Figure 2.

Systems Genetics integrates systems biology and genetic complexity. Here sets of genetically well-defined yet distinct mouse strains (a) are challenged with a pathogen and a variety (b) of disease and molecular phenotypes are collected. Integration of genetic variants within this population and disease phenotypes (c) can identify host genome regions containing polymorphisms controlling disease phenotypes (QTL mapping), and contrasting the expression profiles of individuals with variant polymorphisms at this loci can identify those groups of transcripts that are up-regulated (orange) or down-regulated (purple) due to polymorphisms at this genome location, highlighting mechanisms of virus induced pathology. Furthermore, by contrasting in a strain-specific manner all of those transcripts that are differentially expressed during infection (d), specific transcriptional subsets can be associated with variant disease outcomes. Here each of the three mouse strains have a pool of differentially expressed transcripts (colored circles) following infection. Therefore, the union of red, blue and green describes those transcripts commonly differentially regulated across all genotypes in response to infection. Similarly, the intersection of red and blue transcripts (excluding green transcripts) describes those transcripts differentially regulated in genotypes with severe lung pathologies.