HETEROGENEOUS EXPRESSION OF TRANSKETOLASE IN OCULAR-TISSUES

Purpose. Previous studies have shown that transketolase is preferentia lly expressed in the corneal epithelium and comprises up to 10% of the soluble protein of the mature mouse cornea. The aim of this study is to evaluate the expression and distribution of TKT in the different oc ular tissues. Methods. We have used in situ hybridization and immunohi stochemistry to localize TKT mRNA and protein in the developing and ad ult mouse eye. Results. TKT were found to be widely distributed throug hout the adult mouse eye. Among the ocular tissues examined, the corne al epithelium exhibited the highest levels of TKT mRNA and protein. Wi thin the epithelial layer, TKT mRNA and protein were differentially di stributed with the highest expression occurring in basal cells and the lowest in apical cells, suggesting that TKT expression in the corneal epithelium may be differentiation-related. Enriched expression of TKT was also found in the cornea endothelium, lens epithelium, ciliary bo dy, and iris. Low basal levels of expression were observed in the limb us and conjunctiva. In contrast to the adult eye, TKT expression in th e one-day-old mouse eye was homogeneous at low, but detectable levels, suggesting that TKT expression is developmentally regulated in the co rnea as well as in the other ocular tissues. In the healing corneal ep ithelium, TKT expression in the single cell layer of the leading edge was completely suppressed until the cells began to stratify, at which point TKT expression increased markedly. Conclusions. The results pres ented here suggest that TKT is differentially expressed and developmen tally regulated in the various tissues that comprise the eye.