Mapping Data

Experiment

• Experiment
  TEXT-Congenic
• Chromosome
  1
• Reference
  J:212963 Khan RT, et al., Fine-mapping and phenotypic analysis of the Ity3 Salmonella susceptibility locus identify a complex genetic structure. PLoS One. 2014;9(2):e88009
• ID
  MGI:5912466

Genes

Gene	Assay Type
Ity3	visible phenotype
Ity3a	visible phenotype
Ity3b	visible phenotype

Notes

• Experiment
  Using an F2 cross between the classical inbred strain C57BL/6J and the wild derived strain MOLF/Ei, QTL Ity3 (Immunity to Typhimurium locus 3) was previously identified as a locus contributing to the early susceptibility of MOLF/Ei mice to infection with Salmonella Typhimurium. The MOLF/Ei allele at the Ity3 locus resulted in increased susceptibility to infection. [J:45962]
  
  In the current study 12 subcongenic strains were generated by crossing congenic Slc11a1 (B6.MOLF-Slc11a1, Chr 1, 40.9-78.7 Mb) and congenic Ity3 (B6.MOLF-Slc11a1/Ity3, Chr1, 127.4-189.6 Mb) mice to generate heterozygous mice that were further backcrossed to parental B6.MOLF-Slc11a1 mice. Using marker-assisted breeding, mice with identical breakpoints were intercrossed to generate homozygous mice. This led to the establishment of twelve recombinant B6.MOLF-Slc11a1/Ity3 strains that were different from the strains initially described. The 12 recombinant, subcongenic strains (Ity3.RecA to Ity3.RecS, Table 1) were characterized for susceptibility to infection, bacterial load in target organs, cytokine profile and anti-microbial mechanisms were generated. [Fig 1].
  
  DNA was extracted from tail clippings of all subcongenic strains, as well as from C57BL/6J and MOLF/Ei, Ity and Ity3 congenic control mice. Mice were infected with 3000 CFUs of Salmonella Typhimurium strain Keller. The animals were monitored 2-3 times daily and mice showing signs of distress (piloerection, sunken eyes and abdomen, lethargy) or body condition scoring less than 2.0 were used for clinical endpoints. Survival analysis was conducted using a Kaplan-Meier survival test. For bacterial burden quantification in the spleen and the liver, mice were euthanized at the required day post infection. Blood was collected by cardiac puncture from uninfected (day 0) mice, as well as at day 3 and day 5 post infection. Bone marrow derived macrophages (BMDM) were isolated from femurs of 10-16 week-old male mice.
  
  Based on the survival analyses of the 12 subcongenic mice, the Ity3 interval was refined to a ~23 Mb interval on chromosome 1 located between position 151.0 Mb and 174.2 Mb (Ensembl build 37). The identification of the two subcongenic strains (Ity3.RecG and Ity3.RecN) presenting an intermediate phenotype is suggestive of the presence of at least two loci within the Ity3 locus: Ity3a sub-locus located between 151 Mb and 156.2 Mb and Ity3b from 158.6 Mb to 174.2 Mb, that together contributed to the enhanced susceptibility of the Ity3 congenic mice (Table 1).
  
  The Ity3a sublocus controlled NADPH oxidase activity and was characterized by decreased ROS production, reduced inflammatory cytokine response and increased bacterial burden, supporting a role for Ncf2 (neutrophil cytosolic factor 2 a subunit of NADPH oxidase) as the gene underlying the sublocus. The Ity3b sub-locus was characterized by a hyperresponsive inflammatory cytokine phenotype after exposure to Salmonella.
  
  Overall, the current research provided support to the combined action of hormonal influences and complex genetic factors within the Ity3 locus in the innate immune response to Salmonella infection in wild-derived MOLF/Ei mice.