Localization of EMSP1 expression during tooth formation and cloning of mouse cDNA.

Enamel matrix serine proteinase 1 (EMSP1) is a proteolytic enzyme that has been isolated from the developing enamel of pig teeth. Its apparent function is to degrade the organic matrix in preparation for enamel maturation. The expression of EMSP1 has never been investigated in another organism besides the pig, and EMSP1 expression in the enamel organ has never been specifically demonstrated in ameloblasts. Here we report the expression of recombinant pig EMSP 1 (rpEMSP 1), the generation of rabbit polyclonal antibodies against rpEMSP1, the characterization of the antibodies and EMSP1 expression by Western blot and immunohistochemical analyses, the cloning and characterization of a full-length cDNA encoding mouse EMSP1, and the localization of EMSP1 expression in ameloblasts in mouse day 14 first and second molars by in situ hybridization. The full-length mouse EMSP1 cDNA clone has 1,237 nucleotides, excluding the poly(A+) tail, and encodes a preproprotein of 255 amino acids. Mouse EMSP1 shares 75% amino acid identity with pig EMSP1 and has three potential N-linked glycosylation sites, two of which are conserved in the pig homologue. Western blot analysis shows that the polyclonal antibodies are specific for EMSP1 and do not cross-react with trypsin. Immunohistochemistry of pig incisors shows discrete staining in the surface enamel at the earliest part of the maturation stage. In mouse molars, in situ hybridization gives a distinct and specific signal in maturation-stage ameloblasts, and in the junctional epithelium following tooth eruption. We conclude that EMSP1 is expressed by pig and mouse ameloblasts during the early maturation stage of amelogenesis.

Molecular mimicry between an immunodominant amino acid motif on the 47-kDa lipoprotein of Treponema pallidum (Tpp47) and multiple repeats of analogous sequences in fibronectin.

Molecular mimicry, resulting from structural similarities between self-determinants on host Ags and an organism's antigenic determinants (epitopes), can incite autoimmune events in certain bacterial and viral diseases. In the course of comprehensively mapping the 47-kDa lipoprotein (Tpp47) of Treponema pallidum subsp. pallidum using an overlapping synthetic peptide strategy, we identified a major immunoreactive epitope (411PGTEYT416) that exhibited considerable motif identity with multiple repeats of analogous linear sequences found in mammalian fibronectins. To further explore the importance of this motif as a probable instigator in the induction of polyspecific cross-reactive Abs, mimetic variants were synthesized for immunologic studies. Mimetics with ala (A) replacements in each amino acid position were used to determine which residues were critical for Ab binding. Animals immunized with two mimetics (PGTEYT or PGSEYT) coupled to tetanus toxoid exhibited: 1) modified responses when challenged with viable T. pallidum; and 2) classical Arthus reactions when challenged intradermally with either motif linked to a different carrier. The cross-reactive nature of the Ab responses to both mimetics was confirmed in a variety of ELISAs using mimetics, fibronectins, and collagens. Inhibition-ELISA studies with both fibronectin and an unrelated mimetic of the RGD motif suggest that intra- and intermolecular epitope spreading occurs following mimetic immunization and involves additional self-epitopes. These observations suggest that although molecular mimicry plays a pivotal role in initially triggering the anti-fibronectin and anti-collagen responses associated with disseminated syphilis, expansion of those autoimmune responses may be due to other self-epitopes once tolerance is abrogated.