Exploring the role of non-genetic inheritance in the etiology of human disease

Francisella tularensis is a Gram-negative bacterium that causes a fatal human disease known as tularemia. The Centers for Disease Control have classified F. tularensis as Category A Tier-1 Select Agent. The virulence mechanisms of Francisella are not entirely understood. Francisella possesses very few transcription regulators, and most of these regulate the expression of genes involved in intracellular survival and virulence. The F. tularensis genome sequence analysis reveals an AraC ( FTL_ 0689) transcriptional regulator homologous to the AraC/XylS family of transcriptional regulators. In Gram-negative bacteria, AraC activates genes required for L-arabinose utilization and catabolism. The role of the FTL_ 0689 regulator in F. tularensis is not known. In this study, we characterized the role of FTL_ 0689 in gene regulation of F. tularensis and investigated its contribution to intracellular survival and virulence. The results demonstrate that FTL_0689 in Francisella is not required for L-arabinose utilization. Instead, FTL_ 0689 specifically regulates the expression of the oxidative and global stress response, virulence, metabolism, and other key pathways genes required by Francisella when exposed to oxidative stress. The FTL_0689 mutant is attenuated for intramacrophage growth and virulence in mice. Based on the deletion mutant phenotype, FTL_0689 was termed osrR ( o xidative s tress r esponse r egulator). Altogether, this study elucidates the role of the osrR transcriptional regulator in tularemia pathogenesis. IMPORTANCE: The virulence mechanisms of category A select agent Francisella tularensis , the causative agent of a fatal human disease known as tularemia, remain largely undefined. The present study investigated the role of a transcriptional regulator and its overall contribution to the oxidative stress resistance of F. tularensis . The results provide an insight into a novel gene regulatory mechanism, especially when Francisella is exposed to oxidative stress conditions. Understanding such Francisella - specific regulatory mechanisms will identify potential targets for developing effective therapies and vaccines to prevent tularemia.

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Caspase-8 mediates inflammation and disease in rodent malaria

Nature Communications ◽

10.1038/s41467-020-18295-x ◽

2020 ◽

Vol 11 (1) ◽

Author(s):

Larissa M. N. Pereira ◽

Patrícia A. Assis ◽

Natalia M. de Araújo ◽

Danielle F. Durso ◽

Caroline Junqueira ◽

...

Keyword(s):

Septic Shock ◽

Human Disease ◽

Caspase 8 ◽

Inflammasome Activation ◽

Plasmodium Chabaudi ◽

Experimental Cerebral Malaria ◽

Rodent Malaria ◽

Canonical Pathways ◽

Inflammatory Caspases

Abstract Earlier studies indicate that either the canonical or non-canonical pathways of inflammasome activation have a limited role on malaria pathogenesis. Here, we report that caspase-8 is a central mediator of systemic inflammation, septic shock in the Plasmodium chabaudi-infected mice and the P. berghei-induced experimental cerebral malaria (ECM). Importantly, our results indicate that the combined deficiencies of caspases-8/1/11 or caspase-8/gasdermin-D (GSDM-D) renders mice impaired to produce both TNFα and IL-1β and highly resistant to lethality in these models, disclosing a complementary, but independent role of caspase-8 and caspases-1/11/GSDM-D in the pathogenesis of malaria. Further, we find that monocytes from malaria patients express active caspases-1, -4 and -8 suggesting that these inflammatory caspases may also play a role in the pathogenesis of human disease.

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