Dataset Information

Vps4b heterozygous mice do not develop tooth defects that replicate human dentin dysplasia I.

ABSTRACT: BACKGROUND:Vacuolar protein sorting-associated protein 4B (VPS4B) is a member of the ATP enzyme AAA protein family, and is mainly involved in protein degradation and cell membrane fusion. Recently, a dominant mutation in this gene was identified in human dentin dysplasia type I (DD-I). Herein, we report the generation of Vps4b knockout (Vps4b KO) mice; however, the homozygous Vps4b KO mutation was embryonic lethal at the early stages of embryo development, and we therefore report the results of heterozygous mutant mice. RESULTS:Mice heterozygous for Vps4b did not develop tooth defects replicating human DD-I. Immunohistochemistry showed that gene KO was successful, as there was decreased expression of Vps4b in heterozygous mice; hematoxylin and eosin (H&E) staining also showed that the width of the pre-dentin zone was increased in heterozygous mice, although the arrangement of the odontoblasts was not significantly different from wild-type (WT) mice. However, H&E staining showed no obvious abnormalities in the bones of heterozygous mice. Moreover, stereomicroscopic and X-ray radiography results indicated no abnormal manifestations in teeth or bones. Furthermore, statistical analysis of the volume and density of dentin and enamel, as well as skeletal analysis, including the volume and separation of trabecular bone analyzed by micro-CT, all showed no differences between Vps4b heterozygotes and WT mice. In addition, there also were no significant differences in bone or cartilage mineralization as evaluated by Alcian blue-Alizarin red staining. CONCLUSIONS:The heterozygous Vps4b KO mice do not develop tooth defects that replicate human DD-I and this is likely to be due to differences in tooth development between the two species. Consequently, further studies are needed to determine whether mice are an appropriate animal model for human tooth diseases.

SUBMITTER: Hu A

PROVIDER: S-EPMC6330468 | biostudies-literature | 2019 Jan

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

Vps4b heterozygous mice do not develop tooth defects that replicate human dentin dysplasia I.

Hu Aiqin A Lu Ting T Chen Danna D Huang Jin J Feng Weiwei W Li Yanjun Y Guo Dan D Xu Xiangmin X Chen Dong D Xiong Fu F

BMC genetics 20190111 1

<h4>Background</h4>Vacuolar protein sorting-associated protein 4B (VPS4B) is a member of the ATP enzyme AAA protein family, and is mainly involved in protein degradation and cell membrane fusion. Recently, a dominant mutation in this gene was identified in human dentin dysplasia type I (DD-I). Herein, we report the generation of Vps4b knockout (Vps4b KO) mice; however, the homozygous Vps4b KO mutation was embryonic lethal at the early stages of embryo development, and we therefore report the res ...[more]

PMID: 30634912

Similar Datasets

Project description:Tissue-nonspecific alkaline phosphatase (TNAP) is expressed in mineralizing tissues and functions to reduce pyrophosphate (PP(i) ), a potent inhibitor of mineralization. Loss of TNAP function causes hypophosphatasia (HPP), a heritable disorder marked by increased PP(i) , resulting in rickets and osteomalacia. Tooth root cementum defects are well described in both HPP patients and in Alpl(-/-) mice, a model for infantile HPP. In Alpl(-/-) mice, dentin mineralization is specifically delayed in the root; however, reports from human HPP patients are variable and inconsistent regarding dentin defects. In the current study, we aimed to define the molecular basis for changes in dentinogenesis observed in Alpl(-/-) mice. TNAP was found to be highly expressed by mature odontoblasts, and Alpl(-/-) molar and incisor roots featured defective dentin mineralization, ranging from a mild delay to severely disturbed root dentinogenesis. Lack of mantle dentin mineralization was associated with disordered and dysmorphic odontoblasts having disrupted expression of marker genes osteocalcin and dentin sialophosphoprotein. The formation of, initiation of mineralization within, and rupture of matrix vesicles in Alpl(-/-) dentin matrix was not affected. Osteopontin (OPN), an inhibitor of mineralization that contributes to the skeletal pathology in Alpl(-/-) mice, was present in the generally unmineralized Alpl(-/-) mantle dentin at ruptured mineralizing matrix vesicles, as detected by immunohistochemistry and by immunogold labeling. However, ablating the OPN-encoding Spp1 gene in Alpl(-/-) mice was insufficient to rescue the dentin mineralization defect. Administration of bioengineered mineral-targeting human TNAP (ENB-0040) to Alpl(-/-) mice corrected defective dentin mineralization in the molar roots. These studies reveal that TNAP participates in root dentin formation and confirm that reduction of PP(i) during dentinogenesis is necessary for odontoblast differentiation, dentin matrix secretion, and mineralization. Furthermore, these results elucidate developmental mechanisms underlying dentin pathology in HPP patients, and begin to explain the reported variability in the dentin/pulp complex pathology in these patients.

