One germline mutation of PTCH gene in a Chinese family with non-syndromic keratocystic odontogenic tumours

Keratocystic odontogenic tumours (KOCTs) are common benign cystic tumours that arise sporadically or associated with nevoid basal cell carcinoma syndrome (NBCCS). PTCH mutation can be found in sporadically or NBCCS associated KOCTs. Few PTCH mutations in families with non-syndromic KOCTs have been reported. Through PCR and gene sequence analysis, the authors discovered one missense mutation c.3277G>C in exon 19 of PTCH gene in a Chinese family with non-syndromic KOCTs. This mutation causes one highly conserved glycine residue transit to arginine on the 10th transmembrane region of PTCH protein. This work revealed that the missense mutation of PTCH is the causative and dominant gene of KOCTs in this family.     

PTCH gene mutations in odontogenic keratocysts

An odontogenic keratocyst (OKC) is a benign cystic lesion of the jaws that occurs sporadically or in association with nevoid basal cell carcinoma syndrome (NBCCS). Recently, the gene for NBCCS was cloned and shown to be the human homologue of the Drosophila segment polarity gene Patched (PTCH), a tumor suppressor gene. The PTCH gene encodes a transmembrane protein that acts in opposition to the Hedgehog signaling protein, controlling cell fates, patterning, and growth in numerous tissues, including tooth. We investigated three cases of sporadic odontogenic keratocysts and three other cases associated with NBCCS, looking for mutations of the PTCH gene. Non-radioactive single-strand conformational polymorphism and direct sequencing of PCR products revealed a deletion of 5 base pairs (bp) in exon 3 (518delAAGCG) in one sporadic cyst as well as mutations in two cysts associated with NBCCS, a nonsense (C2760A) and a missense (G3499A) alteration. This report is the first to describe a somatic mutation of PTCH in sporadic odontogenic keratocysts as well as two novel mutations in cysts associated with NBCCS, indicating a similar pathogenesis in a subset of sporadic keratocysts.     

PTCH1 and SMO gene alterations in keratocystic odontogenic tumors

Keratocystic odontogenic tumors (KCOTs, previously known as odontogenic keratocysts) are aggressive jaw lesions that may occur in isolation or in association with nevoid basal cell carcinoma syndrome (NBCCS). Mutations in the PTCH1 (PTCH) gene are responsible for NBCCS and are related in tumors associated with this syndrome. Mutations in the SMO gene have been identified in basal cell carcinoma and in medulloblastoma, both of which are features of NBCCS. To clarify the role of PTCH1 and SMO in KCOTs, we undertook mutational analysis of PTCH1 and SMO in 20 sporadic and 10 NBCCS-associated KCOTs, and for SMO, 20 additional cases of KCOTs with known PTCH1 status were also included. Eleven novel (1 of which occurred twice) and 5 known PTCH1 mutations were identified. However, no pathogenic mutation was detected in SMO. Our findings suggest that mutations are rare in SMO, but frequent in PTCH1 in sporadic and NBCCS-associated KCOTs. Abbreviations: NBCCS, nevoid basal cell carcinoma syndrome; KCOTs, keratocystic odontogenic tumors; BCCs, basal cell carcinomas.     

PCR-SSCP和DNA测序检测牙源性角化囊肿中PTCH基因的突变

目的 检测牙源性角化囊肿（OKC）中PTCH基因突变的特点。方法 采用PCR-SSCP筛查与DNA直接测序的方法对12例OKC进行PTCH基因突变的检测, 其中2例为痣样基底细胞癌综合征（NBCCS）相关OKC,10例为散发OKC。 结果 在4例OKC中发现了4处突变,其中2处生殖细胞突变发生在2例NBCCS相关OKC,2处体细胞突变发生在2例散发OKC。另外,还在10例OKC中检测到了8处PTCH基因多态性。结论 NBCCS相关OKC和散发OKC均可发生PTCH基因突变,但突变水平不同,PTCH基因的突变在二者的发病中可能均起重要作用。     

牙源性角化囊肿中PTCH基因的突变检测

目的检测牙源性角化囊肿（OKC）中PTCH基因突变的发生频率、类型及分布特点，分析散发OKC与伴发痣样基底细胞癌综合征（NBCCS）OKC之间的分子病理联系。方法收集8例OKC新鲜病变组织（4例散发，4例伴发NBCCS），提取DNA，采用PCR直接测序法检测OKC病变组织中的PTCH基因突变。结果分别于4例NBCCS—OKC和2例散发OKC中检测到6处PTCH基因突变，2例为错义突变，引起1个氨基酸的改变；其余4例突变分别为1～7个碱基插入或缺失，其中3例引起读码框的改变（移码突变），并导致蛋白质的提前截断，1例导致了2个氨基酸的插入。结论PTCH基因突变不仅常见于NBCCS—OKC，部分散发OKC病变也可以发生该基因的异常。     

