定量多重PCR在筛查DMD携带者和产前诊断中的应用

基于抗肌萎缩蛋白基因(DMD)多个外显子进行对数增长期多重PCR(多聚酶链反应)产物定量分析的原理,本研究在改进Ioannou等方法基础上建立了假性肥大型肌营养不良症(DMD/BMD)定量多重PCR(QM-PCR)技术,应用于携带者筛查和产前诊断.运用多重PCR技术对12个DMD/BMD家系先证者的检测表明缺失一个或一个以上外显子的家系有7个(58.3%).QM-PCR证实7名缺失型患者中6名母亲是与缺失型患者相同的携带者(86.7%).1例检测出外显子缺失的DMD患者,其母亲及外祖母的外周血淋巴细胞DNA未发现任何DMD基因缺失,可以排除为携带者(13.3%).对一名肯定携带者妊娠9周的胎儿进行了性别测定和DMD检测,确诊胎儿为男性DMD患者.一例可能携带者在排除携带者基础上,进一步对妊娠胎儿产前诊断确诊为正常女婴.本研究的结果进一步证实了该技术筛查DMD携带者的可靠性.将本技术与其它技术相结合可明显改进DMD家系中携带者诊断的准确性,并可应用于谱系及多态性信息不详家系的携带者诊断.该技术对防止缺失型DMD患儿和携带者的出生有重要的意义.     

产前行妊娠相关血浆蛋白A筛查联合FISH诊断Down综合征

目的 :应用单项妊娠相关血浆蛋白A(PAPP A)筛查与羊水间期荧光原位杂交 (FISH)产前诊断相结合预防妊娠Down综合征胎儿。方法 :采用酶联免疫方法 (ELISA)对孕周分别为 6～ 2 7周的 1839例孕妇进行母血PAPP A单项筛查 ,以低于同一孕周的中位数时视为可能妊娠Down综合征胎儿的高风险孕妇。取高风险孕妇羊水细胞直接进行间期FISH产前诊断并同时用部分羊水细胞遗传学检查作对照。结果 :检出 1例孕 7周孕妇其PAPP A值为 0 0 5 1U/L ,低于同一孕周中位数 2 0多倍。羊水细胞间期FISH结果显示 ,含 5个杂交信号的核占所有杂交核的 38 5 % ,与细胞遗传学分析的 2 1三体核型完全一致。结论 :单项PAPP A筛查与羊水间期细胞FISH相结合是早期防治妊娠Down综合征有效可行的方法。     

不同表型肌营养不良症患者抗肌营养不良蛋白基因缺失类型的研究

目的探讨我国东北地区杜氏型肌营养不良症（DMD）及贝克型肌营养不良症（BMD）患者抗肌营养不良蛋白基因缺失类型分布与表型的关系,并用于产前基因诊断。方法采用多重PCR法检测124例来自东北地区的DMD（106例）及BMD（18例）男性患者的抗肌营养不良蛋白基因缺失情况,并对30例高危胎儿行产前抗肌营养不良蛋白基因缺失检测。结果124例患者中,抗肌营养不良蛋白基因缺失检出率为49％（61／124）,其中41例（41／61,67％）缺失分布于外显子45—53,13例（13／61,21％）缺失分布于外显子8—19,5例（5／61,8％）在上述两个外显子缺失区内均有缺失,2例（2／61,3％）缺失分布于外显子34和43;缺失型患者中有9例发生整码缺失（为BMD患者）,49例发生移码突变（为DMD患者）。30例高危胎儿中,17例为男性胎儿,其中10例为抗肌营养不良蛋白基因缺失型,缺失位点与先证者相同;13例为女性胎儿,无一例抗肌营养不良蛋白基因缺失。结论DMD及BMD患者抗肌营养不良蛋白基因缺失主要分布于两个区域,外显子8附近区域可能是东北地区该基因缺失高发区;缺失类型与临床表型有一定的关系,当基因发生整码缺失时,临床表型为BMD,而发生移码突变时,临床表型为DMD。     

