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Conditional knockout of transient receptor potential melastatin 7 in the enamel epithelium: Effects on enamel
Masashi Shin1,2, Aya Matsushima1, Hiroshi Kajiya1,2
1Section of Cellular Physiology, Department of Physiological Science and Molecular Biology, Fukuoka Dental College, Fukuoka, Japan.
Abstract:
Transient receptor potential melastatin 7 (TRPM7) is a unique ion channel connected to a kinase domain. We previously demonstrated that Trpm7 expression is high in mouse ameloblasts and odontoblasts, and that amelogenesis is impaired in TRPM7 kinase-dead mice. Here, we analyzed TRPM7 function during amelogenesis in Keratin 14-Cre;Trpm7fl/fl conditional knockout (cKO) mice and Trpm7 knockdown cell lines. cKO mice showed lesser tooth pigmentation than control mice and broken incisor tips. Enamel calcification and microhardness were lower in cKO mice. Electron probe microanalysis (EPMA) showed that the calcium and phosphorus contents in the enamel were lower in cKO mouse than in control mice. The ameloblast layer in cKO mice showed ameloblast dysplasia at the maturation stage. The morphological defects were observed in rat SF2 cells with Trpm7 knockdown. Compared with mock transfectants, the Trpm7 knockdown cell lines showed lower levels of calcification with Alizarin Red-positive staining and an impaired intercellular adhesion structures. These findings suggest that TRPM7 is a critical ion channel in enamel calcification for the effective morphogenesis of ameloblasts during amelogenesis.
Insights
Transient receptor potential melastatin 7 (TRPM7) is crucial for tooth enamel formation. TRPM7 deficiency in mice and cell lines impairs enamel calcification and ameloblast development, highlighting its role in amelogenesis.
Area of Science:
- Biochemistry
- Cell Biology
- Developmental Biology
Background:
- Transient receptor potential melastatin 7 (TRPM7) is an ion channel with a kinase domain.
- Previous studies indicated high Trpm7 expression in mouse ameloblasts and odontoblasts, with impaired amelogenesis in kinase-dead TRPM7 mice.
Purpose of the Study:
- To investigate the function of TRPM7 in amelogenesis using conditional knockout mice and knockdown cell lines.
- To elucidate the role of TRPM7 in enamel calcification and ameloblast morphology.
Main Methods:
- Generation of Keratin 14-Cre;Trpm7fl/fl conditional knockout (cKO) mice.
- TRPM7 knockdown in rat SF2 ameloblast-like cells.
- Analysis of tooth phenotype, enamel calcification, microhardness, elemental content (EPMA), and ameloblast morphology.
- Assessment of cell calcification and intercellular adhesion in knockdown cells.
Main Results:
- cKO mice exhibited reduced tooth pigmentation, broken incisor tips, decreased enamel calcification, and lower microhardness.
- EPMA revealed reduced calcium and phosphorus content in the enamel of cKO mice.
- Ameloblasts in cKO mice displayed dysplasia during the maturation stage.
- TRPM7 knockdown in SF2 cells resulted in lower calcification and impaired intercellular adhesion.
Conclusions:
- TRPM7 is essential for proper enamel calcification during amelogenesis.
- TRPM7 plays a critical role in the effective morphogenesis of ameloblasts.
- TRPM7 functions as a key ion channel regulating calcium and phosphorus homeostasis in developing enamel.
