Developmental regulation of human gamma- and beta-globin genes in the absence of the locus control region.
Two lines of transgenic mice carrying a normal 40-kb Kpn I beta-globin cluster transgene lacking the locus control region (LCR) were analyzed for the expression of human gamma- and beta-globin genes during mouse development. After RNase protection assays, the ratios of human G gamma-, A gamma-, or beta-mRNAs relative to endogenous mouse zeta + alpha mRNAs were obtained for each stage of development. The two gamma transgenes were expressed in day-11.5 blood (embryonic stage) and day-13.5 blood (early fetal stage), but their expression was markedly decreased by day 16.5 of fetal life. Expression of the beta transgene was essentially absent at day 13.5, appeared at a low level by day 16.5, and was maximal by day 18.5, reaching a level similar to that observed in adult mice. Therefore, developmentally regulated expression of the human gamma- and beta-globin transgenes was obtained in the absence of the LCR. The relative expression of human gamma- and beta-globin genes was also examined in mice carrying 40-kb Kpn I beta-cluster transgenes with two different base substitutions associated with nondeletion forms of hereditary persistence of fetal hemoglobin (HPFH), -202 C-->G G gamma HPFH and -117 G-->A A gamma HPFH. The ratio of G gamma- to beta-globin transcripts was markedly increased in red blood cells of adult mice from three different lines carrying the transgene with the -202 G gamma HPFH mutation. This result confirms our previous preliminary results (Tanaka et al: Ann NY Acad Sci, 612:167, 1990) indicating that the -202 G gamma HPFH phenotype was reproduced in transgenic mice. The relatively low levels of G gamma-mRNA expression in adult mice carrying the non-HPFH transgene excludes a major influence of the 3' beta-globin enhancer, present upstream of the G gamma gene because of the tandem repeat insertion, as a factor in the persistent G gamma gene expression observed in blood of adult mice carrying the -202 G gamma HPFH transgene. This conclusion is also supported by the fact that, in mice carrying the -117 A gamma HPFH transgene, G gamma-globin mRNA was detected in blood of adult animals only at low levels similar to that observed in the non-HPFH lines. However, the A gamma-HPFH phenotype was not reproduced in the transgenic lines carrying the -117A gamma HPFH mice.
Starck
J
J
Department of Internal Medicine, Yale University School of Medicine, New Haven, CT 06520-8021.
Sarkar
R
R
Romana
M
M
Bhargava
A
A
Scarpa
A L
AL
Tanaka
M
M
Chamberlain
J W
JW
Weissman
S M
SM
Forget
B G
BG
D000818:Animals; D004268:DNA-Binding Proteins / Q000096:biosynthesis / Q000235:genetics; D050981:Erythroid-Specific DNA-Binding Factors; D005319:Fetal Hemoglobin / Q000235:genetics*; D005786:Gene Expression Regulation; D005914:Globins / Q000096:biosynthesis* / Q000235:genetics*; D006801:Humans; D051379:Mice; D008822:Mice, Transgenic; D015347:RNA Probes; D012333:RNA, Messenger / Q000096:biosynthesis; D015183:Restriction Mapping; D012867:Skin / Q000378:metabolism; D013154:Spleen / Q000378:metabolism; D014157:Transcription Factors / Q000096:biosynthesis / Q000235:genetics
D004268:DNA-Binding Proteins; D050981:Erythroid-Specific DNA-Binding Factors; D015347:RNA Probes; D012333:RNA, Messenger; D014157:Transcription Factors; D005914:Globins; D005319:Fetal Hemoglobin