Developmental regulation of a complete 70-kb human β-globin locus in transgenic mice

Abstract

We have used a linker-based ligation strategy to combine two 35-kb cosmid inserts from the human β-globin locus into one linear fragment containing the entire locus. This 70-kb fragment was introduced into transgenic mice by microinjection of fertilized eggs. Southern blot analysis showed that a single complete transgene locus can be introduced into the germ line with high efficiency. Analysis of the expression patterns of the locus during development shows that the ε-globin gene behaves as a purely embryonic gene, the γ-globin gene as an embryonic and early fetal gene, and the β-globin gene as a fetal adult gene. Quantitation of expression showed that the levels of transcription of the ε- and γ-globin genes are reversed relative to their mouse homologs but that the total output of the human and mouse loci is constant during development. These results suggest that multiple changes in DNA sequences and transcription factor balance must have occurred for the human γ-globin gene to have evolved into a fetal gene.