Correlation between amelogenin-gene variation and structural diversity of tooth enamel in whales

点击翻译按钮获取中文摘要

In order to identify and characterize the exons 5-6 of the amelogenin gene in whales, PCR was performed by using the genomic DNA in 11 species, with special reference to the conservation of the dental specific gene in baleen whales and the correlation with the expression of variations in the tooth enamel structure of these species. PCR amplification obtained the products in all the species used, and these products were identified as amelogenin genes after the sequence analyses, which confirmed the well conservation of the amelogenin genes in baleen whales. Therefore, it is concluded that these genes have been conserved in genomic DNA for geological period after the degeneration of the expression of teeth. The alignment of the exon 6, a major portion of the gene encoding 70 % amelogenin protein, consisted of 363 bp in the whale and showed a high (95 %) homology each other. In the species used in this study, only the minke whale possessed the 358 bp exon 6 where 5 bp was deleted the central portin of the exon 6. This deletion caused the frameshift of the amino acid component in this species. The present study also demonstrated the presence of stop codons induced by one point mutations at the central portion of the exon 6 in the Phocoenoides, Neophacaena and Ziphius. It has been reported that the enamel of Phocoenoides and Neophocaena shows a considerable hypocalcification and prismless structure as found ; in the human enamel of amelogenesis imperfecta. The present study suggests that these mutations in amelogenin genes cause the variation of normal enamel structure in whales. This study also disclosed that of the intron 5 sequence is a powerful indicator for phylogenetic analyses of whales and other mammals.