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Fetal hemoglobin silencing in humans.
Patricia A Oneal1, Nicole M Gantt, Joseph D Schwartz
1Molecular Medicine Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, 10 Center Drive, Bldg 10, Rm 9B17, Bethesda, MD 20892, USA.
Blood
|June 1, 2006
Summary
Understanding fetal hemoglobin (HbF) silencing is key to treating sickle cell disease and beta-thalassemia. Most newborns express both adult hemoglobin (HbA) and HbF, but HbF expression rapidly declines post-birth.
Area of Science:
- Hematology
- Molecular Biology
- Developmental Biology
Background:
- Sickle cell and beta-thalassemia syndromes are linked to disruptions in the fetal-to-adult hemoglobin transition.
- Understanding the silencing of gamma-globin genes during human development is crucial for therapeutic interventions.
Purpose of the Study:
- To investigate age-related changes in globin phenotypes in human erythroid cells.
- To elucidate the mechanism of gamma-globin gene and protein silencing during the transition from fetal to adult life.
Main Methods:
- Analysis of globin phenotypes in erythroid cells from umbilical cords, infants, and adults.
- Quantification of hemoglobin types (HbA, HbF) and globin gene expression (gamma-globin mRNA).
Main Results:
- Unexpectedly, 95% of cord blood erythrocytes and reticulocytes expressed both HbA and HbF.
- A rapid decline in HbF and gamma-globin mRNA was observed postnatally, with <5% of adult reticulocytes expressing gamma-globin mRNA.
- The silencing of gamma-globin expression is mediated by cellular replacement.
Conclusions:
- Human hemoglobin switching involves initial coexpression of gamma- and beta-globin genes, followed by rapid silencing of gamma-globin expression.
- This silencing pattern, driven by cellular replacement, is a novel finding and may inform the development of HbF-enhancing therapies.