Differences in corneal phenotypes between destrin mutants are due to allelic difference and modified by genetic background

摘要

Purpose: Mutations in destrin (Dstn) cause corneal abnormalities in mice. A null mutation, Dstncorn1, results in corneal epithelial hyperproliferation, inflammation, and neovascularization in the A.BY background (A.BY Dstncorn1). Homozygosity for a point mutation, Dstncorn1–2J, results in mild thickening of the corneal epithelium but no corneal neovascularization in a C57BL/6 (B6) background (B6 Dstncorn1–2J). The goal of this study was to determine whether phenotypic differences are due to allelic differences between Dstncorn1 and Dstncorn1–2J, or are the result of genetic background effects. Methods: We generated two congenic (Cg) mouse lines, B6.Cg-Dstncorn1 and A.BY.Cg-Dstncorn1–2J, to compare to the original A.BY Dstncorn1 and B6 Dstncorn1–2J lines. We performed immunohistochemistry to assay F-actin accumulation, neovascularization, proliferation, and inflammation. By western blot analysis we tested the expression of serum response factor (SRF), a known regulator of the Dstncorn1 phenotype. Results: The Dstncorn1 mutation leads to neovascularization, hyperproliferation, and inflammation in the cornea of A.BY Dstncorn1 as well as B6.Cg-Dstncorn1 mice. We did not observe significant corneal neovascularization or hyperproliferation in either A.BY.Cg-Dstncorn1–2J or B6 Dstncorn1–2J mice. Actin accumulation, neovascularization, epithelial proliferation and inflammation in B6.Cg-Dstncorn1 cornea are significantly reduced when compared to A.BY Dstncorn1cornea. SRF changes are consistent in Dstncorn1 mutants, regardless of genetic background. Conclusions: Differences in the abnormal phenotypes of Dstn mutants result from allelic differences between Dstncorn1 and Dstncorn1–2J . Moreover, phenotypes of Dstncorn1 mice are modified by genetic background, suggesting the existence of genetic modifiers. Protein analysis suggests that a genetic modifier affects phenotypic severity functionally downstream from or in a pathway independent from SRF. These data demonstrate that natural genetic variation affects phenotypic severity in Dstncorn1 mice.