Brief report Regulation of fetal versus embryonic gamma globin genes: appropriate developmental stage expression patterns in the presence of HS2 of the locus control region

The genes provide the major contribution to beta-like globin chain production in the fetal liver of humans. However, the expression of genes in the fetus is a recent evolutionary trend seen only in the primate lineage. In a previous study, it was shown that galago and human genes retain their characteristic stagespecific expression patterns in transgenic mice (galago is expressed exclusively in the embryo, whereas human is expressed in the fetus). In that experiment, human and galago genes were linked to hypersensitive site 3 (HS3) of the locus control region. To rule out the possibility that HS3 is required for these differential expression profiles, additional transgenic lines were tested in which human or galago genes were linked to HS2. Once again, the galago gene was embryonic and the human gene was fetal, indicating that the stage specificity of these genes is driven by elements located within the 4-kb fragments that contain the human and galago genes proper. (Blood. 2002;99:1082-1084)