Johns Hopkins-Led Team Discovers Gene Defect Linked To Lung Disease

Their findings, reported in this week's New England Journal of Medicine, identify a mutation in the surfactant protein C (SP-C) gene linked to interstitial lung disease (ILD), a term defining a group of chronic lung disorders.

Research teams led by Johns Hopkins neonatologist Lawrence M. Nogee, M.D., and Jeffrey A. Whitsett, M.D., of Cincinnati Children's, identified the SP-C mutation in two related individuals who did not have respiratory symptoms at birth but who subsequently developed ILD.

SP-C is one of the components of surfactant, a mixture of fats and proteins which enables the lungs to expand and contract easily with each breath, and which plays an important role in respiratory adaptation in newborns by maintaining the low surface tension needed to prevent lung collapse on exhalation. Deficiency of surfactant causes respiratory distress syndrome (RDS), a common cause of lung disease in premature infants. The newly identified mutation is a single DNA base pair error that results in a defective protein. Researchers speculate the defective protein has a toxic effect on lung metabolism, leaving infants prone to severe lung failure and collapse. The finding also suggests that while SP-C may not be critical for respiratory adaptation at birth, it is important for normal lung function.

"Very little is known about the underlying causes of interstitial lung disease," says Nogee, the report's lead author. "Our findings provide a clue as to what may trigger and perpetuate these disorders. We need to gain a better understanding of how and why some people with mutations in this gene develop this kind of lung disease. It is clear that SP-C has a critical role in the lung, and thus abnormalities in this gene and its protein may be involved in other lung diseases."

ILD accounts for approximately 15 percent of visits to lung specialists, according to the National Jewish Medical and Research Center. ILD includes a group of chronic pneumonias which may lead to scarring of the lungs, and eventually to respiratory failure.

The findings are the latest fruits of a long-standing research collaboration among the team, which has been funded by grants from the National Heart, Lung and Blood Institute, and by the Johns Hopkins Eudowood Foundation. The team has investigated the causes of lung disease in hundreds of patients around the world to gain a better understanding of the nature of lung disease.

Frederic Askin, M.D., of Johns Hopkins; Alston Dunbar, III, M.D., formerly of Johns Hopkins; Susan E. Wert, Ph.D., of Cincinnati Children's; and Aaron Hamvas, M.D., of Washington University in St. Louis, contributed to the study.