Transgenic mice that express amelogenin lacking the C-terminus

Objectives: The objective was to understand the in vivo role of the most abundant amelogenin protein with an engineered C-terminal deletion.

Methods: A plasmid vector was constructed for generation of transgenic mice that expressed a 167 amino acid amelogenin lacking the C-terminal 13 amino acids. Founders were used to develop TgCTRNC18 and TgCTRNC29 strains. Transgenic males were mated with amelogenin null (KO) females for analysis of transgene expression in teeth.

Results: DNA analysis indicated strain copy number. RNA and protein from teeth from TgCTRNCKO males analyzed by RT-PCR and western blot indicated that the transgene was expressed at a higher level in molars compared to incisors. The surfaces of the transgenic molars were rough and pitted. MicroCT of TgCTRNC29 teeth indicated similar molar enamel volume and density compared to wild-type. TgCTRNC18 molar enamel had similar density and volume as KO molar enamel. Density and volume of TgCTRNC18KO and TgCTRNC29KO molar enamel were not different from KO, and therefore neither TgCTRNC18 nor TgCTRNC29 rescued the enamel phenotype in molars. Density was increased in KO, TgCTRNC18KO and TgCTRNC29KO molar dentin compared to wild-type.

Conclusion: We concluded that amelogenin with a C-terminal deletion was unable to rescue the KO enamel phenotype. TgCTRNC29 had a similar phenotype to wild-type molar enamel but TgCTRNC18 was similar to the KO phenotype, indicating that extra copies of the transgene may lead to a more severe phenotype. Because full-length amelogenin partially rescues the KO phenotype, it is concluded that the amelogenin C-terminus plays an important role in vivo. Supported by NIDCR grant DE010189