title: Cleft palate defect of Dlx1/2-/- mutant mice is caused by lack of vertical outgrowth in the posterior palate.
abstract: BACKGROUND
  Mice lacking the activities of Dlx1 and Dlx2 (Dlx1/2-/-) exhibit cleft palate, one of the most common human congenital defects, but the etiology behind this phenotype has been unknown. Therefore, we analyzed the morphological, cellular, and molecular changes caused by inactivation of Dlx1 and Dlx2 as related to palate development.
  
  
  RESULTS
  Dlx1/2-/- mutants exhibited lack of vertical growth in the posterior palate during the earliest stage of palatogenesis. We attributed this growth deficiency to reduced cell proliferation. Expression of a cell cycle regulator Ccnd1 was specifically down-regulated in the same region. Previous studies established that the epithelial-mesenchymal signaling loop involving Shh, Bmp4, and Fgf10 is important for cell proliferation and tissue growth during palate development. This signaling loop was disrupted in Dlx1/2-/- palate. Interestingly, however, the decreases in Ccnd1 expression and mitosis in Dlx1/2-/- mutants were independent of this signaling loop. Finally, Dlx1/2 activity was required for normal expression of several transcription factor genes whose mutation results in palate defects.
  
  
  CONCLUSIONS
  The functions of Dlx1 and Dlx2 are crucial for the initial formation of the posterior palatal shelves, and that the Dlx genes lie upstream of multiple signaling molecules and transcription factors important for later stages of palatogenesis.
authors.affiliation: Department of Basic Science and Craniofacial Biology, New York University College of Dentistry, New York, NY 10010, USA. jj78@nyu.edu
authors.forename: Juhee
authors.initials: J
authors.lastname: Jeong
authors.forename: Jeffry
authors.initials: J
authors.lastname: Cesario
authors.forename: Yangu
authors.initials: Y
authors.lastname: Zhao
authors.forename: Lorel
authors.initials: L
authors.lastname: Burns
authors.forename: Heiner
authors.initials: H
authors.lastname: Westphal
authors.forename: John L R
authors.initials: JL
authors.lastname: Rubenstein
mesh_terms: D000818:Animals; D049109:Cell Proliferation; D002972:Cleft Palate / Q000378:metabolism*; D019938:Cyclin D1 / Q000235:genetics / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental / Q000235:genetics / Q000502:physiology; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D010159:Palate / Q000196:embryology* / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
chemical_list: C088334:Distal-less homeobox proteins; D018398:Homeodomain Proteins; D014157:Transcription Factors; D019938:Cyclin D1