Monday, November 23, 2009

Scientists are trying to grow human eyeballs

Scientists are trying to grow human eyeballs


A genetic switch that gives tadpoles three eyes could allow stem-cell scientists to eventually grow human eyeballs or at least create replacement parts needed for repair jobs. If scientists could grow eyeballs from stem cells in the lab, the process would be a boon to individuals with damage to cells within the eye, including retinal disorders.

Scientists had already established the amphibian genes that initiate and direct eye development, which they refer to as Eye Field Transcription Factors (EFTFs). How these genes get activated in the right location at a certain time during development had been cloaked in mystery. But in 2007, a new study suggested a nitrogen-bearing molecule sets off a series of steps that result in eye formation in frogs. When researchers injected a specific enzyme into frog embryos, the resulting tadpoles showed an extra eye. The mechanism probably also applies to humans and other animals with eyes. Dale and University of Warwick developmental biologist Elizabeth Jones, along with colleagues, discovered the eye-switch while investigating how "ectoenzyme" molecules located on the external surface of cells contributed to the development of locomotion in the African clawed frog (Xenopus laevis). The biologists injected the molecules into frog embryos that comprised just eight cells.

One of the ectoenzymes triggered wonky eye development. When added to cells that would eventually form the head, the resulting tadpole sported three eyes instead of two. An even stranger sight resulted when they injected the ectoenzyme into other developing body cells. The molecule caused an additional "ectopic" eye, leading to tadpoles with a spare peeper growing out of the side, abdomen or even along the tail.


 

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