RUNX2 mutations in cleidocranial dysplasia patients

Objective:  Mutations in the RUNX2 gene, a master regulator of bone formation, have been identified in cleidocranial dysplasia (CCD) patients. CCD is a rare autosomal-dominant disease characterized by the delayed closure of cranial sutures, defects in clavicle formation, and supernumerary teeth. The purposes of this study were to identify genetic causes of two CCD nuclear families and to report their clinical phenotypes.
Materials and methods:  We identified two CCD nuclear families and performed mutational analyses to clarify the underlying molecular genetic etiology.
Results:  Mutational analysis revealed a novel nonsense mutation (c.273T>A, p.L93X) in family 1 and a de novo missense one (c.673C>T, p.R225W) in family 2. Individuals with a nonsense mutation showed maxillary hypoplasia, delayed eruption, multiple supernumerary teeth, and normal stature. In contrast, an individual with a de novo missense mutation in the Runt domain showed only one supernumerary tooth and short stature.
Conclusions:  Mutational and phenotypic analyses showed that the severity of mutations on the skeletal system may not necessarily correlate with that of the disruption of tooth development.     

Diversity of supernumerary tooth formation in siblings with cleidocranial dysplasia having identical mutation in RUNX2 : possible involvement of non-genetic or epigenetic regulation

INTRODUCTION: Cleidocranial dysplasia (CCD, MIM #119600) is an autosomal-dominant disorder characterized by hypoplasia or aplasia of clavicles, patent fontanelles and short stature. The responsible gene has been identified as RUNX2. CCD is also accompanied by characteristic dental abnormalities, e.g. supernumerary teeth, delayed eruption and impaction of permanent teeth. Intrafamilial variations of skeletal abnormalities are reported but those of dental abnormalities are obscure. To clarify this point, a precise examination of the dental features of CCD siblings having identical mutation was performed. DESIGN: Gene mutational analysis of three Japanese CCD siblings and their father was performed. Skeletal and dental characteristics were examined by the inquiry and radiographs. RESULTS: Three siblings uniformly showed patent fontanelles and short stature. They and their father had a novel missense mutation in the RUNT-domain (P210S) of RUNX2. The siblings were completely discordant for the dental characteristics with the position and number of supernumerary teeth being completely different. The youngest, a 12-year-old boy, had six supernumerary teeth, which appeared symmetrically around the maxillary canines and mandibular premolars. The second, a 15-year-old girl, had four supernumerary teeth which appeared around the mandibular incisors. The oldest, a 17-year-old boy, had 11 supernumerary teeth, which were symmetrically around the mandibular lateral dentition and asymmetrically around the maxillary incisors and premolars. CONCLUSION: The present study suggests the involvement of non-genetic or epigenetic regulation in supernumerary tooth formation in CCD.     

Phenotypes of CCAAT/enhancer‐binding protein beta deficiency: hyperdontia and elongated coronoid process

Oral Diseases (2012) Objectives: This investigation aimed to conduct a case–control study of mandibular morphology and dental anomalies to propose a relationship between mandibular/dental phenotypes and deficiency of CCAAT/enhancer‐binding protein beta (CEBPB). Materials and methods: Skulls of CEBPB^?/?, CEBPB^+/? and CEBPB^+/+ mice were inspected with micro‐computed tomography. Mandibular morphology was assessed with a method of Euclidean distance matrix analysis. Results: Elongation of the coronoid process was identified in CEBPB^+/? (P ≤ 0.046) and CEBPB^?/? 12‐month‐olds (P ≤ 0.028) but not in 14‐day‐olds (P ≥ 0.217) and 0‐day‐olds (P ≥ 0.189) of either genotype. Formation of supernumerary teeth in CEBPB^?/? adult mice was demonstrated (χ² = 6.00, df = 1, P = 0.014). Conclusions: CEBPB deficiency was related to elongation of the coronoid process and formation of supernumerary teeth. The mandibular and dental phenotypes of CEBPB deficiency were unseen by the 14th day after birth. Future investigations into the influence of CEBPB on mandibular and dental development are needed.     

