Ameloblastin

Ameloblastin (abbreviated AMBN and also known as sheathlin or amelin) is an enamel matrix protein that in humans is encoded by the AMBN gene.^[5]

AMBN
Identifiers
Aliases	AMBN, AI1F, Sheathlin, ameloblastin
External IDs	OMIM: 601259; MGI: 104655; HomoloGene: 7625; GeneCards: AMBN; OMA:AMBN - orthologs
Gene location (Human) Chr. Chromosome 4 (human)[1] Band 4q13.3 Start 70,592,256 bp[1] End 70,607,288 bp[1]
Gene location (Mouse) Chr. Chromosome 5 (mouse)[2] Band 5 E1|5 43.63 cM Start 88,603,850 bp[2] End 88,616,390 bp[2]
RNA expression pattern Bgee Human Mouse (ortholog) Top expressed in testicle putamen caudate nucleus gonad nucleus accumbens islet of Langerhans Epithelium of choroid plexus ventricular zone prefrontal cortex mesencephalon Top expressed in molar membranous bone maxilla sexually immature organism mandible inner enamel epithelium fossa lumbar subsegment of spinal cord incisor dermis More reference expression data BioGPS n/a
Gene ontology Molecular function structural constituent of tooth enamel growth factor activity protein binding Cellular component extracellular region endoplasmic reticulum lumen Biological process odontogenesis of dentin-containing tooth biomineral tissue development cell adhesion cell population proliferation post-translational protein modification regulation of signaling receptor activity regulation of cell population proliferation signal transduction Sources:Amigo / QuickGO
Orthologs Species Human Mouse Entrez 258 11698 Ensembl ENSG00000178522 ENSMUSG00000029288 UniProt Q9NP70 O55189 RefSeq (mRNA) NM_016519 NM_009664 NM_001303431 RefSeq (protein) NP_057603 NP_001290360 NP_033794 Location (UCSC) Chr 4: 70.59 – 70.61 Mb Chr 5: 88.6 – 88.62 Mb PubMed search [3] [4]
Wikidata
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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.^[6] 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.^[7] 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.^[6][8]

Ameloblastin is generally implicated in enamel development, but may also have a role in root development.^[6] Other possible actions include bone remodeling and repair, although this function has yet to be definitively proven.^[6]

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.^[9] These mutations are rare, and follow an autosomal recessive pattern of inheritance.^[6]