Cleidocranial dysplasia and novel RUNX2 variants: dental, craniofacial, and osseous manifestations

Exploring the complexities of cleidocranial dysplasia: Dental anomalies and treatment interventions

INTRODUCTION

Cleidocranial dysplasia (CCD) is a genetic disorder characterized by distinctive oral manifestations, making dental anomalies a key diagnostic criterion and treatment focus.

METHODS

We retrospectively enrolled 32 patients diagnosed with CCD with detailed dental records (19 males and 13 females; mean age, 20.5 years). The detailed characteristics of impacted permanent teeth and supernumerary teeth were analyzed, and treatment considerations and outcomes for the abnormal dentition were summarized.

RESULTS

Among permanent teeth, 43.53% were impacted. A significant variation in the likelihood of tooth impaction was observed depending on the tooth position. On the basis of nonlinear regression analysis, this study identified a clear trend correlating the probability of impacted teeth with the sequence of permanent tooth eruption, with this probability exhibiting a distinct increase followed by a decrease (with R2 values in female and male patients of 0.65 and 0.84, respectively). In addition, 27 patients (84.4%) had supernumerary teeth, with 206 supernumerary teeth identified, predominantly of the supplemental premolar type (75.73%). There was a correlation between the morphology of supplemental teeth and their locations in the dentition. Among 10 patients with follow-up periods of >2 years, 117 impacted teeth were recorded, 61 teeth were involved in the treatment, 16 (26.23%) erupted after the extraction of retained deciduous or supernumerary teeth, and 33 teeth (54.10%) were successfully erupted through orthodontic traction. However, orthodontic treatment requires an extended period, and the periodontal conditions of treated teeth may require long-term maintenance.

CONCLUSIONS

This study reveals a potential relationship between tooth impaction and the sequence of tooth eruption. It also distinguishes the distribution and morphologic characteristics of supernumerary teeth in patients with CCD from those in the general population. In addition, by analyzing clinical data, this study provides a summary of treatment considerations and outcomes for abnormal dentition in patients with CCD.

Cbfβ: A key regulator in skeletal stem cell differentiation, bone development, and disease

The skeletal system comprises closely related yet functionally distinct bone and cartilage tissues, regulated by a complex network of transcriptional factors and signaling molecules. Among these, core-binding factor subunit beta (Cbfβ) emerges as a critical co-transcriptional factor that stabilizes Runx proteins, playing indispensable roles in skeletal development and homeostasis. Emerging evidence from genetic mouse models has highlighted the essential role of Cbfβ in directing the lineage commitment of mesenchymal stem cells (MSCs) and their differentiation into osteoblasts and chondrocytes. Notably, Cbfβ deficiency is strongly associated with severe skeletal dysplasia, affecting both endochondral and intramembranous ossification during embryonic and postnatal development. In this review, we synthesize recent advancements in understanding the structural and molecular functions of Cbfβ, with a particular focus on its interactions with key signaling pathways, including BMP/TGF-β, Wnt/β-catenin, Hippo/YAP, and IHH/PTHrP. These pathways converge on the Cbfβ/RUNX2 complex, which orchestrates a gene expression program essential for osteogenesis, bone formation, and cartilage development. The integration of these signaling networks ensures the precise regulation of skeletal development, remodeling, and repair. Furthermore, the successful local delivery of Cbfβ to address bone abnormalities underscores its potential as a novel therapeutic target for skeletal disorders such as cleidocranial dysplasia, osteoarthritis, and bone metastases. By elucidating the molecular mechanisms underlying Cbfβ function and its interactions with key signaling pathways, these insights not only advance our understanding of skeletal biology but also offer promising avenues for clinical intervention, ultimately improving outcomes for patients with skeletal disorders.

