Isolation of chicken vitellogenin I and III cDNAs and the developmental regulation of five estrogen-responsive genes in the embryonic liver.

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Abstract
The isolation of cDNA clones that code for portions of the two minor chicken vitellogenin (VTG) genes (VTGI and VTGIII) is reported. These clones represent unique sequences that are expressed exclusively in the livers of estrogenized birds. In the liver of the egg-laying hen, the levels of RNAs encoding VTGI, VTGII, and VTGIII are approximately 11,000, 30,000, and 3,000 molecules per cell, respectively. We have used the newly isolated clones, as well as the yolk protein cDNAs previously available [VTGII, apolipoprotein II (apoVLDLII), and apolipoprotein B], as probes to examine several aspects of the regulation of these genes by estradiol. First, we demonstrate that the capacity of each gene to respond to estradiol is acquired between 8 and 13 days in ovo. The response of four of these genes to estradiol is diminished during late fetal development, but the responsiveness is recovered within a week after hatching. Second, we demonstrate that these genes display distinct kinetic response profiles following the addition of estradiol. Third, as has been described previously for the VTGII and apoVLDLII genes, we demonstrate that a single injection of estradiol effects a long-term reprogramming event (hepatic memory) that allows a faster onset of the rapid accumulation of both VTGI and VTGIII RNAs following a subsequent rechallenge by estradiol. Collectively, these three sets of data suggest molecular parameters that may contribute to both the coordinate and noncoordinate regulation of this set of genes by estradiol.