先天性牙发育不全WNT6基因突变的新位点

目的 探讨先天性牙发育不全病例与相关基因突变可能存在的联系,为疾病的早期诊断提供参考。方法 通过收集1例罕见先天性牙发育不全病例的临床和影像学资料,评估牙齿的形态、数量以及全身健康状况;采集患者静脉外周血,对与牙齿发育紧密关联的PAX9和MSX1基因双向测序;进行全外显子测序,筛查与牙发育异常相关的其他突变位点,对先证者儿子进行新发现突变位点的Sanger测序;通过模拟测算工具和体外细胞转染实验评估突变对基因表达的影响。结果 患者的临床特征是先天性右下颌单侧第一磨牙缺失,第二磨牙为单根,且伴有右下第二前磨牙多生。在PAX9和MSX1基因测序中发现,PAX9基因中c.717C>C/T为同义突变,MSX1基因中c.119C>G为错义突变,Polyphen预测为“良性”。全外显子测序发现WNT6基因的1个全新突变位点,内含子3中的c.637-7 C>A突变,经MAXENT预测,可能影响mRNA的剪切,且先证者及其儿子均携带该突变;细胞转染实验发现,该突变对WNT6基因的mRNA剪切没有影响。结论 单核苷酸多态性之间的相互作用可能与先天性牙发育异常相关。     

多数牙先天缺失可能与MSX1上的3个SNPs相关

目的:探讨多数牙先天缺失患者的MSXl基因突变位点.方法:从4个多数牙先天缺失患者与家庭部分成员、1个唇腭裂并发少数牙先天缺失的患者、1个牙列完整的对照儿童共14人的静脉血中提取DNA,在MSXl基因内设计引物,采用PCR方法扩增MSXl基因外显子1、2的编码区,而后对外显子1、2的PCR纯化产物测序,结合系游进行序列比对分析.结果:发现3个可能的单核苷酸多态性位点(single nucleotide pol-ymorphisms,SNPs).这3个SNPs均位于外显子1中,且来自不同家系的3个患者在这3个位点上同时出现杂合突变.其中,311位点由G变A,对应的密码子由编码甘氨酸的GGC变为编码天门冬氨酸的GAC,发生了错义突变;402位点由C变A,对应的密码子由CCC变为CCA,但仍编码脯氨酸,属同义突变;458位点由C变T,对应的密码子由编码丙氨酸的GCC变为编码缬氨酸的GTC,发生了错义突变.结论:多数牙先天缺失可能与MSX1基因上该3个单核苷酸多态性位点有关.     

一个单纯性先天缺牙家系的临床及基因突变分析

目的探讨多数牙先天缺失患者的人类成对盒基因（PAX9）和肌节同源盒基因（MSX1）突变位点,为该疾病的病因学研究提供依据。方法对于该例患者与部分正常家庭成员进行口内检查及家系调查,取研究模型测量其牙冠宽度,并与正常值比较。拍摄曲面断层片和头颅侧位片进行头影测量分析,对比颅面形态和错畸形类型及特点。从静脉血中提取DNA,根据PAX9和MSX1的全序列设计引物,采用聚合酶链式反应（PCR）扩增PAX9基因的外显子1、2、3、4及MSX1基因外显子1、2,而后通过对分段PCR纯化产物的测序,并结合系谱进行突变分析。结果患者伴有牙齿形态畸形,与中国人正常值相比较,牙冠宽度较小。头影测量分析结果提示先证者在骨面型及颌骨形态等方面无明显遗传倾向。基因筛查结果显示先证者及其母亲的PAX9外显子3第718位点上由G变为C,属错义突变,导致与之对应的第240位氨基酸由丙氨酸变为脯氨酸;MSX1未见突变。结论多数牙先天缺失可能与PAX9基因外显子3的第718位点上的错义突变有关。     