The impact of RUNX2 gene variants on cleidocranial dysplasia phenotype: a systematic review

Cleidocranial Dysplasia (CCD) is a rare genetic disorder characterized by skeletal abnormalities and dental anomalies, primarily caused by variants in the RUNX2 gene. Understanding the spectrum of RUNX2 variants and their effects on CCD phenotypes is crucial for accurate diagnosis and management strategies. This systematic review aimed to comprehensively analyze the genotypic and phenotypic spectra of RUNX2 variants in CCD patients, assess their distribution across functional regions, and investigate genotype-phenotype correlations. This review included 569 reported variants and 453 CCD patients from 103 articles. Of 569 variants, in-frame variants constituted 48.68%, while null variants accounted for 51.32%. Regarding locations, RUNX2 variants were predominantly located in the RHD (55.54%), followed by PST (16.34%), NMTS (6.33%), QA (4.75%), VWRPY (1.23%), and NLS (1.41%) regions while 10.19% were in non-coding regions. In-frame variants occurred primarily in the RHD (90.97%), while null variants were found across various regions of RUNX2. Data analysis revealed a correlation between variant location and specific skeletal features in CCD patients. Missense variants, predominantly found within the functionally critical RHD, were significantly associated with supernumerary teeth, macrocephaly, metopic groove, short ribs, and hypoplastic iliac wings compared to nonsense variants. They were also significantly associated with delayed fontanelle closure, metopic synostosis, hypertelorism, limited shoulder abduction, pubic symphysis abnormalities, and hypoplastic iliac wings compared to in-frame variants found in other regions. These findings underscore the critical role of the RHD, with missense RHD variants having a more severe impact than nonsense and other in-frame variants. Additionally, in-frame insertions and deletions in RUNX2 were associated with fewer CCD features, compared to missense, frameshift, and nonsense variants. Null variants in the NLS region exhibited weaker associations with delayed fontanelle closure, supernumerary teeth, Wormian bones, and femoral head hypoplasia than variants in other regions. Moreover, the NLS variants did not consistently alter nuclear localization, questioning the role of NLS region in nuclear import. In summary, this comprehensive review significantly advances our understanding of CCD, facilitating improved phenotype-genotype correlations, enhanced clinical management, and a deeper insight into RUNX2 functional domains. This knowledge has the potential to guide the development of novel therapeutic targets for skeletal disorders.

A novel perspective of calvarial development: the cranial morphogenesis and differentiation regulated by dura mater

There are lasting concerns on calvarial development because cranium not only accommodates the growing brain, but also safeguards it from exogenous strikes. In the past decades, most studies attributed the dynamic expansion and remodeling of cranium to the proliferation of osteoprecursors in cranial primordium, and the proliferation of osteoprogenitors at the osteogenic front of cranial suture mesenchyme. Further investigations identified series genes expressed in suture mesenchymal cells as the markers of the progenitors, precursors and postnatal stem cells in cranium. However, similar to many other organs, it is suggested that the reciprocal interactions among different tissues also play essential roles in calvarial development. Actually, there are increasing evidence indicating that dura mater (DM) is indispensable for the calvarial morphogenesis and osteogenesis by secreting multiple growth factors, cytokines and extracellular matrix (ECM). Thus, in this review, we first briefly introduce the development of cranium, suture and DM, and then, comprehensively summarize the latest studies exploring the involvement of ECM in DM and cranium development. Eventually, we discussed the reciprocal interactions between calvarium and DM in calvarial development. Actually, our review provides a novel perspective for cranium development by integrating previous classical researches with a spotlight on the mutual interplay between the developing DM and cranium.

Radiographic Orofacial Findings of Systemic Diseases

This article discusses the orofacial clinicoradiographic features of systemic diseases that manifest in the orofacial region. The systemic diseases discussed are grouped into the following: autoimmune diseases, endocrine diseases, bone diseases, hematologic diseases, syndromes, and malignancies. The radiographic manifestation ranges from radiolucent bony destruction, increased bone density, calcification, thinning of cortical plate, loss of trabeculation, missing teeth, and supernumerary teeth. It is imperative for clinicians to be cognizant of these findings, as they may be the first manifestation of these systemic diseases.

Polymorphisms in the Runx2 and osteocalcin genes affect BMD in postmenopausal women: a systematic review and meta-analysis

PURPOSE

Runx2 and osteocalcin have pivotal roles in bone homeostasis. Polymorphism of these two genes could alter the function of osteoblasts and consequently bone mineral density (BMD). Attempts to understand the relationship between these polymorphisms and BMD in postmenopausal women across a variety of populations have yielded inconsistent results. This meta-analysis seeks to define the relationship between these polymorphisms with BMD in postmenopausal women.

