Researchers find new way to make eyes

tadpole embryo with ectopic eyes

The University of Warwick research team led by Professor Nick Dale and Professor Elizabeth Jones from the University of Warwick’s Biological Sciences Department have published their work today, 25th October 2007, in Nature in a paper, “Purine-mediated signaling triggers eye development.”

The researchers were exploring whether release of ATP (an important molecule signaling and energy carrying molecule) influenced the development of locomotion  in frogs. Their experiment introduced molecules called ectoenzymes (normally found on the outside surface of cells) into frog embryos at one of the earliest stages when the frogs-to-be were just 8 cells in size. Three ectoenzymes were used: E-NTPDase1, E-NTPDase2 and E-NTPDase3. These ectoenzymes degrade ATP following its release from cells, however each version of the ectoenzyme has slightly different effects on this degradation.

The Warwick research team’s interest in locomotion was quickly eclipsed when they were amazed to find that the introduction of just one of the ectoenzemes (E-NTPDase2) had a dramatic affect on eye development in the tadpoles grown from these embryos. When introduced in cells that would form the head area of the tadpole multiple eyes appeared to be created. That was not the only surprise. When it was introduced in some cells that formed body parts outside the head area it could still produce an additional “ectopic” eye leading to tadpoles with an additional eye in their side, abdomen or even along their tail….

The genes that initiate and direct eye development are well known and are collectively termed the Eye Field Transcription Factors” (EFTFs). One of the mysteries of the field is how these genes get turned on in the correct location and at the correct time to initiate eye development. The Warwick research shows that this short burst of ATP followed by accumulation of ADP is a key signal for initiating expression of the EFTFs and hence the development of the eye.

The discovery of this surprising new signal that literally switches on eye development it is not restricted to frogs. Mutations to the E-NTPDase2 gene on the human 9th chromosome is already known to cause severe head and eye defects. This suggests that this newly discovered mechanism for triggering eye development applies across a wide range of species.

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