Van der Woude综合征家系先天缺牙患者MSX1基因突变的检测

目的探讨MSX1基因与Van der Woude综合征(VWS)家系中缺牙的关系。方法从VWS家系9中伴发缺牙患者2人及家系正常成员2人、60个牙列完整的健康者共64人的静脉血中提取DNA,设计MSX1基因引物,采用PCR方法扩增MSX1基因外显子1、2的编码区,而后对外显子1、2的PCR纯化产物测序,进行序列比对分析。结果 VWS家系9两个缺牙患者MSX1基因中有ivs2+68 C>T多态;伴IRF6基因突变的VWS患者缺牙较多。结论 VWS家系9中先天缺牙患者的牙先天缺失与MSX1基因的ivs2+68 C>T多态可能相关。     

颅骨锁骨发育不良综合征患者的RUNX2基因突变检测分析

目的:检测鉴定我国一个颅骨锁骨发育不良综合征(CCD)家系RUNX2基因突变情况.方法:采用先证者查证法,对家系各成员进行全身健康状况及口腔专科检查,进行CCD诊断;抽取先证者及其父母外周静脉血,提取基因组DNA, PCR扩增RUNX2基因并测序,BLAST同源分析,同时检测100名健康人的相同位点,排除多态位点的可能.结果:先证者具有典型的CCD临床特征,其母亲亦为CCD患者,父亲则无相应临床表现;将先证者的RUNX2基因测序结果进行Blastn比较分析,在Exon 2上发现了一个A→G突变;实际测序图谱显示双峰结构(G、A),对其CCD母亲的基因检测表明,此突变来自母系染色体该基因478位点的基因突变;密码子AAC→GAC可能部分引起第160位氨基酸的改变,天冬酰胺(Asn,N)变成天冬氨酸(Asp,D);该突变型为478 A>G,N160D.家系健康成员同一位点显示G的单峰,即与野生型序列相同.结论:检测到的478 A＞G,N160D为新的基因突变位点,拓展了国内CCD基因层次的研究领域,为国内外CCD致病基因的突变位点数据库增添了新的资料.     

中国先天性缺失牙患者PAX9基因的新突变

目的 探讨我国先天性缺失牙患者PAX9基因突变的特点，为该病发病的分子机制研究提供依据。方法 应用聚合酶链反应．单链构象多态性(PCR-SSCP)分析方法，对4个常染色体显性遗传少牙畸形家系(共45名成员，22例患者)中的13例患者和9名健康成员、16例散发性牙齿发育不全患者以及196名健康对照者的PAX9基因进行研究。结合DNA序列分析方法，对发现异常SSCP条带的患者进行突变分析。结果 2个少牙畸形家系(家系A和家系B)的先证者出现异常SSCP条带，家系A和家系B内患者均出现与各自先证者相同的异常SSCP条带。经过DNA序列分析，发现PAX9基因第2外显子的2个新突变：碱基插入(109InsG)导致的移码突变，碱基置换(c139T)导致的错义突变。其余家系患者、散发性患者均未发现异常SSCP条带。结论 109InsG和C139T突变扩大了先天性缺失牙患者的PAX9基因突变谱，为我国先天性缺失牙的基因诊断提供依据。     

颅骨锁骨发育不良综合征患者RUNX2基因突变检测

目的鉴定4个颅骨锁骨发育不良（cleidocranial dysplasia,CCD）家系RUNX2基因突变点。方法采用先证者查证法,对各家系成员进行全身健康状况及口腔专科检查,明确CCD诊断;抽取先证者及其父母外周静脉血,提取基因组DNA,PCR扩增RUNX2基因并测序,BLAST同源分析。结果在4个CCD家系患者中均检测到RUNX2不同的突变位点,家系中健康成员同一位点均为野生型序列,进一步证实RUNX2基因是CCD患者的致病基因。其中家系4的c.475G〉C错义突变是此次检测到的新突变位点;家系2的c.673C〉T以及家系3的c.1171C〉G突变位点在中国CCD患者中首次检出;家系1的c.674G〉A,R225Q是国外文献报道突变率最高的位点。结论本研究拓展了国内外CCD基因层次的研究领域,证实RUNX2基因的单倍体不足是CCD的致病原因。     

一个陕西汉族Van der Woude综合征家系IRF6基因的突变筛查

目的对一个陕西省汉族Van der Woude综合征(VWS)家系进行IRF6基因的突变筛查.方法在IRF6(interferon regulatory factor 6)基因内设计引物,经分段PCR(聚合酶链反应)包括剪切位点的9个外显子后DNA测序进行突变筛查,运用PIX-Protein Identification软件对检测结果进行蛋白二级结构分析.结果在所有患者IRF6基因的第2密码子发现与表型一致的GCC>GTC (r.268c→t NM 214278)的突变,该突变引起IRF6蛋白二级预测结构的改变.结论该家系Van der Woude综合征由IRF6基因突变引起,IRF6基因与唇腭、牙齿发育密切相关.     