2837例妊娠中期孕妇羊水间期细胞荧光原位杂交检测胎儿染色体异常的残余风险

目的 评估妊娠中期羊水间期细胞荧光原位杂交(fluorescence in situ hybridization,FISH)检测后漏诊非13、18、21、X或Y染色体非整倍体异常核型的残余风险. 方法 对中国医学科学院北京协和医学院北京协和医院2010年1月1日至2013年7月31日2 837例妊娠中期行羊膜腔穿刺术同时行间期细胞FISH检测和传统核型分析的病例及其结果进行回顾性分析.采用GLP 13/GLP21/CSP 18/CSPX/CSPY探针针对13、18、21、X或Y染色体进行间期细胞FISH检测.计算具有三大产前诊断指征(孕妇高龄、母体血清学筛查18或21-三体高风险、妊娠23周前超声发现胎儿有结构异常)的孕妇间期细胞FISH检测的检出率以及残余风险. 结果 2 837例标本中,共85例(3.0％)羊水细胞染色体核型分析异常.85例中的73例为13、18、21、X或Y染色体非整倍体的异常核型,间期细胞FISH结果均为阳性,其中21-三体共43例(包括2例嵌合体)、18-三体1 5例、13-三体l例、性染色体非整倍体14例(包括4例嵌合体).12例(14.1％)异常结果为非13、1 8、21、X或Y染色体的非整倍体,包括平衡性结构重排6例、非平衡性结构重排5例、其他染色体非整倍体1例.这12例中,间期细胞FISH结果阳性3例,均涉及21号染色体的不平衡性结构异常;阴性9例,其中4例遗传性平衡性重排和2例新生平衡性重排.2 837例病例间期细胞FISH分析对染色体异常的检出率为89.4％(76/85),异常核型漏诊率为14.1％(12/85),残余风险为0.43％(12/2 761). 结论 间期细胞FISH检测是核型分析的有效补充,但不能取代核型分析,单纯间期细胞FISH检测进行产前诊断可能漏诊部分染色体结构异常.在产前遗传咨询时,应向患者解释间期细胞FISH的检出率和残余风险,合理选择产前诊断方法.     

杜氏肌营养不良症产前基因诊断的初步探讨

目的 对杜氏肌营养不良症（duchenne muscular dystrophy，DMD）家族史的胎儿进行dystro-phin基因缺失型的产前诊断，并探讨其产前诊断流程。方法 对3例有DMD家族史的胎儿。利用羊水细胞培养行染色体核型分析及B超检查确定胎儿性别；利用脐带血穿刺标本，应用多重聚合酶链式反应（multiple polymerase chain reaction。mPCR）技术。结合生化检测指标，进行DMD基因缺失型的产前诊断。结果 3例高危胎儿确诊为男性胎儿。存在基因缺失。相应肌酶有不同程度的升高，诊断为DMD患儿。结论 在结合多种临床实验室检查的基础上，mPCR是可应用于DMD的产前诊断。该技术也存在局限性。如只能检测男性胎儿基因缺失型突变。     

荧光原位杂交技术在妊娠晚期应用价值探讨

目的:探讨妊娠晚期宫内发育异常胎儿羊水间期细胞荧光原位杂交(FISH)检测的意义。方法:选取2014年1月至2015年12月青岛市妇女儿童医院胎儿医学中心接诊的妊娠26~40周行羊水细胞FISH检测的83例孕妇。评价妊娠晚期FISH技术用于检测唐氏筛查高风险孕妇、高龄孕妇以及发育异常胎儿染色体异常检测的意义。结果:80例孕妇接受妊娠晚期羊水细胞FISH检测,有妊娠中期产前诊断指征的孕妇中,胎儿染色体异常患病率为26%(8/31)。妊娠晚期发现发育或结构异常的胎儿中,胎儿染色体异常患病率为6%(3/49)。妊娠晚期出现发育或结构异常的胎儿中,3例患儿均为21三体,其妊娠晚期超声表现分别为侧脑室扩张合并脐血流异常、十二指肠闭锁合并羊水扩张及胎儿生长受限。结论:对于妊娠中期有产前诊断指征但错过诊断时机的胎儿,需在妊娠晚期行羊水细胞FISH检测。妊娠晚期超声提示发育或结构异常的胎儿,需考虑行羊水FISH检测。     

