Explore the vast range of titles available.

Classical dendritic cells (cDCs) are essential for immune responses and differentiate from hematopoietic stem cells via intermediate progenitors, such as monocyte–DC progenitors (MDPs) and common DC progenitors (CDPs). Upon infection, cDCs are activated and rapidly express host defense-related genes, such as those encoding cytokines and chemokines. Chromatin structures, including nuclear compartments and topologically associating domains (TADs), have been implicated in gene regulation. However, the extent and dynamics of their reorganization during cDC development and activation remain unknown. In this study, we comprehensively determined higher-order chromatin structures by Hi-C in DC progenitors and cDC subpopulations. During cDC differentiation, chromatin activation was initially induced at the MDP stage. Subsequently, a shift from inactive to active nuclear compartments occurred at the cDC gene loci in CDPs, which was followed by increased intra-TAD interactions and loop formation. Mechanistically, the transcription factor IRF8, indispensable for cDC differentiation, mediated chromatin activation and changes into the active compartments in DC progenitors, thereby possibly leading to cDC-specific gene induction. Using an infection model, we found that the chromatin structures of host defense-related gene loci were preestablished in unstimulated cDCs, indicating that the formation of higherorder chromatin structures prior to infection may contribute to the rapid responses to pathogens. Overall, these results suggest that chromatin structure reorganization is closely related to the establishment of cDC-specific gene expression and immune functions. This study advances the fundamental understanding of chromatin reorganization in cDC differentiation and activation.

Toxoplasma gondii is classified into 16 haplogroups based on a worldwide genotyping study of the parasite. However, only a few isolates from Japan were included in this analysis. To conduct more precise genotyping of T. gondii, we examined the genotypes of Japanese isolates in this study. DNA sequences of 6 loci were determined in 17 Japanese isolates and compared with those of strains of 16 haplogroups. As a result, Japanese isolates were classified into four groups. We investigated the virulence of some Japanese isolates and found a highly virulent strain in mice, comparable to that of RH strain, although this Japanese isolate was sister to strains of haplogroup 2, which show moderate virulence in mice. We further investigated whether this high virulence isolate had different virulence mechanism and strategy to adapt to Japanese host from other strains by comparing the virulence-related genes, ROP5, 18 and the immunomodulatory gene, ROP16 of the isolate with those of archetypical strains (GT1, ME49 and VEG). This analysis indicated the high virulence of the isolate in mice was partly explained by gene sequences of ROP5 and ROP16. These findings lead to the elucidation of biodiversity of T. gondii and have potential to optimize the diagnostic protocol.

Toxoplasma gondii is an obligate parasite whose infection can be detrimental when combined with pregnancy or immunodeficiency. Studies on T. gondii virulence have revealed various secretory proteins that inhibit the host interferon-gamma (IFN-γ) immune response. However, much of the broader virulence landscape remains unclear. To explore the unknown molecular pathways of T. gondii virulence in mice, we searched for immunosuppressive functions in genes encoding non-secretory proteins, associated with fundamental cellular processes of the virulent type I strain. Here, we found that TgJosephin, a highly conserved deubiquitinase, was important for virulence in wild-type mice but not mice lacking the IFN-γ receptor (IFNγR). In addition, TgJosephin expression was dependent on TgRad23, and loss of TgJosephin led to increased ubiquitination of a microtubule protein SPM1. Our results suggest a novel anti-IFN-γ pathway of T. gondii mediated by TgJosephin and SPM1 deubiquitination.

Most intracellular pathogens replicate in a vacuole to avoid the defense system of the host. A few pathogens recruit host mitochondria around those vacuoles, but the molecules responsible for mitochondrial recruitment remain unidentified. It is only in the apicomplexan parasite Toxoplasma gondii, that mitochondrial association factor 1b (MAF1b) has been identified as an association factor for host mitochondria. Here, we show that rhoptry kinase family protein 39 (ROP39) induces host mitochondrial recruitment in T. gondii. We found that the abundance of ROP39 was increased on host mitochondria extracted from human foreskin fibroblasts (HFFs) infected with T. gondii. ROP39 expressed exogenously in HFFs localized on host mitochondria, indicating that it has the potential to bind to host mitochondria without assistance from other parasite factors. Confocal microscopy revealed that ROP39 colocalized with host mitochondria on the membrane of parasitophorous vacuoles, in which the parasites reside. Moreover, we observed about a 10% reduction in the level of mitochondrial association in rop39-knockout parasites compared with a parental strain.

The rapid intraerythrocytic replication of Plasmodium falciparum , a deadly species of malaria parasite, requires a quick but constant supply of phospholipids to support marked cell membrane expansion. In the malarial parasite, many enzymes functioning in phospholipid synthesis pathway have not been identified or characterized. Here, we identify P. falciparum lysophospholipid acyltransferase 1 (PfLPLAT1) and show that PfLPLAT1 is vital for asexual parasite cell cycle progression and cytostome internalization. Deficiency in PfLPLAT1 results in decreased parasitemia and prevents transition to the schizont stage. Parasites lacking PfLPLAT1 also exhibit distinctive omega-shaped vacuoles, indicating disrupted cytostome function. Transcriptomic analyses suggest that this deficiency impacts DNA replication and cell cycle regulation. Mass spectrometry-based enzyme assay and lipidomic analysis demonstrate that recombinant PfLPLAT1 exhibits lysophospholipid acyltransferase activity with a preference for unsaturated fatty acids as its acyl donors and lysophosphatidic acids as an acceptor, with its conditional knockout leading to abnormal lipid composition and marked morphological and developmental changes including stage arrest. These findings highlight PfLPLAT1 as a potential target for antimalarial therapy, particularly due to its unique role and divergence from human orthologs. Pf LPLAT1 has important roles in the phospholipid synthesis pathway of Plasmodium falciparum , particularly phosphatidic acid as an essential substance for cytostome internalization. Its dysfunction leads to cell cycle arrest and death of parasites.