单纯性先天缺牙患者BMP2/BMP4基因位点分析

目的对BMP2/BMP4基因在单纯性先天缺牙患者中的基因表达进行观察,探讨其在先天缺牙疾病中可能的发病机制。方法提取单纯性先天缺牙患者40例及其家系成员外周静脉血基因组DNA,另选择100例非先天缺牙患者作为对照,应用聚合酶链式反应（PCR）扩增BMP2/BMP4基因编码外显子,纯化、测序,应用DNASTAR软件对测序结果进行对比分析。采用SPSS13.0软件包对数据进行统计学处理。结果40例先天缺牙患者中,共检测到BMP2/BMP4基因 5个突变位点,其中BMP2基因4个突变点：3个错义突变c.109T>G, c.166C>G,c.570A>T,检出率分别为7.5%、2.5%和95%;1个同义突变（c.261A>G）,检出率为100%。3个为dbSNP 数据库中已报道过的多态位点：BMP2SNPs c.109T>G p.Ser37Ala; c.261A>G p.Ser87Ser;c.570A>T p.Arg190Ser;家系先证者BMP2 c.166C>G突变在正常对照组未检出,dbSNP 数据库未报道,也未被收录于致病基因数据库,为新突变位点。BMP4基因检测出错义突变c.455T>C,检出率为55%,为dbSNP 数据库中已报道过的多态位点。与对照组等位基因及基因型比较,无显著差异。结论单纯性先天缺牙可能与BMP2/BMP4基因检出SNPs相关。BMP2c.166C>G杂合突变是新发现的突变,可能是单纯性先天缺牙家系的致病突变。     

中国汉族不伴唇腭裂的缺指(趾)-外胚层发育异常-唇腭裂综合征TP63基因的杂合性突变一例

目的 研究不伴唇腭裂表现的缺指(趾)-外胚层发育异常-唇腭裂(ectrodactylyectodermal dysplasia clefting,EEC)综合征1例患者的TP63基因突变,探讨该病基因型与表型的关系.方法 利用DNA单链构象多态性实验对1个中国汉族不伴唇腭裂表现的EEC综合征核心家系进行突变初筛,聚合酶链反应扩增目的 基因片段,直接测序进行突变检测,以200名无先天性缺牙的健康者作为对照.结果 在患者TP63基因第7外显子cDNA838位存在C＞T的单碱基杂合性点突变,使其编码的第280位精氨酸替换为半胱氨酸(Arg280Cys,R280C).患者父母在该位点均显示正常的野生基因型.结论 TP63基因的单碱基杂合性突变(Arg280Cys,R280C)是引起该患者EEC综合征的致病原因,此突变为新生突变.     

Novel mutation of the initiation codon of PAX9 causes oligodontia

Tooth development is under strict genetic control. Oligodontia is defined as the congenital absence of 6 or more permanent teeth, excluding the third molar. The occurrence of non-syndromic oligodontia is poorly understood, but in recent years several cases have been described where a single gene mutation is associated with oligodontia. Several studies have shown that MSX1 and PAX9 play a role in early tooth development. We screened one family with non-syndromic oligodontia for mutations in MSX1 and PAX9. The pedigree showed an autosomal-dominant pattern of inheritance. Direct sequencing and restriction enzyme analysis revealed a novel heterozygous A to G transition mutation in the AUG initiation codon of PAX9 in exon 1 in the affected members of the family. This is the first mutation found in the initiation codon of PAX9, and we suggest that it causes haploinsufficiency.     

