Figure 1

Approach to map QTL for functional motor deficits, CNS vascular permeability, and astrocyte activation. (A) PIFS-susceptible B6 mice were crossed with PIFS-resistant 129S1 mice to yield an F1 generation which was previously determined to be resistant to PIFS. F1 hybrid mice were then brother-sister mated to produce 303 F2 progeny with variable susceptibility to traits associated with PIFS, including functional motor deficits, astrocyte GFAP expression, and CNS vascular permeability measured by FITC-albumin leakage. DNA from 273 randomly selected F2 progeny were analyzed using Illumina Chip Technologies. SNPs with a known cM value were analyzed for the relationship between quantifiable traits (functional motor deficits, CNS vascular permeability, and astrocyte expression of GFAP) and genotype. (B) F2 mice displayed variable susceptibility to each of the traits associated with PIFS and were divided into susceptible and resistant groups based on whether they exhibited the trait or not. CNS vascular permeability was evaluated using a fluorescent plate reader to detect FITC-albumin leakage in brain homogenates. Samples were read at A₄₈₈, and a threshold value of 500 was used to determine susceptibility or resistance. Astrocyte expression of GFAP was detected through Western blot analysis. Expression values were based on GFAP protein levels normalized to GAPDH. We used a threshold value of 50 to categorize F2 mice into susceptible and resistant groups. Functional motor deficit was assessed using the rotarod behavioral assay. A threshold value of 50% initial motor ability was used to categorize mice as susceptible or resistant. All values are displayed as mean ± SEM.