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DMP1-targeted Cre Expression in Odontoblasts and Osteocytes

¹ Department of Oral Biology, School of Dentistry, University of Missouri-Kansas City, Kansas City, MO 64108, USA; and
² Department of Biomedical Sciences, Baylor College of Dentistry, Texas A&M Health Science Center, 3302 Gaston Avenue, Dallas, TX 75246, USA

View larger version (164K): [in this window] [in a new window]   Figure 1. The odontoblast tubular network and osteocyte lacuno-canalicular network showed a high degree of similarity and complexity. Images of acid-etched resin-embedded samples of dentin (a) and mandibular bone (b) are shown at low (left) and high (right) magnifications by SEM.

View larger version (102K): [in this window] [in a new window]   Figure 2. The lacZ reporter controlled by the 9.6-kb murine Dmp1 promoter was highly expressed in osteocytes. We previously generated mice in which beta-galactosidase under control of the 9.6-kb murine Dmp1 promoter was shown to be active in odontoblasts and localized in their processes (Lu et al., 2005). Compared with the Dmp1 lacZ knock-in mice, where lacZ expression reflected the endogenous Dmp1 expression (left panel), the expression pattern under control of the 9.6-kb Dmp1 promoter was similar, but with much higher intensity (middle panel), suggesting strong activity in osteocytes. The wild-type control (WT, right panel) showed no lacZ activity. Staining conditions were identical, since all the tibial frozen sections were stained for 2 hrs in X-gal solution at room temperature at the same time.

View larger version (78K): [in this window] [in a new window]   Figure 3. The 9.6-kb Dmp1-Cre was highly active in odontoblasts. Only positive staining was observed in samples with both ROSA26R and Cre transgenes (left panel), whereas samples that contain the ROSA26R transgene only were negative (right panel). Whole-mount staining of the 1st molar from a two-week-old double-transgenic mouse showed strong blue staining in the odontoblast layer, with weak and diffuse staining in pulp and dentin (a, left panel) compared with the control littermate containing ROSA26R only (a, right panel). X-gal-stained frozen molar sections from the double-transgenic mice showed blue staining in the odontoblast layer in newborns (b), one-month-old (c), and four-month-old (d) mice, compared with their control littermates containing ROSA26R only (right panel).

View larger version (124K): [in this window] [in a new window]   Figure 4. The 9.6-kb Dmp1-Cre was highly active in osteocytes in a bone-specific manner. Only positive staining was observed in samples with both ROSA26R and Cre transgenes (left panel), whereas samples that contained the ROSA26R transgene only were negative (right panel). Whole-mount staining from a two-week-old double-transgenic mouse showed blue staining in calvariae (a) and tibia/fibula (b), compared with the control samples containing ROSA26R only. X-Gal-stained frozen sections from the double-transgenic bone showed blue staining in osteocytes in six-day-old (c) and one-month-old calvariae (d) or tibia (e), and in four-month-old (f) mice, compared with their control littermates containing ROSA26R only.