Eye of newt, and toe of frog: Organogenesis Imagine if complex structures like the eye could be regenerated to correct injury or birth defects.
Developmental biologists studying eye generation previously found a “cocktail of proteins” known as Eye Field Transcription Factors (EFTFs) that determine eye fate in the embryo by turning on precise patterns of gene expression. But is there an even more minimal set of instructions to induce an eye? Can an eye be formed anywhere on the body?
A new study finds that simple bioelectric signals, in the form of voltage gradients across the cell membrane, trigger eye development in the frog, Xenopus laevis . Early on, cells in the eye primordia become hyperpolarized, i.e., the charge difference, Vm, across the membrane is higher than that of neighboring cells. Locally depolarizing these cells blocked only eye development and disrupted the pattern of EFTFs without harming other organ development.
Next, researchers injected into the frog embryo various ion channels with predictable effects on the membrane voltage. Remember that ion channels move charged particles such as Na+ and K+ across the membrane to generate potential differences in the order of ~100 millivolts. Amazingly, they were able to induce eyes ectopically, all over the surface of the embryo. These artificially generated eyes had similar retinal cell arrangement as normal eyes.
Understanding eye development is the first step towards regenerative medicine. That would be good magic, better than the three witches of Macbeth could conjure:
“Eye of newt, and toe of frog,
Wool of bat, and tongue of dog,
Adder’s fork, and blind-worm’s sting,
Lizard’s leg, and owlet’s wing,—
For a charm of powerful trouble,
Like a hell-broth boil and bubble.”
This study, from Michael Levin’s group at Tufts University was just published online (Development 139, 313-323 (2012) doi:10.1242/dev.073759). Thanks to the awesome Rachel Maddow for showcasing this story: http://maddowblog.msnbc.msn.com/_news/2011/12/12/9368699-eye-of-frog-tail-of-worm
The Levin Lab website is pretty cool: http://www.drmichaellevin.org/research.html