Characterization of dentin matrix protein 1 gene in crocodilia.

Several clones containing DMP1 cDNA were isolated from a caiman tooth library by screening with a platypus DMP1 probe. The caiman DMP1 shows little amino acid sequence similarity to mammalian DMP1s for much of its length. A few highly conserved regions can, however, be identified that correspond to the slowly evolving parts of the corresponding mammalian genes. Southern blot analysis using probes comprising either conserved regions or longer segments of the gene indicates that only a single DMP1 locus exists. In coding regions, exon-intron boundaries and reading frames are shared by caiman and mammalian genes with the exception of exons 1 and 5, which are longer in the caiman. The repetitive sequence of the last exon is shared by mammals and caiman as are the high Ser content and acidity due to a high proportion of Asp and Glu residues. The conserved mammalian cell-attachment signal Arg-Gly-Asp is absent in the caiman DMP1. In contrast to the amelogenin gene, the DMP1 gene appears to evolve rapidly in vertebrates.