Possible Roles of Shh in Ameloblast differentiation

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The amiloide-sensitive epithelial sodium channel (ENaC) consisting of three subunits (α,β,γ) is an apical membrane protein which involves control of cell volume and mechano-transduction. These subunits are co-expressed in renal collecting duct and distal colon epithelium at equivalent levels. We have investigated their expression at mRNA level in the dental epithelium of the rat incisor, based on the differentiation stages. RT-PCR analysis demonstrated clear bands for three subunits mRNA in the samples obtained from the enamel organs of early and late maturation stages and secretory stage. Furthermore, in situ hybridization histochemistry and immunocytochemistry confirmed the region-specific expression of Alpha-and Gamma-ENac in the ameloblasts layer.Heat Schock proteins are expressed as chaperons by some cells living in physiological as well as stressful conditions. The Hsp90 functions in the pathways of numerous signal transducers, cell cycle and developmental regulators under normal growth conditions. Our immunocytochemical examinations showed its expression throughout the dental epithelium during the amelobalst-differentiation. Interestingly, intense exhibition for Hsp90-immunoreaction was found in the cytoplasm of cementoblasts on the newly-formed dentin close to the epithelial root sheath.Sonic hedgehog(Shh), a member of the mammalian hedge hog family, plays a key role during embryogenesis and organogenesis. Shh influences behavior and fate of cells located within its range of diffusion. We immunocytochemically investigated the distribution of Shh protein in the rat incisor. Abundant immunoreation for Shh was recognizable both in multi-layered stratum intermedium and its adjacent inner dental epithelium. Immunoreation became weak in the ameloblasts towards cervical regions. Furthermore, Shh-immunoreation was distributed in the mesenchyme close to inner dental epithelium in a gradient manner.