TBK1 recruitment to STING mediates autoinflammatory arthritis caused by defective DNA clearance

Defective DNA clearance in DNase II−/− mice leads to lethal inflammatory diseases that can be rescued by deleting cGAS or STING, but the role of distinct signaling pathways downstream of STING in the disease manifestation is not known. We found that the STING S365A mutation, which abrogates IRF3 binding and type I interferon induction, rescued the embryonic lethality of DNase II−/− mice. However, the STING S365A mutant retains the ability to recruit TBK1 and activate NF-κB, and DNase II−/−STING-S365A mice exhibited severe polyarthritis, which was alleviated by neutralizing antibodies against TNF-α or IL-6 receptor. In contrast, the STING L373A mutation or C-terminal tail truncation, which disrupts TBK1 binding and therefore prevents activation of both IRF3 and NF-κB, completely rescued the phenotypes of DNase II−/− mice. These results demonstrate that TBK1 recruitment to STING mediates autoinflammatory arthritis independently of type I interferons. Inhibiting TBK1 binding to STING may be a therapeutic strategy for certain autoinflammatory diseases instigated by self-DNA.

Cytosolic dsDNA of mitochondrial origin induces cytotoxicity and neurodegeneration in cellular and zebrafish models of Parkinson’s disease

Mitochondrial dysfunction and lysosomal dysfunction have been implicated in Parkinson’s disease (PD), but the links between these dysfunctions in PD pathogenesis are still largely unknown. Here we report that cytosolic dsDNA of mitochondrial origin escaping from lysosomal degradation was shown to induce cytotoxicity in cultured cells and PD phenotypes in vivo. The depletion of PINK1, GBA and/or ATP13A2 causes increases in cytosolic dsDNA of mitochondrial origin and induces type I interferon (IFN) responses and cell death in cultured cell lines. These phenotypes are rescued by the overexpression of DNase II, a lysosomal DNase that degrades discarded mitochondrial DNA, or the depletion of IFI16, which acts as a sensor for cytosolic dsDNA of mitochondrial origin. Reducing the abundance of cytosolic dsDNA by overexpressing human DNase II ameliorates movement disorders and dopaminergic cell loss in gba mutant PD model zebrafish. Furthermore, IFI16 and cytosolic dsDNA puncta of mitochondrial origin accumulate in the brain of patients with PD. These results support a common causative role for the cytosolic leakage of mitochondrial DNA in PD pathogenesis.

DNase II mediates a parthanatos-like developmental cell death pathway in Drosophila primordial germ cells

During Drosophila embryonic development, cell death eliminates 30% of the primordial germ cells (PGCs). Inhibiting apoptosis does not prevent PGC death, suggesting a divergence from the conventional apoptotic program. Here, we demonstrate that PGCs normally activate an intrinsic alternative cell death (ACD) pathway mediated by DNase II release from lysosomes, leading to nuclear translocation and subsequent DNA double-strand breaks (DSBs). DSBs activate the DNA damage-sensing enzyme, Poly(ADP-ribose) (PAR) polymerase-1 (PARP-1) and the ATR/Chk1 branch of the DNA damage response. PARP-1 and DNase II engage in a positive feedback amplification loop mediated by the release of PAR polymers from the nucleus and the nuclear accumulation of DNase II in an AIF- and CypA-dependent manner, ultimately resulting in PGC death. Given the anatomical and molecular similarities with an ACD pathway called parthanatos, these findings reveal a parthanatos-like cell death pathway active during Drosophila development.

Comparative multi-omics analyses reveal differential expression of key genes relevant for parasitism between non-encapsulated and encapsulated Trichinella

Genome assemblies provide a powerful basis of comparative multi-omics analyses that offer insight into parasite pathogenicity, host-parasite interactions, and invasion biology. As a unique intracellular nematode, Trichinella consists of two clades, encapsulated and non-encapsulated. Genomic correlation of the distinct differences between the two clades is still unclear. Here, we report an annotated draft reference genome of non-encapsulated Trichinella, T. pseudospiralis, and perform comparative multi-omics analyses with encapsulated T. spiralis. Genome and methylome analyses indicate that, during Trichinella evolution, the two clades of Trichinella exhibit differential expansion and methylation of parasitism-related multi-copy gene families, especially for the DNase II members of the phospholipase D superfamily and Glutathione S-transferases. Further, methylome and transcriptome analyses revealed divergent key excretory/secretory (E/S) genes between the two clades. Among these key E/S genes, TP12446 is significantly more expressed across three life stages in T. pseudospiralis. Overexpression of TP12446 in the mouse C2C12 skeletal muscle cell line could induce inhibition of myotube formation and differentiation, further indicating its key role in parasitism of T. pseudospiralis. This multi-omics study provides a foundation for further elucidation of the mechanism of nurse cell formation and immunoevasion, as well as the identification of pharmacological and diagnostic targets of trichinellosis.

Deoxyribonucleases and Their Applications in Biomedicine

Extracellular DNA, also called cell-free DNA, released from dying cells or activated immune cells can be recognized by the immune system as a danger signal causing or enhancing inflammation. The cleavage of extracellular DNA is crucial for limiting the inflammatory response and maintaining homeostasis. Deoxyribonucleases (DNases) as enzymes that degrade DNA are hypothesized to play a key role in this process as a determinant of the variable concentration of extracellular DNA. DNases are divided into two families—DNase I and DNase II, according to their biochemical and biological properties as well as the tissue-specific production. Studies have shown that low DNase activity is both, a biomarker and a pathogenic factor in systemic lupus erythematosus. Interventional experiments proved that administration of exogenous DNase has beneficial effects in inflammatory diseases. Recombinant human DNase reduces mucus viscosity in lungs and is used for the treatment of patients with cystic fibrosis. This review summarizes the currently available published data about DNases, their activity as a potential biomarker and methods used for their assessment. An overview of the experiments with systemic administration of DNase is also included. Whether low-plasma DNase activity is involved in the etiopathogenesis of diseases remains unknown and needs to be elucidated.

Molecular basis of differential parasitism between non-encapsulated and encapsulated Trichinella revealed by a high-quality genome assembly

Understanding roles of repetitive sequences in genomes of parasites could offer insights into their evolution, speciation, and parasitism. As a unique intracellular nematode, Trichinella consists of two clades, encapsulated and non-encapsulated. Genomic correlation to the distinct differences between the two clades is still unclear. Here we report an annotated draft reference genome of non-encapsulated Trichinella, T. pseudospiralis, and performed comparative analyses with encapsulated T. spiralis. Genome analysis revealed that, during Trichinella evolution, repetitive sequence insertions played an important role in gene family expansion in synergy with DNA methylation, especially for the DNase II members of the phospholipase D superfamily and Glutathione S-transferases. We further identify the genomic and epigenomic regulation of excretory/secretory products in relation to differences in parasitism, pathology and immunology between the two clades Trichinella. The present study provided a foundation for further elucidation of mechanism of nurse cell formation and immunoevasion as well as identification of phamarcological and diagnostic targets of trichinellosis.