Amelogenin

Last updated
amelogenin, X-linked
Identifiers
Symbol AMELX
Alt. symbolsAMG, AIH1
NCBI gene 265
HGNC 461
OMIM 300391
RefSeq NM_001142
UniProt Q99217
Other data
Locus Chr. X p22.3-p22.1
Search for
Structures Swiss-model
Domains InterPro
amelogenin, Y-linked
Identifiers
Symbol AMELY
Alt. symbolsAMGL
NCBI gene 266
HGNC 462
OMIM 410000
RefSeq NM_001143
UniProt Q99218
Other data
Locus Chr. Y p11
Search for
Structures Swiss-model
Domains InterPro

Amelogenins are a group of protein isoforms produced by alternative splicing or proteolysis from the AMELX gene, on the X chromosome, and also the AMELY gene in males, on the Y chromosome. [1] They are involved in amelogenesis, the development of enamel. [2] Amelogenins are type of extracellular matrix protein, which, together with ameloblastins, enamelins and tuftelins, direct the mineralization of enamel to form a highly organized matrix of rods, interrod crystal and proteins.

Contents

Although the precise role of amelogenin(s) in regulating the mineralization process is unknown, it is known that amelogenins are abundant during amelogenesis. Developing human enamel contains about 70% protein, 90% of which are amelogenins.

Function

Amelogenins are believed to be involved in the organizing of enamel rods during tooth development. The latest research indicates that these proteins regulate the initiation and growth of hydroxyapatite crystals during the mineralization of enamel. In addition, amelogenins appear to aid in the development of cementum by directing cementoblasts to the tooth's root surface.

Variants

The amelogenin gene has been most widely studied in humans, where it is a single copy gene, located on the X and Y chromosomes at Xp22.1–Xp22.3 and Yp 11.2 [5]. [3] The amelogenin gene's location on sex chromosomes has implications for variability both between the X chromosome form (AMELX) and the Y chromosome form (AMELY), and between alleles of AMELY among different populations. This is because AMELY exists in the non-recombining region of chromosome Y, effectively isolating it from normal selection pressures. Other sources of amelogenin variation arise from the various isoforms of AMELX obtained from alternative splicing of mRNA transcripts. Specific roles for isoforms have yet to be established. Among other organisms, amelogenin is well conserved among eutherians, and has homologs in monotremes, reptiles and amphibians.

Application in sex determination

Differences between the X chromosome and Y chromosome versions of the amelogenin gene (AMELX and AMELY respectively) enable it to be used in sex determination of unknown human samples. AMELX’s intron 1 contains a 6-base-pair deletion relative to intron 1 of AMELY. This can be detected at low cost using polymerase chain reaction (PCR) of intron 1, followed by gel electrophoresis. Two bands of DNA, at 555 bps and 371 bps, are resolved if both the AMELX and AMELY versions of the gene are present (i.e. the sample is from a male) or one band of DNA, at 555 bps, if the AMELX version only is present (i.e. the sample is from a female). [4]

However, because of AMELY variation among individuals and populations, this method of sex determination is not 100% accurate. Mutation in regions of AMELY intron 1 commonly used as primer annealing sites may disable PCR amplification. A 6bp insertion to AMELY intron 1 results in an amplicon identical in length to that of AMELX. In some males AMELY may be deleted entirely. In any of these cases only one band is visualized during gel electrophoresis of PCR products, causing misidentification of the sample as female. [4] The misidentification rate may vary among populations, but in general appears to be low. In one study in Spain, the amelogenin sex determination test using AMELX (977bps) and AMELY (790bps) bands was performed for 1224 individuals of known gender with a 99.84% (1222/1224) accuracy rate. [5] Another study in India, however, found 5 of its 270 men studied (1.85%) possessed an AMELY deletion, terming them "deleted-amelogenin males" (DAMs). In response the authors suggested that while the amelogenin sex test may be accurate in general, other Y chromosome markers such as SRY, STR, or 50f2 can be used for less ambiguous gender identification. [6]

Clinical significance

Mutations in AMELX can cause amelogenesis imperfecta, a disorder of tooth enamel development. [7]

Related Research Articles

<span class="mw-page-title-main">Ameloblast</span>

Ameloblasts are cells present only during tooth development that deposit tooth enamel, which is the hard outermost layer of the tooth forming the surface of the crown.

<span class="mw-page-title-main">Y linkage</span> Traits produced by genes located on the Y chromosome

Y linkage, also known as holandric inheritance, describes traits that are produced by genes located on the Y chromosome. It is a form of sex linkage.

