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J. Biol. Chem., Vol. 278, Issue 42, 40933-40942, October 17, 2003
Functions of HNF1 Family Members in Differentiation of the Visceral Endoderm Cell Lineage* ![]() ¶From the Unité 423 INSERM, Hôpital Necker-Enfants Malades, 149 Rue de Sèvres, 75015 Paris, France The two members of the hepatocyte nuclear factor 1 (HNF1) transcription factor family, HNF1 and variant HNF1 (vHNF1), show a strong homology in their atypical POU-homeodomain and dimerization domain but differ in their transactivation domains. Moreover, two vHNF1 isoforms generated by alternative splicing are present in all tissues expressing this gene. vHnf1-deficient mouse embryos die soon after implantation due to defective visceral endoderm formation, an extraembryonic tissue essential for development and survival of the embryo proper. In contrast, invalidation of Hnf1, which is expressed at later developmental stages than vHnf1, does not lead to embryonic lethality or developmental defects. To examine the specific or potential equivalent functions of vHNF1 isoforms and HNF1 during the process of visceral endoderm differentiation, we stably reexpressed these factors in vHnf1-deficient embryonic stem cells. Analysis of these embryonic stem cells upon differentiation into embryoid bodies shows that vHNF1 isoforms exhibit specific behaviors depending on particular target genes and cooperate in the establishment of a functional visceral endoderm. Furthermore, forced expression of HNF1 in vHnf1-deficient embryonic stem cells fully restores the formation of a mature visceral endoderm with the correct expression profile of early and late markers of this lineage. Thus, in this context, HNF1 functionally replaces both vHNF1 isoforms, suggesting that the different developmental functions of these transcription factors are mainly due to the acquisition of novel expression patterns.
Received for publication, April 28, 2003 , and in revised form, July 2, 2003. * This work was supported by Association pour la Recherche contre le Cancer (ARC) Contract 5824 and INSERM. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
¶ A fellow from ARC. Present address: Molecular Neurobiology Laboratory, The Salk Institute, La Jolla, CA 92037.
|| To whom correspondence should be addressed: Biologie du Développement, UMR 7622, CNRS, Université Pierre et Marie Curie, 9 Quai St Bernard, B
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