4568例孕妇脊髓性肌萎缩症携带者筛查及产前诊断分析

目的:对4568例孕妇进行脊髓性肌萎缩症(SMA)突变携带者筛查,并对已明确携带者夫妇胎儿进行产前诊断,了解运动神经元生存基因(SMN)变异携带率及SMA产前诊断并分析临床意义。方法:将变性高效液相色谱(DHPLC)分析法及Sanger测序联合应用,对石家庄市第四医院4568例孕妇进行SMN1缺失/点突变检测,进行携带频率统计;对携带者配偶进行筛查并对双方均为携带者夫妇胎儿进行产前诊断。结果:(1)4568例孕妇共检出SMA患者3例,2例SMN1外显子7纯合缺失,1例患者检测出SMN1外显子杂合缺失,拷贝数"1",该患者同时检出SMN1点突变变异位点p.Q164X,临床诊断为"1+1型"SMA患者,发病率0.066%。(2)126例拷贝数异常携带者(SMN1杂合缺失/转换个体),84例为缺失携带者,含SMN1∶SMN 2=1∶1样本35例,SMN1∶SMN 2=1∶2样本49例。35例转换携带者SMN1转换成SM N 2基因,含SMN1∶SMN 2=1∶3样本32例,SMN1∶SMN 2=1∶4样本3例。7例携带者SMN1∶SMN 2=1∶0。(3)126例携带者配偶中25例同为携带者。(4)应用DHPLC联合Sanger测序技术对25例SMA高危胎儿行产前诊断。结果显示3例胎儿SMN1外显子7/8纯合缺失(SMA患者);1例胎儿SMN1外显子7/8杂合缺失(SMA携带者)。余胎儿检测未见SMN1拷贝数异常。Sanger测序1例胎儿携带p.Q164X点突变变异位点,余样本未见SMN异常。结论:本研究检出SMN1变异携带率高于中国南方地区报道,且在北方地区属高携带率地区。DHPLC联合Sanger检测技术可以完成SMA携带者筛查及产前诊断,二者联合应用对于优生优育、有效预防SMA胎儿的出生具有重要的临床意义。     

1例嵌合型45,X/46,X,r(Y)患者的遗传学分析

目的:应用细胞遗传学和分子生物学技术分析1例嵌合型45,X/46,X,r(Y)患者的核型。方法:应用常规染色体标本制备方法进行G-显带和C-显带;并应用CEPX(DXZ1,Xp11.1-q11.1,Spectrum Green,Vysis)探针、LSI SRY(Yp11.3,Spectrum Orange,Vysis)探针和CEP18(D18Z1,18p11.1-q11.1,Spectrum Aqua,Vysis)与患者的中期分裂相进行荧光原位杂交(fluorescence in situ hybridization,FISH);同时应用PCR技术对患者进行Y染色体微缺失检测。结果:结合G-显带、C-显带、FISH检测结果和Y染色体微缺失的检测结果,确定该患者核型为46,X,r(Y)(p11.3q12)[85]/45,X[15]。Yq11区生精基因微缺失检测未显示该患者存在缺失。结论:细胞遗传学检测结合FISH可以诊断复杂的染色体异常,为患者提供正确的遗传咨询和生育指导。     

CNV-seq意外发现DMD基因部分重复的不致病胎儿家系分析及遗传咨询

目的明确低深度高通量全基因组拷贝数变异测序(CNV-seq)发现的胎儿携带的DMD基因部分重复变异的致病性,为其遗传咨询及产前诊断提供依据。方法对2例染色体异常高风险的孕妇分别抽取羊水,提取羊水和外周血基因组DNA,应用CNV-seq技术检测胎儿DNA,并应用多重连接探针扩增(MLPA)技术验证DMD基因的重复情况。通过数据库及家系验证分析DMD基因重复片段的致病性。结果2例胎儿通过CNV-seq分别检出Xp21.1存在大小为1.38 Mb和0.36 Mb的重复,经MLPA验证分别覆盖DMD基因5′端非编码区的第1~11外显子和3′端非编码区的第64~79外显子。经家系验证,两家系中均有临床表现正常的男性携带相同的DMD基因部分重复变异,结合数据库和家系分析,此2例DMD基因重复变异为多态性变异的可能性大,2例男性胎儿均继续妊娠并足月分娩,随访无DMD基因变异的临床表现。结论CNV-seq技术可以检测出大片段缺失或重复的DMD基因变异,但需结合家系及常规基因检测进一步分析并验证其致病性,特别是包含DMD基因第1或第79外显子的重复变异,以免误诊。     

