GTPases RhoA and Rac1 are important for amelogenin and DSPP expression during differentiation of ameloblasts and odontoblasts |
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Authors: | Michelle Tillmann Biz Mara Rúbia Marques Virgínia Oliveira Crema Anselmo Sigari Moriscot Marinilce Fagundes dos Santos |
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Institution: | 1. Department of Cell and Developmental Biology, Institute of Biomedical Sciences, University of S?o Paulo, Av. Prof. Lineu Prestes 1524, S?o Paulo, SP, CEP 05508-000, Brazil 4. Department of Cell and Developmental Biology, Institute of Biomedical Sciences, University of S?o Paulo, Rua Apeninos 76 ap402, Florianópolis, SC, Brazil, CEP 88037-620 2. Morphology Department, Institute of Biology Sciences, Federal University of Goias, Goiania, GO, CEP 74001-970, Brazil 3. Department of Biological Sciences, Federal University of Triangulo Mineiro, P?a Manoel Terra 330, Uberaba, MG, CEP 38025-050, Brazil
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Abstract: | Morphogenesis and cytodifferentiation are distinct processes in tooth development. Cell proliferation predominates in morphogenesis;
differentiation involves changes in form and gene expression. The cytoskeleton is essential for both processes, being regulated
by Rho GTPases. The aim of this study was to verify the expression, distribution, and role of Rho GTPases in ameloblasts and
odontoblasts during tooth development in correlation with actin and tubulin arrangements and amelogenin and dentin sialophosphoprotein
(DSPP) expression. RhoA, Rac1, and Cdc42 were strongly expressed during morphogenesis; during cytodifferentiation, RhoA was
present in ameloblasts and odontoblasts, Rac1 and its effector Pak3 were observed in ameloblasts; and Cdc42 was present in
all cells of the tooth germ and mesenchyme. The expression of RhoA mRNA and its effectors RockI and RockII, Rac1 and Pak3,
as analyzed by real-time polymerase chain reaction, increased after ameloblast and odontoblast differentiation, according
to the mRNA expression of amelogenin and DSPP. The inhibition of all Rho GTPases by Clostridium difficile toxin A completely abolished amelogenin and DSPP expression in tooth germs cultured in anterior eye chamber, whereas the
specific inhibition of the Rocks showed only a partial effect. Thus, both GTPases are important during tooth morphogenesis.
During cytodifferentiation, Rho proteins are essential for the complete differentiation of ameloblasts and odontoblasts by
regulating the expression of amelogenin and DSPP. RhoA and its effector RockI contribute to this role. A specific function
for Rac1 in ameloblasts remains to be elucidated; its punctate distribution indicates its possible role in exocytosis/endocytosis. |
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