Effects of Fam83h truncation mutation on enamel developmental defects in male C57/BL6J mice

CRISPR/Cas9-Induced Fam83h Knock-out Leads to Impaired Wnt/β-Catenin Pathway and Altered Expression of Tooth Mineralization Genes in Mice

Background

Dental enamel formation is a complex process that is regulated by various genes. One such gene, Family With Sequence Similarity 83 Member H (Fam83h), has been identified as an essential factor for dental enamel formation. Additionally, Fam83h has been found to be potentially linked to the Wnt/β-catenin pathway.

Objectives

This study aimed to investigate the effects of the Fam83h knockout gene on mineralization and formation of teeth, along with mediators of the Wnt/β-catenin pathway as a development aspect in mice.

Materials and Methods

To confirm the Fam83h-KnockOut mice, both Sanger sequencing and Western blot methods were used. then used qPCR to measure the expression levels of genes related to tooth mineralization and formation of dental root, including Fam20a, Dspp, Dmp1, Enam, Ambn, Sppl2a, Mmp20, and Wnt/β-catenin pathway mediators, in both the Fam83h-Knockout and wild-type mice at 5, 11 and 18 days of age. also the expression level of Fgf10 and mediators of the Wnt/β-catenin pathway was measured in the skin of both Knockout and wild-type mice using qPCR. A histological assessment was then performed to further investigate the results.

Results

A significant reduction in the expression levels of Ambn, Mmp20, Dspp, and Fgf10 in the dental root of Fam83h-Knockout mice compared to their wild-type counterparts was demonstrated by our results, indicating potential disruptions in tooth development. Significant down-regulation of CK1a, CK1e, and β-catenin in the dental root of Fam83h-Knockout mice was associated with a reduction in mineralization and formation-related gene. Additionally, the skin analysis of Fam83h-Knockout mice revealed reduced levels of Fgf10, CK1a, CK1e, and β-catenin. Further histological assessment confirmed that the concurrent reduction of Fgf10 expression level and Wnt/β-catenin genes were associated with alterations in hair follicle maturation.

Conclusions

The concurrent reduction in the expression level of both Wnt/β-catenin mediators and mineralization-related genes, resulting in the disruption of dental mineralization and formation, was caused by the deficiency of Fam83h. Our findings suggest a cumulative effect and multi-factorial interplay between Fam83h, Wnt/Β-Catenin signaling, and dental mineralization-related genes subsequently, during the dental formation process.

Tooth ultrastructure changes induced by a nonsense mutation in the FAM83H gene: insights into the diversity of amelogenesis imperfecta

OBJECTIVES

The current research on single-nucleotide polymorphism (SNP) mutation sites at different positions of the FAM83H gene and their phenotypic changes leading to amelogenesis imperfecta (AI) is inconsistent. We identified a previously reported heterozygous nonsense mutation c.1192C>T (p.Q398*) in the FAM83H gene and conducted a comprehensive analysis of the dental ultrastructure and chemical composition changes induced by this mutation. Additionally, we predicted the protein feature affected by this mutation site. The aim was to further deepen our understanding of the diversity of AI caused by different mutation sites in the FAM83H gene.

METHODS

Whole-exome sequencing (WES) and Sanger sequencing were used to confirm the mutation sites. Physical features of the patient's teeth were investigated using various methods including cone beam computer tomography (CBCT), scanning electron microscopy (SEM), contact profilometry (roughness measurement), and a nanomechanical tester (nanoindentation measurement). The protein features of wild-type and mutant FAM83H were predicted using bioinformatics methods.

RESULTS

One previously discovered FAM83H heterozygous nonsense mutation c.1192C>T (p.Q398*) was detected in the patient. SEM revealed inconsistent dentinal tubules, and EDS showed that calcium and phosphorus were lower in the patient's dentin but higher in the enamel compared to the control tooth. Roughness measurements showed that AI patients' teeth had rougher occlusal surfaces than those of the control tooth. Nanoindentation measurements showed that the enamel and dentin hardness values of the AI patients' teeth were both significantly reduced compared to those of the control tooth. Compared to the wild-type FAM83H protein, the mutant FAM83H protein shows alterations in stability, hydrophobicity, secondary structure, and tertiary structure. These changes could underlie functional differences and AI phenotype variations caused by this mutation site.

CONCLUSIONS

This study expands the understanding of the effects of FAM83H mutations on tooth structure.

CLINICAL RELEVANCE

Our study enhances our understanding of the genetic basis of AI and may contribute to improved diagnostics and personalized treatment strategies for patients with FAM83H-related AI.

