CDNA CLONING OF S100 CALCIUM-BINDING PROTEINS FROM BOVINE PERIODONTAL-LIGAMENT AND THEIR EXPRESSION IN ORAL-TISSUES

The periodontal ligament (PDL) is a unique tissue that is crucial for tooth function. However, little is known of the molecular mechanisms c ontrolling PDL function. To characterize PDL cells at the molecular le vel, we constructed a cDNA Library from bovine PDL tissue; We then foc used on the isolation of S100 calcium-binding proteins (CaBPs), becaus e they mediate Ca2+ signaling and control important cellular processes such as differentiation and metabolism We screened the PDL cDNA libra ry with a mouse S100A4 cDNA, and cloned the bovine cDNAs of two S100 C aBPs (S100A4 and S100A2). In Northern blotting analysis, the highest e xpression of S100A4 was detected in PDL from erupted teeth (PDLE). PDL from teeth under eruption (PDLU) showed a lower expression of S100A4, and its expression in gingiva was faintly detectable. S100A4 expressi on was also high in the pulp tissue followed by the dental papilla of the tooth germ; S100A2 expression was high in PDLE and gingiva. Intere stingly, only PDLE exhibited a high expression of both S100A4 and S100 A2. PDLE also expressed the highest level of beta-actin, a-target cyto skeletal protein for S100A4. It is conceivable that the high expressio n of S100A4 in PDLE is a result of the maturation of the PDL and/or a response to mechanical stress generated by mastication. Since there wa s a marked difference of S100A4 expression between PDL and gingiva, we propose that S100A4 could be a useful marker for distinguishing cells from these two tissues.