The position of integration affects expression of the A gamma-globin-encoding gene linked to HS3 in transgenic mice.
Proper expression of the human beta-globin (beta Glb) locus is dependent on the presence of a major regulatory element located upstream from the beta Glb gene cluster, the locus control region (LCR). The LCR, as well as the individual DNase-I-hypersensitive sites from which it is composed, have been shown to provide position-of-integration-independent expression in transgenic mice. Here, we report that a transgenic founder carrying multiple integrations of a hypersensitive site 3::A gamma globin gene (HS3::A gamma) construct produced three types of progeny, one with zero A gamma expression in the adult stage, one with minimal A gamma expression (1% of A gamma-expressing cells) and one with abundant A gamma expression (100% A gamma-expressing cells). The possibility that these phenotypes were due to parental imprinting or to DNA rearrangements of the transgene or to point mutations of the HS3 core or the A gamma promoter were excluded. The pattern of inheritance of the three HS3::A gamma transgene phenotypes indicate that the transgene has integrated into three different chromosomes. These results provide direct evidence that the HS3 of the LCR is not sufficient to protect the A gamma gene from position effects excerted by the surrounding chromatin.
Navas
P A
PA
Division of Medical Genetics, School of Medicine, University of Washington, Seattle 98195, USA.
Josephson
B
B
Furukawa
T
T
Stamatoyannopoulos
G
G
Li
Q
Q
D000818:Animals; D004274:DNA, Recombinant / Q000235:genetics*; D003850:Deoxyribonuclease I; D005260:Female; D018507:Gene Expression Regulation, Developmental; D005914:Globins / Q000235:genetics*; D006801:Humans; D008297:Male; D051379:Mice; D008822:Mice, Transgenic; D010375:Pedigree; D011401:Promoter Regions, Genetic; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis* / Q000235:genetics; D011995:Recombination, Genetic; D012045:Regulatory Sequences, Nucleic Acid
D004274:DNA, Recombinant; D011993:Recombinant Fusion Proteins; D005914:Globins; D003850:Deoxyribonuclease I