The molecule that triggers the fertilisation of a mammalian egg and prompts it to begin growing and dividing has been discovered. The identification of this 鈥渟park of life鈥� is significant for work on infertility treatments, male contraceptives and cloning, researchers say.
It was known that immediately after an egg and sperm fuse, a wave of calcium ions sweeps through the cell, triggering fertilisation. But scientists have spent the last decade trying to discover what triggered this calcium release.
Tony Lai, of the University of Wales College of Medicine, tackled the problem by taking a candidate enzyme, PLC-zeta, and injecting it into unfertilised eggs. He immediately saw the wave of calcium sweep through the cell. The egg cell then began to divide and grow as if it had been fertilised.
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鈥淚t鈥檚 only when you get to the blastocyst stage that the embryo stops growing,鈥� says Lai 鈥淚t鈥檚 at this stage that you require the male genes to kick in. You need the full genetic complement after this.鈥�
Jerry Schatten, at the University of Pittsburgh School of Medicine, calls the work a 鈥渞emarkable discovery鈥�. He says: 鈥淭he search for the sperm signal that awakens the egg began two centuries ago and is vital for understanding how a fertilised egg starts life anew.鈥�
Efficient and reliable
Although the discovery has obvious implications for fertility treatments, Lai expects it to have most impact on therapeutic cloning and the production of stem cells.
鈥淭he potential for this is immense,鈥� says Lai. 鈥淲e hope that it will be possible to produce a cloned embryo by taking a nucleus from an adult cell and injecting it into an empty egg cell along with PLC-zeta. This could produce a line of cloned stem cells that would be useful for treating degenerative diseases such as Parkinson鈥檚.鈥�
This approach could be far more efficient than conventional cloning, which uses electric shocks to encourage the egg cell to divide. 鈥淭hat technique is like banging it with a hammer and hoping it works,鈥� says Lai. 鈥淲e hope our molecule will make the process far more efficient and reliable.鈥�
Despite his hopes, Lai鈥檚 research has now ground to a halt through lack of money. 鈥淲e now desperately need more research money to continue our work. We still have to work out how PLC-zeta does its job,鈥� says Lai.
Journal reference: Development (vol 129, p 3533)