Tuesday August 31 6:09 PM ET
Gene mutation causes mental retardation
By Theresa Tamkins
NEW YORK, Aug 31 (Reuters Health) -- A gene normally involved in immune system
function can cause mental retardation when it is mutated, a new study suggests.
The genetic mutation has so far been found to be the cause of mental
retardation in at least six patients, and may be the cause of problems in
people who have large deletions in the X chromosome, according to a report in
September issue of Nature Genetics.
The mutation, known as IL1RAPL, most commonly causes problems in men, who have
only one X chromosome. Because women have two copies of the X chromosome, they
have a ``good'' copy of the gene to take over if IL1RAPL is mutated, the
Normally, IL1RAPL makes a protein similar to one that plays a key role in the
body's response to interleukin 1-beta, an immune system molecule that can cause
fevers and is important in inflammation. The protein is found in high levels in
certain areas of the brain, suggesting it may have a special role in the
development of learning and memory.
The study is the ``first reliable and unambiguous demonstration about the link
between proteins of the immune system and cognitive functions,'' said senior
investigator Dr. Jamel Chelly of INSERM Unite in Paris, France.
Only a handful of genes have been directly linked to mental retardation, which
can be caused by a complex number of factors or genetic problems, according to
Chelly and colleagues.
The finding may help in the diagnosis of mental retardation or in the genetic
counseling of families who have mutations or deletions of the gene, according
``Also, I believe that our finding will open (a) new avenue for the development
of therapeutic approaches,'' Chelly said. ''This aspect will require further
investigations, but it is reasonable to think that it would be possible in the
future to develop drugs that might have beneficial effect on some forms of
SOURCE: Nature Genetics 1999;23:25-30.