BOVINE ENAMEL ORGAN CELLS EXPRESS TISSUE NONSPECIFIC ALKALINE-PHOSPHATASE MESSENGER-RNA

Alkaline phosphatase (AP) is expressed at high levels in all mineraliz ing tissues, and the isoform identified in developing enamel has bioch emical properties similar to that found in bone. While the bone AP is referred to as the liver/bone/kidney or tissue non-specific (TNS) form , other APs are highly specific for tissue of expression. To determine unequivocally the AP isoform made by enamel organ cells, we construct ed a fetal bovine enamel organ cDNA library, which yielded eight AP cD NA clones. Tn each case, the DNA sequence was homologous to the partia l cDNA reported for bovine kidney AF (Garattini et nl., 1987). It is c oncluded that enamel organ cells express the TNS-AP isoform. The exten ded 3' untranslated region of the cDNA has considerable homology to hu man TNS-AP, and the conservation of sequence suggests that the 3' end may have a role in post-transcriptional regulation of expression.