Differential induction of HNF-3 transcription factors during neuronal differentiation.
We have investigated the regulation of transcription factors HNF-3alpha and HNF-3beta during the retinoic acid-mediated differentiation of mouse P19 cells. Retinoic acid treatment converts P19 stem cells into neurons and astrocytes and we have clearly shown that gene expression of both HNF-3alpha and HNF-3beta is activated during this process. HNF-3alpha transcription was detected 2 h after addition of retinoic acid and took place in the absence of de novo protein synthesis. This suggests that HNF-3alpha is a primary target for retinoic acid action. HNF-3alpha induction displays a biphasic profile and HNF-3alpha mRNA reaches maximal levels at 2 and 6 days postdifferentiation. Additional experiments strongly suggest that the second peak is due to HNF-3alpha induction in postmitotic neurons. P19 stem cells, on the other hand, do not contain any detectable HNF-3alpha mRNA. According to our studies, the retinoic acid-mediated induction of HNF-3alpha occurs at the level of transcriptional initiation and is conferred by distal promoter sequences. In comparison to HNF-3alpha, HNF-3beta induction is a subsequent event and detectable levels of HNF-3beta mRNA materialize approximately 1 day after addition of retinoic acid to P19 stem cells. Time course studies firmly demonstrate that HNF-3beta mRNA peaks at about 2 days postdifferentiation and then declines to virtually unreadable levels. This temporal pattern is consistent with HNF-3beta being a secondary target for retinoic acid. In analogy to HNF-3alpha, HNF-3beta activation also takes place at the level of transcriptional initiation. Recent studies implicate HNF-3alpha and HNF-3beta in early mammalian neurogenesis. The detection of HNF-3alpha/beta activation during P19 cell differentiation provides us with a convenient cell culture system to elucidate the induction mechanism and the precise role of both transcriptional regulators in the formation of neuronal cells.
Jacob
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Department of Pharmacology and Molecular Biology, The Chicago Medical School, Illinois 60064, USA.
Budhiraja
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Reichel
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D000818:Animals; D001253:Astrocytes / Q000166:cytology / Q000502:physiology; D002454:Cell Differentiation; D003561:Cytarabine / Q000494:pharmacology; D004268:DNA-Binding Proteins / Q000235:genetics*; D051541:Hepatocyte Nuclear Factor 3-alpha; D051542:Hepatocyte Nuclear Factor 3-beta; D051379:Mice; D014411:Neoplastic Stem Cells; D009474:Neurons / Q000166:cytology / Q000502:physiology*; D009687:Nuclear Proteins / Q000235:genetics*; D016372:RNA, Antisense; D012333:RNA, Messenger / Q000096:biosynthesis; D014157:Transcription Factors / Q000235:genetics*; D015533:Transcriptional Activation / Q000502:physiology*; D014212:Tretinoin / Q000494:pharmacology
D004268:DNA-Binding Proteins; C496500:Foxa1 protein, mouse; C496503:Foxa2 protein, mouse; D051541:Hepatocyte Nuclear Factor 3-alpha; D009687:Nuclear Proteins; D016372:RNA, Antisense; D012333:RNA, Messenger; D014157:Transcription Factors; D003561:Cytarabine; D051542:Hepatocyte Nuclear Factor 3-beta; D014212:Tretinoin