Hif-1α-Induced Expression of Il-1β Protects against Mycobacterial Infection in Zebrafish.

Drug-resistant mycobacteria are a rising problem worldwide. There is an urgent need to understand the immune response to tuberculosis to identify host targets that, if targeted therapeutically, could be used to tackle these currently untreatable infections. In this study we use an Il-1β fluorescent transgenic line to show that there is an early innate immune proinflammatory response to well-established zebrafish models of inflammation and Mycobacterium marinum infection. We demonstrate that host-derived hypoxia signaling, mediated by the Hif-1α transcription factor, can prime macrophages with increased levels of Il-1β in the absence of infection, upregulating neutrophil antimicrobial NO production, leading to greater protection against infection. Our data link Hif-1α to proinflammatory macrophage Il-1β transcription in vivo during early mycobacterial infection and importantly highlight a host protective mechanism, via antimicrobial NO, that decreases disease outcomes and that could be targeted therapeutically to stimulate the innate immune response to better deal with infections

NR4A orphan nuclear receptor family members, NR4A2 and NR4A3, regulate neutrophil number and survival.

Neutrophil lifespan is plastic and highly responsive to factors that regulate cellular survival. Defects in neutrophil number and survival are common to both hematologic disorders and chronic inflammatory diseases. At sites of inflammation, neutrophils respond to multiple signals that activate protein kinase A (PKA) signaling, which positively regulates neutrophil survival. The aim of this study was to define transcriptional responses to PKA activation and to delineate the roles of these factors in neutrophil function and survival. In human neutrophil gene array studies, we show that PKA activation upregulates a significant number of apoptosis related genes, the most highly regulated of these being NR4A2 and NR4A3 Direct PKA activation by the site-selective PKA agonist pair N6/8-AHA and treatment with endogenous activators of PKA, including adenosine and PGE2, results in a profound delay of neutrophil apoptosis and concomitant upregulation of NR4A2/3 in a PKA dependent manner. NR4A3 expression is also increased at sites of neutrophilic inflammation in a human model of intradermal inflammation. PKA activation also promotes survival of murine neutrophil progenitor cells, and siRNA to NR4A2 decreases neutrophil production in this model. Antisense knockdown of NR4A2 and NR4A3 homologues in zebrafish larvae significantly reduces absolute neutrophil number without affecting cellular migration. In summary, we show that NR4A2 and NR4A3 are components of a downstream transcriptional response to PKA activation in the neutrophil, and that they positively regulate neutrophil survival and homeostasis

A152T tau allele causes neurodegeneration that can be ameliorated in a zebrafish model by autophagy induction.

Mutations in the gene encoding tau (MAPT) cause frontotemporal dementia spectrum disorders. A rare tau variant p.A152T was reported as a risk factor for frontotemporal dementia spectrum and Alzheimer's disease in an initial case-control study. Such findings need replication in an independent cohort. We analysed an independent multinational cohort comprising 3100 patients with neurodegenerative disease and 4351 healthy control subjects and found p.A152T associated with significantly higher risk for clinically defined frontotemporal dementia and progressive supranuclear palsy syndrome. To assess the functional and biochemical consequences of this variant, we generated transgenic zebrafish models expressing wild-type or A152T-tau, where A152T caused neurodegeneration and proteasome compromise. Impaired proteasome activity may also enhance accumulation of other proteins associated with this variant. We increased A152T clearance kinetics by both pharmacological and genetic upregulation of autophagy and ameliorated the disease pathology observed in A152T-tau fish. Thus, autophagy-upregulating therapies may be a strategy for the treatment for tauopathies

