Proper differentiation of odontoblasts is crucial for the development of tooth roots. Previous studies have reported the osteogenic/odontogenic potential of pre-odontoblasts during root odontoblast differentiation. However, the underlying molecular pathway that orchestrates these processes remains largely unclear. In this study, ablation of transforming growth factor- β receptor type 2 ( Tgfbr2 ) in root pre-odontoblasts resulted in abnormal formation of root osteodentin, which was associated with ectopic osteogenic differentiation of root odontoblasts. Disrupting TGF-β signaling caused upregulation of Wnt signaling characterized by increased Wnt6 , Wnt10a , Tcf-1 , and Axin2 expression. Interestingly, inhibiting Wnt signaling by deleting Wntless ( wls ) in Osteocalcin ( Ocn ) -Cre; Tgfbr2 fl/fl ; Wls fl/fl mice or overexpressing the Wnt antagonist Dkk1 in Ocn-Cre; Tgfbr2 fl/fl ; ROSA26 Dkk 1 mice decreased ectopic osteogenic differentiation and arrested odontoblast differentiation. Our results suggest that TGF-β signaling acts with Wnt signaling to regulate root odontogenic differentiation.
Objective To explore the relationship between single nuclear polymorphisms (SNPs) in ectodysplasin A receptor (EDAR) and EDAR-associated death domain (EDARADD) genes and non-syndromic tooth agenesis. Methods Ten putative SNPs in EDAR and EDARADD were selected, and a case-control study was conducted in 112 subjects with non-syndromic tooth agenesis and 112 normal control subjects. DNA was obtained from peripheral blood samples. Genotyping was performed by Sanger sequencing. Results Three SNPs (rs3749098, rs3749099, and rs10432616) in EDAR exhibited significant differences in the alleles and/or genotype frequencies between the case group (individuals with non-syndromic tooth agenesis) and control group (normal individuals). The T allele was identified in the SNP rs3749098 in 99.1% of the case group and in 96.0% of the control group (P = 0.0326). Regarding the SNP rs3749099, the C allele was identified in 99.1% of the case group and in 96.0% of the control group (P = 0.0326). Regarding the SNP rs10432616, the C allele was identified in 97.8% of the case group and in 100.0% of the control group (P = 0.0245). Conclusion Our results suggested that SNPs in EDAR could be a pathogenic factor for non-syndromic tooth agenesis. Furthermore, EDAR can be regarded as a marker gene for the risk of tooth agenesis.
The purpose of this research was to investigate and identify PAX9 gene variants in four Chinese families with non-syndromic tooth agenesis. We identified pathogenic gene variants by whole-exome sequencing (WES) and Sanger sequencing and then studied the effects of these variants on function by bioinformatics analysis and in vitro experiments. Four novel PAX9 heterozygous variants were identified: two missense variants (c.191G > T (p.G64V) and c.350T > G (p.V117G)) and two frameshift variants (c.352delC (p.S119Pfs*2) and c.648_649insC(p.Y217Lfs*100)). The bioinformatics analysis showed that these variants might be pathogenic. The tertiary structure analysis showed that these four variants could cause structural damage to PAX9 proteins. In vitro functional studies demonstrated that (1) the p.Y217Lfs*100 variant greatly affects mRNA stability, thereby affecting endogenous expression; (2) the p. S119Pfs* 2 variant impairs the subcellular localization of the nuclear expression of the wild-type PAX9 protein; and (3) the four variants (p.G64V, p.V117G, p.S119Pfs*2, and p.Y217Lfs*100) all significantly affect the downstream transcriptional activity of the BMP4 gene. In addition, we summarized and analyzed tooth missing positions caused by PAX9 variants and found that the maxillary second molar (84.11%) and mandibular second molar (84.11%) were the most affected tooth positions by summarizing and analyzing the PAX9-related non-syndromic tooth agenesis positions. Our results broaden the variant spectrum of the PAX9 gene related to non-syndromic tooth agenesis and provide useful information for future genetic counseling.
