A novel epithelial wound-related gene is abundantly expressed in developing rat cornea and skin

Purpose. We previously used mRNA differential display and identified a nove l gene that is up regulated in the healing corneal epithelium. To understan d the potential in vivo role of this gene, termed T4a, we cloned the full-l ength T4a cDNA and investigated its temporal and spatial transcription expr ession in healing rat corneas, as well as in developing cornea and skin. Methods. The displayed T4a cDNA was used to identify clones from a rat cDNA library derived from healing corneal epithelia. The cDNA clones were seque nced and the sequence was analyzed with the Blast program. In situ hybridiz ation was performed using digoxigenin-labeled riboprobes and cryostat secti ons from healing and developing cornea as well as skin. Results. The T4a cDNA had 2538 bp with an open reading frame of 2178 bp, co nsistent with a conceptual translation product of 725 amino acid residues, a calculated molecular mass of 83.1 kD and theoretical pI of 6.93. Although T4a exhibited no sequence homology with known genes in the GenBank, it mat ched a large number of Expressed Sequence Tags (ESTs) from human, mouse and rat tissue cDNA libraries; more than half of the murine T4a ESTs were from embryonic DNA libraries. Sequence analysis revealed numerous phosphorylati on and myristoylation sites in the deduced amino acid sequence of T4a. In t he wounded rat cornea, intensive T4a mRNA staining was observed in the epit helium at all stages of re-epithelialization indicating that the expression of T4a is wound-related. In 7 day old mice, an abundant level of T4a trans cripts was found in the epidermis and hair follicles, as well as in the cor neal epithelial layer. High levels of T4a mRNA staining persisted in the de veloping postnatal corneal epithelia. In contrast, weak mRNA staining was o nly detected in the basal layer of the adult epidermis and corneal epitheli um. Conclusion. These results indicate that T4a expression correlates with re-e pithelialization of the cornea and maturation of the cornea and skin, sugge sting a role for this gene in epithelial development, differentiation, and wound healing.