改良荧光原位杂交技术在产前诊断中的应用

目的:评价改良荧光原位杂交(fluorescent in situ hybridization,FISH)技术在产前诊断中的应用。方法:用改良FISH技术检测119例孕16~24周孕妇的羊水间期细胞及10例孕25~32周胎儿脐血间期细胞,5例孕9~12周绒毛间期细胞,每例均行常规染色体核型分析。结果:应用改良FISH法,所有样本均在6h内获得检测结果,除2例羊水培养失败外,其余样本均在3周内获得细胞遗传学诊断。两种方法均检出特氏综合征、18-三体综合征、21-三体综合征各1例,另5例常规染色体核型分析异常,因超出检测范围,FISH法未能检出,所有样本的两种方法检测结果均一致。结论:经改良后的FISH技术缩短了诊断时间,缓解了孕妇及家属的焦虑心情,且可用于多种不同样本的检测,因其高效、省时、取材多样等优点在产前诊断具有重要的临床价值。     

Multiplex ligation-dependent probe amplification identification of deletions and duplications of the Duchenne muscular dystrophy gene in Taiwanese subjects.

BACKGROUND/PURPOSE: Duchenne muscular dystrophy (DMD) and Becker muscular dystrophy (BMD) are X-linked recessive disorders caused by mutations in the DMD gene. We intended to determine the distribution of DMD gene deletions and duplications in local Taiwanese male patients and potential female carriers. METHODS: A total of 102 unrelated subjects, including 89 unrelated DMD/BMD male patients and another 13 unrelated potential female carriers, were recruited for this study. Multiplex ligation-dependent probe amplification (MLPA) was employed to detect DMD gene deletions and duplications in the 102 subjects. RESULTS: MLPA was informative in 60.7% (54/89) of these patients, identifying deletions in 36.0% (32/89) and duplications in 24.7% (22/89) of these patients. This assay revealed deletions in 30.8% (4/13) and duplications in 30.8% (4/13) of the 13 potential carriers. Deletions and duplications were detected in 35.3% (36/102) and 25.5% (26/102) of a total of 102 affected families, respectively in this series. The "hotspot" regions of the duplications were close to those of the deletions. CONCLUSION: MLPA was proven to be a powerful tool for the detection of DMD gene deletions and duplications in male patients and female carriers. There was a relatively lower frequency of deletion and a higher frequency of duplication of DMD gene in this population compared to previous reports.     

Prenatal diagnosis of DMD in a female foetus affected by Turner syndrome

OBJECTIVES: We report on a prenatal diagnosis of DMD complicated by a 45,X karyotype that was revealed only in the chorionic villus long-term culture. METHODS: Cytogenetic investigations were performed on both short-term (STC) and long-term cultures (LTC) of the chorionic villus sample. Familial segregation was performed using a panel of intragenic polymorphic markers, and multiplex PCR was used to characterize exonic deletion. RESULTS: Investigations performed for sex determination after STC of the chorionic villus sample showed a normal karyotype 46,XX, while the karyotype performed after LTC revealed a homogeneous monosomy X. Cytogenetic analysis performed on amniotic fluid cells showed 45,X/46,XX mosaicism. Familial segregation analysis for DMD showed loss of heterozygosity for the STR49 marker in the DNA of the proband, her mother and the foetus. Dystrophin gene analysis on the 45,X cells led to the identification of a deletion of exon 50. CONCLUSIONS: The report described a rare situation of monosomy X associated with a DMD genotype. The data confirmed the DMD carrier status of the proband and her mother and indicated that the foetus had a high risk to combine a Turner phenotype and DMD. This study illustrated the potential risk of using short-term culture of villi as the only source of biological material for prenatal diagnosis.     

FISH analysis of fetal nucleated red blood cells from CVS washings in cases of aneuploidy.

OBJECTIVE: In chorionic villus sampling (CVS) the chromosome analysis is inconclusive in 1-2% of the samples. In many cases follow-up amniocentesis is performed. Fetal nucleated red blood cells (FNRBCs) are present in washings of chorionic villus samples. We wanted to establish whether analysis of these true fetal cells, using fluorescence in situ hybridization (FISH), could support the CVS karyotype. METHODS: We analysed washings of first trimester chorionic villi from non-mosaic 45,X (n=6) and full trisomy 18 cases (n=7). FNRBCs were identified by immunostaining and FISH was performed with chromosome-specific probes for X, Y and 18. RESULTS: In all 13 samples FNRBCs were present (between 4 and 30 cells per sample). Five cases of monosomy X showed one X signal in 89-100% of the nuclei; in the other case 50% of the nuclei displayed one signal. In the trisomy 18 cases three spots were seen in 60-100% of the cells. CONCLUSION: The CVS aneuploidy was confirmed in FNRBCs in all samples, so FISH on FNRBCs can be used in cases of non-mosaic numerical chromosomal abnormalities. This test can confirm a CVS diagnosis of monosomy X or trisomy 18 and thus minimize the risk for false-positive diagnoses. An additional invasive test may be prevented.     

