Why does the human body deteriorate as a person ages? Two research teams have found a new clue to this longstanding mystery. Both groups have identified a mutation that causes children to suffer a form of accelerated aging that usually results in death in their teens from heart attack, stroke, or other problems more typically associated with elderly people.
While investigators continue to debate exactly how well this so-called Hutchinson-Gilford progeria syndrome mirrors normal aging, many are convinced that the newly discovered mutation could provide insight into the process.
This finding "will help scientists across the globe to explore the fundamental mechanisms that drive human aging. We hope this will also lead to treatment and an eventual cure for progeria," says Leslie Gordon of Tufts University School of Medicine in Boston.
Hutchinson-Gilford progeria syndrome, also known simply as progeria--Greek for early aging--affects only an estimated 1 in 4 million children. "It's been a very difficult disease to get a handle on. There's no more than 100 case reports in the literature," says W. Ted Brown of New York State Institute for Basic Research in Developmental Disabilities in Staten Island.
Children with progeria are usually diagnosed 6 months to a year after birth, when their physical development starts to lag. They rarely grow taller than 4 feet, and their heads are oversized for their bodies. The children become bald and have skin problems such as scleroderma. While their mental development is normal, children with progeria rapidly develop atherosclerosis and die, on average, at the age of 13.
In a report to appear in an upcoming Science, Nicolas Levy of Hopital de la Timone in Marseille, France, and his colleagues identify a subtle but identical mutation in two kids with progeria. The defect is in a gene that encodes two proteins called lamin A and lamin C. Strengthening the case against this gene, Nature last week released a similar report from a group of researchers including Gordon and Brown. This second team, led by Francis S. Collins of the National Human Genome Research Institute in Bethesda, Md., found the same change in the gene's DNA sequence in 18 of 20 children with progeria that the team studied.
The lamin proteins are the main structural elements forming the envelope of a cell's nucleus, where DNA resides. Although it doesn't alter lamin C, the progeria mutation shortens lamin A. As a result, the majority of cells from children with the progeria mutation have abnormally shaped nuclei, both research teams found.
It's still unclear how a mutant lamin A and the misshaped cell nuclei lead to the symptoms of progeria, but Huber Warner of the National Institute on Aging in Bethesda speculates that such a defect could prevent so-called stem cells from replacing worn-out or damaged cells and tissues.
"This discovery opens one or two doors for aging research," he says. "Nuclear structure and function now become targets of research."
In terms of progeria, Gordon and Collins predict that within a year, there will be a genetic test that can confirm a diagnosis. Correcting the genetic defect through gene therapy, drugs, or other means is much further off but is now a possibility, say these researchers.
"This is a great springboard," says Gordon. Collins adds that researchers will quickly introduce the progeria mutation into mice to create a model for testing treatments for the syndrome.
In previous studies, researchers have attributed a form of muscular dystrophy and five other human disorders to defects in the same lamin gene. Now with the addition of progeria, Collins calls that tally a record for one gene.
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