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.     

一个中国汉族遗传性出血性毛细血管扩张症家系致病基因的定位研究

目的定位一个中国汉族遗传性出血性毛细血管扩张症家系的致病基因。方法选择基因ALK-1及endoglin作为该HHT家系致病基因的候选基因，在候选基因染色体区域进行定位。结果连锁分析结果发现ALK-1染色体区域微卫星遗传标记D12s1586LODZMAX为1．82，D12s1677LODZMAX为1．74，D12s1635LODZMAX为1．65，D12s368 LODZMAX为1．87，支持连锁。构建单体型发现家系内所有患者在ALK-1染色体区域都连锁，无交换重组现象。而endoglin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HHT家系的致病基因定位在ALK-1染色体区域。     

牙本质发育不全Ⅱ型的遗传异质性研究

目的：明确牙本质涎磷蛋白(dentin sialophosphoprotein，DSPP)是否为该家系的致病基因，并对该家系做进一步的基因定位研究。方法：通过DNA测序方法对DSPP基因进行突变检测，用位于4q21区域的7个微卫星位点对家系进行遗传连锁分析。结果：测序结果显示DSPP在该家系中不存在突变，基因定位研究表明致病基因在该家系位于IMS1534和DSPP之间。结论：DSPP在该家系不是致病基因，牙本质发育不全Ⅱ型存在遗传异质性。     

遗传性乳光牙本质家系致病基因的染色体定位

目的　研究一个在天津塘沽地区发现的遗传性乳光牙本质回族家系致病基因是否与染色体 4q2 1连锁。方法　提取该家系 1 3名成员的外周血DNA ,选择染色体 4q2 1上的 8个短串联重复序列多态性标记 (shorttandemrepeatpolymorphisms ,STRPs)做荧光标记PCR等位片段分析 ,用lod连锁分析法分析该家系致病基因位点与上述 8个STRPs的连锁关系。结果　得到 1 3名个体 8个位点的基因型和单体型 ,连锁分析结果显示 :8个STRPs的最大lod值均大于 0 ,其中 5个STRPs的lod值大于 1。结论　该家系致病基因定位在染色体 4q2 1上 ,表明中国回族人和报道的欧美人的DGI Ⅱ的基因座位是一致的     

遗传性釉质发育不全家系致病基因的定位研究

目的定位遗传性釉质发育不全（AI）家系的致病基因。方法收集1个常染色体显性AI家系,提取该家系19名成员（其中患者9例）的外周血DNA,选择横跨釉蛋白基因、成釉蛋白基因、釉丛蛋白基因、基质金属蛋白酶基因、丝氨酸蛋白酶基因5个候选基因的短串联重复序列（STR）,进行PCR扩增,经变性聚丙烯酰胺凝胶电泳确定基因型,并进行连锁分析。结果得到19名个体的8个STR位点的基因型,分别为D1s498、D1s2343、D4s1543、D4s2361、D4s2969、D11s1339、mmp20、D19s246。连锁分析结果显示各位点的LOD值在重组率为0时均小于1,不支持该家系的致病基因与5个侯选基因上的STR位点的连锁关系。结论连锁分析结果不支持该家系致病基因定位于已知基因座处,提示至少某些常染色体显性AI家系的致病基因不是文献所报道的AI候选基因,进一步证实了常染色体显性遗传性釉质发育不全的遗传异质性。     

遗传性牙本质发育不全Ⅱ型家系致病基因的连锁分析及DMP1的突变检测

目的：对中国江苏淮阴一个遗传性牙本质发育不全Ⅱ型家系的致病基因进行定位,同时对该疾病的侯选基因之一DMP1进行突变检测。方法：用位于4q21区域的7个微卫星位点对家系进行遗传连锁分析,并通过聚合酶链反应－单链构象多态分析（PCR－SSCP）和DNA测序方法对DMP1基因进行突变检测。结果：所选的7个位点,除D4S451和D4S1534之外,最大Lod值Zmax均大于3（θ＝0）;PCR－SSCP和测序结果显示DMP1Exon2－6均无突变。结论：遗传性牙本质发育不全Ⅱ型与位于4q21区域的微卫星位点GATA62A11、DSP、DMP1、SPP1和D4S1563连锁;排除DMP1做为该病致病基因的可能性。     

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。     

EDA基因大片段缺失X连锁隐性遗传无汗/少汗型外胚叶发育不全家系研究

目的:收集X连锁隐性遗传无汗/少汗型外胚叶发育不全(XLHED)家系,并分析家系的遗传方式、表型特点及致病基因型。方法:采用课题组制定的临床检查和家系调查技术路线,对通过先证者法收集的XLHED家系进行遗传方式和临床表现分析。利用直接测序法对家系EDA基因开放阅读框内外显子编码区及外显子-内含子接头区进行核苷酸序列分析。结果:收集到的外胚叶发育不全家系为X连锁隐性遗传,男性患者临床表现典型,女性携带者有轻度临床表现,家系内表现度差异小。家系患者EDA基因外显子3缺失。结论:本研究收集一个典型XLHED大家系,患者临床特征明显。家系患者EDA基因存在大片段缺失。     

