title: Multi-layered hypertrophied MEE formation by microtubule disruption via GEF-H1/RhoA/ROCK signaling pathway.
abstract: BACKGROUND
  Formation of the secondary palate is complex and disturbance during palatal fusion may result in cleft palate. The processes of adhesion, intercalation, and disappearance of medial edge epithelia (MEE) are characterized by morphological changes requiring dynamic cytoskeletal rearrangement. Microtubules are one of the cytoskeletal elements involved in maintenance of cell morphology. Microtubule-disrupting drugs have been reported to cause craniofacial malformations including cleft palate. The mechanisms underlying the failure of palatal fusion remain poorly understood. We evaluated the effect of nocodazole (NDZ), a drug that disrupts microtubules, on palatal fusion in organ culture.
  
  
  RESULTS
  NDZ caused failure of palatal fusion due to the induction of a multi-layered hypertrophied MEE in the mid-region of the secondary palatal shelves. Microtubule disruption increased RhoA activity and stress fiber formation. Pharmacological inhibition of the RhoA/ROCK pathway blocked multi-layered MEE formation. Partial prevention of hypertrophied MEE was observed with Y27632 and cytochalasin, but not with blebbistatin. NDZ induced re-localization of GEF-H1 into cytoplasm from cell-cell junctions.
  
  
  CONCLUSIONS
  The present study provided evidence that the GEF-H1/RhoA/ROCK pathway plays a pivotal role in linking microtubule disassembly to the remodeling of the actin cytoskeleton, which resulted in a multi-layered hypertrophied MEE and failure of palatal fusion.
authors.affiliation: Department of Oral Biological and Medical Sciences, Faculty of Dentistry, University of British Columbia, Vancouver, British Columbia, Canada.
authors.forename: Yukiko
authors.initials: Y
authors.lastname: Kitase
authors.forename: Charles F
authors.initials: CF
authors.lastname: Shuler
mesh_terms: D000818:Animals; D015153:Blotting, Western; D049109:Cell Proliferation / Q000187:drug effects; D005260:Female; D005455:Fluorescent Antibody Technique; D020662:Guanine Nucleotide Exchange Factors; D006984:Hypertrophy; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008870:Microtubules / Q000187:drug effects / Q000378:metabolism; D015739:Nocodazole / Q000494:pharmacology; D009924:Organ Culture Techniques; D010159:Palate / Q000187:drug effects / Q000196:embryology / Q000378:metabolism; D011247:Pregnancy; D011518:Proto-Oncogene Proteins; D060888:Real-Time Polymerase Chain Reaction; D064067:Rho Guanine Nucleotide Exchange Factors; D015398:Signal Transduction / Q000187:drug effects; D016212:Transforming Growth Factor beta / Q000235:genetics / Q000378:metabolism; D020742:rhoA GTP-Binding Protein / Q000235:genetics / Q000378:metabolism*
chemical_list: C577402:Arhgef2 protein, mouse; D020662:Guanine Nucleotide Exchange Factors; D011518:Proto-Oncogene Proteins; D064067:Rho Guanine Nucleotide Exchange Factors; D016212:Transforming Growth Factor beta; D020742:rhoA GTP-Binding Protein; D015739:Nocodazole