METHODS

Eligible studies were identified from three electronic databases. Data were extracted from the eligible studies (4 studies on Runx2 and 6 studies on osteocalcin), and associations of Runx2 T > C and osteocalcin HindIII polymorphisms with BMD in postmenopausal women were assessed using standard difference in means (SDM) and 95% confidence intervals (CI) as statistical measures.

RESULTS

A significant difference in the lumbar spine (LS) BMD in postmenopausal women was observed between the TT and CC homozygotes for the Runx2 T > C (SDM = -0.445, p-value = 0.034). The mutant genotypes (CC) showed significantly lower LS BMD in comparison to wild type genotypes under recessive model of genetic analysis (TC + TT vs. CC: SDM = -0.451, p-value = 0.032). For osteocalcin, HindIII polymorphism, the mutant genotypes (HH) was associated with significantly higher BMD for both LS and femoral neck (FN) than the wild type (hh) homozygotes (SDM = 0.152, p-value = 0.008 and SDM = 0.139, p-value = 0.016 for LS and FN, respectively). There was no association between total hip (TH) BMD and the osteocalcin HindIII polymorphism.

CONCLUSIONS

Runx2 T > C and osteocalcin HindIII polymorphisms influence the level of BMD in postmenopausal women and may be used as predictive markers of osteoporosis.

Dental abnormalities in rare genetic bone diseases: Literature review

Currently, over 500 rare genetic bone disorders are identified. These diseases are often accompanied by dental abnormalities, which are sometimes the first clue for an early diagnosis. However, not many dentists are sufficiently familiar with phenotypic abnormalities and treatment approaches when they encounter patients with rare diseases. Such patients often need dental treatment but have difficulties in finding a dentist who can treat them appropriately. Herein we focus on major dental phenotypes and summarize their potential causes and mechanisms, if known. We discuss representative diseases, dental treatments, and their effect on the oral health of patients and on oral health-related quality of life. This review can serve as a starting point for dentists to contribute to early diagnosis and further investigate the best treatment options for patients with rare disorders, with the goal of optimizing treatment outcomes.

Dental characteristics of patients with four different types of skeletal dysplasias

OBJECTIVE

Skeletal dysplasia (SD) comprises more than 450 separate disorders. We hypothesized that their dental features would be distinctive and investigated the tooth characteristics of four patients with different SDs.

MATERIAL AND METHODS

Four SD patients with molecularly confirmed diagnoses, Pt-1 acromicric dysplasia, Pt-2 hypophosphatasia and hypochondroplasia, Pt-3 cleidocranial dysplasia, and Pt-4 achondroplasia, were recruited. A tooth from each patient was evaluated for mineral density (micro-computerized tomography), surface roughness (surface profilometer), microhardness, mineral contents (energy-dispersive X-ray), and ultrastructure (scanning electron microscopy and histology), and compared with three tooth-type matched controls.

RESULTS

Pt-1 and Pt-3 had several unerupted teeth. Pt-2 had an intact-root-exfoliated tooth at 2 years old. The lingual surfaces of the patients' teeth were significantly smoother, while their buccal surfaces were rougher, than controls, except for Pt-1's buccal surface. The patients' teeth exhibited deep grooves around the enamel prisms and rough intertubular dentin. Pt-3 demonstrated a flat dentinoenamel junction and Pt-2 had an enlarged pulp, barely detectable cementum layer, and ill-defined cemento-dentinal junction. Reduced microhardnesses in enamel, dentin, and both layers were observed in Pt-3, Pt-4, and Pt-1, respectively. Pt-1 showed reduced Ca/P ratio in dentin, while both enamel and dentin of Pt-2 and Pt-3 showed reduced Ca/P ratio.

CONCLUSION

Each SD has distinctive dental characteristics with changes in surface roughness, ultrastructure, and mineral composition of dental hard tissues.

CLINICAL RELEVANCE

In this era of precision dentistry, identifying the specific potential dental problems for each patient with SD would help personalize dental management guidelines.

