In the Duke experiments, Sullenger said the sickle cell mutation was corrected by changing the instructions contained in the RNA molecule. Other attempts at gene therapy have targeted the genes that write the instructions instead of the RNA that carries the instructions to the cell. Sickle cell anemia is a genetic disorder that causes the production of an abnormal type of hemoglobin, the molecule in red blood cells that carries oxygen to all the cells in the body. Cells with sickle-shaped hemoglobin are fragile and easily destroyed and do not circulate with the ease of normal, rounded hemoglobin cells. This can cause stroke, kidney disease, swollen and painful joints and difficulty in breathing.
Death often is caused when blood flow is cut off to vital organs.
Sickle cell disease was once lethal at an early age, but now patients, treated with blood transfusions and other therapies, often live past age 40. Eight percent to 13 percent of Americans whose ancestors came from Africa or the Middle East carry at least one sickle cell gene. However, both genes that make hemoglobin must be mutated for the disease to occur. About one-third of 1 percent of all blacks in America have the disease. In the Duke study, scientists created a ribozyme, a type of enzyme that can clip and correct the message carried in RNA, to fix sickled hemoglobin in a test tube and in laboratory dishes.