RESUMO
OBJECTIVE: To compare the expression patterns of two multiple transcripts derived from DSP-PP gene during tooth development. One is DSP-only transcript (i.e. does not encode PP) and the other is DSP-PP523 transcript, a main DSP-PP transcript. DESIGN: Unique antisense and sense riboprobes were generated from DSP-only and DSPPP523 cDNAs for in situ studies to examine DSP-only and DSP-PP523 transcript expression in developing molars. Paraffin-embedded sections (5-7µ m) from embryonic 20day, postnatal 2, 3 and 6days were deparaffined and hydrated. Tissues were prehybridized, then hybridized with DSP-only and DSP-PP523 anti-sense (AS) or sense (S) Digoxigenin labeled-riboprobes overnight, and washed. Anti-Digoxigenin antibodies conjugated to alkaline phosphatase were used to detect the presence of bound riboprobes by color reaction with NBT/BCIP. Stro-1 antibody was used for immunohistochemical analysis of Stro-1 protein expression in rat molars. RESULTS: We found that unlike the DSP-PP523 transcript, the DSP-only transcript does not express in the entire polarized mature odontoblasts but is expressed in the areas subjacent to the mature odontoblast layer. In addition, DSP-only transcript is expressed in the dental pulp. Interestingly, Stro-1 protein, a stem cell marker, was also identified in the areas subjacentto odontoblasts and in dental pulp. CONCLUSION: Differential expression of DSP-only and DSP-PP523 transcripts suggest that these two kinds of transcripts may play different roles during dentinogenesis. DSP-PP523 transcript is expressed in mature odontoblasts, which actively participates in dentin formation. DSP-only transcript might have a different function.
