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Mol. Cell. Biol., 04 1997, 2076-2089, Vol 17, No. 4
MO Arcasoy, M Romana, ME Fabry, E Skarpidi, RL Nagel and BG Forget
Persistent expression of the gamma-globin genes in adults with deletion
types of hereditary persistence of fetal hemoglobin (HPFH) is thought to be
mediated by enhancer-like effects of DNA sequences at the 3' breakpoints of
the deletions. A transgenic mouse model of deletion-type HPFH was generated
by using a DNA fragment containing both human gamma- globin genes and
HPFH-2 breakpoint DNA sequences linked to the core sequences of the locus
control region (LCR) of the human beta-globin gene cluster. Analysis of
gamma-globin expression in six HPFH transgenic lines demonstrated
persistence of gamma-globin mRNA and peptides in erythrocytes of adult HPFH
transgenic mice. Analysis of the hemoglobin phenotype of adult HPFH
transgenic animals by isoelectric focusing showed the presence of hybrid
mouse alpha2-human gamma2 tetramers as well as human gamma4 homotetramers
(hemoglobin Bart's). In contrast, correct developmental regulation of the
gamma-globin genes with essentially absent gamma-globin gene expression in
adult erythroid cells was observed in two control non-HPFH transgenic
lines, consistent with autonomous silencing of normal human gamma-globin
expression in adult transgenic mice. Interestingly, marked preferential
overexpression of the LCR-distal (A)gamma-globin gene but not of the
LCR-proximal (G)gamma-globin gene was observed at all developmental stages
in erythroid cells of HPFH-2 transgenic mice. These findings were also
associated with the formation of a DNase I-hypersensitive site in the
HPFH-2 breakpoint DNA of transgenic murine erythroid cells, as occurs in
normal human erythroid cells in vivo. These results indicate that
breakpoint DNA sequences in deletion-type HPFH-2 can modify the
developmentally regulated expression of the gamma-globin genes.
Copyright © 1997, American Society for Microbiology
High levels of human gamma-globin gene expression in adult mice carrying a transgene of deletion-type hereditary persistence of fetal hemoglobin
Department of Medicine, Yale University School of Medicine, New Haven, Connecticut 06510, USA.
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