Expression of mRNA Encoding Tissue-Nonspecific Alkaline Phosphatase in Human Dental Tissues

Tissue-nonspecific-type alkaline phosphatase (TNSALP) is found in the bone, liver, kidney, and other tissues, and its gene consists of 12 exons with the coding sequence beginning in the second exon. Recently, a noncoding first exon was identified in the liver message (liver type) which differed from that of the previously known osteoblast-derived cDNA sequence (bone type). Although these two mRNAs produce an identical protein, they have different promoter regions. It is known that ALPs in dental pulp and periodontal ligament are classified into TNSALP by their enzymatic and immunological properties, but little is known about the expression of ALP mRNAs and the transcriptional mechanisms. In order to examine the expression of their mRNA type, specific oligonucleotide primers corresponding to two types of mRNAs of human TNSALP were designed and amplified by reverse transcription-polymerase chain reaction (RT-PCR). It was found that bone-type mRNA was expressed in the human dental tissues such as dental pulp, periodontal ligament, and dental sac, whereas liver-type mRNA was not expressed. Thus, it was concluded that the human dental tissues express the bone-type isozymes and are regulated by the same transcriptional mechanism as in the bone.