Amtn, also known as amelotin, is a secreted protein specialized for enamel biomineralization. It plays a crucial role in the maturation stage of amelogenesis, and is localized at the interface between the enamel surface and the apical surface of ameloblasts, as well as in the junctional epithelium of gingiva [1,2,3,4,5]. It may be involved in the attachment between the junctional epithelium and tooth enamel, and its expression is regulated by various factors such as microRNAs, inflammatory cytokines, and SNAI2 [2,3,5]. Genetic models, like knockout mice, are valuable for studying its function.

In Amtn -/- mice, the mandibular incisors were chalky-white and chipped. Micro-computed tomography showed a delay in enamel maturation compared to wild-type mice. The Knoop hardness of the outer enamel was significantly reduced relative to the wild-type, and was not as hard as the middle or inner enamel. This indicates that Amtn is necessary for proper enamel maturation [1].

In conclusion, Amtn is essential for the proper maturation of dental enamel. The study of Amtn knockout mouse models has provided important insights into its role in enamel formation, highlighting its significance in maintaining the integrity and hardness of enamel, which is relevant to understanding enamel-related diseases such as amelogenesis imperfecta [1,4].

References:

1. Núñez, Stephanie M, Chun, Yong-Hee P, Ganss, Bernhard, Hu, Jan C-C, Simmer, James P. 2015. Maturation stage enamel malformations in Amtn and Klk4 null mice. In Matrix biology : journal of the International Society for Matrix Biology, 52-54, 219-233. doi:10.1016/j.matbio.2015.11.007. https://pubmed.ncbi.nlm.nih.gov/26620968/

2. Yamazaki-Takai, Mizuho, Takai, Hideki, Iwai, Yasunobu, Nakayama, Yohei, Ogata, Yorimasa. 2020. MiR-200b suppresses TNF-α-induced AMTN production in human gingival epithelial cells. In Odontology, 109, 403-410. doi:10.1007/s10266-020-00555-3. https://pubmed.ncbi.nlm.nih.gov/32980912/

3. Nakayama, Yohei, Tsuruya, Yuto, Noda, Keisuke, Ganss, Bernhard, Ogata, Yorimasa. 2018. Negative feedback by SNAI2 regulates TGFβ1-induced amelotin gene transcription in epithelial-mesenchymal transition. In Journal of cellular physiology, 234, 11474-11489. doi:10.1002/jcp.27804. https://pubmed.ncbi.nlm.nih.gov/30488439/

4. Gasse, B, Silvent, J, Sire, J-Y. 2012. Evolutionary analysis suggests that AMTN is enamel-specific and a candidate for AI. In Journal of dental research, 91, 1085-9. doi:10.1177/0022034512460551. https://pubmed.ncbi.nlm.nih.gov/22968158/

5. Nakayama, Yohei, Takai, Hideki, Matsui, Sari, Ganss, Bernhard, Ogata, Yorimasa. . Proinflammatory cytokines induce amelotin transcription in human gingival fibroblasts. In Journal of oral science, 56, 261-8. doi:. https://pubmed.ncbi.nlm.nih.gov/25500923/