Human gamma- to beta-globin gene switching in transgenic mice.

Abstract

Previous studies demonstrated correct tissue-and temporal-specific expression of human 7-and ~-globin genes in transgenic mice; however, expression was extremely low. When the erythroid-specific DNase I superhypersensitive (HS) sites that are normally located upstream of the human 13-globin locus were fused individually to 7" or 13-globin genes, expression increased to endogenous mouse globin levels but temporal specificity was lost. In contrast, when the HS sequences were combined with fragments containing both 7" and 13-globin genes, correct developmental regulation was restored. We suggest that human 7" to 13-globin gene switching during development results from competition of individual globin gene family members for interaction with the HS sequences and that factors influencing these competitive interactions determine temporal specificity.

Proteins binding to the 5′-flanking regulatory elements of the human β-globin gene

“…β -globin gene is silenced in embryonic and fetal erythroid tissue. Later, a similar stage specific expression has also been obtained with γ-globin gene [5,6]. These results have led to the suggestion that cis-acting regulatory elements closely associated with the human β and γ globin genes could confer tissue-and temporal-specific expression [5,6].…”

“…Previous studies in transgenic mice have shown that human β -globin gene alone is expressed specifically in adult erythroid tissue in a temporal pattern parallelling that of the endogenous mouse β-globin genes [5,6,19,20]. β -globin gene is silenced in embryonic and fetal erythroid tissue.…”

“…The entire set of β -like globin genes is controlled by the LCR [3,4]. Experiments in transgenic mice have shown that human γ and β -globin genes expressed sequentially during development but at a lower level in the absence of LCR [5,6,7]. The linkage of LCR to γ or β -globin gene confers high level expression and position independence on human globin transgene in mice [4,8].…”

“…The linkage of LCR to γ or β -globin gene confers high level expression and position independence on human globin transgene in mice [4,8]. Initially, Behringer et al [5] and Enver et al [7] reported that linkage of γ -globin gene alone to LCR resulted in γ globin gene expression throughout the developmental stages, while linkage of both γ and β -globin genes to LCR conferred a correct stage developmental expression, which led to a proposition that γ to β -globin switching is regulated by reciprocal competition.…”

Non‐anemic homozygous βo thalassemia in an African‐American family: Association of high fetal hemoglobin levels with β thalassemia alleles

“…The PCR product was then digested with an A ␥ globinspecific restriction enzyme-PstI-and analyzed on a denaturing 7 M urea 6% polyacrylamide gel. In addition, the relative quantities of ␤ and ␥ globin mRNA from reticulocytes were analyzed by primer extension [25]. The ␤: (5Ј-CCACAGGGCAGTAACGGCAGA-3Ј) and ␥ (5Ј-CCAGCATCTTCCACATTCACC-3Ј) globinspecific oligonucleotides were 32 P end-labeled, hybridized with 10 ng of total reticulocyte RNA, and extended with reverse transcriptase (AMV, Promega).…”