Scientists at Johns Hopkins have identified the genetic culprits that trigger a hereditary form of a fatal lung disease. The findings, published in the March 29, 2007 issue of the New England Journal of Medicine, may provide new directions in diagnosis and treatment for families that inherit genes for the disease, as well as for those that develop non-inherited forms of the illness.
A progressive scarring of the lungs with no effective treatment, idiopathic pulmonary fibrosis (IPF) affects approximately 50,000 Americans annually, and like some cancers often is fatal within three years. As many as 20 percent of IPF sufferers are thought to have inherited genetic mistakes that predispose them to the disease; and until now, these gene flaws remained unknown.
To locate the genetic problem, Hopkins investigators screened DNA from blood samples of 73 people with inherited IPF and discovered that six of them (eight percent) had mutations in two genes that produce an enzyme which helps lengthen the fragile ends of chromosomes. Chromosome ends, or telomeres, contain repetitive bits of DNA code that wear down each time a cell divides. The mutations were spotted in two genes that regulate the enzyme telomerase, which keeps telomere length extended just beyond the borders of needed genes. With mutations in telomerase, however, chromosome ends fray and wear down far more quickly, which can trigger cell death.
The scientists first hint that telomerase plays a role in IPF came from studying the genetic traits of a family with a rare, premature-aging disorder caused by short telomeres. Many of the family members were suffering from the disorders second-leading cause of death -- pulmonary fibrosis. "We thought that perhaps there might be a link between telomerase mutations and IPF," says Mary Armanios, M.D., assistant professor of oncology at the Johns Hopkins Kimmel Cancer Center.