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Title: Analysis of differential hepatocyte nuclear factor 4 isoform expression during hepatic de‐differentiation and re‐differentiation in‐vitro
Author(s) -
Bell Aaron W,
Stoops John
Publication year - 2008
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.22.1_supplement.465.1
Subject(s) - hepatocyte nuclear factor 4 , gene isoform , cellular differentiation , phenotype , hepatocyte , microbiology and biotechnology , biology , smad , hepatocyte growth factor , signal transduction , chemistry , in vitro , gene , biochemistry , transcription factor , nuclear receptor , receptor
Hepatocyte nuclear factor 4α is essential for liver development and maintenance of liver‐specific gene expression. HNF4α isoform expression is developmentally regulated. We have established a serum‐free hepatocyte culture system in which primary rat hepatocytes de‐differentiate and acquire a simplified morphologic phenotype resembling hepatoblasts. Addition of Matrigel, DMSO or phenobarbital to the cells induces re‐differentiation and restoration of hepatocyte‐specific gene expression and mature phenotype. Western blot and real‐time PCR analyses reveals that HNF4α isoform expression is directly correlated with hepatic differentiation status and mimics embryonic liver development. To determine the mechanism(s) of this differential regulation we examined the activation and/or inhibition of various kinase pathways with each of the differentiation‐inducing agents. Inhibition of TGFβRkinase or PI3Kinase with specific chemical inhibitors induces re‐expression of P1 isoforms and augments the re‐differentiation induced by DMSO, PB and Matrigel which also requires activation of the CaMKinase pathway. We propose that TGFβ□/Smad signaling and PI3Kinase are responsible for the expression of the P2‐derived isoforms and de‐differentiated phenotype and their inhibition coupled with activation of the CaMKinase pathway induces the P1‐derived HNF4α isoforms and the differentiated phenotype.