title: Role of Indian hedgehog signaling in palatal osteogenesis.
abstract: BACKGROUND
  Cleft lip-cleft palate is a common congenital disability and represents a large biomedical burden. Through the use of animal models, the molecular underpinnings of cleft palate are becoming increasingly clear. Indian hedgehog (Ihh) has been shown to be associated with craniofacial development and to be active in the palatine bone. The authors hypothesize that Indian hedgehog activity plays a role in osteogenesis within the secondary palate and that defects in this pathway may inhibit osteogenesis of the secondary palate.
  
  
  METHODS
  Palates were isolated from wild-type mice during the period of palate development (embryonic days 9.5 to 17.5). Quantitative real-time polymerase chain reaction was used for detecting gene expression during osteogenic differentiation and cellular differentiation (Shh, Ihh, Ptc1, Gli1, Gli2, Gli3, Runx2, Alp, and Col1a1). Next, palates were analyzed by hematoxylin and eosin, aniline blue, pentachrome, and in situ hybridization to assess osteogenesis of the palatal shelf and expression of hedgehog pathway genes. Finally, the palates of Indian hedgehog-null mice were analyzed to determine the effect of genetic deficiency on palatal development osteogenesis.
  
  
  RESULTS
  Increased Indian hedgehog and osteogenic signaling coincided with ossification and fusion of the palate in wild-type mice. This included a fivefold to 150-fold peak in expression of hedgehog elements, including Ihh, at embryonic day 15.5 as compared with embryonic day 9.5. Contrarily, loss of Indian hedgehog by genetic knockout (Ihh-/-) resulted in decreased secondary palate ossification.
  
  
  CONCLUSIONS
  The authors' results suggest a role for hedgehog signaling during palatal ossification. The hedgehog pathway is activated during palatal fusion, and deletion of Indian hedgehog leads to diminished ossification of the secondary hard palate.
authors.affiliation: Stanford, Calif. From the Hagey Laboratory for Pediatric Regenerative Medicine, Department of Surgery, Plastic and Reconstructive Surgery Division, Stanford University School of Medicine.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Levi
authors.forename: Aaron W
authors.initials: AW
authors.lastname: James
authors.forename: Emily R
authors.initials: ER
authors.lastname: Nelson
authors.forename: Samantha A
authors.initials: SA
authors.lastname: Brugmann
authors.forename: Michael
authors.initials: M
authors.lastname: Sorkin
authors.forename: Alina
authors.initials: A
authors.lastname: Manu
authors.forename: Michael T
authors.initials: MT
authors.lastname: Longaker
mesh_terms: D000818:Animals; D005260:Female; D018507:Gene Expression Regulation, Developmental; D053823:Hedgehog Proteins / Q000096:biosynthesis / Q000235:genetics*; D051379:Mice; D008810:Mice, Inbred C57BL; D010012:Osteogenesis / Q000502:physiology*; D021362:Palate, Hard / Q000196:embryology* / Q000378:metabolism; D016133:Polymerase Chain Reaction; D011247:Pregnancy; D011270:Pregnancy, Animal; D012313:RNA / Q000235:genetics*; D015398:Signal Transduction / Q000502:physiology*
chemical_list: D053823:Hedgehog Proteins; C514061:ihh protein, mouse; D012313:RNA