Delayed tooth eruption and suppressed osteoclast number in the eruption pathway of heterozygous Runx2/Cbfa1 knockout mice

Genetic studies have recently identified a mutation of one allele of runt-related gene 2 (RUNX2/CBFA1) as the cause for an autosomal-dominant skeletal disorder, cleidocranial dysplasia (CCD), which is characterised by hypoplasia of the clavicles and calvariae and widened sutures and fontanelles. In addition, CCD is frequently affected with multiple supernumerary teeth and the impaction and delayed eruption of teeth, the causes of all these dental abnormalities are still unknown. To clarify the cellular mechanism of the delayed tooth eruption in CCD, the process of tooth eruption was examined in heterozygous Runx2/Cbfa1 (mouse homolog of RUNX2/CBFA1) knockout mice, known to mimic most of the bone abnormalities of CCD. The timing of the appearance of maxillary and mandibular teeth into the oral cavity was significantly delayed in heterozygous mutant mice compared with wild-type mice. From postnatal days 8 to 10, an active alveolar bone resorption and a marked increase of the osteoclast surfaces was observed in the eruption pathway of both genotypes, but this increase was significantly suppressed in the mutant mice. In contrast, the osteoclast surfaces did not show a significant difference between the two genotypes in the future cortical area of femora. These results suggest that haploinsufficiency of Runx2/Cbfa1 does not effect the femoral bone remodelling but is insufficient for the active alveolar bone resorption essential for the prompt timing of tooth eruption. These results also suggest the possibility that impaired recruitment of osteoclasts is one of the cellular mechanisms of delayed tooth eruption in CCD patients.     

Dysostosis cleidocranialis

Background

Cleidocranial dysplasia (CCD) is a rare dysplasia of bony and dental tissue. Characteristic are typical craniofacial and dental findings including morphological anomalies. CCD is possibly the only general syndrome that can be diagnosed based on the dental findings alone. CCD correlates with mutations in the RUNX2 gene.

Purpose

The present interdisciplinary study correlates phenotypic findings with genetic variations in the corresponding gene.

Patients and methods

The coding sequence of the RUNX2 gene from 31 CCD patients from 20 families was analyzed using molecular genetic methods including polymerase chain reaction and direct sequencing. The craniofacial and dental findings of each patient were evaluated according to a standardized scoring scheme and tested with homogeneity analysis for general phenotypic findings.

Results

Several mutations of the RUNX2 gene were identified. Depending on the mutation type, they showed different distribution patterns within the gene coinciding with the functional domains of the gene product. With homogeneity analysis of the phenotype cardinal (especially dental findings) and minor findings (pneumatization disturbances, Wormian bones) were identified. In combination with the genetic data, the statistical analysis showed that loss-of-function mutations of the RUNX2 gene result in a milder markedness of the CCD phenotype than gain-of-function or decrease-of-function mutations.

Conclusions

We found that type and location of a specific mutation within the RUNX2 gene might have an impact on the expressivity of CCD. Due to the limited sampling size this hypothesis must be verified by investigations in larger patient groups.     

锁骨颅骨发育不全综合征(CCD)的牙面畸形特征分析

目的：分析锁骨颅骨发育不全综合征牙面畸形的表现.方法：收集15年（1990～2004年）诊断为锁骨颅骨发育不全综合征（CCD）患者.其中男性2例、女性2例,就诊时年龄12～18岁,平均年龄14.2岁.所有病例均填写病历、询问其囟门关闭情况,并拍摄胸片,上下颌骨曲面断层片,头颅正、侧位片位,TMJ片、面（牙合）像.结果：1）4例均有多生牙,2）乳牙滞留,3）颌骨发育异常,下颌骨发育过度、上颌骨正常或发育不足,下颌肥大、反（牙合）面型.牙槽骨较一般致密,局部区域骨小梁排列致密.4）4例患者均表现面部异常,头大面小,面下1/3短.眶间距较正常人大且颧弓突出、下弯.结论：分析锁骨颅骨发育不全综合征牙面畸形的表现有助于临床诊断.     

Cleidocranial dysplasia: report of six clinical cases

Cleidocranial dysplasia (CCD) is an autosomal‐dominant disorder that occurs due to mutations in the Cbfa 1 gene, also called Runx 2, located on the short arm of chromosome 6, affecting osteoblast skeletal‐specific bones that have intramembranous ossification. This condition is characterized by hypoplastic clavicles, short stature, and great clinical significance in the stomatognathic complex, with involvement of facial bones, changes in the eruption patterns, including multiple supernumerary and retained teeth. This study reports six subjects of the same family with CCD identified in the Dentistry Clinic of Oral Diagnosis Department, Universidade Paulista, Campus Sorocaba, Sao Paulo State, Brazil. All cases had clinical and radiographic aspects of this important condition, such as short stature, hypertelorism, severe mobility of the shoulders, and supernumerary and retained teeth. Due to the rare incidence and phenotypic manifestations, CCD can be easily misdiagnosed. The oral commitments are one of the main (functional and aesthetic) causes of complaints in these subjects; and a dentist must establish the diagnosis as early as possible, followed by behaviors and practices that can minimize harmful manifestations of the syndrome and improve health associated with oral and multidisciplinary integration offering improvements in quality of life of these subjects.     

