Finding could usher in new treatments for sickle cell disease and thalassemia
THURSDAY, Dec. 4 (HealthDay News) -- Scientists have identified a gene mutation that inhibits the production of fetal hemoglobin and causes two life-threatening anemias -- sickle cell disease and thalassemia.
The finding could eventually lead to new treatments that could restore some hemoglobin production, turning these life-threatening diseases into manageable chronic conditions.
"We have identified a gene that directly silences the fetal hemoglobin gene," said lead researcher Dr. Stuart Orkin, an investigator at the Howard Hughes Medical Institute and Children's Hospital Boston. "The regulation of fetal hemoglobin is probably the most important modifier of the severity of sickle cell anemia and thalassemia."
Targeting that gene could be the key to treating both diseases, Orkin said.
"We now have a target that if we could modulate it directly, we could increase fetal hemoglobin and reverse the silencing and reawaken the fetal gene in an adult," Orkin said. "That would have tremendous therapeutic implications in both of those disorders."
While he does not see such treatment as a cure, "it would certainly be a very effective treatment," Orkin said.
The report was published in the Dec. 4 online edition of Science.
In an earlier study, Orkin's team identified five gene variants involved in hemoglobin production and the severity of disease in 1,600 people with sickle cell anemia. They identified one variant that had the most effect on hemoglobin in a gene called BCL11A, located in chromosome 2.
In the current study, the researchers show that BCL11A directly blocks the production of hemoglobin. To prove the connection, Orkin's group blocked BCL11A, and red blood cells started producing large amounts of hemoglobin.
Hemoglobin is a protein in red blood cells that transports oxygen throughout the body. In sickle cell disease, there is an abnormality in hemoglobin that makes red blood cells stiff and sickle-shaped. In thalassemia, the ability to produce hemoglobin is severely compromised.
Both diseases result in anemia that can range from mild to life-threatening. Sickle cell disease can cause severe pain and eventual organ damage. Treating thalassemia requires frequent blood transfusions and then chelation therapy, which gets rid of excess iron that can lead to organ failure.
At birth, fetal hemoglobin makes up between 50 percent to 95 percent of a child's hemoglobin before switching to adult hemoglobin production. The fetal hemoglobin may be an adaptation to the low oxygen in the fetal environment. Fetal hemoglobin has a higher affinity for oxygen, allowing it to take oxygen more easily from the mother.
Dr. Cage S. Johnson, director of the Comprehensive Sickle Cell Center at the University of Southern California Keck School of Medicine, agreed that this finding will lead to new therapies.
"This research adds to our understanding of the genetic mechanisms underlying gamma-globin production," Johnson said. "Increased understanding of the genetic control of globin will provide the basis for gene therapy of these disorders. This research is another step in the process of developing gene therapy."
For more on sickle cell anemia and thalassemia, go to the Children's Cancer & Blood Foundation.
SOURCES: Stuart Orkin, M.D., investigator, Howard Hughes Medical Institute, Children's Hospital Boston, Cage S. Johnson, M.D., professor, director, Comprehensive Sickle Cell Center, University of Southern California Keck School of Medicine, Los Angeles; Dec. 4, 2008, Science, online
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