Aberrant DNA methylation distorts developmental trajectories in atypical teratoid/rhabdoid tumors.

Atypical teratoid/rhabdoid tumors (AT/RTs) are pediatric brain tumors known for their aggressiveness and aberrant but still unresolved epigenetic regulation. To better understand their malignancy, we investigated how AT/RT-specific DNA hypermethylation was associated with gene expression and altered transcription factor binding and how it is linked to upstream regulation. Medulloblastomas, choroid plexus tumors, pluripotent stem cells, and fetal brain were used as references. A part of the genomic regions, which were hypermethylated in AT/RTs similarly as in pluripotent stem cells and demethylated in the fetal brain, were targeted by neural transcriptional regulators. AT/RT-unique DNA hypermethylation was associated with polycomb repressive complex 2 and linked to suppressed genes with a role in neural development and tumorigenesis. Activity of the several NEUROG/NEUROD pioneer factors, which are unable to bind to methylated DNA, was compromised via the suppressed expression or DNA hypermethylation of their target sites, which was also experimentally validated for NEUROD1 in medulloblastomas and AT/RT samples. These results highlight and characterize the role of DNA hypermethylation in AT/RT malignancy and halted neural cell differentiation.

FURIN regulates cytotoxic T-lymphocyte effector function and memory cell transition in mice.

The proprotein convertase subtilisin/kexins (PCSKs) regulate biological actions by cleaving immature substrate proteins. The archetype PCSK, FURIN, promotes the pathogenicity of viruses by proteolytically processing viral proteins. FURIN has also important regulatory functions in both innate and adaptive immune responses but its role in the CD8+ CTLs remains enigmatic. We used a T-cell-specific FURIN deletion in vivo to demonstrate that FURIN promotes host response against the CTL-dependent lymphocytic choriomeningitis virus by virtue of restricting viral burden and augmenting interferon gamma (IFNG) production. We also characterized Furin KO CD8+ T cells ex vivo, including after their activation with FURIN regulating cytokines IL12 or TGFB1. Furin KO CD8+ T cells show an inherently activated phenotype characterized by the upregulation of effector genes and increased frequencies of CD44+ , TNF+ , and IFNG+ cells. In the activated CTLs, FURIN regulates the productions of IL2, TNF, and GZMB and the genes associated with the TGFBR-signaling pathway. FURIN also controls the expression of Eomes, Foxo1, and Bcl6 and the levels of ITGAE and CD62L, which implies a role in the development of CTL memory. Collectively, our data suggest that the T-cell expressed FURIN is important for host responses in viral infections, CTL homeostasis/activation, and memory development.

Proprotein convertase subtilisin/kexin type 9 regulates the production of acute-phase reactants from the liver.

BACKGROUND & AIMS: Proprotein convertase subtilisin/kexin type 9 (PCSK9) controls blood cholesterol levels by fostering the LDL receptor (LDLR) degradation in hepatocytes. Additionally, PCSK9 has been suggested to participate in immunoregulation by modulating cytokine production. We studied the immunological role of PCSK9 in Streptococcus pneumoniae bacteraemia in vivo and in a human hepatocyte cell line. METHODS: CRISPR/Cas9 mutagenesis was utilized to create pcsk9 knock-out (KO) zebrafish, which were infected with S pneumoniae to assess the role of PCSK9 for the survival of the fish and in the transcriptomic response of the liver. The direct effects of PCSK9 on the expression of acute-phase reaction (APR) genes were studied in HepG2 cells. RESULTS: The pcsk9 KO zebrafish lines (pcsk9tpu-13 and pcsk9tpu-2,+15 ) did not show developmental defects or gross phenotypical differences. In the S pneumoniae infected zebrafish, the mortality of pcsk9 KOs was similar to the controls. A liver-specific gene expression analysis revealed that a pneumococcal challenge upregulated pcsk9, and that the pcsk9 deletion reduced the expression of APR genes, including hepcidin antimicrobial peptide (hamp) and complement component 7b (c7b). Accordingly, silencing PCSK9 in vitro in HepG2 cells using small interfering RNAs (siRNAs) decreased HAMP expression. CONCLUSIONS: We demonstrate that PCSK9 is not critical for zebrafish survival in a systemic pneumococcal infection. However, PCSK9 deficiency was associated with the lower expression of APR genes in zebrafish and altered the expression of innate immunity genes in a human hepatocyte cell line. Overall, our data suggest an evolutionarily conserved function for PCSK9 in APR in the liver.