Non-syndromic multiple supernumerary teeth: meta-analysis

J Oral Pathol Med (2012) 41 : 361–366 Background: Non‐syndromic multiple supernumerary teeth (NSMST) is a condition with a very low prevalence and which is opportunely described in the literature by case reports or group of cases. This represents a problem when it comes to describing and discussing the characteristics of this disorder. Materials and Methods: A search was conducted in PubMed, Web of Knowledge, Science Direct, and Scopus databases to locate and identify cases and series of cases about articles on multiple supernumerary teeth not associated with syndromes that have been reported so far. The following data were recorded: age, gender, total number of supernumerary teeth, number of teeth in both the maxilla and mandible, respectively, and number of teeth in each dental series (incisor, canine‐premolar, and molar). Bilaterality in dental series and its localization in either maxilla or mandible were also determined. Results: A total of 46 cases including patients of both genders with a mean age of 19 years (SD = 6.826) and a ratio of 2.14:1 were identified. A total of 393 supernumeraries were reported; 43.26% (n = 170) were located in the maxilla and 56.74% (n = 223) in the mandible. No significant differences were found between genders with respect to the total number, involvement of the dental series, or distribution of supernumerary teeth in each of the arches. Conclusion: Although NSMST is a condition that has a higher incidence in the male gender, no differences have been found as to their number and localization in both genders. Bilaterality seems to be a common characteristic of this disorder.     

一颅锁骨发育不全综合征家族的RUNX2基因分析研究

目的 检测一个颅锁骨发育不全综合征（CCD）家系RUNX2基因突变情况。方法 采用先证者查证法,对CCD家系各成员进行全身健康状况及口腔专科检查,拍摄X线片;抽取先证者及其父母、姐姐外周静脉血,提取基因组DNA,聚合酶链反应（PCR）扩增RUNX2基因并测序,将先证者及其父母、姐姐RUNX2基因测序结果进行Blastn比较分析。结果 在先证者RUNX2基因的外显子2上发现了一个C→T突变,此突变来自母系染色体该基因568位点的基因突变;密码子CGG→TGG引起RUNX2编码的转录因子第190位保守的精氨酸变成色氨酸,突变型为c.568C>T。结论 c.568C>T突变是导致该家系发病的分子基础。     

Metabolomics profiling of cleidocranial dysplasia

Objectives

Cleidocranial dysplasia (CCD) is a rare autosomal-dominantly inherited skeletal dysplasia that is predominantly associated with heterozygous mutations of RUNX2. However, no information is available regarding metabolic changes associated with CCD at present.

Materials and methods

We analyzed members of a CCD family and checked for mutations in the RUNX2 coding sequence using the nucleotide BLAST program. The 3D protein structure of mutant RUNX2 was predicted by I-TASSER. Finally, we analyzed metabolites extracted from plasma using LC-MS/MS.

Results

We identified a novel mutation (c.1061insT) that generates a premature termination in the RUNX2 coding region, which, based on protein structure prediction models, likely alters the protein’s function. Interestingly, metabolomics profiling indicated that 30 metabolites belonging to 13 metabolic pathways were significantly changed in the CCD patients compared to normal controls.

Conclusions

The results highlight interesting correlations between a RUNX2 mutation, metabolic changes, and the clinical features in a family with CCD. The results also contribute to our understanding of the pathogenetic processes underlying this rare disorder.

Clinical relevance

This study provides the first metabolomics profiling in CCD patients, expands our insights into the pathogenesis of the disorder, may help in diagnostics and its refinements, and may lead to novel therapeutic approaches to CCD.

