title: TGF-beta3-induced palatogenesis requires matrix metalloproteinases.
abstract: Cleft lip and palate syndromes are among the most common congenital malformations in humans. Mammalian palatogenesis is a complex process involving highly regulated interactions between epithelial and mesenchymal cells of the palate to permit correct positioning of the palatal shelves, the remodeling of the extracellular matrix (ECM), and subsequent fusion of the palatal shelves. Here we show that several matrix metalloproteinases (MMPs), including a cell membrane-associated MMP (MT1-MMP) and tissue inhibitor of metalloproteinase-2 (TIMP-2) were highly expressed by the medial edge epithelium (MEE). MMP-13 was expressed both in MEE and in adjacent mesenchyme, whereas gelatinase A (MMP-2) was expressed by mesenchymal cells neighboring the MEE. Transforming growth factor (TGF)-beta3-deficient mice, which suffer from clefting of the secondary palate, showed complete absence of TIMP-2 in the midline and expressed significantly lower levels of MMP-13 and slightly reduced levels of MMP-2. In concordance with these findings, MMP-13 expression was strongly induced by TGF-beta3 in palatal fibroblasts. Finally, palatal shelves from prefusion wild-type mouse embryos cultured in the presence of a synthetic inhibitor of MMPs or excess of TIMP-2 failed to fuse and MEE cells did not transdifferentiate, phenocopying the defect of the TGF-beta3-deficient mice. Our observations indicate for the first time that the proteolytic degradation of the ECM by MMPs is a necessary step for palatal fusion.
authors.affiliation: Division of Hematology-Oncology, Department of Pediatrics, Childrens Hospital Los Angeles and the Keck School of Medicine of the University of Southern California, Los Angeles, California 90027, USA.
authors.forename: L
authors.initials: L
authors.lastname: Blavier
authors.forename: A
authors.initials: A
authors.lastname: Lazaryev
authors.forename: J
authors.initials: J
authors.lastname: Groffen
authors.forename: N
authors.initials: N
authors.lastname: Heisterkamp
authors.forename: Y A
authors.initials: YA
authors.lastname: DeClerck
authors.forename: V
authors.initials: V
authors.lastname: Kaartinen
mesh_terms: D000818:Animals; D002972:Cleft Palate / Q000196:embryology; D004622:Embryo, Mammalian / Q000378:metabolism*; D004848:Epithelium / Q000378:metabolism; D005109:Extracellular Matrix / Q000378:metabolism; D005260:Female; D005347:Fibroblasts / Q000502:physiology; D006801:Humans; D006877:Hydroxamic Acids / Q000494:pharmacology; D017403:In Situ Hybridization; D020782:Matrix Metalloproteinases / Q000235:genetics / Q000378:metabolism*; D008648:Mesoderm / Q000166:cytology / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D009924:Organ Culture Techniques; D010159:Palate / Q000196:embryology* / Q000378:metabolism; D011247:Pregnancy; D011480:Protease Inhibitors / Q000494:pharmacology; D019714:Tissue Inhibitor of Metalloproteinases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D016212:Transforming Growth Factor beta / Q000378:metabolism*; D053782:Transforming Growth Factor beta3
chemical_list: C108282:BB 3103; D006877:Hydroxamic Acids; D011480:Protease Inhibitors; C509045:Tgfb3 protein, mouse; D019714:Tissue Inhibitor of Metalloproteinases; D016212:Transforming Growth Factor beta; D053782:Transforming Growth Factor beta3; D020782:Matrix Metalloproteinases