Identification of a novel missense mutation of MSX1 gene in Chinese family with autosomal-dominant oligodontia

OBJECTIVES: Oligodontia is defined as the congenital absence of 6 or more permanent teeth excluding the third molar. The occurrence of non-syndromic still remains poorly understood, but in recent years some cases have been reported where mutations or polymorphisms of PAX9 and MSX1 had been associated with non-syndromic oligodontia. The objective of the present work was to study the phenotype and genotype of three generations of a Han Chinese family affected by non-syndromic autosomal-dominant oligodontia. DESIGN: We examined all individuals of the oligodontia family by clinical and radiographic examinations. Based on clinical manifestations, candidate genes MSX1 and PAX9 were picked up to analyse and screen mutations. RESULTS: Dental evaluation showed that the most commonly missing teeth are the mandibular second premolars, followed by the maxillary second premolars and maxillary lateral incisors, and subsequently the maxillary first premolars. The probability of missing a particular type of tooth is not always bilaterally symmetrical, and differences exist between maxilla and mandible. PCR-SSCP analysis and DNA sequencing revealed a novel missense mutation c.662C>A in a highly conserved homeobox sequence of MSX1 and a known polymorphisms c.347C>G. CONCLUSION: Our finding suggests the missense transversion (c.662C>A) and the polymorphisms (c.347C>G) may be responsible for oligodontia phenotype in this Chinese family.     

Clinical and genetic evaluation of a Chinese family with isolated oligodontia

Objectives

Oligodontia is defined as the congenital absence of 6 or more permanent teeth excluding the third molar. Tooth agenesis may be classified as syndromic/non-syndromic and as familial/sporadic. To date, more than 300 genes have been found to be involved in tooth development, but only a few of these genes, such as MSX1, PAX9 and AXIN2, are related to the condition of non-syndromic oligodontia. The objective of the present work was to investigate the disease-causing gene of non-syndromic oligodontia in a Han Chinese family and analyse the pathogenesis of mutations that result in oligodontia.

Design

We examined all individuals of the oligodontia family by clinical and radiographic examinations. Based on the clinical manifestations, the candidate genes MSX, PAX9 and AXIN2 were selected to analyse and screen for mutations.

Results

The clinical evaluation suggested that the family might show non-syndromic oligodontia. DNA sequencing of the MSX1 gene revealed two mutations in the two patients with oligodontia: a heterozygotic silent mutation, c.348C > T (P.Gly116=), in exon 1 and a homozygotic deletion of 11 nucleotides (c.469 + 56delins GCCGGGTGGGG) in the intron. However, the silent mutation and the deletion mutation were thought to be known polymorphisms (rs34165410 and rs34341187) by bioinformatics analysis. We did not detect any mutations in the PAX9 and AXIN2 genes of oligodontia patients.

Conclusion

Our finding suggests that identified polymorphisms (c.348C > T and c.469 + 56delins GCCGGGTGGGG) may be responsible for the oligodontia phenotype in this Chinese family, but the association requires further study.     

A screen of a large Czech cohort of oligodontia patients implicates a novel mutation in the PAX9 gene

Tooth agenesis is one of the most common developmental anomalies in humans. To date, many mutations involving paired box 9 (PAX9), msh homeobox 1 (MSX1), and axin 2 (AXIN2) genes have been identified. The aim of the present study was to perform screening for mutations and/or polymorphisms using the capillary sequencing method in the critical regions of PAX9 and MSX1 genes in a group of 270 individuals with tooth agenesis and in 30 healthy subjects of Czech origin. This screening revealed a previously unknown heterozygous g.9527G>T mutation in the PAX9 gene in monozygotic twins with oligodontia and three additional affected family members. The same variant was not found in healthy relatives. This mutation is located in intron 2, in the region recognized as the splice site between exon 2 and intron 2. We hypothesize that the error in pre‐mRNA splicing may lead to lower expression of PAX9 protein and could have contributed to the development of tooth agenesis in the affected subjects.     

Sequence analysis of PAX9, MSX1 and AXIN2 genes in a Chinese oligodontia family

Objectives

The goal of our research was to look into the clinical traits and genetic mutations in nonsyndromic oligodontia in a Chinese family and to gain insight into the role of mutations of PAX9, MSX1 and AXIN2 in oligodontia phenotypes.

Materials and methods

6 subjects from a family underwent complete oral examination, including panoramic radiographs. Retrospective data were reviewed and blood samples were collected. PCR primers for PAX9, MSX1, and AXIN2 were designed through the Oligo Primer Analysis Software. PCR products were purified and sequenced using the BigDye Terminator Kit and analysed by the 3730 DNA Analyzer.