Abstract Odonto‐onycho‐dermal dysplasia (OODD) is a rare autosomal recessive syndrome characterized by multiple ectodermal abnormalities. Mutations of the wingless‐type MMTV integration site family member 10A ( WNT10A ) gene have been associated with OODD. To date, only 11 OODD‐associated WNT10A mutations have been reported. In this report, we Characterized the clinical manifestations with focusing on dental phenotypes in four unrelated OODD patients. By Sanger sequencing, we identified five novel mutations in the WNT10A gene, including two homozygous nonsense mutations c.1176C>A (p.Cys392*) and c.742C>T (p.Arg248*), one homozygous frame‐shift mutation c.898‐899delAT (p.Ile300Profs*126), and a compound heterozygous mutation c.826T>A (p.Cys276Ser) and c.949delG (p.Ala317Hisfs*121). Our findings confirmed that bi‐allelic mutations of WNT10A were responsible for OODD and greatly expanded the mutation spectrum of OODD. For the first time, we demonstrated that bi‐allelic WNT10A mutations could lead to anodontia of permanent teeth, which enhanced the phenotypic spectrum of WNT10A mutations. Interestingly, we found that bi‐allelic mutations in the WNT10A gene preferentially affect the permanent dentition rather the primary dentition, suggesting that the molecular mechanisms regulated by WNT10A in the development of permanent teeth and deciduous teeth might be different.
Keratinocyte differentiation factor 1 (KDF1) is a recently identified and rare candidate gene for human tooth agenesis; however, KDF1-related morphological characteristics and pathological changes in dental tissue and the oral epithelium remain largely unknown. Here, we employed whole-exome sequencing (WES) and Sanger sequencing to screen for the suspected variants in a cohort of 151 tooth agenesis patients, and we segregated a novel KDF1 heterozygous missense variation, c.920G>C (p.R307P), in a non-syndromic tooth agenesis family. Essential bioinformatics analyses and tertiary structural predictions were performed to analyze the structural changes and functional impacts of the novel KDF1 variant. The subsequent functional assessment using a TOP-flash/FOP-flash luciferase reporter system demonstrated that KDF1 variants suppressed the activation of canonical Wnt signaling in 293T cells. To comprehensively investigate the KDF1-related oral morphological anomalies, we performed scanning electron microscopy and ground section of the lower right lateral deciduous incisor extracted from #285 proband, and histopathological assessment of the gingiva. The phenotypic analyses revealed a series of tooth morphological anomalies related to the KDF1 variant R307P, including a shovel-shaped lingual surface of incisors and cornicione-shaped marginal ridges with anomalous morphological occlusal grooves of premolars and molars. Notably, keratinized gingival epithelium abnormalities were revealed in the proband and characterized by epithelial dyskeratosis with residual nuclei, indistinct stratum granulosum, epithelial hyperproliferation, and impaired epithelial differentiation. Our findings revealed new developmental anomalies in the tooth and gingival epithelium of a non-syndromic tooth agenesis individual with a novel pathogenic KDF1 variant, broadening the phenotypic spectrum of KDF1-related disorders and providing new evidence for the crucial role of KDF1 in regulating human dental and oral epithelial development.
Abstract Enamel protects teeth from external irritation and its formation involves sequential differentiation of ameloblasts, a dental epithelial cell. Keratinocyte differentiation factor 1 ( KDF1 ) is important in the development of epithelial tissues and organs. However, the specific role of KDF1 in enamel formation and corresponding regulatory mechanisms are unclear. This study demonstrated that KDF1 was persistently expressed in all stages of ameloblast differentiation, through RNAscope in situ hybridization. KDF1 expression in the mouse ameloblast cell line LS8 was demonstrated via immunofluorescence assay. KDF1 was knocked out in LS8 cells using the CRISPR/Cas‐9 system or overexpressed in LS8 cells through lentiviral infection. In vitro ameloblast differentiation induction, quantitative reverse transcription PCR, western blot analysis, and alkaline phosphatase (ALP) assay indicated that knockout or overexpression of KDF1 in LS8 cells decreased or increased the mRNA and protein levels of several key amelogenesis markers, as well as ALP activity. Furthermore, liquid chromatography‐mass spectrometry and co‐immunoprecipitation analyses revealed that KDF1 can interact with the IKK complex, thereby inhibiting the NF‐κB pathway. Suppressing NF‐κB activity partially recovered the decreased ameloblast differentiation in LS8 cells induced by KDF1‐ knockout. This study demonstrated that KDF1 can promote ameloblast differentiation of LS8 cells by inhibiting the IKK/IκB/NF‐κB axis, and is a potential target for functional enamel regeneration.
'/%3e%3cuse xlink:href='%23a' transform='rotate(23.036 .093 25.536)'/%3e%3cuse xlink:href='%23a' transform='rotate(45.87 1.273 16.18)'/%3e%3cuse xlink:href='%23a' transform='rotate(69.945 .996 12.078)'/%3e%3cuse xlink:href='%23a' transform='rotate(20.66 -19.689 31.932)'/%3e%3c/svg%3e)