Project description:Dentin sialophosphoprotein (DSPP) is an extracellular matrix protein that is highly expressed in odontoblasts, but only transiently expressed in presecretory ameloblasts during tooth development. We previously generated a knockin mouse model expressing a mouse equivalent (DSPP, p.P19L) of human mutant DSPP (p.P17L; referred to as "DsppP19L/+ "), and reported that DsppP19L/+ and DsppP19L/P19L mice manifested a dentin phenotype resembling human dentinogenesis imperfecta (DGI). In this study, we analyzed pathogenic effects of mutant P19L-DSPP on enamel development in DsppP19L/+ and DsppP19L/P19L mice. Micro-Computed Tomography (μCT) analyses of 7-week-old mouse mandibular incisors showed that DsppP19L/P19L mice had significantly decreased enamel volume and/or enamel density at different stages of amelogenesis examined. Acid-etched scanning electron microscopy (SEM) analyses of mouse incisors demonstrated that, at the mid-late maturation stage of amelogenesis, the enamel of wild-type mice already had apparent decussating pattern of enamel rods, whereas only minute particulates were found in DsppP19L/+ mice, and no discernible structures in DsppP19L/P19L mouse enamel. However, by the time that incisor enamel was about to erupt into oral cavity, distinct decussating enamel rods were evident in DsppP19L/+ mice, but only poorly-defined enamel rods were revealed in DsppP19L/P19L mice. Moreover, μCT analyses of the mandibular first molars showed that DsppP19L/+ and DsppP19L/P19L mice had a significant reduction in enamel volume and enamel density at the ages of 2, 3, and 24weeks after birth. Backscattered and acid-etched SEM analyses revealed that while 3-week-old DsppP19L/+ mice had similar pattern of enamel rods in the mandibular first molars as age-matched wild-type mice, no distinct enamel rods were observed in DsppP19L/P19L mice. Yet neither DsppP19L/+ nor DsppP19L/P19L mice showed well-defined enamel rods in the mandibular first molars by the age of 24weeks, as judged by backscattered and acid-etched SEM. In situ hybridization showed that DSPP mRNA level was markedly reduced in the presecretory ameloblasts, but immunohistochemistry revealed that DSP/DSPP immunostaining signals were much stronger within the presecretory ameloblasts in Dspp mutant mice than in wild-type mice. These results suggest that mutant P19L-DSPP protein caused developmental enamel defects in mice, which may be associated with intracellular retention of mutant DSPP in the presecretory ameloblasts.

Project description:Dentin Sialoprotein (DSP) and phosphophoryn (PP) are two most dominant non-collagenous proteins in dentin, which are the cleavage products of the DSPP (dentin sialophosphoprotein) precursor protein. The absence of the DSPP gene in DSPP knock-out (KO) mice results in characteristics that are consistent with dentinogenesis imperfecta type III in humans. Symptoms include thin dentin, bigger pulp chamber with frequent pulp exposure as well as abnormal epithelial-mesenchymal interactions, and the appearance of chondrocyte-like cells in dental pulp. To better understand how DSPP influences tooth development and dentin formation, we used a bacterial artificial chromosome transgene construct (BAC-DSPP) that contained the complete DSPP gene and promoter to generate BAC-DSPP transgenic mice directly in a mouse DSPP KO background. Two BAC-DSPP transgenic mouse strains were generated and characterized. DSPP mRNA expression in BAC-DSPP Strain A incisors was similar to that from wild-type (wt) mice. DSPP mRNA expression in BAC-DSPP Strain B animals was only 10% that of wt mice. PP protein content in Strain A incisors was 25% of that found in wt mice, which was sufficient to completely rescue the DSPP KO defect in mineral density, since microCT dentin mineral density analysis in 21-day postnatal animal molars showed essentially identical mineral density in both strain A and wt mice. Strain B mouse incisors, with 5% PP expression, only partially rescued the DSPP KO defect in mineral density, as microCT scans of 21-day postnatal animal molars indicated a reduced dentin mineral density compared to wt mice, though the mineral density was still increased over that of DSPP KO. Furthermore, our findings showed that DSPP dosage in Strain A was sufficient to rescue the DSPP KO defect in terms of epithelial-mesenchymal interactions, odontoblast lineage maintenance, along with normal dentin thickness and normal mineral density while DSPP gene dosage in Strain B only partially rescued the aforementioned DSPP KO defect.

Dataset Information

Vps4b heterozygous mice do not develop tooth defects that replicate human dentin dysplasia I.

Publications

Vps4b heterozygous mice do not develop tooth defects that replicate human dentin dysplasia I.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure