Downregulation of ROR2 promotes dental pulp stem cell senescence by inhibiting STK4-FOXO1/SMS1 axis in sphingomyelin biosynthesis.

Dental pulp stem cells (DPSCs) play a vital role in tooth restoration, regeneration, and homeostasis. The link between DPSC senescence and tooth aging has been well-recognized. ROR2 plays an important role in aging-related gene expression. However, the expression and function of ROR2 in DPSC aging remain largely unknown. In this study, we found that ROR2 expression was significantly decreased in aged pulp tissues and DPSCs. The depletion of ROR2 in young DPSCs inhibits their self-renewal capacity, while its overexpression in aged DPSCs restores their self-renewal capacity. Interestingly, we found that sphingomyelin (SM) is involved in the senescence of DPSCs regulated by ROR2. Mechanistically, we confirmed that ROR2 inhibited the phosphorylation of STK4, which promoted the translocation of Forkhead Box O1 (FOXO1) to the nucleus. STK4 inhibition or knockdown of FOXO1 markedly increased the proliferation of DPSCs and upregulated the expression of SMS1, which catalyzed SM biogenesis. Moreover, FOXO1 directly bound to the SMS1 promoter, repressing its transcription. Our findings demonstrated the critical role of the ROR2/STK4-FOXO1/SMS1 axis in the regulation of SM biogenesis and DPSC senescence, providing a novel target for antagonizing tooth aging.

Investigation of a Novel LRP6 Variant Causing Autosomal-Dominant Tooth Agenesis.

BACKGROUND: The low-density lipoprotein receptor-related protein 6 (LRP6) gene is a recently defined gene that is associated with the autosomal-dominant inherited tooth agenesis (TA). In the present study, a family of four generations having TA was recruited and subjected to a series of clinical, genetic, in silico, and in vitro investigations. METHODS: After routine clinical evaluation, the proband was subjected to whole-exome sequencing (WES) to detect the diagnostic variant. Next, in silico structural and molecular dynamics (MD) analysis was conducted on the identified novel missense variant for predicting its intramolecular impact. Subsequently, an in vitro study was performed to further explore the effect of this variant on protein maturation and phosphorylation. RESULTS: WES identified a novel variant, designated as LRP6: c.2570G > A (p.R857H), harbored by six members of the concerned family, four of whom exhibited varied TA symptoms. The in silico analysis suggested that this novel variant could probably damage the Wnt bonding function of the LRP6 protein. The experimental study demonstrated that although this novel variant did not affect the LRP6 gene transcription, it caused a impairment in the maturation and phosphorylation of LRP6 protein, suggesting the possibility of the disruption of the Wnt signaling. CONCLUSION: The present study expanded the mutation spectrum of human TA in the LRP6 gene. The findings of the present study are insightful and conducive to understanding the functional significance of specific LRP6 variants.

A clinical and multi­omics study of Van der Woude syndrome in three generations of a Chinese family.

Previous studies have suggested that pathogenic variants in interferon regulatoryse factor 6 (IRF6) can account for almost 70% of familial Van der Woude Syndrome (VWS) cases. However, gene modifiers that account for the phenotypic variability of IRF6 in the context of VWS remain poorly characterized. The aim of this study was to report a family with VWS with variable expressivity and to identify the genetic cause. A 4­month­old boy initially presented with cleft palate and bilateral lower lip pits. Examination of his family history identified similar, albeit milder, clinical features in another four family members, including bilateral lower lip pits and/or hypodontia. Peripheral blood samples of eight members in this three­generation family were subsequently collected, and whole­exome sequencing was performed to detect pathogenic variants. A heterozygous missense IRF6 variant with a c.1198C>T change in exon 9 (resulting in an R400W change at the amino acid level) was detected in five affected subjects, but not in the other three unaffected subjects. Moreover, subsequent structural analysis was indicative of damaged stability to the structure in the mutant IRF protein. Whole­transcriptome sequencing, expression analysis and Gene Ontology enrichment analysis were conducted on two groups of patients with phenotypic diversity from the same family. These analyses identified significant differentially expressed genes and enriched pathways in these two groups. Altogether, these findings provide insight into the mechanism underlying the variable expressivity of VWS.