Complicated gene expression processes regulate the cytodifferentiation of odontogenic cells for dental hard tissue formation. Therefore, research has progressed in identifying key molecules involved in tooth development. This study aimed to identify genes associated with odontogenic cell differentiation in rats using a differential display PCR. We identified a differentially expressed band between maxillary 3rd molars (cap or early bell stage) and maxillary 2nd molars (dental hard tissue formation stage) on postnatal day 9. A GenBank search revealed this band as V-erbA-related protein 2 (EAR-2). The mRNA expression level of EAR-2 was higher during the root formation stage than during the cap or early bell stage. In 2nd molar germs, EAR-2 expression increased time-dependently across postnatal days 3, 6, and 9, corresponding to the early bell, crown, and root stages. Western blot analysis identified EAR-2 as a 43 kDa molecule, which exhibits an expression pattern consistent with that observed at the mRNA level. This molecule was spatio-temporally expressed in odontoblasts. Alendronate treatment significantly reduced EAR-2 expression, which is known for interfering with dental tissue mineralization. This is the first study to report EAR-2 expression in tooth development, suggesting ...