AMELOGENIN    

Content:

1. Function/Mechanism

2. Crystal Structure

3. Human Disease

4. Biomedical Applications

Function/Mechanism 

Amelogenin is a signaling protein found in developing tooth enamel, and it belongs to a family of extracellular matrix (ECM) proteins. Developing enamel contains about 30% protein, and 90% of this is amelogenins. The ability of amelogenin to promote the nucleation and growth of calcium phosphate was studied in an in vitro system involving metastable supersaturated solutions, but the mechanism is not well understood (Barbara J. Tarasevich et al, 2008).

The most abundant protein of forming enamel is amelogenin (Snead, ML. 2003).

Tooth enamel development is your teeth's first line of defense against corrosive bacteria and the constant pounding and stresses that come with chewing. Strong as it is, enamel is also brittle. What keeps it from shattering is an underlying protein-rich layer of dentin, a softer, more compliant substance that acts like a shock absorber (Alexandra Goho, 2005).

Crystal Structure

Enamel crystals are some of the most astounding structures in nature featuring extremely long and parallel organized hydroxyapatite crystals organized in bundles which are called prisms. Rows of enamel prisms are often organized perpendicular to each other

    The first step in in-vitro enamel production is the cooperative formation of composite nanospheres of nanocrystallite apatite and amelogenin. The composite nanoparticles then aggregated into nanorods that are about 50 nm in diameter and 250 nm long. The nanorods, in turn, further assembled to form organized, elongated crystals that began to resemble biological enamel.

Human Disease

 Amelogenesis imperfecta, (AI), is a group of inherited disorders with defective tooth enamel formation caused by various gene mutations. One suggested mechanism for the disease is a 9-bp deletion in exon 2 of the amelogenin gene (AMGX) causing X-linked hypoplastic amelogenesis imperfecta.  Also, mutations in AMELX can cause amelogenesis imperfecta.

Amelogenesis imperfecta is also inherited in an autosomal recessive pattern; this form of the disorder can result from mutations in the ENAM or MMP20 gene.  (Gopinath, VK et all, 2008)

Biomedical Applications

Sex determination:

Gender identification (sex-typing) is commonly performed in conjunction with STR typing kit using PCR products generated from the amelogenin gene that occurs on both the X- and Y-chromosome.

Development of Emdogain:

Emdogain is a recently introduced product that fools the body into forming new bone, cementum, and attachment fibers. Technically, it is enamel matrix proteins (amelogenins) that are taken from developing teeth in pigs.  The cell-adhesive activity of amelogenin may play a role in development and may provide a partial explanation for the therapeutic effects of Emdogain in periodontal regeneration (A.M. Hoang et al, 2002).

Root Reabsorption Prevention:

Root Reabsorption is generally related to trauma or a tooth that has been re-implanted. It is also sometimes seen in teeth that have been moved by orthodontics. However, it can happen within a tooth for no apparent reason, and unfortunately the prognosis for a tooth with this problem is was very poor, until now.  Dentists in Japan discovered that amelogenin may help suppress root reapasorption (Yagi Y et al, 2009).