<span class="mw-page-title-main">Enamelin</span> Mammalian protein found in Homo sapiens

Enamelin is an enamel matrix protein (EMPs), that in humans is encoded by the ENAM gene. It is part of the non-amelogenins, which comprise 10% of the total enamel matrix proteins. It is one of the key proteins thought to be involved in amelogenesis. The formation of enamel's intricate architecture is thought to be rigorously controlled in ameloblasts through interactions of various organic matrix protein molecules that include: enamelin, amelogenin, ameloblastin, tuftelin, dentine sialophosphoprotein, and a variety of enzymes. Enamelin is the largest protein (~168kDa) in the enamel matrix of developing teeth and is the least abundant of total enamel matrix proteins. It is present predominantly at the growing enamel surface.

<span class="mw-page-title-main">Ameloblastin</span> Protein-coding gene in the species Homo sapiens

Ameloblastin is an enamel matrix protein that in humans is encoded by the AMBN gene.

<span class="mw-page-title-main">Tuftelin</span> Protein-coding gene in the species Homo sapiens

Tuftelin is an acidic phosphorylated glycoprotein found in tooth enamel. In humans, the Tuftelin protein is encoded by the TUFT1 gene. It is an acidic protein that is thought to play a role in dental enamel mineralization and is implicated in caries susceptibility. It is also thought to be involved with adaptation to hypoxia, mesenchymal stem cell function, and neurotrophin nerve growth factor mediated neuronal differentiation.

<span class="mw-page-title-main">Enamel organ</span> Aggregate of cells involved in tooth development

The enamel organ, also known as the dental organ, is a cellular aggregation seen in a developing tooth and it lies above the dental papilla. The enamel organ which is differentiated from the primitive oral epithelium lining the stomodeum. The enamel organ is responsible for the formation of enamel, initiation of dentine formation, establishment of the shape of a tooth's crown, and establishment of the dentoenamel junction.

<span class="mw-page-title-main">Dentinogenesis imperfecta</span> Medical condition

Dentinogenesis imperfecta (DI) is a genetic disorder of tooth development. It is inherited in an autosomal dominant pattern, as a result of mutations on chromosome 4q21, in the dentine sialophosphoprotein gene (DSPP). It is one of the most frequently occurring autosomal dominant features in humans. Dentinogenesis imperfecta affects an estimated 1 in 6,000-8,000 people.

<span class="mw-page-title-main">AMELY</span> Protein-coding gene in humans

Amelogenin, Y isoform is a protein that in humans is encoded by the AMELY gene. AMELY is located on the Y chromosome and encodes a form of amelogenin. Amelogenin is an extracellular matrix protein involved in biomineralization during tooth enamel development.

Multiplex ligation-dependent probe amplification (MLPA) is a variation of the multiplex polymerase chain reaction that permits amplification of multiple targets with only a single primer pair. It detects copy number changes at the molecular level, and software programs are used for analysis. Identification of deletions or duplications can indicate pathogenic mutations, thus MLPA is an important diagnostic tool used in clinical pathology laboratories worldwide.

<span class="mw-page-title-main">AMELX</span> Protein-coding gene in humans

Amelogenin, X isoform is a protein that in humans is encoded by the AMELX gene. AMELX is located on the X chromosome and encodes a set of isoforms of amelogenin by alternative splicing. Amelogenin is an extracellular matrix protein involved in the process of amelogenesis, the formation of enamel on teeth.

<span class="mw-page-title-main">KLK4</span> Mammalian protein found in Homo sapiens

Kallikrein-related peptidase 4 is a protein which in humans is encoded by the KLK4 gene.

<span class="mw-page-title-main">BCL9</span> Protein-coding gene in the species Homo sapiens

B-cell CLL/lymphoma 9 protein is a protein that in humans is encoded by the BCL9 gene.

<span class="mw-page-title-main">MMP20</span>

Matrix metalloproteinase-20 (MMP-20) also known as enamel metalloproteinase or enamelysin is an enzyme that in humans is encoded by the MMP20 gene.

Dentin sialophosphoprotein is a precursor protein for other proteins found in the teeth. It is produced by cells (odontoblasts) inside the teeth, and in smaller quantities by bone tissues. It is required for normal hardening (mineralisation) of teeth. During teeth development, it is broken down into three proteins such as dentin sialoprotein (DSP), dentin glycoprotein (DGP), and dentin phosphoprotein (DPP). These proteins become the major non-collagenous components of teeth. Their distribution in the collagen matrix of the forming dentin suggests these proteins play an important role in the regulation of mineral deposition. Additional evidence for this correlation is phenotypically manifested in patients with mutant forms of dentin sialophosphoprotein. Such patients suffer dental anomalies including type III dentinogenesis imperfecta.

<span class="mw-page-title-main">FAM83H</span> Protein-coding gene in the species Homo sapiens

FAM83H is a protein, which in humans is encoded by the FAM83H gene. The protein is also known as uncharacterized protein FAM83H. FAM83H is targeted for the nucleus. It is predicted to play a role in the structural development and calcification of tooth enamel.

