The strange case of chimeraplasty
For first time, scientists repair gene defectBy Tim Friend, USA TODAY
Scientists report they have for the first time permanently repaired a genetic disease in animals with a single drug infusion. They will test the treatment in humans next year.
The achievement, detailed in Tuesday's Proceedings of the National Academy of Sciences, holds implications for disorders from inherited single-gene defects, such as hemophilia, sickle cell anemia and thalassemia (chronic anemia), experts say.
"To my knowledge, this is the first permanent correction of a mutation and heretofore only fantasized about," says Clifford Steer of the University of Minnesota Medical Center in Minneapolis.
Steer and co-researcher Jayanta Roy-Chowdhury, at Albert Einstein College of Medicine in New York, conducted their study on rats that have a version of a rare human disease, Crigler-Najjar syndrome. The disease is caused by one missing piece of genetic code in the instructions of a gene in liver cells that aids the breakdown of bilirubin, a red blood cell byproduct.
The disease affects Amish children and causes fatal brain damage. Children must be treated by exposure to blue lights up to 14 hours a day to break down the bilirubin.
The genetic defect in rats was fixed with small pieces of synthetic genetic codes. These man-made codes get into a liver cell's nucleus and attach to segments of the gene where the defect occurs. The attachment triggers a natural DNA repair system in the cells that corrects the error. The correction is passed on to new liver cells and becomes permanent.
The synthetic codes are packaged in fat molecules that target liver cells. When injected into rats' tails, 95% of the molecules hit the liver.
The first human study of the genetic fix is being developed for Amish children with Crigler-Najjar syndrome, says Gerald Messerschmidt of Kimeragen Inc. in Newton, Pa. The company owns patents and licenses to the technology. It will apply to the Food and Drug Administration in January to do studies in children. The technology also may be useful for studying gene function.
Eric Kamiec of Thomas Jefferson University in Philadelphia developed the idea for the gene repair technology.
Gene repair differs from gene therapy, in which disabled viruses usually are used to deliver genes into cells to replace defective ones.