Zebrafish as a Novel Vertebrate Model To Dissect Enterococcal Pathogenesis

Enterococcus faecalis is an opportunistic pathogen responsible for a wide range of life-threatening nosocomial infections, such as septicemia, peritonitis, and endocarditis. E. faecalis infections are associated with a high mortality and substantial health care costs and cause therapeutic problems due to the intrinsic resistance of this bacterium to antibiotics. Several factors contributing to E. faecalis virulence have been identified. Due to the variety of infections caused by this organism, numerous animal models have been used to mimic E. faecalis infections, but none of them is considered ideal for monitoring pathogenesis. Here, we studied for the first time E. faecalis pathogenesis in zebrafish larvae. Using model strains, chosen isogenic mutants, and fluorescent derivatives expressing green fluorescent protein (GFP), we analyzed both lethality and bacterial dissemination in infected larvae. Genetically engineered immunocompromised zebrafish allowed the identification of two critical steps for successful establishment of disease: (i) host phagocytosis evasion mediated by the Epa rhamnopolysaccharide and (ii) tissue damage mediated by the quorum-sensing Fsr regulon. Our results reveal that the zebrafish is a novel, powerful model for studying E. faecalis pathogenesis, enabling us to dissect the mechanism of enterococcal virulence

A152T tau allele causes neurodegeneration that can be ameliorated in a zebrafish model by autophagy induction

Mutations in the gene encoding tau (MAPT) cause frontotemporal dementia spectrum disorders. A rare tau variant p.A152T was reported as a risk factor for frontotemporal dementia spectrum and Alzheimer’s disease in an initial case-control study. Such findings need replication in an independent cohort. We analysed an independent multinational cohort comprising 3100 patients with neurodegenerative disease and 4351 healthy control subjects and found p.A152T associated with significantly higher risk for clinically defined frontotemporal dementia and progressive supranuclear palsy syndrome. To assess the functional and biochemical consequences of this variant, we generated transgenic zebrafish models expressing wild-type or A152T-tau, where A152T caused neurodegeneration and proteasome compromise. Impaired proteasome activity may also enhance accumulation of other proteins associated with this variant. We increased A152T clearance kinetics by both pharmacological and genetic upregulation of autophagy and ameliorated the disease pathology observed in A152T-tau fish. Thus, autophagy-upregulating therapies may be a strategy for the treatment for tauopathies

Multiscale Modeling of Nucleosome Dynamics

Nucleosomes form the fundamental building blocks of chromatin. Subtle modifications of the constituent histone tails mediate chromatin stability and regulate gene expression. For this reason, it is important to understand structural dynamics of nucleosomes at atomic levels. We report a novel multiscale model of the fundamental chromatin unit, a nucleosome, using a simplified model for rapid discrete molecular dynamics simulations and an all-atom model for detailed structural investigation. Using a simplified structural model, we perform equilibrium simulations of a single nucleosome at various temperatures. We further reconstruct all-atom nucleosome structures from simulation trajectories. We find that histone tails bind to nucleosomal DNA via strong salt-bridge interactions over a wide range of temperatures, suggesting a mechanism of chromatin structural organization whereby histone tails regulate inter- and intranucleosomal assemblies via binding with nucleosomal DNA. We identify specific regions of the histone core H2A/H2B-H4/H3-H3/H4-H2B/H2A, termed “cold sites”, which retain a significant fraction of contacts with adjoining residues throughout the simulation, indicating their functional role in nucleosome organization. Cold sites are clustered around H3-H3, H2A-H4 and H4-H2A interhistone interfaces, indicating the necessity of these contacts for nucleosome stability. Essential dynamics analysis of simulation trajectories shows that bending across the H3-H3 is a prominent mode of intranucleosomal dynamics. We postulate that effects of salts on mononucleosomes can be modeled in discrete molecular dynamics by modulating histone-DNA interaction potentials. Local fluctuations in nucleosomal DNA vary significantly along the DNA sequence, suggesting that only a fraction of histone-DNA contacts make strong interactions dominating mononucleosomal dynamics. Our findings suggest that histone tails have a direct functional role in stabilizing higher-order chromatin structure, mediated by salt-bridge interactions with adjacent DNA