title: Hedgehog-responsive mesenchymal clusters direct patterning and emergence of intestinal villi.
abstract: In the adult intestine, an organized array of finger-like projections, called villi, provide an enormous epithelial surface area for absorptive function. Villi first emerge at embryonic day (E) 14.5 from a previously flat luminal surface. Here, we analyze the cell biology of villus formation and examine the role of paracrine epithelial Hedgehog (Hh) signals in this process. We find that, before villus emergence, tight clusters of Hh-responsive mesenchymal cells form just beneath the epithelium. Cluster formation is dynamic; clusters first form dorsally and anteriorly and spread circumferentially and posteriorly. Statistical analysis of cluster distribution reveals a patterned array; with time, new clusters form in spaces between existing clusters, promoting approximately four rounds of villus emergence by E18.5. Cells within mesenchymal clusters express Patched1 and Gli1, as well as Pdgfrα, a receptor previously shown to participate in villus development. BrdU-labeling experiments show that clusters form by migration and aggregation of Hh-responsive cells. Inhibition of Hh signaling prevents cluster formation and villus development, but does not prevent emergence of villi in areas where clusters have already formed. Conversely, increasing Hh signaling increases the size of villus clusters and results in exceptionally wide villi. We conclude that Hh signals dictate the initial aspects of the formation of each villus by controlling mesenchymal cluster aggregation and regulating cluster size.
authors.affiliation: Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI 48109, USA.
authors.forename: Katherine D
authors.initials: KD
authors.lastname: Walton
authors.forename: Asa
authors.initials: A
authors.lastname: Kolterud
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Czerwinski
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Bell
authors.forename: Ajay
authors.initials: A
authors.lastname: Prakash
authors.forename: Juhi
authors.initials: J
authors.lastname: Kushwaha
authors.forename: Ann S
authors.initials: AS
authors.lastname: Grosse
authors.forename: Santiago
authors.initials: S
authors.lastname: Schnell
authors.forename: Deborah L
authors.initials: DL
authors.lastname: Gumucio
mesh_terms: D000818:Animals; D053823:Hedgehog Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D007413:Intestinal Mucosa / Q000166:cytology / Q000378:metabolism*; D051741:Kruppel-Like Transcription Factors / Q000235:genetics / Q000378:metabolism; D051379:Mice; D008822:Mice, Transgenic; D000072079:Patched Receptors; D000072081:Patched-1 Receptor; D020796:Receptor, Platelet-Derived Growth Factor alpha / Q000235:genetics / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*; D000071676:Zinc Finger Protein GLI1
chemical_list: C498520:Gli1 protein, mouse; D053823:Hedgehog Proteins; D051741:Kruppel-Like Transcription Factors; C000606236:PTCH1 protein, human; D000072079:Patched Receptors; D000072081:Patched-1 Receptor; C000606240:Ptch1 protein, mouse; D011956:Receptors, Cell Surface; D000071676:Zinc Finger Protein GLI1; D020796:Receptor, Platelet-Derived Growth Factor alpha