Persistent γ-globin expression in adult transgenic mice is mediated by HPFH-2, HPFH-3, and HPFH-6 breakpoint sequences

Persistent Fetal γ-Globin Expression in Adult Transgenic Mice following Deletion of Two Silencer Elements Located 3′ to the Human Aγ-Globin Gene

“…It also has been suggested (18), without being mutually exclusive, that the juxtaposition of distal sequences located downstream of the 3′ breakpoint of these deletions with enhancer-like function also may be involved in persistent γ-globin expression. The validity of the latter hypothesis for the HPFH deletions has been documented conclusively (experimentally) in vivo by us (19,20) and by others (21) with the identification and functional characterization of a series of HPFH enhancers (19)(20)(21). A similar mechanism may be operating in the HPFH-5 and HPFH Kenya deletions via the juxtaposition of the 3′ β-globin enhancer to the proximity of the fetal genes (1,16).…”

“…The cosmid construct used was generated by ligation and packaging into phage of the following fragments: a) a 27-kb PvuI-ClaI fragment from LCR-loxP-Aγ-3′HS cosmid (20) containing the cos site of the pTCF cosmid vector (1), the LCR, and the loxP site; b) a ClaI-KpnI fragment from a pBluescript-Aγ plasmid containing the Aγ gene (3.3 kb); c) a 14-kb KpnINotI fragment from the LCRε cosmid (4) containing a cos site and sequences downstream of the ε-globin gene. Packaging was performed using Gigapack Gold extracts (Stratagene, La Jolla, CA, USA) according to the manufacturer's instructions.…”

Fetal hemoglobin chemical inducers for treatment of hemoglobinopathies

“…In the African-type of deletion HPFH, large deletions have been observed, beginning just 3′ to the A γ gene and extending for 3′ of the β-globin gene: Therefore, the deletion involves intergenic γ-δ sequences and the entire β and δ genes. To explain the phenotype of this HPFH form, it was proposed that the juxtaposition of enhancer elements, normally located downstream of the globin locus and the HPFH breakpoint, exerts a markedly positive effect on γ-globin transcription [23].…”

Characterization of a novel deletion causing (δβ)0‐thalassemia in a Thai family

“…The first sequence located immediately downstream to the 3 0 breakpoint of the HPFH-1and HPFH-2 deletion was shown to act as enhancers in transient transfection assays and in transgenic mice. This region was marked by an erythroid specific DNase I hypersensitive site extending from 1.1 to 1.4 kb 3 0 to the HPFH-1 breakpoint [1][2][3][4]. A second region with enhancer activity in a transient system lies between the breakpoints of HPFH-6 and Chinese G g( A gdb) 0 -thalassemia [4,5].…”

“…This region was marked by an erythroid specific DNase I hypersensitive site extending from 1.1 to 1.4 kb 3 0 to the HPFH-1 breakpoint [1][2][3][4]. A second region with enhancer activity in a transient system lies between the breakpoints of HPFH-6 and Chinese G g( A gdb) 0 -thalassemia [4,5]. The third region, 0.7 kb HPFH-3 core enhancer sequence, had been identified immediately downstream to the 3 0 breakpoint of HPFH-3 and 2 kb downstream of the HPFH-4 breakpoint [4,6].…”