Paracrine Hedgehog signaling in stomach and intestine: new roles for hedgehog in gastrointestinal patterning.
OBJECTIVE
Hedgehog signaling is critical in gastrointestinal patterning. Mice deficient in Hedgehog signaling exhibit abnormalities that mirror deformities seen in the human VACTERL (vertebral, anal, cardiac, tracheal, esophageal, renal, limb) association. However, the direction of Hedgehog signal flow is controversial and the cellular targets of Hedgehog signaling change with time during development. We profiled cellular Hedgehog response patterns from embryonic day 10.5 (E10.5) to adult in murine antrum, pyloric region, small intestine, and colon.


METHODS
Hedgehog signaling was profiled using Hedgehog pathway reporter mice and in situ hybridization. Cellular targets were identified by immunostaining. Ihh-overexpressing transgenic animals were generated and analyzed.


RESULTS
Hedgehog signaling is strictly paracrine from antrum to colon throughout embryonic and adult life. Novel findings include the following: mesothelial cells of the serosa transduce Hedgehog signals in fetal life; the hindgut epithelium expresses Ptch but not Gli1 at E10.5; the 2 layers of the muscularis externa respond differently to Hedgehog signals; organogenesis of the pyloric sphincter is associated with robust Hedgehog signaling; dramatically different Hedgehog responses characterize stomach and intestine at E16; and after birth, the muscularis mucosa and villus smooth muscle consist primarily of Hedgehog-responsive cells and Hh levels actively modulate villus core smooth muscle.


CONCLUSIONS
These studies reveal a previously unrecognized association of paracrine Hedgehog signaling with several gastrointestinal patterning events involving the serosa, pylorus, and villus smooth muscle. The results may have implications for several human anomalies and could potentially expand the spectrum of the human VACTERL association.
Kolterud
Asa
A
Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, Michigan 48109-2200, USA.
Grosse
Ann S
AS
Zacharias
William J
WJ
Walton
Katherine D
KD
Kretovich
Katherine E
KE
Madison
Blair B
BB
Waghray
Meghna
M
Ferris
Jennifer E
JE
Hu
Chunbo
C
Merchant
Juanita L
JL
Dlugosz
Andrzej A
AA
Kottmann
Andreas H
AH
Gumucio
Deborah L
DL
D000818:Animals; D019521:Body Patterning / Q000235:genetics* / Q000502:physiology; D005753:Gastric Mucosa / Q000378:metabolism* / Q000473:pathology; D041981:Gastrointestinal Tract / Q000196:embryology* / Q000254:growth & development; D018507:Gene Expression Regulation, Developmental; D053823:Hedgehog Proteins / Q000378:metabolism*; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D007413:Intestinal Mucosa / Q000473:pathology; D007421:Intestine, Small / Q000196:embryology / Q000378:metabolism* / Q000473:pathology; D051379:Mice; D008822:Mice, Transgenic; D023421:Models, Animal; D015398:Signal Transduction / Q000235:genetics*; D013270:Stomach / Q000196:embryology / Q000473:pathology
D053823:Hedgehog Proteins