Although the genetic defect that causes sickle cell disease has been known for more than 30 years, researchers have not been able to develop an effective therapy for the disease, which strikes one in 400 blacks born in the United States. When the oxygen content of blood from individuals with the disease falls below normal levels, as from exercise, red blood cells become deformed and impair circulation, causing damage to organs.
One problem in developing potential therapies is that researchers had never been able to produce the disease in animals to provide a testing ground. Molecular biologists from the Universities of Alabama, Pennsylvania and Washington reported last week in Science, however, that they used genetic engineering to produce mice with sickle cell disease.
The researchers inserted the defective human gene for hemoglobin (the oxygen-carrying component of red blood cells) into mice, where the gene produced human hemoglobin. These animals were then cross-bred with mice who normally produce inadequate quantities of mouse hemoglobin.
More than 90% of the red blood cells in the resultant mice contained the defective hemoglobin, and these cells sickle when their oxygen content is reduced. The researchers are studying the long-term effects of such sickling in the animals.