Deletion in β-Globin ID'd in Fetal Hemoglobin Silencing

Intergenic region for fetal hemoglobin silencing identified near the δ-globin gene

WEDNESDAY, Aug. 31 (HealthDay News) -- A small intergenic region required for γ-globin (fetal hemoglobin) gene silencing has been identified near the 5' end of the δ-globin gene, according to a study published in the Sept. 1 issue of the New England Journal of Medicine.

Vijay G. Sankaran, M.D., Ph.D., from the Children's Hospital Boston, and colleagues investigated the genomic regions responsible for the phenotypic differences between thalassemia mutations. Three families with unusual patterns of hemoglobin expression suggesting deletion in the locus of the β-globin gene were identified and these deletions were mapped using array comparative genomic hybridization. The breakpoints were confirmed using polymerase-chain-reaction assays and DNA sequencing. These deletions and previously mapped deletions were compared and chromatin immunoprecipitation was used to study trans-acting factors binding to these sites in the β-globin locus.

The investigators found a new (δ-β)0-thalassemia deletion and a rare hereditary persistence of fetal hemoglobin deletion with identical downstream breakpoints which led to the identification of a small intergenic region required for γ-globin gene silencing on comparison. A Kurdish β0 thalassemia deletion was mapped and found to retain the intergenic region, delete other surrounding sequences, and maintain fetal hemoglobin silencing. A 3.5-kb intergenic region near the 5' ends of δ-globin gene that is necessary for γ-globin sequencing was explained by comparing these deletions and other previously mapped deletions. Within the region in the chromatin of adult erythroid cells, is where a critical fetal hemoglobin silencing factor, BCL11A, and its partners bind.

"By studying three families with unusual deletions in the β-globin locus, we identified an intergenic region near the δ-globin gene that is necessary for fetal hemoglobin silencing," the authors write.

One author disclosed a financial relationship with Signature Genomics LLC.

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