title: Adenomatous polyposis coli control of retinoic acid biosynthesis is critical for zebrafish intestinal development and differentiation.
abstract: Mutations in the APC (adenomatous polyposis coli) tumor suppressor gene cause uncontrolled proliferation and impaired differentiation of intestinal epithelial cells. Recent studies indicate that human colon adenomas and carcinomas lack retinol dehydrogenases (RDHs) and that APC regulates the expression of human RDHL. These data suggest a model wherein APC controls enterocyte differentiation by controlling retinoic acid production. However, the importance of APC and retinoic acid in mediating control of normal enterocyte development and differentiation remains unclear. To examine the relationship between APC and retinoic acid biosynthesis in normal enterocytes, we have identified two novel zebrafish retinol dehydrogenases, termed zRDHA and zRDHB, that show strong expression within the gut of developing zebrafish embryos. Morpholino knockdown of either APC or zRDHB in zebrafish embryos resulted in defects in structures known to require retinoic acid. These defects included cardiac abnormalities, pericardial edema, failed jaw and pectoral fin development, and the absence of differentiated endocrine and exocrine pancreas. In addition, APC or zRDHB morphant fish developed intestines that lacked columnar epithelial cells and failed to express the differentiation marker intestinal fatty acid-binding protein. Treatment of either APC or zRDHB morphant embryos with retinoic acid rescued the defective phenotypes. Downstream of retinoic acid production, we identified hoxc8 as a retinoic acid-induced gene that, when ectopically expressed, rescued phenotypes of APC- and zRDHB-deficient zebrafish. Our data establish a genetic link supporting a critical role for retinoic acid downstream of APC and confirm the importance of retinoic acid in enterocyte differentiation.
authors.affiliation: Department of Oncological Sciences, University of Utah, Salt Lake City 84112, USA.
authors.forename: Lincoln D
authors.initials: LD
authors.lastname: Nadauld
authors.forename: Imelda T
authors.initials: IT
authors.lastname: Sandoval
authors.forename: Stephanie
authors.initials: S
authors.lastname: Chidester
authors.forename: H Joseph
authors.initials: HJ
authors.lastname: Yost
authors.forename: David A
authors.initials: DA
authors.lastname: Jones
mesh_terms: D025601:Adenomatous Polyposis Coli Protein / Q000502:physiology*; D000429:Alcohol Oxidoreductases / Q000737:chemistry / Q000235:genetics*; D000595:Amino Acid Sequence; D000818:Animals; D030801:Animals, Genetically Modified; D002454:Cell Differentiation; D002851:Chromatography, High Pressure Liquid; D018076:DNA, Complementary / Q000378:metabolism; D020895:Enterocytes / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D018398:Homeodomain Proteins / Q000378:metabolism; D007422:Intestines / Q000196:embryology* / Q000254:growth & development*; D008969:Molecular Sequence Data; D010641:Phenotype; D010802:Phylogeny; D012313:RNA / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid; D014212:Tretinoin / Q000378:metabolism / Q000502:physiology*; D015027:Zebrafish; D029961:Zebrafish Proteins / Q000378:metabolism
chemical_list: D025601:Adenomatous Polyposis Coli Protein; D018076:DNA, Complementary; D018398:Homeodomain Proteins; D012333:RNA, Messenger; D029961:Zebrafish Proteins; C489818:hoxc8a protein, zebrafish; D014212:Tretinoin; D012313:RNA; D000429:Alcohol Oxidoreductases; C022520:retinol dehydrogenase