<span class="mw-page-title-main">Amelogenesis imperfecta</span> Genetic disorder resulting in abnormal enamel

Amelogenesis imperfecta (AI) is a congenital disorder which presents with a rare abnormal formation of the enamel or external layer of the crown of teeth, unrelated to any systemic or generalized conditions. Enamel is composed mostly of mineral, that is formed and regulated by the proteins in it. Amelogenesis imperfecta is due to the malfunction of the proteins in the enamel as a result of abnormal enamel formation via amelogenesis.

<span class="mw-page-title-main">FAM20A</span> Protein-coding gene in the species Homo sapiens

FAM20A is a protein that in humans is encoded by the FAM20A gene.

<span class="mw-page-title-main">Kohlschütter-Tönz syndrome</span> Medical condition

Kohlschütter-Tönz syndrome (KTS), also called amelo-cerebro-hypohidrotic syndrome, is a rare inherited syndrome characterized by epilepsy, psychomotor delay or regression, intellectual disability, and yellow teeth caused by amelogenesis imperfecta. It is a type A ectodermal dysplasia.

<span class="mw-page-title-main">Tricho–dento–osseous syndrome</span> Medical condition

Tricho–dento–osseous syndrome (TDO) is a rare, systemic, autosomal dominant genetic disorder that causes defects in hair, teeth, and bones respectively. This disease is present at birth. TDO has been shown to occur in areas of close geographic proximity and within families; most recent documented cases are in Virginia, Tennessee, and North Carolina. The cause of this disease is a mutation in the DLX3 gene, which controls hair follicle differentiation and induction of bone formation. All patients with TDO have two co-existing conditions called enamel hypoplasia and taurodontism in which the abnormal growth patterns of the teeth result in severe external and internal defects. The hair defects are characterized as being rough, course, with profuse shedding. Hair is curly and kinky at infancy but later straightens. Dental defects are characterized by dark-yellow/brownish colored teeth, thin and/or possibly pitted enamel, that is malformed. The teeth can also look normal in color, but also have a physical impression of extreme fragility and thinness in appearance. Additionally, severe underbites where the top and bottom teeth fail to correctly align may be present; it is common for the affected individual to have a larger, more pronounced lower jaw and longer bones. The physical deformities that TDO causes become more noticeable with age, and emotional support for the family as well as the affected individual is frequently recommended. Adequate treatment for TDO is a team based approach, mostly involving physical therapists, dentists, and oromaxillofacial surgeons. Genetic counseling is also recommended.

<span class="mw-page-title-main">Sodium/potassium/calcium exchanger 4</span> Protein-coding gene in the species Homo sapiens

Sodium/potassium/calcium exchanger 4 also known as solute carrier family 24 member 4 is a protein that in humans is encoded by the SLC24A4 gene.

References

  1. Bansal, Ajay Kumar; Shetty, Devi Charan; Bindal, Ruchi; Pathak, Aparna (2012). "Amelogenin: A novel protein with diverse applications in genetic and molecular profiling". Journal of Oral and Maxillofacial Pathology. 16 (3): 395–399. doi: 10.4103/0973-029X.102495 . ISSN   0973-029X. PMC   3519216 . PMID   23248473.
  2. Amelogenin at the U.S. National Library of Medicine Medical Subject Headings (MeSH)
  3. Nakahori Y, Takenaka O, Nakagome Y (1991). "A human X-Y homologous region encodes "amelogenin"". Genomics. 9 (2): 264–9. doi:10.1016/0888-7543(91)90251-9. PMID   2004775.
  4. 1 2 Kashyap VK, Sahoo S, Sitalaximi T, Trivedi R (2006). "Deletions in the Y-derived amelogenin gene fragment in the Indian population". BMC Med Genet. 7: 37. doi: 10.1186/1471-2350-7-37 . PMC   1458324 . PMID   16603093.
  5. Francès F, Portolés O, González JI, Coltell O, Verdú F, Castelló A, Corella D (2007). "Amelogenin test: From forensics to quality control in clinical and biochemical genomics". Clin Chim Acta. 386 (1–2): 53–6. doi:10.1016/j.cca.2007.07.020. PMID   17716640.
  6. Thangaraj K, Reddy AG, Singh L (2002). "Is the amelogenin gene reliable for sex identification in forensic casework and prenatal diagnosis?". Int J Legal Med. 116 (2): 121–3. doi:10.1007/s00414-001-0262-y. PMID   12056520. S2CID   33160466.
  7. Wright JT (December 2006). "The molecular etiologies and associated phenotypes of amelogenesis imperfecta". American Journal of Medical Genetics Part A. 140 (23): 2547–55. doi:10.1002/ajmg.a.31358. PMC   1847600 . PMID   16838342.