Developmental regulation of alpha-fetoprotein genes in transgenic mice.

Abstract

The mouse alpha-fetoprotein gene is activated in embryonic development in the visceral endoderm of the extraembryonic yolk sac and the fetal liver and gut. Transcription of the gene is subsequently repressed in the neonatal liver. To ask whether the DNA sequence elements required for tissue-specific activation are the same or different from those required for postnatal developmental regulation of the gene, modified copies of the alpha-fetoprotein gene were microinjected into fertilized mouse eggs. Those animals which developed to term and carried integrated copies of the modified gene were analyzed for expression. In approximately 50% of such animals, the introduced gene was active only in the three cell lineages which expressed the authentic alpha-fetoprotein gene. Furthermore, its expression was repressed in the neonatal liver. Thus, we conclude that the modified genes, which included either 7 or 14 kilobase pairs of 5'-flanking DNA, contained the DNA sequence information to direct both tissue-specific expression and developmental regulation. The observation that 50% of the mice which carried the modified gene did not express it in any tissue, combined with the fact that the level of expression was highly variable between expressing transgenic animals, suggested that the gene was susceptible to its site of integration in the mouse genome.

HNF-1 shares three sequence motifs with the POU domain proteins and is identical to LF-B1 and APF.

“…For example, the cq-antitrypsin promoter is expressed in the kidney and intestine and in macrophages such as those in the spleen (Koopman et al 1989). ~-Fetoprotein HNF-1 is a broadly expressed homeo domain protein is expressed in both the intestine and the liver (Tilghman and Belayew 1982;Krumlauf et al 1985). Most of the genes thought to be liver specific have not been rigorously examined with sensitive techniques such as ribonuclease protection and could possibly be more broadly expressed than indicated from initial studies.…”

Tg(Afp‐GFP) expression marks primitive and definitive endoderm lineages during mouse development

“…An oncodevelopmental protein that is expressed at high levels in the embryonic yolk sac and fetal liver, its expression decreases dramatically after birth (Andrews et al, 1982;Tilghman and Belayew, 1982). Whereas only trace amounts of Afp are synthesized in the adult liver, owing to a dominant repression domain (Emerson et al, 1992;Ramesh et al, 1995) ensconced within a much larger 5Ј upstream regulatory region (Krumlauf et al, 1985;Hammer et al, 1987), Afp gene expression is reactivated during conditions involving rapid hepatocyte proliferation, such as liver regeneration or tumorigenesis. Afp has provided an excellent model system for studying the tissue-and developmental stage-specific regulation of gene expression (reviewed by Spear, 1999).…”

“…Afp has provided an excellent model system for studying the tissue-and developmental stage-specific regulation of gene expression (reviewed by Spear, 1999). In particular, the 7.6-kb Afp promoter/ enhancer fragment has been characterized previously in the yolk sac and fetal liver of transgenic mice (Krumlauf et al, 1985;Hammer et al, 1987) and during the directed differentiation of transgenic embryonic stem (ES) cells (Paparella et al, 2002).…”

The zonal expression of α‐fetoprotein transgenes in the livers of adult mice

“…A construct (ZE) that contains the three AFP enhancers, the AFP promoter, and the AFP minigene is repressed in parallel with the endogenous gene in transgenic mice (Krumlauf et al, 1985;Hammer et al, 1987). One mechanism that could mediate the transcriptional repression of the AFP gene in liver is the appearance after birth of a dominant repressor, which The endogenous AFP gene is drawn on the first line.…”