Credit: Ren West

Stem cells from frog eggs can be genetically prodded to develop into functional eyes in tadpoles, according to research presented at the Society of Neurosciences conference in Washington, DC. Michael Zuber and his colleagues from SUNY Upstate Medical University, in Syracuse, NY, genetically engineered the stem cells to express a set of transcription factors (proteins that trigger expression of other genes) that are known to regulate eye development.

When transplanted onto frog embryos that had had one eye removed, the cells developed into all seven types of cells found in the retina and also grew connections to the appropriate target in the brain. Swim tests showed that the new eyes functioned properly: tadpoles stayed in the part of their tank with a white background, which is normal tadpole behavior, rather than a black background.

It's not clear if the same genetic programming would work in mammalian cells: frogs have much greater regenerative potential than mammals to begin with, and it's difficult to simultaneously express all the required transcription factors in mammalian cells for technical reasons. But Zuber hopes to use the frog system to find chemicals that activate the transcription factors without genetic engineering. If successful, the research might one day lead to new treatments for diseases linked to cell loss in the retina.

In related findings, Sujeong Jang of Chonnam National University, in South Korea, and colleagues were able to restore hearing in deafened guinea pigs by transplanting neural stem cells derived from human bone marrow.

Restoring sight: Scientists removed one eye from tadpoles (left image) and then implanted genetically engineered stem cells in its place. They grew to form a functioning eye (right). Credit: Michael Zuber