PTCH germline mutations in Chinese nevoid basal cell carcinoma syndrome patients

OBJECTIVES: PTCH, the human homologue of the Drosophila segment polarity gene, patched, has been identified as the gene responsible for nevoid basal cell carcinoma syndrome. The aim of this study was to investigate PTCH gene mutation in Chinese patients with nevoid basal cell carcinoma syndrome. MATERIALS AND METHODS: DNA was isolated from both odontogenic keratocyst tissue and peripheral blood of five patients with syndrome and one patient with only multiple odontogenic keratocysts, and mutational analysis of the PTCH gene performed by direct sequencing after amplification of all 23 exons by polymerase chain reaction (PCR). RESULTS: A previously reported germline mutation (c.2619C>A) was identified in two familial cases involving the mother and the daughter, with the mother also carrying a novel somatic mutation (c.361_362insGAGC). Three novel germline PTCH mutations (c.1338_1339insGCG, c.331delG and c.1939A>T) were detected in three unrelated patients with syndrome. The patient with multiple odontogenic keratocysts who failed to fulfill the diagnostic criteria of the syndrome also carried a novel germline mutation (c.317T>G). CONCLUSION: The frequent germline PTCH mutations detected in our series provide further evidence for the crucial role of PTCH in the pathogenesis of nevoid basal cell carcinoma syndrome in Chinese.     

牙源性角化囊肿SMO基因突变检测

目的检测牙源性角化囊肿(odontogenic keratocyst,OKC)是否存在SMO基因突变,进一步完善对OKC发病机制的认识。方法收集2012年9月至2017年6月就诊于北京大学口腔医学院·口腔医院口腔颌面外科的OKC患者,10例为痣样基底细胞癌综合征性OKC(女性4例,男性6例),20例为散发性OKC(女性7例,男性13例)。采集患者的病变组织,分离衬里上皮和纤维间质,采用Sanger测序法分别检测上皮与间质DNA中SMO基因突变情况。结果检测发现3个SMO基因突变位点,即1例综合征性OKC携带c.2081C>G(p.P694R)突变,2例散发性OKC分别携带c.907C>T(p.L303F)突变和c.1247_1248delinsAA(p.G416E)突变,前2例突变为未被报道过的SMO新突变,且2例散发性OKC均不伴PTCH1突变。结论除PTCH1突变外,OKC还存在SMO基因突变,可能与OKC的发病机制有关。     

家族性锁骨颅骨发育不全的基因突变检测

目的 研究家族性锁骨颅骨发育不全家系的Cbfal基因突变。方法 对临床收集到的一个牙列异常、锁骨颅骨发育不全家系行外周血基因组DNA的提取，利用聚合酶链式反应，DNA直接测序检测突变。结果在该家系中每例患者均存在Cbfal基因外显子3中的杂合性突变，即cDNA674位G〉A的单碱基突变，从而使255位的精氨酸替换为谷氨酰胺（Pa55Q），改变了runt结构域的氨基酸序列。结论Cbfal基因的突变是引起此家系锁骨颅骨发育不全的致病原因。突变检测的结果可用于该家系后代的产前诊断。这也是在中国人家族性锁骨颅骨发育不全患者中首次检测到的基因突变。     

一个中国汉族痣样基底细胞癌综合征家系致病基因的定位研究

目的定位一个中国汉族痣样基底细胞癌综合征(NBCCS)家系的致病基因.方法选择SHH信号系统的基因作为该NBCCS家系致病基因的候选基因,用微卫星遗传标记在候选基因染色体区域定位致病基因.结果连锁分析结果发现,PTCH2基因所在染色体区域微卫星遗传标记D1 s2797 LODZMAX为1.31(平均遗传距离73.81)、D1 s2802 LODZMAX为1.26(平均遗传距离73.81),支持连锁.构建单体型发现家系内所有病变表型的个体D1s2797和D1 s2802的基因型一致,无交换重组现象.而SHH,PTCH,SMO基因染色体区域微卫星遗传标记连锁分析结果不支持连锁.结论这个中国汉族NBCCS家系的致病基因定位在PTCH2基因染色体区域1p32.3,遗传距离为1.85cM.     

