Control of hemoglobin expression in chick embryonic development.

We have investigated the presence or absence of methylation of cytosine (5-MeCpG) at specific sites of the chick alpha-globin gene cluster in DNA from embryonic and adult erythroid cells, as well as from brain and sperm cells. We find that these sites are totally methylated in sperm DNA and, with some exceptions, in brain DNA. In erythroid cells no methylation or undermethylation is found in certain sites that are in or near those globin genes that are expressed in embryonic or adult cells, respectively, as predicted by the model. Other sites, away from these genes, do not necessarily follow the prediction. We have also detected a cluster of 5-MeCpC methylation sites in all tissues which is 5' to the alpha-globin cluster.