The odontogenic ameloblast-associated protein (ODAM) cooperates with RUNX2 and modulates enamel mineralization via regulation of MMP-20.
We have previously reported that the odontogenic ameloblast-associated protein (ODAM) plays important roles in enamel mineralization through the regulation of matrix metalloproteinase-20 (MMP-20). However, the precise function of ODAM in MMP-20 regulation remains largely unknown. The aim of the present study was to uncover the molecular mechanisms responsible for MMP-20 regulation. The subcellular localization of ODAM varies in a stage-specific fashion during ameloblast differentiation. During the secretory stage of amelogenesis ODAM was localized to both the nucleus and cytoplasm of ameloblasts. However, during the maturation stage of amelogenesis, ODAM was observed in the cytoplasm and at the interface between ameloblasts and the enamel layer, but not in the nucleus. Secreted ODAM was detected in the conditioned medium of ameloblast-lineage cell line (ALC) from days 14 to 21, which coincided with the maturation stage of amelogenesis. Interestingly, the expression of Runx2 and nuclear ODAM correlated with MMP-20 expression in ALC. We therefore examined whether ODAM cooperates with Runx2 to regulate MMP-20 and modulate enamel mineralization. Increased expression of ODAM and Runx2 augmented MMP-20 expression, and Runx2 expression enhanced expression of ODAM, although overexpression of ODAM did not influence Runx2 expression. Conversely, loss of Runx2 in ALC decreased ODAM expression, resulting in down-regulation of MMP-20 expression. Increased MMP-20 expression accelerated amelogenin processing during enamel mineralization. Our data suggest that Runx2 regulates the expression of ODAM and that nuclear ODAM serves an important regulatory function in the mineralization of enamel through the regulation of MMP-20 apart from a different, currently unidentified, function of extracellular ODAM.
Lee
Hye-Kyung
HK
Department of Oral Histology-Developmental Biology, School of Dentistry and Dental Research Institute, BK 21, Seoul National University, Seoul 110-749, Korea.
Lee
Dong-Seol
DS
Ryoo
Hyun-Mo
HM
Park
Jong-Tae
JT
Park
Su-Jin
SJ
Bae
Hyun-Sook
HS
Cho
Moon-Il
MI
Park
Joo-Cheol
JC
D000565:Ameloblasts; D000566:Amelogenesis; D000818:Animals; D002460:Cell Line; D002467:Cell Nucleus; D050659:Core Binding Factor Alpha 1 Subunit / Q000502:physiology*; D003743:Dental Enamel / Q000378:metabolism*; D047908:Intracellular Signaling Peptides and Proteins; D053519:Matrix Metalloproteinase 20 / Q000378:metabolism*; D051379:Mice; D011506:Proteins / Q000502:physiology*; D013997:Time Factors; D014074:Tooth Calcification
D050659:Core Binding Factor Alpha 1 Subunit; D047908:Intracellular Signaling Peptides and Proteins; C555400:ODAM protein, mouse; D011506:Proteins; C493716:Runx2 protein, mouse; D053519:Matrix Metalloproteinase 20