The critical interval of chromosome 7 retains both infarct volume and collateral artery number phenotypes in congenic animals.

<p>A. Schematic map of two <i>Civq1</i> congenic lines carrying segments of B6 chromosome 7 introgressed into the BALB/c background, and heterozygous BALB/c alleles on B6 background. The latter could only be maintained as a heterozygote with B6. B. The posterior faces of representative 1-mm coronal sections from the B6, C.B6-<i>Civq1</i>-3, and BALB/c mice are shown. The size of the infarct is much smaller in C.B6-<i>Civq1</i>-3 than control BALB/c mouse. C. Congenic mice (C.B6-<i>Civq1</i>-1 and -3) exhibit a reduction in infarct volume by ∼30% compared to BALB/c mice. Infarct volume in congenic mice carrying heterozygous BALB/c alleles on B6 background (B6.C-<i>Civq1</i>(HET)) is 2.5-fold larger than that of control B6 mice. ## <i>P<0.001</i> vs. BALB/c; *<i>P<0.05</i>, ** <i>P<0.001</i> vs. B6. Values represent mean ± SEM. D. Superficial angioarchitecture of the brain in 4-week old B6, C.B6-<i>Civq1</i>-3, and BALB/c mice. Magnified images of the box in the upper panels are shown in the lower panels. The red arrowheads indicate the vessels of pial anastomoses between the MCA and ACA. E. C.B6-<i>Civq1</i> congenic lines show an increase in the number of collaterals connecting the distal MCA and ACA compared control BALB/c strains. Heterozygous congenic mice show no difference compared to control B6 mice. ## <i>P<0.001</i> vs. BALB/c; ** <i>P<0.001</i> vs. B6. F. Cortical brain slices from B6, BALB/c, and C.B6-<i>Civq1</i>-3 mice biolistically transfected with an YFP expression plasmid under normal conditions and 24 hr after 5.5 min of OGD. G. C.B6-<i>Civq1</i>-3 mice exhibit ∼50% increased neuronal viability compared to control BABL/c mice. Total numbers of healthy and YFP-positive neurons in the cortical region of the brain slices were counted at 24 hr after transient OGD. Cell viability was normalized from their non-OGD controls. Values represent mean±SEM from at least 5 animals per group. * <i>P<0.05</i> and ** <i>P<0.001</i>.