Fam83h mutation causes mandible underdevelopment via CK1α-mediated Wnt/β-catenin signaling in male C57/BL6J mice

Truncation mutations in FAM83H are the major cause of autosomal dominant hypocalcified amelogenesis imperfecta. Some studies also indicated that FAM83H could be involved in osteogenic differentiation; however, the function of FAM83H in bone formation was rarely explored. This study aimed to explore the effect of Fam83h mutation on skeletal development. We generated Fam83h c.1186C>T (p.Q396*) knockin C57/BL6J mice by CRISPR/Cas9 technology and found that the Fam83hQ396⁎/Q396⁎ male mice presented skeletal development retardation that was inconspicuous at birth but progressively worsened as they grew up. Alcian and Alizarin Red staining of the whole-mount skeleton showed Fam83hQ396⁎/Q396⁎ mice presented obvious skeletal development retardation. Moreover, Micro-computed tomography (Micro-CT) analysis and H&E staining showed that the mandible of Fam83hQ396⁎/Q396⁎ mice exhibited decreased bone trabecula and slight bone rarefaction compared with wild-type mice. Calcium and phosphorus content of serum and bone, and serum ALP activity analysis showed that the serum ALP activity and value of bone calcium were decreased in Fam83hQ396⁎/Q396⁎ mice. The reduced expression of mineralization markers of RUNX2, OSX, OCN, and COL1, the reduced ALP activity and the weakened ARS staining exhibited in osteoblasts isolated from 3-day-old Fam83hQ396⁎/Q396⁎ mice. The increased protein expression of casein kinase 1α (CK1α) in the cytoplasm and the decreased expression of β-CATENIN in the nucleus indicated the inhibiting Wnt/β-catenin signaling in osteoblasts from Fam83hQ396⁎/Q396⁎ mice. Furthermore, agonists of Wnt/β-catenin signaling and Ck1α siRNA partially reversed the mineralization inhibition and the decreased expression of key signaling molecules in osteoblasts of Fam83hQ396⁎/Q396⁎ mice. In conclusion, Fam83h mutation caused the increase of cytoplasmic CK1α (as one of the components of the degradation complex), which in turn promoted degradation of β-CATENIN in the cytoplasm and reduced β-CATENIN translocation into the nucleus, subsequently inhibited Wnt/β-catenin signaling in osteoblast differentiation, and thus resulted in the mandible underdevelopment in Fam83hQ396⁎/Q396⁎ male mice.

Crucial Role of microRNAs as New Targets for Amelogenesis Disorders Detection

INTRODUCTION

Amelogenesis imperfecta (AI) refers to a heterogeneous group of conditions with multiple factors which contribute to the hypomineralisation of enamel. Preventive measures are necessary to predict this pathology. Prospects for preventive medicine are closely related to the search for new informative methods for diagnosing a human disease. MicroRNAs are prominent for the non-invasive diagnostic platform.

THE AIM OF THE STUDY

The aim of the review is to review the heterogeneous factors involved in amelogenesis and to select the microRNA panel associated with the AI type.

METHODS

We used DIANA Tools (algorithms, databases and software) for interpreting and archiving data in a systematic framework ranging from the analysis of expression regulation from deep sequencing data to the annotation of miRNA regulatory elements and targets (https://dianalab. e-ce.uth.gr/). In our study, based on a gene panel associated with the AI types, twenty-four miRNAs were identified for the hypoplastic type (supplement), thirty-five for hypocalcified and forty-- nine for hypomaturation AI. The selection strategy included the microRNA search with multiple targets using the AI type's gene panel.

RESULTS

Key proteins, calcium-dependent and genetic factors were analysed to reveal their role in amelogenesis. The role of extracellular non-coding RNA sequences with multiple regulatory functions seems to be the most attractive. We chose the list of microRNAs associated with the AI genes. We found four microRNAs (hsa-miR-27a-3p, hsa-miR-375, hsa-miR-16-5p and hsamiR- 146a-5p) for the gene panel, associated with the hypoplastic type of AI; five microRNAs (hsa- miR-29c-3p, hsa-miR-124-3p, hsa-miR-1343-3p, hsa-miR-335-5p, and hsa-miR-16-5p - for hypocalcified type of AI, and seven ones (hsa-miR-124-3p, hsa-miR-147a, hsa-miR-16-5p, hsamiR- 429, hsa-let-7b-5p, hsa-miR-146a-5p, hsa-miR-335-5p) - for hypomaturation. It was revealed that hsa-miR-16-5p is included in three panels specific for both hypoplastic, hypocalcified, and hypomaturation types. Hsa-miR-146a-5p is associated with hypoplastic and hypomaturation type of AI, which is associated with the peculiarities of the inflammatory response immune response. In turn, hsa-miR-335-5p associated with hypocalcified and hypomaturation type of AI.

CONCLUSION

Liquid biopsy approaches are a promising way to reduce the economic cost of treatment for these patients in modern healthcare. Unique data exist about the role of microRNA in regulating amelogenesis. The list of microRNAs that are associated with AI genes and classified by AI types has been uncovered. The target gene analysis showed the variety of functions of selected microRNAs, which explains the multiple heterogeneous mechanisms in amelogenesis. Predisposition to mineralisation problems is a programmed event. Many factors determine the manifestation of this problem. Additionally, it is necessary to remember the variable nature of the changes, which reduces the prediction accuracy. Therefore, models based on liquid biopsy and microRNAs make it possible to take into account these factors and their influence on the mineralisation. The found data needs further investigation.