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Objective Disruption of the third zinc finger domain of specificity protein 6 ( SP6) presents an enamel-specific defect in a rat model of amelogenesis imperfecta ( AMI rats). To understand the molecular basis of amelogenesis imperfecta caused by the Sp6 mutation, we established and characterized AMI-derived rat dental epithelial ( ARE) cells. Materials and Methods ARE cell clones were isolated from the mandibular incisors of AMI rats, and amelogenesis-related gene expression was analyzed by reverse transcription polymerase chain reaction ( RT- PCR). Localization of wild-type SP6 ( SP6 WT) and mutant-type SP6 ( SP6 AMI) was analyzed by immunocytochemistry. SP6 transcriptional activity was monitored by rho-associated protein kinase 1 (Rock1) promoter activity with its specific binding to the promoter region in dental (G5 and ARE) and non-dental ( COS-7) epithelial cells. Results Isolated ARE cells were varied in morphology and gene expression. Both SP6 WT and SP6 AMI were mainly detected in nuclei. The promoter analysis revealed that SP6 WT and SP6 AMI enhanced Rock1 promoter activity in G5 cells but that enhancement by SP6 AMI was weaker, whereas no enhancement was observed in the ARE and COS-7 cells, even though SP6 WT and SP6 AMI bound to the promoter in all instances. Conclusion ARE cell clones can provide a useful in vitro model to study the mechanism of SP6-mediated amelogenesis imperfecta. [ABSTRACT FROM AUTHOR]