PTCH mutations in sporadic and Gorlin-syndrome-related odontogenic keratocysts

Odontogenic keratocysts are relatively common lesions that may occur in isolation or in association with nevoid basal cell carcinoma syndrome (or Gorlin syndrome). The PTCH gene has been reported to be associated with Gorlin syndrome. We investigated 10 cases of non-syndromic keratocysts and two other cases associated with Gorlin syndrome, looking for PTCH mutations. Four novel and 1 known PTCH mutations were identified in five individual patients. Of the 5 mutations identified, 2 were germ-line mutations (2619C>A; 1338_1339insGCG) in 2 cysts associated with Gorlin syndrome, and 3 were somatic mutations (3124_3129dupGTGTGC; 1361_1364delGTCT; 3913G>T) in 3 non-syndromic cysts. This report describes PTCH mutations in both non-syndromic and Gorlin-syndrome-related odontogenic keratocysts in Chinese patients, and suggests that defects of PTCH are associated with the pathogenesis of syndromic as well as a subset of non-syndromic keratocysts.     

基底细胞痣综合征中国一家系致病相关基因连锁及突变分析

目的 揭示基底细胞痣综合征中国一个家系发病的分子遗传基础，为家系中的年轻患者实行早期监测和治疗。方法 首先选择家系中先证者和其患病母亲及家系中一名健康人，提取外周血DNA，聚合酶链反应（PCR）扩增PTCH基因编码氨基酸的23个外显子，对扩增产物进行DNA测序后；采用位于9q22．3-q31区的3个微卫星DNA标记对该家系行遗传连锁分析。结果 先证者患病母亲PTCH基因未发现突变；先证者（V4）14号外显子发生同义突变；连锁分析显示，在位点D9S283、D9S1690和D9S1677，Lod值＜-2（θ=0．00）。结论 排除了PTCH基因作为基底细胞痣综合征该家系致病基因的可能。     

痣样基底细胞癌综合征伴先天性左眼缺失1例

痣样基底细胞癌综合征（NBCCS）又称基底细胞痣综合征或Goltz-Gorlin综合征，是一种复杂且罕见的常染色体显性遗传疾病，大量研究文献证实PTCH1基因与NBCCS有关。本文报道1例NBCCS伴先天性左眼缺失的病例，并结合相关文献探讨以进一步了解该综合征。     

Clinical,pathological and genetic evaluations of Chinese patients with autosomal-dominant hypophosphatasia

ObjectivesHypophosphatasia (HPP) is an inherited disorder characterised by defective bone and tooth mineralisation and deficient serum and bone alkaline phosphatase activity, and it results from mutations in alkaline phosphatase (ALPL) encoding tissue-nonspecific alkaline phosphatase (TNAP). The objective of the present work was to explore the correlations between genotype and phenotype in a Chinese family affected by autosomal-dominant HPP.DesignWe examined all individuals of a HPP family by clinical and radiographic examinations as well as laboratory assays. Furthermore, a prematurely exfoliated tooth was observed histopathologically. Based on the clinical and pathological manifestations, the causative gene ALPL was selected for further analysis and screened for mutations.ResultsThe proband presented the characteristic clinical features of childhood HPP such as rachitic skeletal changes, early loss of primary teeth, and short root anomalies of the permanent teeth. Histopathological evaluation of a tooth revealed a “shell” structure, severe mineralisation defects of dentin, and an absence of cementum. The patient's mother and grandfather were clinically diagnosed with adult HPP. The family showed autosomal-dominant moderate hypophosphatasia. DNA sequencing and analysis revealed a novel missense mutation (c.251A>T) in exon4 of ALPL. This mutation (p.E84V) is located in the secondary structure of TNAP's homodimer interface, and it was predicted to have a dominant negative effect.ConclusionOur findings suggest the missense transversion (c.251A>T, p.E84V) should be responsible for the HPP phenotype in this Chinese family.     

Novel identification of a four-base-pair deletion mutation in PITX2 in a Rieger syndrome family

Rieger syndrome is one of the most serious causes of tooth agenesis. Mutations in the PITX2, FOXC1, and PAX6 genes have been associated with Rieger syndrome. We have studied a three-generation Chinese family affected with Rieger syndrome and showing prominent dental abnormalities. Mutational screening and sequence analysis of the PITX2 gene revealed a previously unidentified four-base-pair deletion of nucleotides 717-720 in exon 5 in all affected members. The mutation causes a frame shift after Thr44, the 7th amino acid of the homeo-domain, and introduces a premature stop codon in the gene sequence. This deletion is the first unquestionable loss-of-function mutation, deleting all the functionally important parts of the protein. Our novel discovery indicates that the oligodontia and other phenotypes of Rieger syndrome observed in this family are due to this PITX2 mutation, and these data further support the critical role of PIXT2 in tooth morphogenesis.     

A novel FGFR2 gene mutation in Crouzon syndrome associated with apparent nonpenetrance.

