Loss of Transglutaminase-2 results in accelerated enamel mineralization in mouse

Objectives: Tissue Transglutaminase (TG) has effect on numerous physiological and/or pathological functions. The role of extracellular TG2 has been demonstrated previously in cell adhesion, extracellular matrix assembly or bone ossification, however in vivo / in vitro studies have not been carried out yet to assess the effect of TG2 on tooth development. Samples taken from TG2 null mice were studied to characterize its tooth phenotype. Methods: Mice were sacrificed at different developmental stages as follows: intraembryonic developmental stages (E 14, 15, 16), prior to tooth eruption (postnatal day 1), and adulthood (2 months postnatal). Microscopical and computer aided 3D morphological measurements and enamel hardness test were carried out. Results: We could not detect any obvious morphologic alterations due to the loss of TG2 during early tooth development phases, when the tooth germs were going through bud, cap and bell morphogenetic stages. Significant differences in the hardness of the enamel were measured at postnatal stage, which implies accelerated enamel mineralisation. It has been revealed by 3D analysis of incisors from the knockout mice that they were slightly longer with a thicker enamel layer than their wild-type controls. Conclusions: Our findings suggest that TG2 may have an effect on enamel bio-mineralization processes. The work/publication is supported by the TÁMOP 4.2.1/B-09/1/KONV-2010-0007 project. The project is co-financed by the European Union and the European Social Fund.