London: Scientists claim to have found a
a genetic change which makes men less fertile than usual, a
discovery they say could lead to new tests to identify those
who will take longer to father a child.
The change was found in a gene, called DEFB126, which
codes for a protein that clings to sperm, helping them swim
through the woman`s body to fertilise the egg.
Sperm lacking in the substance find it harder to swim
to the egg, the researchers reported in the journal Science
However, the researchers believe that a man with the
altered gene can still get his partner pregnant, but this will
take longer than usual.
"If you`ve got this gene variant you should allow that
little bit longer if your partner`s planning to get pregnant,"
study co-author Edward Hollox of the University of Leicester
was quoted as saying by a news channel.
"It takes two -- it`s the genetic variation in a man
that affects fertility in this particular case."
Dr Hollox said the discovery raised the possibility of
a new test to identify couples who might need treatment. "It`s
another tool in the toolkit of fertility treatment."
Researchers believe men with the defective gene have
sperm that find it harder to make their way through mucus,
causing low fertility.
A study of more than 500 married couples in China
found that women who had partners with two copies of the
defective gene (one from the mother and one from the father)
were less likely to get pregnant. The women also took longer
to get pregnant by a couple of months.
Further studies, carried out in people from the US,
UK, China, Japan and Africa, found the gene mutation is common
around the world.
According to the researchers, about half of all men
carry one copy of the defective gene; while a quarter have two
Commenting on the study, Dr Allan Pacey of the
University of Sheffield, said: "We actually understand very
little about the subtle molecular events which occur in sperm
as they make their journey through the woman`s body to
fertilise an egg.
"We know even less about how a man`s genes may
contribute to how his sperm work, in the absence of an obvious
defect that we can see down the microscope.
"Therefore, this paper is an important step forward
and makes a significant contribution to our sperm-knowledge."