Expression of the duck alpha-enolase/tau-crystallin gene in transgenic mice

In many vertebrates, metabolic enzymes have been directly recruited to an additional structural role as crystallins in the eye lens. In some species the glycolytic enzyme alpha-enolase (alpha ENO) attains high concentrations in the lens, as tau-crystallin (tau CRY). A line of transgenic mice was constructed containing the entire duck alpha ENO/tau CRY gene with 5'- and 3'-flanking regions and all introns. Full-sized duck alpha ENO mRNA was expressed in the transgenic mice with the same pattern as the endogenous mouse alpha ENO isozyme. Although there was no evidence for tissue preference, the concentration of enolase increased markedly in transgenic lens as well as in other tissues. In spite of this, transgenic lenses were transparent and the animals were normal in appearance. The increase in enolase levels in the transgenic lens mimics the stepped increase that might occur in the early stages of enzyme crystallin recruitment. These results demonstrate that lens transparency is sufficiently robust to be refractory to some increase in metabolic enzyme concentration without the need for compensatory adaptation.