VIC: Problem gene a cause of male infertility: scientists

AAP General News (Australia)
08-20-1999
VIC: Problem gene a cause of male infertility: scientists

MELBOURNE, Aug 20 AAP - Scientists in Melbourne believe they have found a genetic cause of
infertility in men.

The team at Monash Institute have found that an abnormality in the gene responsible for
detecting the presence of testosterone can dramatically reduce a man's sperm count.

"This is a major advance in understanding the causes of male infertility," Professor Alan
Trounson and Professor David de Kretser, leaders of the Monash Institute team, said today.

Their findings are due to be published in the distinguished international medical journal
The Lancet tomorrow.

The professors said testosterone, the male sex hormone essential for normal sperm
production, could generate sperm only when it was detected by a sensor called the testosterone
or androgen receptor.

This was where the problem lay.

"It is the gene responsible for making this receptor which appears to cause the problem,"
said Prof de Kretser, Director of the Monash Institute of Reproduction and Development.

This "master gene" not only detected testosterone but also set off events in other genes
crucial to sperm production, muscle growth and certain neural controls, he said.

The study found that in men with no other reason for a low sperm count there were an
abnormally high number of repeating units in their receptor gene.

"These repeating sequences in the gene cause the receptor to malfunction," Professor
Trounson said.

This meant it could no longer correctly sense the level of testosterone stimulation, so
only limited quantities of sperm were produced.

"Indications are that the longer the repeating sequence, the more severe the disorder and
the lower the sperm count," he said.

The Monash study has been conducted in conjunction with the National University of
Singapore and Dr Robert McLachlan from Prince Henry's Institute of Medical Research in
Melbourne.

Prof Trounson said the discovery may offer hope to infertile men in future.

"It opens the possibility for us to explore new methods of treatment for the men with low
sperm counts caused by this change."

He said the discovery would mean steps could be taken to avoid passing the defect on to the
offspring and there was also a "possibility in the future that we can correct the problem".

AAP er/arb/br

KEYWORD: INFERTILE

1999 AAP Information Services Pty Limited (AAP) or its Licensors.