Full-length Sequence, Localization, and Chromosomal Mapping of Ameloblastin

Krebsbach, Paul H.; Lee, Suk Keun; Matsuki, Yutaka; Kozak, Christine A.; Yamada, Kenneth M.; Yamada, Yoshihiko

doi:10.1074/jbc.271.8.4431

Cited by 287 publications

(227 citation statements)

References 27 publications

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“…35 Ameloblastin was cloned from an enamel protein in rat incisor tooth germs. 4,7,18 Sheathlin, considered to be part of the same protein as ameloblastin, was recently cloned from porcine tooth germs. 16 An immunohistochemical study using antibodies that recognize different regions of that protein showed that sheathlin is synthesized by ameloblasts and secreted into the immature enamel matrix with posttranslational and postsecretory modifications and that cleaved NH 2 -terminal polypeptides concentrate in the prism sheath.…”

Section: Discussionmentioning

confidence: 99%

Biochemical and Immunohistochemical Characterization of the Amyloid in Canine Amyloid-Producing Odontogenic Tumor

Hirayama

Miyasho

Ohmachi³

et al. 2010

Vet Pathol

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The amyloid of canine amyloid-producing odontogenic tumor (APOT) was evaluated biochemically and immunohistochemically. The N-terminal amino-acid sequence of purified amyloid protein from a canine APOT was strikingly similar to the sequence in both rat ameloblastin and porcine sheathlin. Immunohistochemically, the amyloid in APOT from 9 dogs was strongly reactive with anti-rat ameloblastin, anti-porcine sheathlin, and anti-canine APOT amyloid and weakly reactive with anti-porcine amelogenin but negative for antibodies to cytokeratins, vimentin, desmin, a-smooth muscle actin, amyloid A, glial fibrillary acidic protein, or S100 protein. The neoplastic epithelial cells of APOT were focally reactive with antibodies to ameloblastin, sheathlin, amelogenin, and canine APOT amyloid. The similarity in amino-acid sequence of the amyloid protein of canine APOT to that of enamel proteins, such as ameloblastin, sheathlin, and amelogenin, and the expression of these antigens in both APOT amyloid and in the neoplastic cells suggest that the amyloid of canine APOT is derived from enamel proteins secreted by ameloblasts. Keywords ameloblasts, amyloid, dogs, enamel proteins, odontogenic tumorAmyloidosis is a heterogeneous group of disorders characterized by the deposition of amyloid proteins derived from any of at least 25 different precursor molecules. Amyloid is considered a pathologic substance that appears histologically as an extracellular, amorphous, congophilic protein with applegreen birefringence under polarized light. Amyloidosis can be categorized as systemic or localized. Common human types of localized amyloidosis include amyloidosis of endocrine organs associated (or not) with neoplastic conditions and cerebral amyloidosis of Alzheimer's disease. 21,51 Localized amyloid deposits with or without association with neoplasia also have been described in the human mammary gland, 41,52 respiratory tract, 26,34 gastrointestinal tract, 5,38 genitourinary tract, 13,17 skin, 24,25 and bone. 23 In animals, localized amyloidosis has been associated with neoplastic conditions such as calcifying epithelial odontogenic tumor (CEOT), 2,29 pancreatic endocrine tumor, 28 medullary thyroid carcinoma, 15 ameloblastoma, 10 mammary carcinoma, 43 intestinal carcinoid, 40 extramedullary plasmacytoma, 31,36 and myeloma. 12 CEOT is a rare neoplasm of the tooth-forming apparatus that produces a mineralized substance and amyloid. 30 The origin of the amyloid in human and animal CEOT is often debated but is still unknown. 2,19,27,29,37,42,46 Recent studies indicate that the amyloid in human CEOT is secreted by the neoplastic epithelial cells, but its precise nature remains unclear. 27,39,42 CEOT in veterinary medicine is classified as amyloidproducing odontogenic tumor (APOT). 9,14 In the present study, we partially sequenced the amino acids of the major amyloid protein of canine APOT and compared the amino-terminal sequence with that of the enamel proteins rat ameloblastin and porcine sheathlin, which are transcribed in cells of the epi...

