Protein can kick-start male fertility.

The team from Cardiff University's School of Medicine first found that sperm transfers a vital protein, known as PLC-zeta (PLCz), to the egg upon fertilisation. Then it initiates a process called 'egg activation,' which switches on all the biological processes necessary for development of an embryo.

The team has found that eggs that don't fertilise because of a defective PLCz, as in some forms of male infertility, can be treated with the active protein to produce egg activation. The added PLCz kick-starts the fertilisation process and significantly improves the chance of a successful pregnancy.

"We know that some men are infertile because their sperm fail to activate eggs. Even though their sperm fuses with the egg, nothing happens," said Tony Lai, professor at Cardiff, who with professor Karl Swann, led the team at Cardiff University's Institute of Molecular and Experimental Medicine and funded by the Wellcome Trust, according to a Cardiff statement.

"These sperm may lack a proper functioning version of PLCz, which is essential to trigger the next stage in becoming pregnant," Lai added. "What's important from our research is that we have used human sperm PLCz to obtain the positive results that we had previously observed only in experiments with mice," Lai said.

"In the lab we have been able to prepare human PLCz protein that is active. If this protein is inactive or missing from sperm, it fails to trigger the process necessary for egg activation the next crucial stage of   embryo development," Lai said.