The objective of this study was to examine the expression pattern of Kelch-like ECH-associated protein 1 (Keap1) in the maxillary 2nd molar germs of rats. We used the maxillary 2nd molar germs in rats’ pup at postnatal day 3 (bell stage), 6 (crown formation stage) and 9 (root formation stage). The investigation on mRNA and protein levels were done using reverse transcription - polymerase chain reaction and western blot. Localization of Keap 1 in the maxillary 2nd molar germs were revealed through immunofluorescence staining. Keap1 from the maxillary 2nd molar germs were mostly manifested on postnatal day 3 and dramatically decreased on postnatal day 6 and 9 at mRNA and protein levels, while amelogenin and ameloblastin increased during the development of maxillary 2nd molar germs. During immunofluorescence analysis, the strong immunoreactivity against Keap1 was detected in the apical side of ameloblasts at the presecretory and secretory stages. However, Keap1 expression was hardly observed in the ameloblasts at the maturation stage. These results shows that Keap1 is strongly expressed in the presecretory and secretory ameloblasts of amelogenesis, and suggest that Keap1 may be a crucial molecule for the regulatory mechanisms tasked with the formation of enamel layer.

Introduction
 Materials and Methods
  Animals
  Preparation of tissue sections and morphologicalanalysis
  Isolation of RNA from the maxillary molar tooth germs
  RT-PCR
  real-time PCR
  Western blot analysis
  Immunofluorescent staining
 Results
  Histological findings
  Keap1 mRNA expression
  Keap1 Western blot
  Immunofluorescent findings
 Discussion
 References

• Sun-Hun Kim(Dental Science Research Institute, Chonnam National University)
• Yong-Ouk You(Institute of Biomaterial ･Implant, Department of Oral Biochemistry, School of Dentistry, Wonkwang University)
• Hyun-Mi Ko(Dental Science Research Institute, Chonnam National University)
• Hyun-Jin Kim(Institute of Biomaterial ･Implant, Department of Oral Anatomy, School of Dentistry, Wonkwang University) Correspondence to