Developmental regulation of albumin and alpha-fetoprotein gene expression in the rat.

Albumin and AFP comprise a developmentally regulated gene family expressed predominantly in liver and yolk sac. In this study, we have analyzed the developmental changes in the levels of transcripts in liver and yolk sac, and the methylation of the genes in yolk sac. We have previously analyzed the gene methylation in developing liver and non-expressing tissues (Kunnath and Locker, 1983, EMBO J., 2, 317-324). From these analyses we can distinguish 3 active modes of coordinated expression. The adult liver synthesizes albumin, the yolk sac synthesizes AFP, and the fetal liver synthesizes both. In the yolk sac, the relatively inactive albumin gene is hypermethylated, while the active AFP gene is undermethylated. Our data suggest that the genes are activated simultaneously but that subsequent enhancement is specific for tissue and developmental stage.