OBJECTIVE: To determine whether specific mutations within the fibroblast growth factor receptor 2 (FGFR2) gene that are associated with Crouzon syndrome can be present in an individual who had been assumed to be "clinically normal." METHODS: Most mutations responsible for Crouzon syndrome occur in exons IIIa (U) or IIIc (B) of the FGFR2 gene, which facilitates allelotyping using polymerase chain reaction (PCR)-mediated mutation analysis. Once a specific mutation was identified in the index case, remaining affected family members and "clinically normal" first-degree relatives were analyzed in order to correlate genotype with phenotype. RESULTS: A novel missense mutation--a G to T transversion--involving the first base of codon 362 was identified in all Crouzon syndrome-affected family members and in one "clinically normal"-appearing parent following DNA sequencing of exon B of the FGFR2 gene and specific BstNI restriction fragment length polymorphism. Pattern profile analysis demonstrated a consistent collection of abnormal cephalometric measurements in the Crouzon-affected family members and, to a lesser degree, in the "clinically normal" parent. CONCLUSION: We have identified a novel missense mutation in the FGFR2 gene that predicts an Ala362Ser substitution shared by all family members affected by Crouzon syndrome and by a "clinically normal"-appearing father. These data support nonpenetrance of Crouzon syndrome when the diagnosis is based on clear clinical findings. Only through cephalometry was there an indication of minimal expression of Crouzon syndrome in the "clinically normal"-appearing father.     

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.     

Contributions of PTCH gene variants to isolated cleft lip and palate.

OBJECTIVE: Mutations in patched (PTCH) cause the nevoid basal cell carcinoma syndrome (NBCCS), or Gorlin syndrome. Nevoid basal cell carcinoma syndrome may present with developmental anomalies, including rib and craniofacial abnormalities, and predisposes to several tumor types, including basal cell carcinoma and medulloblastoma. Cleft palate is found in 4% of individuals with nevoid basal cell carcinoma syndrome. Because there might be specific sequence alterations in PTCH that limit expression to orofacial clefting, a genetic study of PTCH was undertaken in cases with cleft lip and/or palate (CL/P) known not to have nevoid basal cell carcinoma syndrome. RESULTS: Seven new normal variants spread along the entire gene and three missense mutations were found among cases with cleft lip and/or palate. One of these variants (P295S) was not found in any of 1188 control samples. A second variant was found in a case and also in 1 of 1119 controls. The third missense (S827G) was found in 5 of 1369 cases and in 5 of 1104 controls and is likely a rare normal variant. Linkage and linkage desequilibrium also was assessed using normal variants in and adjacent to the PTCH gene in 220 families (1776 individuals), each with two or more individuals with isolated clefting. Although no statistically significant evidence of linkage (multipoint HLOD peak = 2.36) was uncovered, there was borderline evidence of significant transmission distortion for one haplotype of two single nucleotide polymorphisms located within the PTCH gene (p = .08). CONCLUSION: Missense mutations in PTCH may be rare causes of isolated cleft lip and/or palate. An as yet unidentified variant near PTCH may act as a modifier of cleft lip and/or palate.     

一个掌跖角化-牙周破坏综合征患者家系组织蛋白酶C基因突变分析

目的 对一个掌跖角化-牙周破坏综合征（PLS）患者及其家系组织蛋白酶C基因（CTSC）突变位点进行分析,探讨PLS的分子致病机制。方法 提取1例PLS先证者及其直系血亲（父母、弟弟）的基因组DNA,应用聚合酶链反应和DNA直接测序技术分析先证者及其直系血亲CTSC基因的突变情况。结果 PLS先证者CTSC基因存在复合型杂合突变。先证者位于外显子6的第800位碱基发生了一个杂合错义突变,该碱基对中的碱基T被C取代（c.800T>C）,其编码的氨基酸由亮氨酸改变为脯氨酸（p.L267P）;位于外显子7的第1015位碱基发生了一个杂合错义突变,该碱基对中的碱基C被T取代（c.1015C>T）,其编码的氨基酸由精氨酸改变为半胱氨酸（p.R339C）。其中,c.800T>C来自母亲,c.1015C>T来自父亲,弟弟的CTSC基因未见突变。结论 PLS的临床表征与CTSC基因突变有关。     

A mandibular swelling

Nevoid basal cell carcinoma syndrome (NBCCS) is characterised by skeletal anomalies, cutaneous basal cell carcinomas and multiple keratocysts. NBCCS is an autosomal dominant disorder, but can have a variable phenotypic penetration. NBCCS can also arise spontaneously. The prevalence is 1:60.000 and 50-65% of patients with NBCCS have affected family members. A recently diagnosed patient is presented and the manifestations of the syndrome are discussed.