A splicing mutation in VPS4B causes dentin dysplasia I.

BACKGROUND: Dentin dysplasia I (DDI) is a genetically heterogeneous autosomal-dominant disorder characterised by rootless teeth with abnormal pulpal morphology, the aetiology of which presents as genetically heterogeneous. METHODS AND RESULTS: Using a cohort of a large Chinese family with 10 patients with DDI, we mapped to a 9.63 Mb candidate region for DDI on chromosome 18q21.2-q21.33. We then identified a mutation IVS7+46C>G which resulted in a novel donor splice site in intron 7 of the VPS4B gene with co-segregation of all 10 affected individuals in this family. The aberrant transcripts encompassing a new insert of 45 bp in size were detected in gingival cells from affected individuals. Protein structure prediction showed that a 15-amino acid insertion altered the ATP-binding cassette of VPS4B. The mutation resulted in significantly reduced expression of mRNA and protein and altered subcellular localisation of VPS4B, indicating a loss of function of VPS4B. Using human gingival fibroblasts, the VPS4B gene was found to act as an upstream transducer linked to Wnt/ß-catenin signalling and regulating odontogenesis. Furthermore, knockdown of vps4b in zebrafish recapitulated the reduction of tooth size and absence of teeth similar to the tooth phenotype exhibited in DDI index cases, and the zebrafish mutant phenotype could be partially rescued by wild-type human VPS4B mRNA. We also observed that vps4b depletion in the zebrafish negatively regulates the expression of some major genes involved in odontogenesis. CONCLUSIONS: This study identifies VPS4B as a disease-causing gene for DDI, which is one of the important contributors to tooth formation, through the Wnt/ß-catenin signalling pathway.

Dentin dysplasia type I-novel findings in deciduous and permanent teeth.

BACKGROUND: Dentin dysplasia type I (DD-I) is a rare autosomal dominant hereditary disorder which seriously affects the root development of teeth, causing spontaneous tooth loss (in teenagers). At present, the study of DD-I focuses on familial and phenotypic analyses and reports regarding the ultrastructural study of DD-I are few. The purpose of this study was to clarify and discuss the clinical, histopathological, and ultrastructural features of the dentin defects in DD-I. In addition, the study further explores the root development and provides clues for uncovering virulent genes associated with the disease. METHODS: We recruited 31 members of a four-generation Chinese family, including eleven with dentin defects. Four permanent teeth and four deciduous teeth were obtained from individuals affected by DD-I. At the same time, two caries-free like-numbered permanent teeth and deciduous teeth served as controls, respectively. Analyses of these teeth were carried out using stereomicroscopy, light microscopy, and scanning and transmission electron microscopy, respectively. RESULTS: Similar to previous reports, extracted teeth showed typical histopathological and ultrastructural features of DD-I and teeth had short roots with obliterated pulp chambers. Furthermore, several novel discoveries were found in teeth affected by DD-I, including; (1) thinner dentin; (2) larger scalloped dentinoenamel junctions; (3) teardrop-shaped lacunae in the enamel; (4) rodless enamel and (5) irregular collagen fibers. CONCLUSIONS: The results exhibited defined features of DD-I in the family and further confirmed that abnormal dentin structure affected both the deciduous and permanent dentitions. In addition, these findings may contribute to a better understanding of the pathogenesis of DD-I as well as aid in the subclassification of this disease.

Smart pH-responsive nanocarriers based on nano-graphene oxide for combined chemo- and photothermal therapy overcoming drug resistance.

A pH-responsive nanocarrier is developed by coating nanoscale graphene oxide (NGO) with dual types of polymers, polyethylene glycol (PEG) and poly(allylamine hydrochloride) (PAH), the latter of which is then modified with 2,3-dimethylmaleic anhydride (DA) to acquire pH-dependent charge reversibility. After loading with doxorubicin (DOX), a chemotherapy drug, the obtained NGO-PEG-DA/DOX complex exhibits a dual pH-responsiveness, showing markedly enhanced cellular uptake under the tumor microenvironmental pH, and accelerated DOX release under a further lowered pH inside cell lysosomes. Combining such a unique behavior with subsequently slow efflux of DOX, NGO-PEG-DA/DOX offers remarkably improved cell killing for drug-resistant cancer cells under the tumor microenvironmental pH in comparison with free DOX. Exploiting its excellent photothermal conversion ability, combined chemo- and photothermal therapy is further demonstrated using NGO-PEG-DA/DOX, realizing a synergistic therapeutic effect. This work presents a novel design of surface chemistry on NGO for the development of smart drug delivery systems responding to the tumor microenvironment and external physical stimulus, with the potential to overcome drug resistance.