Transcription co-regulator Clim2 plays a role in the maintenance of limbal stem cells

Clim1 and Clim2 are transcriptional cofactors that mediate protein-protein interactions within DNA-binding complexes in many cell types. Epithelial specific expression of a dominant negative Clim construct causes epithelial hyperplasia, neovascularization, inflammation, and blistering, followed by epithelial thinning and subsequent epidermal-like differentiation of the cornea epithelium. This phenotype resembles some aspects of limbal stem cell deficiency, suggesting that Clim proteins may be involved in regulating stem cell mainenance for the cornea. K14 DN-Clim cornea epithelium has a decrease in progenitor cells and altered proliferation during epithelial development. Gene expression profiling on DN-Clim corneas identified disrupted genes and pathways, including pathways crucial for stem cell mainenance, as well as regulation of proliferation. In vivo ChIP-Seq experiments confirm that many genes that are highly expressed in the limbus, as well as genes with known roles in stem cell maintenance are directly regulated by Clim factors. Additionally, factors that regulate corneal epithelial differentiation are direct targets of Clim. Together our results identify a role for Clim proteins in regulating stem cell maintenance and the proliferation dynamics of cornea epithelial proliferation. Whole corneas were dissected from P7 K14 DN-Clim mouse eye globes, taking care to remove all non-corneal tissues. Corneal epithelium was isolated by digestion in 50% EMEM/dispase II with 50 mM sorbitol and 10 ml/ml bME for two hours at 37°C. ChIP was performed with an anit-Myc antibody to the Myc tag of the DN-Clim construct.