Induction of lens regeneration from the ventral iris of the newt, Notophthalmus viridescens, through BMP inhibition-driven regulation of Six3.

摘要

The ability to regenerate body parts is one of the most amazing feats of nature that scientists have the opportunity to study. The urodeles perhaps possess the greatest regenerative abilities in the animal kingdom, with some of them able to regenerate limbs, tails, lenses, retinas, brains, hearts, and more. It has been clearly established that in vivo lens regeneration in urodele amphibians comes from the dorsal iris only. Some studies have shown that lens regeneration from the dorsal iris can be blocked or interrupted successfully. Several studies have shown an induction of lens regeneration from the dorsal iris with and without lens removal. While many scientists have successfully inhibited lens regeneration from the dorsal iris, the "Holy Grail" of lens regeneration studies is the one that is able to induce lens regeneration from the regeneration incompetent ventral iris. To date only one known treatment, that of the potent carcinogen MNNG (methyl-nitro-nitrosoguanidine), has elucidated such an induction. Nevertheless, these experiments clearly show that induction is possible and remains one of the greatest challenges in the field.;We initially set out to perform two tasks, the first being to induce lens regeneration from the ventral iris in the newt. The second goal was to examine expression levels of some important developmental eye genes in the newt intact iris and regenerating iris in the attempt to underscore the mechanism of regeneration. In our attempts at inducing lens regeneration from the ventral iris, we focused on factors that play a role in lens development. The study shows that we indeed were able to induce lens regeneration from the ventral iris in the newt. This was accomplished in two separate ways. The first was by inhibiting the bone morphogenetic protein (BMP) pathway in newt ventral iris tissue either using the BMP signaling antagonist Chordin or a truncated form of bone morphogenetic protein receptor-IA (BMPR-IA). The second was accomplished by transfecting newt ventral iris pigmented epithelial cells (PECs) with Six3, a homeobox-containing transcription factor, and adding retinoic acid (RA). These results demonstrate the ventral iris of the newt has been successfully induced to regenerate a lens with known molecules. We were also able to show in our study that expression levels of some important developmental eye genes are drastically different than originally thought. (Abstract shortened by UMI.).