Multiple regulatory regions control the complex expression pattern of the mouse Cdx2 homeobox gene.
OBJECTIVE
The Cdx2 homeobox gene exerts multiple functions including trophectoderm specification, antero-posterior patterning, and determination of intestinal identity. The aim of this study was to map genomic regions that regulate the transcription of Cdx2, with a particular interest in the gut.


METHODS
Genomic fragments covering 13 kilobase (kb) of the mouse Cdx2 locus were analyzed in transgenic mice and in cell assays.


RESULTS
No fragment was active in the trophectoderm. Fragments containing the first intron and extending up to -5-kb upstream of the transcription start site became active posteriorly at gastrulation and then inactive at midgestation in every tissue including the endoderm. Specific persistence of activity in the intestinal endoderm/epithelium beyond midgestation requires extending the genomic fragment up to -9 kb. We identified a 250-base pair segment around -8.5-kb binding and responding to endodermal factors, with a stimulatory effect exerted synergistically by HNF4alpha, GATA6, Tcf4, and beta-catenin. These factors were able to activate endogenous expression of Cdx2 in nonintestinal Hela cells.


CONCLUSIONS
Multiple regulatory regions control the complex developmental pattern of Cdx2, including far upstream sequences required for the persistence of gene expression specifically in the gut epithelium throughout life. Cooperation between HNF4alpha, GATA6, beta-catenin, and Tcf4 contributes to the intestine-specific expression of Cdx2.
Benahmed
Fairouz
F
INSERM, U682, Strasbourg, France.
Gross
Isabelle
I
Gaunt
Stephen J
SJ
Beck
Felix
F
Jehan
Frédéric
F
Domon-Dell
Claire
C
Martin
Elisabeth
E
Kedinger
Michèle
M
Freund
Jean-Noël
JN
Duluc
Isabelle
I
D000367:Age Factors; D000818:Animals; D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; D001755:Blastocyst / Q000166:cytology / Q000502:physiology; D000071616:CDX2 Transcription Factor; D002432:Cecum / Q000196:embryology / Q000502:physiology; D002460:Cell Line; D004707:Endoderm / Q000196:embryology / Q000502:physiology; D050993:GATA6 Transcription Factor / Q000235:genetics / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D023281:Genomics; D006367:HeLa Cells; D051557:Hepatocyte Nuclear Factor 4 / Q000235:genetics / Q000378:metabolism; D018398:Homeodomain Proteins / Q000235:genetics* / Q000378:metabolism*; D006801:Humans; D007422:Intestines / Q000166:cytology / Q000196:embryology* / Q000502:physiology*; D007763:Lac Operon; D051379:Mice; D008822:Mice, Transgenic; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism; D012045:Regulatory Sequences, Nucleic Acid / Q000235:genetics; D013270:Stomach / Q000196:embryology / Q000502:physiology; D051820:TCF Transcription Factors / Q000235:genetics / Q000378:metabolism; D000073940:Transcription Factor 4; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism*; D014162:Transfection; D014327:Trophoblasts / Q000166:cytology / Q000502:physiology; D051176:beta Catenin / Q000235:genetics / Q000378:metabolism
D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; D000071616:CDX2 Transcription Factor; C495267:CTNNB1 protein, mouse; C487514:Cdx2 protein, mouse; D050993:GATA6 Transcription Factor; C494760:Gata6 protein, mouse; D051557:Hepatocyte Nuclear Factor 4; C496593:Hnf4a protein, mouse; D018398:Homeodomain Proteins; D009419:Nerve Tissue Proteins; D051820:TCF Transcription Factors; C090743:Tcf4 protein, mouse; D000073940:Transcription Factor 4; D014157:Transcription Factors; D051176:beta Catenin