EXPRESSION OF THE ALBUMIN GENE IN THE YOLK-SAC AND LIVER DURING CHICK EMBRYOGENESIS

1. Albumin mRNA is first detectable in vascular yolk sac on the third day of egg incubation, increases to peak level on day 14 and declines to zero by day 19. 2. Vascular yolk sac RNA contains a 6-10-fold higher level of albumin transcripts compared to non-vascularized yolk sac, suggesting a role for vascularization in promoting albumin gene expression. 3. Embryonic liver albumin transcripts are first detectable at day 6.5, increase 6-fold by day 8, continue to rise at a lower rate until day 14 and remain constant thereafter. 4. Albumin protein synthesis in liver cubes also exhibits a large increase over days 7-10. In contrast, another liver-specific constitutive protein, apolipoprotein B, shows a different biosynthetic pattern. 5. The data suggest development of hepatic albumin gene-specific regulatory factor- over days 7-10.