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 novel gene that is up regulated in the healing corneal epithelium. To understand the potential in vivo role of this gene, termed T4a, we cloned the full-length T4a cDNA and investigated its temporal and spatial transcription expression 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 sequenced and the sequence was analyzed with the Blast program. In situ hybridization was performed using digoxigenin-labeled riboprobes and cryostat sections from healing and developing cornea as well as skin.

RESULTS

The T4a cDNA had 2538 bp with an open reading frame of 2178 bp, consistent 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 matched 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 phosphorylation and myristoylation sites in the deduced amino acid sequence of T4a. In the wounded rat cornea, intensive T4a mRNA staining was observed in the epithelium 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 transcripts was found in the epidermis and hair follicles, as well as in the corneal epithelial layer. High levels of T4a mRNA staining persisted in the developing postnatal corneal epithelia. In contrast, weak mRNA staining was only detected in the basal layer of the adult epidermis and corneal epithelium.

CONCLUSION

These results indicate that T4a expression correlates with re-epithelialization of the cornea and maturation of the cornea and skin, suggesting a role for this gene in epithelial development, differentiation, and wound healing.