     

颅骨锁骨发育不良综合征患者的临床检查及诊断

目的探讨颅骨锁骨发育不良(CCD)的口腔综合表现,明确其诊断特征。方法收集4例CCD患者临床资料,对具有相关临床症状的先证者详细采集病史,明确单发或家族聚集倾向;利用X线检查全面了解患者及其父母的全身骨骼发育情况;详细进行口腔检查,记录恒牙萌出及乳牙迟萌以及埋藏牙、多生牙等;综合临床资料,明确诊断。结果4例患者均具有明显的临床特征,较典型的CCD特殊面容;口腔内表现为乳牙滞留,多数恒牙及多生牙埋伏于颌骨中不能萌出,仅1例未见明显多生牙;均伴有锁骨发育不全、囟门闭合迟缓、身材矮小等症状。并发现一些新的畸形表现,如病例3先证者的尺、桡骨向桡侧偏斜致肱尺关节、肱桡关节畸形,肘外侧呈三角变形;病例2先证者的多生牙发生在磨牙区。结论乳牙列正常、恒牙迟萌以及多个埋伏多生牙等口腔综合表现是比较明确的CCD诊断特征,通过详细的临床资料采集,不难对CCD作出早期诊断。     

Cementum analysis in cleidocranial dysostosis

Objective: Cleidocranial dysostosis (CCD) is a skeletal disorder associated with dental anomalies such as failure or delayed eruption of permanent teeth and multiple impacted supernumerary or permanent teeth. Absence of cellular cementum at the root apex is presumed to be one of the factors for failure or delayed eruption. The aim of this study was to analyze the root cementum of supernumerary(S) and permanent teeth (P) of a CCD patient and to compare the findings with those of normal individuals with special emphasis on delayed eruption. Materials and Methods: Ground sections of 12 extracted teeth (9S + 3P) of a CCD patient and 12 teeth of normal individuals (5S + 7P) were taken for the study. The sections were longitudinal and 50 microm thick. Root characteristics were recorded with the aid of a light microscope. Results: The absence of apical cellular cementum, increased root resorption and increased percentage of the gap type of cemento-enamel (C-E) junctions were significant findings noted both in the supernumerary and permanent teeth of the CCD patient. Conclusion: The presumption of cellular cementum is essential for tooth eruption is not supported by the findings of the present study. Delayed exception could be attributed to various other factors like mechanical obstruction, reduced serum alkaline phosphatase levels etc. Also, the significance of the increased percentage of the gap type of C-E junctions and its role in tooth eruption has to be further evaluated.     

Runx2 (Cbfa1) inhibits Shh signaling in the lower but not upper molars of mouse embryos and prevents the budding of putative successional teeth

Heterozygous mutations in the RUNX2 (CBFA1) gene cause cleidocranial dysplasia, characterized by multiple supernumerary teeth. This suggests that Runx2 inhibits successional tooth formation. However, in Runx2 knockout mice, molar development arrests at the late bud stage, and lower molars are more severely affected than upper ones. We have proposed that compensation by Runx3 may be involved. We compared the molar phenotypes of Runx2/Runx3 double-knockouts with those of Runx2 knockouts, but found no indication of such compensation. Shh and its mediators Ptc1, Ptc2, and Gli1 were down-regulated only in the lower but not the upper molars of Runx2 and Runx2/Runx3 knockouts. Interestingly, in front of the mutant upper molar, a prominent epithelial bud protruded lingually with active Shh signaling. Similar buds were also present in Runx2 heterozygotes, and they may represent the extension of dental lamina for successional teeth. The results suggest that Runx2 prevents the formation of Shh-expressing buds for successional teeth.     

Il trattamento chirurgico di elementi dentari soprannumerari: tre casi di quarti molari

ObjectivesTo review the diagnosis, causes, treatment, and possible complications of impacted supernumerary fourth molars on the basis of data reported in the literature and our own clinical experience.Materials and methodsWe report three cases of supernumerary fourth molars that were treated by surgical extraction.Results and conclusionsNone of the patients who underwent surgery experienced intraoperative- or postoperative complications. Surgical extraction of the supernumerary tooth eliminates the risk of complications such as root resorption involving adjacent teeth, delayed eruption of permanent teeth, dental crowding, and the development of odontogenic cysts.     

A Case of Cleidocranial Dysostosis: Dilemma for a Prosthodontist

Cleidocranial dysostosis (CCD) is an uncommon, generalized skeletal disorder characterized by delayed ossification of the skull, aplastic or hypoplastic clavicles, and complex dental abnormalities such as retention of multiple deciduous teeth, impaction or delayed eruption of permanent teeth and presence of supernumerary teeth. This case report describes a 30-year old male patient of CCD with classical findings and the challenges faced in his prosthodontic rehabilitation. Conventional complete dentures following interim complete dentures therapy had to be given as all other treatment modalities were ruled out because of anatomic limitations. Despite the disadvantages of removable dentures the patient adapted admirably to them with significant improvement in self-esteem. Though orthodontic and surgical correction may be the treatment of choice, the need to preserve the alveolar ridge could make fabrication of removable dentures in such patients, a viable option.