ABSTRACT
In the male mouse germ line, PIWI-interacting RNAs (piRNAs), bound by the PIWI protein MIWI2 (PIWIL4), guide DNA methylation of young active transposons through SPOCD1. However, the underlying mechanisms of SPOCD1-mediated piRNA-directed transposon methylation and whether this pathway functions to protect the human germ line remain unknown. We identified loss-of-function variants in human SPOCD1 that cause defective transposon silencing and male infertility. Through the analysis of these pathogenic alleles, we discovered that the uncharacterized protein C19ORF84 interacts with SPOCD1. DNMT3C, the DNA methyltransferase responsible for transposon methylation, associates with SPOCD1 and C19ORF84 in fetal gonocytes. Furthermore, C19ORF84 is essential for piRNA-directed DNA methylation and male mouse fertility. Finally, C19ORF84 mediates the in vivo association of SPOCD1 with the de novo methylation machinery. In summary, we have discovered a conserved role for the human piRNA pathway in transposon silencing and C19ORF84, an uncharacterized protein essential for orchestrating piRNA-directed DNA methylation.
Subject(s)
DNA Methylation , Piwi-Interacting RNA , Male , Humans , Animals , Mice , RNA, Small Interfering/genetics , RNA, Small Interfering/metabolism , Proteins/metabolism , Germ Cells/metabolism , Argonaute Proteins/genetics , Argonaute Proteins/metabolism , DNA Transposable Elements/genetics , Mammals/metabolismABSTRACT
In both sickle cell disease and malaria, red blood cells (RBCs) are phagocytosed in the spleen, but receptor-ligand pairs mediating uptake have not been identified. Here, we report that patches of high mannose N-glycans (Man5-9GlcNAc2), expressed on diseased or oxidized RBC surfaces, bind the mannose receptor (CD206) on phagocytes to mediate clearance. We find that extravascular hemolysis in sickle cell disease correlates with high mannose glycan levels on RBCs. Furthermore, Plasmodium falciparum-infected RBCs expose surface mannose N-glycans, which occur at significantly higher levels on infected RBCs from sickle cell trait subjects compared to those lacking hemoglobin S. The glycans are associated with high molecular weight complexes and protease-resistant, lower molecular weight fragments containing spectrin. Recognition of surface N-linked high mannose glycans as a response to cellular stress is a molecular mechanism common to both the pathogenesis of sickle cell disease and resistance to severe malaria in sickle cell trait.
Subject(s)
Anemia, Sickle Cell/metabolism , Erythrocytes/metabolism , Mannose/metabolism , Phagocytes/metabolism , Polysaccharides/metabolism , Erythrocyte Membrane/metabolism , Erythrocyte Membrane/parasitology , Erythrocytes/parasitology , Flow Cytometry/methods , Hemolysis , Humans , Ligands , Malaria, Falciparum/metabolism , Malaria, Falciparum/parasitology , Membrane Glycoproteins/metabolism , Phagocytosis , Plasmodium falciparum/physiology , Protein Binding , Receptors, Immunologic/metabolismABSTRACT
DISCLOSURES: Vickers: University of Aberdeen: Patents & Royalties: About to apply for patent. Barker: University of Aberdeen: Employment, Patents & Royalties: About to apply for patent. Cao: University of Aberdeen: Patents & Royalties: About to apply for patent.
