Genetic Architecture of Group A Streptococcal Necrotizing Soft Tissue Infections in the Mouse

PLoS Pathog. 2016 Jul 11;12(7):e1005732. doi: 10.1371/journal.ppat.1005732. eCollection 2016 Jul.

Abstract

Host genetic variations play an important role in several pathogenic diseases, and we have previously provided strong evidences that these genetic variations contribute significantly to differences in susceptibility and clinical outcomes of invasive Group A Streptococcus (GAS) infections, including sepsis and necrotizing soft tissue infections (NSTIs). Our initial studies with conventional mouse strains revealed that host genetic variations and sex differences play an important role in orchestrating the severity, susceptibility and outcomes of NSTIs. To understand the complex genetic architecture of NSTIs, we utilized an unbiased, forward systems genetics approach in an advanced recombinant inbred (ARI) panel of mouse strains (BXD). Through this approach, we uncovered interactions between host genetics, and other non-genetic cofactors including sex, age and body weight in determining susceptibility to NSTIs. We mapped three NSTIs-associated phenotypic traits (i.e., survival, percent weight change, and lesion size) to underlying host genetic variations by using the WebQTL tool, and identified four NSTIs-associated quantitative genetic loci (QTL) for survival on mouse chromosome (Chr) 2, for weight change on Chr 7, and for lesion size on Chr 6 and 18 respectively. These QTL harbor several polymorphic genes. Identification of multiple QTL highlighted the complexity of the host-pathogen interactions involved in NSTI pathogenesis. We then analyzed and rank-ordered host candidate genes in these QTL by using the QTLminer tool and then developed a list of 375 candidate genes on the basis of annotation data and biological relevance to NSTIs. Further differential expression analyses revealed 125 genes to be significantly differentially regulated in susceptible strains compared to their uninfected controls. Several of these genes are involved in innate immunity, inflammatory response, cell growth, development and proliferation, and apoptosis. Additional network analyses using ingenuity pathway analysis (IPA) of these 125 genes revealed interleukin-1 beta network as key network involved in modulating the differential susceptibility to GAS NSTIs.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Disease Models, Animal
  • Enzyme-Linked Immunosorbent Assay
  • Fasciitis, Necrotizing / genetics*
  • Female
  • Gene Regulatory Networks
  • Genetic Predisposition to Disease / genetics*
  • Humans
  • Male
  • Mice
  • Phenotype
  • Quantitative Trait Loci
  • Real-Time Polymerase Chain Reaction
  • Risk Factors
  • Soft Tissue Infections / genetics*
  • Soft Tissue Infections / microbiology*
  • Streptococcal Infections / genetics*
  • Streptococcus pyogenes*

Grant support

This study was funded by European Union (Seventh Framework Program) under the grant agreement number 305340 to ANT MK; and the Swedish Research Council under grant number 20150338 to MS ANT MK. The funders had no role in the study design, data collection and analysis, and in the preparation of the manuscript.