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Section: Discussionmentioning

confidence: 99%

Biochemical and Immunohistochemical Characterization of the Amyloid in Canine Amyloid-Producing Odontogenic Tumor

Hirayama

Miyasho

Ohmachi³

et al. 2010

Vet Pathol

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“…During the secretory stage, ameloblasts secrete mostly amelogenin, enamelin and ameloblastin (Hu et al, 1997a;Hu et al, 1997b;Krebsbach et al, 1996;Snead et al, 1985). These proteins catalyze the extension of ribbon-like enamel crystallites comprised of the mineral calcium hydroxyapatite.…”

Section: Dental Enamel Formationmentioning

confidence: 99%

Functions of KLK4 and MMP-20 in dental enamel formation

Papagerakis²,

Yamakoshi

et al. 2008

BCHM

221

190

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Two proteases are secreted into the enamel matrix of developing teeth. The early protease is enamelysin . The late protease is kallikrein 4 (KLK4). Mutations in MMP20 and KLK4 both cause autosomal recessive amelogenesis imperfecta, a condition featuring soft, porous enamel containing residual protein. MMP-20 is secreted along with enamel proteins by secretory stage ameloblasts. Enamel protein cleavage products accumulate in the space between the crystal ribbons, helping to support them. MMP-20 steadily cleaves accumulated enamel proteins, so their concentration decreases with depth. Kallikrein 4 is secreted by transition and maturation stage ameloblasts. KLK4 aggressively degrades the retained organic matrix following the termination of enamel protein secretion. The principle functions of MMP-20 and KLK4 in dental enamel formation are to facilitate the orderly replacement of organic matrix with mineral, generating an enamel layer that is harder, less porous, and unstained by retained enamel proteins.

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“…The major secretory stage enamel proteins are amelogenin (21,22), ameloblastin (23)(24)(25), and enamelin (26,27). These proteins function specifically during enamel formation, and the disease phenotypes exhibited by mice lacking these genes are confined to the developing teeth and include enamel agenesis (28 -30).…”

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Hypomaturation Enamel Defects in Klk4 Knockout/LacZ Knockin Mice

Simmer

Lertlam

et al. 2009

Journal of Biological Chemistry

135

184

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Kallikrein 4 (Klk4) is believed to play an essential role in enamel biomineralization, because defects in KLK4 cause hypomaturation amelogenesis imperfecta. We used gene targeting to generate a knockin mouse that replaces the Klk4 gene sequence, starting at the translation initiation site, with a lacZ reporter gene. Correct targeting of the transgene was confirmed by Southern blot and PCR analyses. Histochemical X-gal (5-bromo-4-chloro-3-indolyl-␤-D-galactopyranoside) staining demonstrated expression of ␤-galactosidase in maturation stage ameloblasts. No X-gal staining was observed in secretory stage ameloblasts or in odontoblasts. Retained enamel proteins were observed in the maturation stage enamel of the Klk4 null mouse, but not in the Klk4 heterozygous or wild-type mice. The enamel layer in the Klk4 null mouse was normal in thickness and contained decussating enamel rods but was rapidly abraded following weaning, despite the mice being maintained on soft chow. In function the enamel readily fractured within the initial rod and interrod enamel above the parallel enamel covering the dentinoenamel junction. Despite the lack of Klk4 and the retention of enamel proteins, significant levels of crystal maturation occurred (although delayed), and the enamel achieved a mineral density in some places greater than that detected in bone and dentin. An important finding was that individual enamel crystallites of erupted teeth failed to grow together, interlock, and function as a unit. Instead, individual crystallites seemed to spill out of the enamel when fractured. These results demonstrate that Klk4 is essential for the removal of enamel proteins and the proper maturation of enamel crystals.Dental enamel is composed of highly ordered, very long crystals of calcium hydroxyapatite (Ca 10 (PO 4 ) 6 (OH) 2 ). Mature enamel crystallites are about 70 nm wide and 30 nm thick, but are of unmeasurable length (1), probably extending all the way from the dentin layer to the surface of the tooth (2). Enamel crystallites are organized into bundles called rods, with about 10,000 parallel crystals in a rod (3). Each enamel rod is the product of a single ameloblast, the cell type that forms a continuous sheet over the developing enamel and orchestrates its formation. Dental enamel of erupted teeth is ϳ95% mineral (by weight) (4), with most of the non-mineral component being water. Protein comprises Ͻ1% of its weight. Forming enamel, however, is over 30% protein (5). Much of the protein is reabsorbed by ameloblasts and degraded in lysosomes (6, 7), but extracellular proteases also play a role in matrix protein removal (8 -10).Dental enamel formation is divided into secretory, transition, and maturation stages (11,12). During the secretory stage, enamel crystals grow primarily in length. As the crystals extend, the enamel layer expands. Enamel crystallites lengthen along a mineralization front at the secretory surface of the ameloblast cell membrane. There, mineral deposits rapidly on the crystallite tips, and very slowly on their sides...

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Full-length Sequence, Localization, and Chromosomal Mapping of Ameloblastin

Cited by 287 publications

References 27 publications

Biochemical and Immunohistochemical Characterization of the Amyloid in Canine Amyloid-Producing Odontogenic Tumor

Biochemical and Immunohistochemical Characterization of the Amyloid in Canine Amyloid-Producing Odontogenic Tumor

Functions of KLK4 and MMP-20 in dental enamel formation

Hypomaturation Enamel Defects in Klk4 Knockout/LacZ Knockin Mice

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