PARIS, Oct 24: Researchers say they have identified a key enzyme that triggers eye development, in a discovery that could one day lead to “eye in a dish” replacement tissue for the visually impaired.

Writing in Nature, a team from the University of Warwick, central England, say the switch, called E-NTPDase2, is a so-called ectoenzyme, which is normally found on the outside surface of cells.

E-NTPDase2 initiates a molecular cascade that cause the eye to grow, they believe.

The researchers, experimenting on eight-cell frog embryos, introduced the enzyme into cells that would form the head area of the tadpole, and found that multiple eyes appeared to be created.

When the enzyme was introduced to some cells that would form parts of the body, eye-like structures began to grow there, too, leading to tadpoles with an additional eye in their side, abdomen or even along their tail.

The researchers believe that E-NTPDase2 latches onto an important signal- and energy carrying molecule called ATP and converts it into another molecule, ADP.

Previous research has already identified the genes that initiate and direct eye development, but what has hitherto been unknown are the triggers -- and the sequence of triggers -- to turn them on.

The Warwick team believe that a short burst of ATP, followed by a build-up of ADP, are the main signals for setting this genetic mechanism in motion. E-NTPDase2 is known to play a rule in human eye development. Mutations in the gene, which lies on the 9th human chromosome, have been associated with severe head and eye defects.

“This new understanding of how eye development is triggered will greatly assist researchers exploring stem cells connected to eye development and opens up an avenue of research that could in just a few decades lead to the ability to produce an ‘eye in a dish’,” the University of Warwich said in a press release. Stem cells are immature cells that grow into the various organs of the body.

Scientists hope to be able to coax these cells into becoming replacement tissue that can be grown in a lab, but many hurdles remain to be overcome before this dream becomes reality.—AFP