X连锁隐性遗传无汗/少汗型外胚叶发育不全家系表型和基因型分析

目的:探讨X连锁隐性遗传无汗/少汗型外胚叶发育不全(XLHED)家系的遗传方式和表型特点,并对家系基因型进行分析。方法:采用临床检查和家系调查的方法,对通过先证者法收集的XLHED家系进行遗传方式和临床表现分析。利用直接测序法对家系EDA基因开放阅读框内外显子编码区及外显子-内含子接头区核苷酸进行序列分析。结果:收集到的家系为X连锁隐性遗传,男性患者临床表现典型,女性携带者有轻度临床表现或无症状,家系内表现度差异小。家系患者EDA基因第491位核苷酸由腺嘌呤颠变为胞嘧啶(c.491A>C)。结论:本研究收集家系的患者临床症状明显,为典型的XLHED家系。家系致病突变为一已知突变(E164A)。     

遗传性牙龈纤维瘤病中国家系中SOS1基因突变的研究

目的 筛查中国遗传性牙龈纤维瘤病(hereditary gingival fibromatosis,HGF)家系中SOS1基因,为寻找HGF致病基因突变提供线索.方法 收集到两个中国非综合征性HGF家系,患者表现出典型而且一致的临床表型.采取受试对象的外周血,提取基因组DNA.针对SOS1基因的23个外显子序列设计引物,PCR扩增纯化后进行Sanger测序.结果 两个中国HGF家系的患者均未携带已知SOS1基因的插入突变(c.3248-3249insC),在SOS1基因的外显子区,以及外显子与内含子交接的剪接区,均未发现其他的突变位点.结论 SOS1基因不是HGF中国家系的致病基因,中国HGF具有不同的遗传背景,存在其他潜在的致病基因和突变.应该利用全外显子组测序等方法,在中国HGF家系中寻找新的致病基因.     

Mapping of a gene influencing initial dental caries susceptibility to chromosome 11

In the present study, our purpose was to identify candidate gene(s) influencing initial dental caries susceptibility on chromosomes 7 and 11 using a Quantitative Trait Loci (QTL) analysis. On chromosome 7, five suggestive QTLs were detected in D7Mit31, D7Mit148, D7Mit262, D7Mit126 and D7Mit101. On chromosome 7, the peak LRS score was located in a region 50 cM from the centromere between marker D7Mit31 and PTH. On chromosome 11, five significant QTLs were detected in D11Mit242, D11Mit26, D11Mit339, D11Mit177 and D11Mit262. On chromosome 11, one highly significant QTL was detected in Kcnj12, the peak LRS score was located in a region 34.15 cM from the centromere marker Kcnj12. These results suggest that Kcnj12 on chromosome 11 might be one of the major gene(s) responsible for initial dental caries susceptibility.     

Identification of chromosomal region(s) influencing initial dental caries susceptibility in mice

Predicting the host genetic factors influencing dental caries susceptibility is important to developing preventive strategies in individuals. In this study, Quantitative Trait Locus (QTL) analysis was used to identify the candidate regions for gene(s) influencing initial dental caries susceptibility in mice, and that performed on genetic crosses of BALB/cJ and C3H/HeJ mice. Two significant QTLs on chromosomes 7 and 11 and five suggestive QTLs on chromosomes 3, 8, 16 and 17 were detected. Around the region 50 cM on Chromosome 7 and 46 cM on chromosome 11, the likelihood ratio statistic (LRS) scores showed higher than significant levels. Around 52.5 cM on chromosome 3, 38.4 cM on chromosome 8, 38.0 cM on chromosome 16, and 6.5 cM and 44.5 cM on chromosome 17, LRS scores showed higher than suggestive levels. Based on these results, it is suggested that the candidate gene(s) responsible for dental caries are located in the specified regions of six chromosomes, chromosomes 7 and 11 in particular are associated with initial dental caries.     

Novel COL1A1 mutation (G559C) [correction of G599C] associated with mild osteogenesis imperfecta and dentinogenesis imperfecta

A genotype-phenotype analysis of a three-generation family segregating for an autosomal-dominant osteogenesis imperfecta (OI) variant is reported here. The family was ascertained through the presentation of a proband concerned about discoloration of her teeth, found to be dentinogenesis imperfecta (DGI). Examination of 36 family members identified 15 individuals with DGI. Linkage studies were performed for genetic markers from candidate intervals known to contain genes responsible for DGI on chromosomes 4q, 7q, and 17q. Conclusive evidence for linkage of DGI was obtained to genetic markers on chromosome 17q21-q22 (DLX-3, Z(max) = 5.34, theta = 0.00). All DGI-affected family members shared a common haplotype, which was not present in individuals without DGI. Haplotype analysis sublocalized the gene to a 5-cM genetic interval that contained the collagen 1 alpha 1 (COL1A1) gene. More than 150 different COL1A1 gene mutations have been associated with various forms of OI, and five of these have been associated with DGI and type IV OI. After excluding these five mutations, mutational analysis was performed on the remaining exons including intron--exon boundaries, which resulted in identification of a Gly559Cys mutation in exon 32, present in all DGI-affected family members. Clinical features segregating with this G559C mutation included hyperextensible joints, joint pain and an increased propensity for bone fractures with moderate trauma. This is the first report of joint pain associated with a COL1A1 mutation and DGI. The mild skeletal features and reduced penetrance of the non-dental findings illustrate the importance of genetic evaluations for families with a history of DGI.     

