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MONDAY, Oct. 28 (HealthScoutNews) -- Researchers have discovered
a gene mutation that's partially to blame for the genetic underpinnings
of lupus, a disease in which the immune system attacks the body's
own tissues.
Swedish scientists have identified a mutation of a
gene, named PDCD1, that's more prevalent in people with lupus than
in those without lupus. The mutated gene isn't doing its job, thus
contributing to the malfunctioning immune system, the study found.
Previous research has shown that genetically engineered
mice that lacked the PDCD1 developed a lupus-like disease.
"It's not going to be the sole cause of lupus, but
it's certainly a strong movement in better understanding the disease,"
says Dr. Duane Superneau, chief of the section of medical genetics
at the Ochsner Clinical Foundation in New Orleans.
The study appears in the October issue of Nature Genetics.
In lupus, the immune system attacks the body's own tissues, most
often the skin, joints, blood and kidneys. This can cause painful
and debilitating inflammation.
Researchers sequenced, or diagrammed, the PDCD1 gene in 1,000 people
with lupus and 1,500 family members and non-family members who didn't
have lupus.
They found that a variant of the PDCD1 gene was more prevalent
in people with lupus than people without the disease. Based on statistical
analysis, researchers estimate the gene variant could account for
as much as 20 percent of the underlying cause of lupus.
What exactly does PDCD1 do?
Found on chromosome 2, the gene plays a role in helping the immune
system distinguish itself from foreign invaders, says study author
Marta Alarcón-Riquelme, an assistant professor of medical genetics
at the University of Uppsala in Uppsala, Sweden.
The study found the mutated gene prevents a key protein from binding
with it. The protein is in charge of regulating the gene's production
of antibodies to fight invaders.
"One of the possibilities is that PDCD1 might work to inhibit antibody
activation," Alarcón-Riquelme says. "This should happen normally.
But when PDCD1 is not functioning, the cells are going crazy and
activating and producing too many antibodies."
"What remains unknown is how this process starts and what makes
it happen," she adds.
While the PDCD1 mutation is an important finding, there are surely
other genes and environmental factors at play, Superneau says.
Firstly, the PDCD1 gene variant was not present in everyone who
had lupus in the study, Superneau says.
Secondly, because lupus varies so much from person to person, doctors
believe a single gene cannot be blamed for the disease in everyone,
he adds.
While some people with the disease suffer only occasional flare-ups,
lupus can be a constant and life-threatening affliction for others,
he says. For some, only one organ is involved, for others, it's
many organs throughout the body.
And while about 10 percent have a family member that has the disease,
others don't have any family history of lupus, according to the
Lupus Foundation of America.
"It's a very complicated disease," Superneau says. "There are many
factors and/or many genes acting in concert to cause the disease."
Because it's such a complicated disease, diagnosing lupus is difficult,
says Duane Peters, vice president for advocacy and communications
at the Lupus Foundation of America.
There is no specific test for lupus. Doctors have identified 11
symptoms ranging from skin rashes to joint pain. A person who has
four of the 11 is considered to have lupus, Peters says.
The hope is that the gene discovery would help lead to both earlier
detection of the disease, or who's at risk of getting it, and treatments
that would target the malfunction of the gene, Superneau says.
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