Congenic Fine-Mapping Identifies a Major Causal Locus for Variation in the Native Collateral Circulation and Ischemic Injury in Brain and Lower Extremity
Rationale: Severity of tissue injury in occlusive disease is dependent on the extent (number and diameter) of collateral vessels, which varies widely among healthy mice and humans. However, the causative genetic elements are unknown. Recently, much of the variation among different mouse strains, including C57Bl/6J (B6, high extent) and BALB/cByJ (Bc, low), was linked to a QTL on chromosome 7 (Candq1).
Objective: We used congenic mapping to refine Candq1 and its candidate genes and create an "isogenic" strain-set with large differences in collateral extent to assess their and Candq1's impact, alone, on ischemic injury.
Methods and Results: Six congenic strains possessing portions of Candq1 introgressed from B6 into Bc were generated and phenotyped. Candq1 was refined from 27 to 0.737 Mb with full retention of effect, i.e., return/rescue of phenotypes from the poor values in Bc to nearly those of wildtype B6 in the B6/B6 congenic mice: 83% rescue of low pial collateral extent, and 4.5-fold increase in blood flow and 85% reduction of infarct volume after middle cerebral artery occlusion; 54% rescue of low skeletal muscle collaterals, and augmented recovery of perfusion (83%) and function after femoral artery ligation. Gene deletion and in-silico analysis further delineated the candidate genes.
Conclusions: We have significantly refined Candq1 (now designated Determinant of collateral extent-1, Dce1), demonstrated that genetic background-dependent variation in collaterals is a major factor underlying differences in ischemic tissue injury, and generated a congenic strain-set with wide, allele-dose-dependent variation in collateral extent for use in investigations of the collateral circulation.
- ischemic stroke
- stroke genetics
- mouse strain
- collateral circulation
- cerebrovascular disease/stroke
- peripheral vascular disease
- genetics, animal models
- Received October 25, 2013.
- Revision received November 28, 2013.
- Accepted December 3, 2013.