Results

The proband missed 4 permanent canines, 2 permanent maxillary lateral incisors, 2 permanent mandibular lateral incisors, and 2 permanent mandibular central incisors, whilst his maternal grandfather lacked only 2 permanent mandibular central incisors. Moreover, the size of some permanent teeth appeared smaller than normal values of crown width of Chinese people. Oligodontia and abnormalities of teeth were not present in other family members. Radiographic examination showed that the proband and the rest of family members retained all germs of the third molars. There was one known mutation A240P (rs4904210) of PAX9 in the coding region in the proband and the maternal family members (II-2, II-3, and II-4), which possibly contributed to structural and functional changes of proteins. No mutations were identified in MSX1 and AXIN2.

Conclusions

Our findings may imply that the PAX9 A240P mutation is a risk factor for oligodontia in the Chinese population. A240P is likely to be a genetic cause of oligodontia though previous literature suggested it as a polymorphism only.     

Novel nonsense mutation in MSX1 in familial nonsyndromic oligodontia: subcellular localization and role of homeodomain/MH4

Nonsyndromic tooth agenesis is one of the most common anomalies in human development. Part of the malformation is inherited and is associated with paired box 9 (PAX9), msh homeobox 1 (MSX1), and axin 2 (AXIN2) mutations. To obtain a comprehensive understanding of the genetic and molecular mechanisms that underlie this genetic disease, we investigated six familial and seven sporadic Japanese cases of nonsyndromic tooth agenesis. Searches for mutations in these candidate genes detected a novel nonsense mutation (c.416G>A) in exon 1 of MSX1 from a family with oligodontia. This mutation co‐segregated in the affected family members. Moreover, this mutation produced a termination codon in the first exon and therefore the gene product (W139X) was truncated at the C terminus, hence, the entire homeodomain/MH4, which has many functions, such as DNA binding, protein‐protein interaction, and nuclear localization, was absent. We characterized the properties of this truncated MSX1 by investigating the subcellular localization of the mutant gene product in transfected cells. The wild‐type MSX1 localized exclusively at the nuclear periphery of transfected cells, whereas the mutant MSX1 was stable but localized diffusely throughout the whole cell. These results indicate that W139X MSX1 is responsible for tooth agenesis.     

Genetic background of nonsyndromic oligodontia: a systematic review and meta-analysis

Objectives

The goal of this work was to identify all known gene mutations that have been associated with the development of nonsyndromic oligodontia.

Methods

A systematic literature search was performed electronically in two databases (PubMed, Medpilot) supplemented by a hand search. Articles published up to March 2012 were considered. Search terms were combined as follows: oligodontia and genes, oligodontia and mutations, tooth agenesis and genes, and tooth agenesis and mutations. A meta-analysis of the data was conducted based on the Tooth Agenesis Code (TAC).

Results

Seven genes are currently known to have a potential for causing nonsyndromic oligodontia. All these genes vary both in terms of number of identified mutations and in terms of number of documented patients: 33 mutations and 93 patients are on record for PAX9, 10 mutations and 51 patients for EDA, 12 mutations and 33 patients for MSX1, 6 mutations and 17 patients for AXIN2, and 1 mutation in 1 patient for EDARADD, NEMO, and KRT17 each. A total TAC score of 250 was found to have cutoff properties, as 100% of MSX1 and 80% of EDA patients exhibited TAC ≤250, whereas 96.9% of PAX9 and 90% of AXIN2 patients exhibited TAC >250. Furthermore, 94.3% of EDA patients but only 28.6% of MSX1 patients exhibited odd-numbered TAC scores in at least one quadrant, and 72.7% of PAX9 but none of the AXIN2 patients were found to show TAC scores of 112 in at least one quadrant.

Conclusion

In order of decreasing frequency, PAX9, EDA, MSX1, AXIN2, EDARADD, NEMO, and KRT17 are the seven genes currently known to have a potential for causing nonsyndromic oligodontia. TAC scores enabled us to identify an association between oligodontia phenotypes and genotypes in the patients covered by this meta-analysis.