Differential expression between “DSP-only” and DSP-PP523 transcripts in rat molar teeth

- DSP-PP523 transcript expressed in the entire differentiated, columnar mature odontoblasts.
- DSP-only transcript expressed in the areas subjacent to odontoblasts.
- DSP-only transcript did not express in the entire differentiated, columnar mature odontoblasts.
- Stro-1 positive cells also located in the areas subjacent to mature odontoblasts.
- DSP-only positive cells likely present a less differentiated pre-odontoblast.

ObjectiveTo 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.DesignUnique 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 (5-7 μ m) from embryonic 20 day, postnatal 2, 3 and 6 days 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.ResultsWe 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.ConclusionDifferential 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.