Mutational analysis of X-linked amelogenesis imperfecta in multiple families

Seven mutations in the amelogenin gene are associated with X-linked amelogenesis imperfecta. These mutations can produce reductions in the amount of enamel and the degree of mineralization. Two families have been identified from western North Carolina exhibiting features of amelogenesis imperfecta, characterized by brown enamel in affected males and interposed vertical bands of normal appearing and brown enamel in presumably heterozygous females. Mutational analysis reveals a C-A mutation in exon 6 at codon 41 of the X-chromosomal amelogenin gene, resulting in a pro-thr change in all individuals having the amelogenesis imperfecta phenotype. This mutation was previously reported in a family with X-linked hypomaturation amelogenesis imperfecta. There is no known relationship between any of the three families but the presence of similar phenotypes and common mutations suggests they may be distantly related. For individuals from all three families, the haplotype for six highly polymorphic loci flanking the amelogenin gene was determined. A common haplotype was demonstrated among two of the three families, suggesting that the mutation may have been inherited from a common ancestor. The finding that the third family had a distinct haplotype may indicate that the C-A mutation at codon 41 represents a mutational hotspot that occurs with greater frequency than other known amelogenin gene mutations. The phenotype resulting from this mutation was highly consistent in affected male members of the same family and between families.     

Detection of a novel mutation in X-linked amelogenesis imperfecta

Amelogenesis imperfecta (AI) is a heterogeneous group of inherited disorders of defective enamel formation. The major protein involved in enamel formation, amelogenin, is encoded by a gene located at Xp22.1-Xp22.3. This study investigated the molecular defect producing a combined phenotype of hypoplasia and hypomineralization in a family with the clinical features and inheritance pattern of X-linked amelogenesis imperfecta (XAI). Genomic DNA was prepared from buccal cells sampled from family members. The DNA was subjected to the polymerase chain-reaction (PCR) in the presence of a series of oligonucleotide primers designed to amplify all 7 exons of the amelogenin gene. Cloning and sequencing of the purified amplification products identified a cytosine deletion in exon VI at codon 119. The deletion resulted in a frameshift mutation, introducing a premature stop signal at codon 126, producing a truncated protein lacking the terminal 18 amino acids. Identifying mutations assists our understanding of the important functional domains within the gene, and finding another novel mutation emphasizes the need for family-specific diagnosis of amelogenesis imperfecta.     

A novel de novo mutation in LAMB3 causes localized hypoplastic enamel in the molar region

Amelogenesis imperfecta (AI) is a collection of diseases characterized by hereditary enamel defects and is heterogeneous in genetic etiology and clinical phenotype. In this study, we recruited a nuclear AI family with a proband having unique irregular hypoplastic pits and grooves in all surfaces of the deciduous molar teeth but not in the deciduous anterior teeth. Based on the candidate gene approach, we screened the laminin subunit beta 3 (LAMB3) gene and identified a novel de novo mutation in the proband. The mutation was a frameshift mutation caused by a heterozygous 7‐bp deletion in the last exon (c.3452_3458delAGAAGCG, p.Glu1151Valfs*57). This study not only expands the mutational spectrum of the LAMB3 gene causing isolated AI but also broadens the understanding of genotype–phenotype correlations.     

Autosomal-dominant hypoplastic form of amelogenesis imperfecta caused by an enamelin gene mutation at the exon-intron boundary

Amelogenesis imperfecta (AI) is currently classified into 14 distinct subtypes based on various phenotypic criteria; however, the gene responsible for each phenotype has not been defined. We performed molecular genetic studies on a Japanese family with a possible autosomal-dominant form of AI. Previous studies have mapped an autosomal-dominant human AI locus to chromosome 4q11-q21, where two candidate genes, ameloblastin and enamelin, are located. We studied AI patients in this family, focusing on these genes, and found a mutation in the enamelin gene. The mutation detected was a heterozygous, single-G deletion within a series of 7 G residues at the exon 9-intron 9 boundary of the enamelin gene. The mutation was detected only in AI patients in the family and was not detected in other unaffected family members or control individuals. The male proband and his brother showed hypoplastic enamel in both their deciduous and permanent teeth, and their father showed local hypoplastic defects in the enamel of his permanent teeth. The clinical phenotype of these patients is similar to that of the first report of AI caused by an enamelin gene mutation. Thus, heterogeneous mutations in the enamelin gene are responsible for an autosomal-dominant hypoplastic form of AI.