Dads Deliver More Than Just DNA
Wed May 12, 2004
By Patricia Reaney

LONDON (Reuters) - Men can breathe a sigh of relief

Despite the specter of cloning and the birth of a fatherless mouse, scientists have uncovered evidence that men play a more vital role in procreation than they may have thought.

Male sperm not only fertilizes the female egg, it also delivers male chromosomes and messenger RNA, molecules that carry codes which may help the embryo develop and grow.

"Men have a greater role in early development than we previously thought," said Stephen Krawetz, of Wayne State University in Detroit, Michigan.

Krawetz and colleagues in the United States and Britain have identified six messenger RNAs found in sperm and fertilized eggs but not in unfertilized eggs.

The finding, reported in the science journal Nature on Wednesday, suggests that messenger molecules are delivered when the sperm fertilize the egg. It may also improve understanding of infertility and cloning.

"We have been able to show that in humans, along with delivering the DNA component, there is an RNA component which is also delivered. This is the first time that has been shown," Krawetz said in an interview.

"Dad is delivering more than just his DNA."

Krawetz suspects the paternal RNA plays an important role in the early development of the embryo and believes the research could help to explain why cloning is so difficult.

"We think the RNA that is being delivered could possibly act as a developmental or mechanistic switch that sets off the correct developmental program early on," he said.

In cloning, the egg develops without sperm fertilization and although it can be manipulated or 'tricked' in the laboratory some of the time, if the RNA isn't being delivered by the sperm it could explain the very small success rate in cloning.

Last month scientists in Japan and Korea reported creating the first mammal without using sperm. The mouse is the daughter of two female mice. Although bees, ants and some fish and reptiles reproduce without having sex in a process known as parthenogenesis, it was thought to be impossible in mammals.

Mammals inherit one set of chromosomes from their mothers and another from their fathers. Embryos containing only female chromosomes usually die early in the womb and those with only male genetic material are abnormal.

The fatherless mouse sparked headlines and suggestions that males could soon be obsolete.

"In contrast, we show that men are not obsolete," said Krawetz.

"Men do have a function," he added.