Dense granules (DG) are understudied apical organelles in merozoites, the malaria parasite stage that invades erythrocytes. Only six proteins have been identified which localize to DGs, despite that DG proteins play crucial roles in multiple steps of intraerythrocytic parasite development. To develop a tool for investigating DG structure and function, this study applied ultrastructural expansion microscopy (U-ExM) to visualize the ring-infected erythrocyte surface antigen (RESA) in Plasmodium falciparum merozoites. Merozoites were expanded to approximately four times their original size, allowing the identification of DGs without the need for electron microscopy. RESA localization in merozoite DGs was confirmed by staining with a combination of anti-RESA mAb and protein staining by NHS-ester. The translocation of RESA to the infected erythrocyte membrane was also observed in early ring-stage parasites. These results are in good agreement with the RESA localization reported using immunoelectron microscopy (IEM). By using U-ExM, the identification of novel DG proteins will be facilitated without time-consuming IEM, thereby contributing to describing erythrocyte parasitism by P. falciparum.Competing Interest StatementThe authors have declared no competing interest.

Plasmodium falciparum is the causative agent of human malaria, a life-threating infectious disease that imposes a major global health burden. Lipid metabolism is indispensable for this parasite’s replication and survival, yet most of the molecular components and mechanisms involved remain poorly understood. In eukaryotes, lipid droplets (LDs) serve as dynamic organelles that store neutral lipids (NLs), buffer lipotoxic stress, and regulate signaling pathways, with their biogenesis controlled by diacylglycerol o-acyltransferases (DGATs). Although P. falciparum encodes a putative DGAT (PF3D7_0322300), its role in the parasite life cycle has not been elucidated. We generated conditional PfDGAT-knockout parasites to investigate the enzyme’s functional significance. PfDGAT deficiency led to parasite death, accompanied by reduced LD formation, elevated phospholipid levels, and induction of ER stress. Moreover, PfDGAT deletion altered protein trafficking, resulting in the decreased cytoadherence of parasite-infected erythrocytes to human brain microvascular endothelial cells, and suppressed parasite sexual differentiation. Thus, PfDGAT deletion affected multiple aspects of the parasite’s life cycle, highlighting its critical role in parasite survival and pathogenesis. Our findings provide new insights into parasite lipid homeostasis and highlight DGAT as a potential target of antimalarial intervention.

The rapid intraerythrocytic replication of Plasmodium falciparum, a deadly species of malaria parasite, requires a quick but constant supply of phospholipids to support marked cell membrane expansion. In the malarial parasite, many enzymes functioning in phospholipid synthesis pathway have not been identified or characterized. Here, we identified P. falciparum lysophospholipid acyltransferase 1 (PfLPLAT1; PF3D7_1444300) and showed that PfLPLAT1 is vital for asexual parasite cell cycle progression and cytostome internalization. Deficiency in PfLPLAT1 resulted in decreased parasitemia and prevented transition to the schizont stage. Parasites lacking PfLPLAT1 also exhibited distinctive omega-shaped vacuoles, indicating disrupted cytostome function. Transcriptomic analyses suggested that this deficiency impacted DNA replication and cell cycle regulation. Mass spectrometry-based enzyme assay and lipidomic analysis demonstrated that recombinant PfLPLAT1 exhibited lysophospholipid acyltransferase activity with a preference for unsaturated fatty acids as its acyl donors and lysophosphatidic acids as an acceptor, with its conditional knockout leading to abnormal lipid composition and marked morphological and developmental changes including stage arrest. These findings highlight PfLPLAT1 as a potential target for antimalarial therapy, particularly due to its unique role and divergence from human orthologs.Competing Interest StatementThe authors have declared no competing interest.Footnotes* Author's affilations were revised.

The cusp overlap technique allows greater visual separation between the basal annular plane and the conduction system and decreases the permanent pacemaker implantation rate. We assessed the impact of the cusp overlap technique on conduction disturbance and paravalvular leakage after transcatheter aortic valve replacement. A total of 97 patients underwent transfemoral transcatheter aortic valve replacement with self-expandable valves at our institution from November 2018 to January 2023. The mean age of the patients was 85 years, and 23% were male. The patients were divided into two groups: the cusp overlap technique group and the non-cusp overlap technique group. We compared the clinical results between the two groups. The 30-day permanent pacemaker implantation rate was similar between the two groups (cusp overlap technique: 6.3% vs. non-cusp overlap technique: 10.2%, p = 0.48). The rate of new-onset conduction disturbance was slightly lower in the cusp overlap than non-cusp overlap technique group (18.8% vs. 34.7%, respectively; p = 0.08). The implanted valve function was similar between the two groups, but the rate of trivial or less paravalvular leakage (PVL) was significantly higher in the cusp overlap technique group on echocardiography (69% vs. 45%, p = 0.02). On multidetector computed tomography, the implantation depth at the membranous septum was significantly shorter in the cusp overlap technique group (2.0 ± 2.3 vs. 2.9 ± 1.5 mm, p = 0.02). The degree of canting was slightly smaller in the cusp overlap technique group (1.0 ± 2.2 vs. 1.7 ± 1.9 mm, p = 0.07). The relative risk of PVL equal to or greater than mild was 1.76 times higher for valve implantation without the cusp overlap technique (adjusted odds ratio, 3.74; 95% confidence interval, 1.45–9.69; p < 0.01). Transcatheter aortic valve replacement using the cusp overlap technique is associated with an optimized implantation depth, leading to fewer conduction disturbances. Optimal deployment may also maximize the radial force of self-expanding valves to reduce paravalvular leakage.