title: Characterization of the inner enamel epithelium in the enamel-free area based on the ability to secrete enamel protein demonstrated by in situ hybridization and immunohistochemistry.
abstract: Both the expression of amelogenin mRNA and secretion of amelogenin were investigated in rat molars by in situ hybridization and immunohistochemistry. Probes were designed by multiple-labeling of oligonucleotide probes for in situ hybridization. Amelogenin mRNA first appeared in differentiating ameloblasts of the distal region and some inner enamel epithelial cells of enamel-free area (EFA cells) of the second cusp at postnatal day 0. At the same time, amelogenin protein was detected in the extracellular matrix between dentin and differentiating ameloblasts and in some EFA cells of the second cusp. At postnatal day 1-3, amelogenin was expressed in the secretory ameloblasts, and in the matrix beneath these cells. Both amelogenin mRNA and amelogenin were detected in the EFA cells and their extracellular matrix. After postnatal day 5, amelogenin mRNA and amelogenin were detected in the secretory ameoloblasts and extracellular matrix in the enamel-forming region, respectively. At this time, amelogenin mRNA was not detected in the EFA cells, but a small amount of amelogenin was found in the matrix beneath the EFA cells. These findings suggest that EFA cells differentiate into amelogenin-secreting cells, i.e. ameloblasts, but that the secretion lasts for only a short period at the early stage of tooth development.
authors.affiliation: Department of Oral Anatomy, School of Dentistry, Iwate Medical University, Morioka, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Yamamoto
authors.forename: J
authors.initials: J
authors.lastname: Sasaki
authors.forename: J
authors.initials: J
authors.lastname: Matsuura
authors.forename: T
authors.initials: T
authors.lastname: Nomura
authors.forename: E F
authors.initials: EF
authors.lastname: Sato
authors.forename: H
authors.initials: H
authors.lastname: Shimokawa
authors.forename: K
authors.initials: K
authors.lastname: Ishizeki
authors.forename: T
authors.initials: T
authors.lastname: Nawa
mesh_terms: D053523:Amelogenin; D000818:Animals; D000831:Animals, Newborn; D001483:Base Sequence; D003746:Dental Enamel Proteins / Q000235:genetics / Q000378:metabolism*; D004658:Enamel Organ / Q000166:cytology / Q000378:metabolism*; D004848:Epithelium / Q000378:metabolism; D005109:Extracellular Matrix / Q000378:metabolism; D005260:Female; D007124:Immunoenzyme Techniques; D017403:In Situ Hybridization; D008963:Molar / Q000378:metabolism*; D008969:Molecular Sequence Data; D011247:Pregnancy; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D053523:Amelogenin; C507201:Amelx protein, rat; D003746:Dental Enamel Proteins; D012333:RNA, Messenger