title: The stomach mesenchymal transcription factor Barx1 specifies gastric epithelial identity through inhibition of transient Wnt signaling.
abstract: Inductive interactions between gut endoderm and the underlying mesenchyme pattern the developing digestive tract into regions with specific morphology and functions. The molecular mechanisms behind these interactions are largely unknown. Expression of the conserved homeobox gene Barx1 is restricted to the stomach mesenchyme during gut organogenesis. Using recombinant tissue cultures, we show that Barx1 loss in the mesenchyme prevents stomach epithelial differentiation of overlying endoderm and induces intestine-specific genes instead. Additionally, Barx1 null mouse embryos show visceral homeosis, with intestinal gene expression within a highly disorganized gastric epithelium. Barx1 directs mesenchymal cell expression of two secreted Wnt antagonists, sFRP1 and sFRP2, and these factors are sufficient replacements for Barx1 function. Canonical Wnt signaling is prominent in the prospective gastric endoderm prior to epithelial differentiation, and its inhibition by Barx1-dependent signaling permits development of stomach-specific epithelium. These results define a transcriptional and signaling pathway of inductive cell interactions in vertebrate organogenesis.
authors.affiliation: Department of Medical Oncology, Dana-Farber Cancer Institute, Brigham & Women's Hospital and Harvard Medical School, Boston, Massachusetts 02115, USA.
authors.forename: Byeong-Moo
authors.initials: BM
authors.lastname: Kim
authors.forename: Georg
authors.initials: G
authors.lastname: Buchner
authors.forename: Isabelle
authors.initials: I
authors.lastname: Miletich
authors.forename: Paul T
authors.initials: PT
authors.lastname: Sharpe
authors.forename: Ramesh A
authors.initials: RA
authors.lastname: Shivdasani
mesh_terms: D000818:Animals; D005753:Gastric Mucosa / Q000196:embryology / Q000378:metabolism*; D020869:Gene Expression Profiling; D018507:Gene Expression Regulation, Developmental; D018390:Gene Targeting; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000378:metabolism*; D007422:Intestines / Q000033:anatomy & histology / Q000196:embryology / Q000502:physiology; D008648:Mesoderm / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D009024:Morphogenesis; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*; D013270:Stomach / Q000033:anatomy & histology / Q000196:embryology / Q000502:physiology; D046509:Tissue Culture Techniques; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D051153:Wnt Proteins
chemical_list: C095587:Barx1 protein, mouse; D018398:Homeodomain Proteins; D036341:Intercellular Signaling Peptides and Proteins; D034741:RNA, Small Interfering; D014157:Transcription Factors; D051153:Wnt Proteins