quorum sensing signaling in mice, and also for pleomorphic cell lines in which stumpy cells were observed at unusually low parasitemia levels. SUMO chain mutants showed a stumpy compatible transcriptional profile and better competence to differentiate into procyclics. Our study indicates that SUMO depolymerization may represent a coordinated signal triggered during stumpy activation program. Overall design: We performed RNA-Seq on parasites isolated from the blood of infected mice at the peak of parasitemia (5 days post-infection, dpi) and performed differential gene expression analyses between WT and SUMO chain mutants