Angiogenesis, the formation of new blood vessels, is a tightly regulated function determined by the local balance of endogenous angiogenesis stimulators versus inhibitors. The central hypothesis for this proposal is that the angiogenic balance varies between individuals and that this variation is in large part genetically determined. Indeed, epidemiological data suggests that different racial populations have varied susceptibility to ocular neovascularization. We have surveyed inbred mouse strains to see if mice have a range of angiogenic diversity that models that of humans. Using the corneal micro pocket neovascularization assay, we have observed a greater than ten-fold difference in responsiveness to either basic fibroblast growth factor (bFGF) or vascular endothelial growth factor (VEGF) among various mouse strains. The inheritance pattern observed for these traits supported a QTL (quantitative trait locus) approach to mapping the genes responsible for the differences in angiogenic responsiveness. To overcome variability in the assay, we used recombinant inbred lines to map this phenotype. In BXD (C57BL/6J x DBA/2J) mice, we have mapped the regions responsible for regulating VEGF and bFGF induced angiogenesis. VEGF responsiveness is associated with regions on chromosomes 2 and 10, while bFGF responsiveness is associated with regions on chromosomes 4, 13, 15 and 18. We now propose to confirm these areas of linkage by testing the phenotype in congenic and consomic mice that have been bred to isolate each of the above linked DBA/2J areas onto a C57BL/6J genetic background. We are also mapping the phenotype in a different set of recombinant inbred mice known as AXB (A/J x C57BL/6J) to confirm overlapping associated areas. Next we will refine our linked regions by performing fine mapping. Lastly, we plan to identify and screen candidate genes in our strongest linked regions by utilizing the Celera mouse SNP database. Candidate genes will then be validated by a variety of methods.
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