Serum response factor: positive and negative regulation of an epithelial gene expression network in the destrin mutant cornea

Abstract

Increased angiogenesis, inflammation, and proliferation are hallmarks of diseased tissues, and in vivo models of these disease phenotypes can provide insight into disease pathology. Dstn corn1 mice, deficient for the actin depolymerizing factor destrin (DSTN), display an increase of serum response factor (SRF) that results in epithelial hyperproliferation, inflammation, and neovascularization in the cornea. Previous work demonstrated that conditional ablation of Srf from the corneal epithelium of Dstn corn1 mice returns the cornea to a wild-type (WT) like state. This result implicated SRF as a major regulator of genes that contributes to abnormal phenotypes in Dstn corn1 cornea. The purpose of this study is to identify gene networks that are affected by increased expression of Srf in the Dstn corn1 cornea. Microarray analysis led to characterization of gene expression changes that occur when conditional knockout of Srf rescues mutant phenotypes in the cornea of Dstn corn1 mice. Comparison of gene expression values from WT, Dstn corn1 mutant, and Dstn corn1 rescued cornea identified >400 differentially expressed genes that are downstream from SRF. Srf ablation had a significant effect on genes associated with epithelial cell-cell junctions and regulation of actin dynamics. The majority of genes affected by SRF are downregulated in the Dstn corn1 mutant cornea, suggesting that increased SRF negatively affects transcription of SRF gene targets. ChIP-seq analysis on Dstn corn1 mutant and WT tissue revealed that, despite being present in higher abundance, SRF binding is significantly decreased in the Dstn corn1 mutant cornea. This study uses a unique model combining genetic and genomic approaches to identify genes that are regulated by SRF. These findings expand current understanding of the role of SRF in both normal and abnormal tissue homeostasis.