Functional consequences of C-terminal mutations in RUNX2

Cleidocranial dysplasia (CCD) is a genetic disorder caused by mutations in the RUNX2 gene, affecting bone and teeth development. Previous studies focused on mutations in the RUNX2 RHD domain, with limited investigation of mutations in the C-terminal domain. This study aimed to investigate the functional consequences of C-terminal mutations in RUNX2. Eight mutations were analyzed, and their effects on transactivation activity, protein expression, subcellular localization, and osteogenic potential were studied. Truncating mutations in the PST region and a missense mutation in the NMTS region resulted in increased transactivation activity, while missense mutations in the PST showed activity comparable to the control. Truncating mutations produced truncated proteins, while missense mutations produced normal-sized proteins. Mutant proteins were mislocalized, with six mutant proteins detected in both the nucleus and cytoplasm. CCD patient bone cells exhibited mislocalization of RUNX2, similar to the generated mutant. Mislocalization of RUNX2 and reduced expression of downstream genes were observed in MSCs from a CCD patient with the p.Ser247Valfs*3 mutation, leading to compromised osteogenic potential. This study provides insight into the functional consequences of C-terminal mutations in RUNX2, including reduced expression, mislocalization, and aberrant transactivation of downstream genes, contributing to the compromised osteogenic potential observed in CCD.

Precision Medicine in Oral Health and Diseases: A Systematic Review

Precision medicine (PM) is personalized medicine that can develop targeted medical therapies for the individual patient, in which "omics" sciences lead to an integration of data that leads to highly predictive models of the functioning of the individual biological system. They enable rapid diagnosis, assessment of disease dynamics, identification of targeted treatment protocols, and reduction of costs and psychological stress. "Precision dentistry" (DP) is one promising application that need further investigation; the purpose of this paper is therefore to give physicians an overview of the knowledge they need to enhance treatment planning and patient response to therapy. A systematic literature review was conducted on the PubMed, Scopus, and Web of Science databases by analyzing the articles examining the role of precision medicine in dentistry. PM aims to shed light on cancer prevention strategies, by identifying risk factors, and on malformations such as orofacial cleft. Another application is pain management by repurposing drugs created for other diseases to target biochemical mechanisms. The significant heritability of traits regulating bacterial colonization and local inflammatory responses is another result of genomic research, and is useful for DP in the field of caries and periodontitis. This approach may also be useful in the field of orthodontics and regenerative dentistry. The possibility of creating an international network of databases will lead to the diagnosis, prediction, and prevention of disease outbreaks, providing significant economic savings for the world's health care systems.

Detection and diagnosis of cleidocranial dysplasia by panoramic radiography: a retrospective study

BACKGROUND

Cleidocranial dysplasia (CCD) is a rare and underdiagnosed congenital disorder in dentistry. The purpose of this study was to illustrate and quantify the maxillofacial bone abnormalities detected on panoramic radiographs from a relatively large retrospective case series and to provide a series of diagnostic references for dentists to indicate the presence of disease and help in making an early and accurate diagnosis.

METHODS

The dental panoramic radiographs of thirty CCD patients aged 11 to 45 years (18 males and 12 females) were examined retrospectively. The dentition states, including supernumerary teeth and impacted teeth, were recorded. Twelve quantified measurements were adopted to determine the abnormalities of maxillofacial bones, including the degree of the zygomatic arch downward bend, bicondylar breadth, ramal height, mandibular height, mandibular aspect ratio, mandibular body height, condylar height, coronoid height, distance between the coronoid process and the condyle, bigonial width, gonial angle and best-fit gonial circle diameter. The Wilcoxon rank-sum test was used to compare the findings of the CCD patients with those of their matched controls (n = 300).

RESULTS

Supernumerary teeth were detected in 27 patients (90.0%), and all 30 patients presented impacted teeth. Compared to the matched controls, the CCD patients had a significantly larger degree of zygomatic arch downward bend (ZAD), a larger diameter of the best-fit gonial circle (BGC), and a shorter distance between the coronoid process and the condyle (DCC) in panoramic radiographs (P < 0.001). According to the reference cutoff values established from the 5th or 95th percentile of the measurements in the control group, ZAD higher than 6.90 mm, DDC less than 22.37 mm and BGC higher than 52.41 mm were significantly associated with the CCD features identified. Other panoramic measurements were not significantly different between the two groups.

CONCLUSIONS

Panoramic radiographs had great value in the diagnosis of CCD. In this study, we identified some dental and maxillofacial features on panoramic radiographs from a relatively large retrospective case series of CCD. A series of reliable quantitative indicators were provided for dentists that can indicate the presence of disease and improve the diagnostic specificity.