MYEOV is a novel marker of differentiated corneal epithelium

PURPOSE. Myeloma Overexpressed gene (MYEOV) was initially identified as a gene amplified in several malignancies, and it was found to promote cell proliferation and metastasis. Our previous comparative RNA-seq and epigenetic analyses revealed high MYEOV levels in differentiated corneal epithelial cells and showed that MYEOV expression was epigenetically regulated by TET2. In the current study, we aimed to characterize further the expression and regulation of MYEOV in the human ocular surface epithelium. METHODS. MYEOV expression was examined by immunostaining and publicly available single-cell RNA-seq data. Gene knockdown (KD) of MYEOV and the regulators of corneal epithelial differentiation, PAX6 and KLF4, in in vitro-expanded corneal epithelial cells was performed by siRNA transfection. Protein expression levels were examined by Western blot. MYEOV KD cells were subjected to colony-forming assay and RNA-seq analysis. RESULTS. Human cornea immunostaining revealed high MYEOV expression in the nuclei of KRT12-positive differentiated corneal epithelial cells, while KRT13-positive differentiated conjunctival epithelial cells were MYEOV-negative. MYEOV expression was not detected in the other surface ectoderm-derived epithelia: epidermis and oral mucosa. Both PAX6 KD and KLF4 KD led to the reduction of MYEOV and KRT12 protein expression. MYEOV KD decreased colony-forming efficiency while afflicting limited global gene expression change. CONCLUSIONS. Our study revealed specific MYEOV expression in KRT12-positive corneal epithelial cells among surface ectoderm-derived epithelia. Similar to KRT12, MYEOV expression is regulated by PAX6 and KLF4. Functionally, MYEOV regulates cell proliferation of corneal epithelial cells.