Ameloblastin Explained

Ameloblastin (abbreviated AMBN and also known as sheathlin or amelin) is an enamel matrix protein that in humans is encoded by the AMBN gene.^[1]

Function

Ameloblastin is a specific protein found in tooth enamel. Although less than 5% of enamel consists of protein, ameloblastins constitute 5–10% of all enamel protein, making it the second most abundant enamel matrix protein.^[2] This protein is formed by ameloblasts during the early secretory to late maturation stages of amelogenesis. Although not completely understood, the function of ameloblastins is believed to be in controlling the elongation of enamel crystals and generally directing enamel mineralization during tooth development. Ameloblastin helps in the growth of a crystalline enameloid layer consisting of randomly oriented short enamel crystals.^[3] Ameloblastin cleavage products are found in the sheath space between rod and interrod enamel, while intact ameloblastin accumulates on the enamel rods. This difference in localization is thought to maintain the boundary between rod and interrod enamel.^[4]

Ameloblastin is generally implicated in enamel development, but may also have a role in root development. Other possible actions include bone remodeling and repair, although this function has yet to be definitively proven.

Other significant proteins in enamel are amelogenins, enamelins, and tuftelins.

Clinical significance

Mutations in AMBN cause amelogenesis imperfecta, a disease characterized by abnormal enamel formation resulting in discolored, pitted, or spotted enamel.^[5] These mutations are rare, and follow an autosomal recessive pattern of inheritance.

Further reading

• Bartlett JD, Simmer JP . Proteinases in developing dental enamel . Critical Reviews in Oral Biology and Medicine . 10 . 4 . 425–441 . 1999 . 10634581 . 10.1177/10454411990100040101 . free .
• MacDougall M, DuPont BR, Simmons D, Reus B, Krebsbach P, Kärrman C, Holmgren G, Leach RJ, Forsman K . 6 . Ameloblastin gene (AMBN) maps within the critical region for autosomal dominant amelogenesis imperfecta at chromosome 4q21 . Genomics . 41 . 1 . 115–118 . April 1997 . 9126491 . 10.1006/geno.1997.4643 .
• Kuroda S, Wazen R, Sellin K, Tanaka E, Moffatt P, Nanci A . Ameloblastin is not implicated in bone remodelling and repair . European Cells & Materials . 22 . 56–66; discussion 66–7 . July 2011 . 21761392 . 10.22203/eCM.v022a05 . free .
• Perdigão PF, Carvalho VM, DE Marco L, Gomez RS . Mutation of ameloblastin gene in calcifying epithelial odontogenic tumor . Anticancer Research . 29 . 8 . 3065–3067 . August 2009 . 19661317 .
• Tamburstuen MV, Reseland JE, Spahr A, Brookes SJ, Kvalheim G, Slaby I, Snead ML, Lyngstadaas SP . 6 . Ameloblastin expression and putative autoregulation in mesenchymal cells suggest a role in early bone formation and repair . Bone . 48 . 2 . 406–413 . February 2011 . 20854943 . 4469498 . 10.1016/j.bone.2010.09.007 .
• Toyosawa S, Fujiwara T, Ooshima T, Shintani S, Sato A, Ogawa Y, Sobue S, Ijuhin N . 6 . Cloning and characterization of the human ameloblastin gene . Gene . 256 . 1–2 . 1–11 . October 2000 . 11054529 . 10.1016/s0378-1119(00)00379-6 .
• Patir A, Seymen F, Yildirim M, Deeley K, Cooper ME, Marazita ML, Vieira AR . Enamel formation genes are associated with high caries experience in Turkish children . Caries Research . 42 . 5 . 394–400 . 2008 . 18781068 . 2820320 . 10.1159/000154785 .
• Lee SK, Krebsbach PH, Matsuki Y, Nanci A, Yamada KM, Yamada Y . Ameloblastin expression in rat incisors and human tooth germs . The International Journal of Developmental Biology . 40 . 6 . 1141–1150 . December 1996 . 9032019 .
• Niu CH, Li TJ . [Mutation and polymorphism of the ameloblastin gene in ameloblastomas] . zh . Zhonghua Kou Qiang Yi Xue Za Zhi = Zhonghua Kouqiang Yixue Zazhi = Chinese Journal of Stomatology . 41 . 11 . 678–681 . November 2006 . 17331365 .

Notes and References

1. Web site: Entrez Gene: Ameloblastin (enamel matrix protein).
2. Hu JC, Chun YH, Al Hazzazzi T, Simmer JP . Enamel formation and amelogenesis imperfecta . Cells Tissues Organs . 186 . 1 . 78–85 . 2007 . 17627121 . 10.1159/000102683 . 28367304 .
3. Pandya M, Diekwisch TG . Amelogenesis: Transformation of a protein-mineral matrix into tooth enamel . Journal of Structural Biology . 213 . 4 . 107809 . December 2021 . 34748943 . 8665087 . 10.1016/j.jsb.2021.107809 .
4. Bartlett JD . Dental enamel development: proteinases and their enamel matrix substrates . ISRN Dentistry . 2013 . 684607 . September 2013 . 24159389 . 3789414 . 10.1155/2013/684607 . free .
5. Poulter JA, Murillo G, Brookes SJ, Smith CE, Parry DA, Silva S, Kirkham J, Inglehearn CF, Mighell AJ . 6 . Deletion of ameloblastin exon 6 is associated with amelogenesis imperfecta . Human Molecular Genetics . 23 . 20 . 5317–5324 . October 2014 . 24858907 . 4168819 . 10.1093/hmg/ddu247 .