MMP20

The MMP20 gene provides instructions for making a protein called enamelysin, which is essential for normal tooth development. Enamelysin is involved in the formation of enamel, which is the hard, white material that forms the protective outer layer of each tooth. Enamel is composed mainly of mineral-containing crystals. These microscopic crystals are arranged in organized bundles that give enamel its strength and durability.

Certain proteins are needed to shape and organize the crystals as they form, but these proteins must be removed for enamel to harden normally. Enamelysin cuts (cleaves) other proteins involved in enamel formation, such as amelogenin and ameloblastin, into smaller pieces. Cleavage of these proteins makes them easier to remove when they are no longer needed.

amelogenesis imperfecta - caused by mutations in the MMP20 gene

At least two mutations in the MMP20 gene have been identified in people with an autosomal recessive form of amelogenesis imperfecta. Autosomal recessive inheritance means that two copies of the MMP20 gene in each cell are altered. Each of the known mutations alters a single DNA building block (base pair) in a critical region of the MMP20 gene, preventing cells from producing any functional enamelysin. Without this protein, amelogenin and other proteins are not cleaved properly during enamel formation. The resulting enamel is soft and has an abnormal crystal structure. Teeth with this defective enamel are abnormally rough, discolored, and prone to breakage.