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Exp Hematol. 2009 Oct;37(10):1131-42. doi: 10.1016/j.exphem.2009.06.007. Epub 2009 Jul 2.

Transcriptional activation of the gamma-globin gene in baboons treated with decitabine and in cultured erythroid progenitor cells involves different mechanisms.

Author information

1
Department of Medicine, University of Illinois at Chicago, Chicago, Illinois, USA.

Abstract

OBJECTIVE:

To investigate the mechanism(s) responsible for increased gamma-globin expression in vivo in decitabine-treated baboons and in vitro in cultured erythroid progenitor cells (EPC) from adult baboon bone marrow (BM).

MATERIALS AND METHODS:

Fetal liver, adult BM erythroid cells pre- and post-decitabine, and cultured EPCs were analyzed for distribution of RNA polymerase II, histone acetylation, and histone H3 (lys4) trimethyl throughout the gamma-globin gene complex by chromatin immunoprecipitation. DNA methylation of the gamma-globin promoter was determined by bisulfite sequencing. Expression of the baboon Igamma- and Vgamma-globin chains was determined by high performance liquid chromatography (HPLC). Expression of BCL11A, a recently identified repressor of gamma-globin expression, was analyzed by Western blot.

RESULTS:

Increased gamma-globin expression in decitabine-treated baboons and cultured EPC correlated with increased levels of RNA polymerase II, histone acetylation, and histone H3 (lys4) trimethyl associated with the gamma-globin gene consistent with a transcriptional activation mechanism. Cultured EPC expressed the Igamma- and Vgamma-globin chains in a pattern characteristic of fetal development. The level of DNA methylation of the gamma-globin gene promoter in EPC cultures was similar to BM erythroid cells from normal adult baboons. Different BCL11A isoforms were observed in BM erythroid cells and cultured EPC.

CONCLUSION:

The mechanism responsible for increased gamma-globin expression in cultured EPC was unexpectedly not associated with increased DNA hypomethylation of the gamma-globin gene promoter compared to normal BM erythroid cells, in contrast to BM erythroid cells of decitabine-treated baboons. Rather, increased fetal hemoglobin in EPC cultures was associated with a fetal Igamma/Vgamma chain ratio and a difference in the size of the BCL11A protein compared to normal BM erythroid cells.

PMID:
19576949
DOI:
10.1016/j.exphem.2009.06.007
[Indexed for MEDLINE]

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