Prenatal diagnosis of Duchenne muscular dystrophy by restriction fragment length polymorphism analysis with pERT 87 intragenomic deoxyribonucleic acid probes.

Prenatal diagnosis of DMD was performed with three intragenic genomic probes and chorionic villus sampling. A total of 8 unrelated families with at least one DMD were analysed. DNA was extracted from peripheral white blood cells for carrier testings (50 individuals). For prenatal detection, it was extracted from chorionic villi obtained by chorionic villus sampling at 9 menstrual weeks. DNA was digested with an appropriate restriction enzyme followed by overnight electrophoresis in 1% agarose gels. DNA was transferred from the gel to nylon membrane according to the protocol of an alkaline transfer method. The pERT 87 probes were labeled by nick translation. The membranes were hybridized overnight after prehybridization. After washing, the membranes were exposed to X-ray films to make autoradiograms for restriction fragment length polymorphism analysis. Fetal sex was determined by a rapid screening test with a Y chromosome-specific repeat sequence. Out of 8 fetuses, 4 were males and 4 were females. All of 4 male fetuses were determined to be unaffected. Out of 4 female fetuses, 3 were diagnosed as non-carriers, and the carrier status of the remaining one was not able to be determined because her mother was not informative for all testings.     

Molecular analysis of 25 Chinese families with Duchenne/Becker muscular dystrophy

Duchenne muscular dystrophy (DMD) and Becker muscular dystrophy (BMD) are allelic X-linked progressive neuromuscular diseases. We have collected 25 Chinese families each with at least one DMD/BMD patient for DNA analysis in the Xp21 region. Eight genomic probes, 6 within and 2 flanking the DMD gene, and 7 restriction enzymes were used to detect 9 restriction fragment length polymorphisms (RFLPs): C7-EcoRV, J-Bir-BamHI, pERT87-30-BglII, pERT87-15-BamHI, pERT87-15-XmnI, pERT87-1-XmnI, XJ1.1-TaqI, XJ5.1-SphI, and 754-PstI. From analysis of unrelated subjects, we found that the 4 most informative RFLPs in the linkage study were pERT87-15-XmnI, pERT87-1-XmnI, XJ5.1-SphI and J-Bir-BamHI. Two flanking markers, C7 and 754, were noninformative in most families. Three families (12%) had gene deletion: family M-25 at pERT87-1 to 87-30; M-105 at XJ 5.1, 1.1, pERT87-1, and 87-15; and M-110 at XJ5.1, 1.1, and pERT87-1 to 87-30. Two recombinations were detected: M-10 between C7 and pERT87-15; and M-39 between J-Bir and pERT87-15. In the 25 mothers with affected sons, 2 had gene deletion, 1 was homozygous at all 9 polymorphic loci and the other 22 were heterozygous at more than one locus. Twenty-four at-risk female siblings were studied for carriership. Nine were classified as at high risk of carriership, 13 at low risk of carriership by haplotyping, and the remaining two were uncertain, with one due to recombination and the other to maternal homozygous haplotypes. Gene deletion and RFLP analysis are very useful in genetic counseling of Chinese DMD/BMD.     

Immunohistochemical study of dystrophin in neuromuscular disorders.

Dystrophin, a protein product of the gene that is affected in Duchenne/Becker muscular dystrophy (DMD/BMD), is localized on the sarcolemma of muscle fibers. We tried to study various neuromuscular disorders, including DMD/BMD and their carriers, by the immunohistochemical method with two types of anti-dystrophin antibodies. No dystrophin stain was found on the muscles of cases of DMD. In cases of BMD, partial deficiency or a mosaic appearance of dystrophin was found. In members of DMD/BMD families, polyclonal antibody stains did not show definite membrane abnormality. However, partial deficiency or a mosaic appearance of dystrophin on muscle membranes was found in the carriers by a monoclonal anti C-terminal antibody stain. The explanation may be: 1) more non-specific antigen-antibody cross reactions occurred in the polyclonal antibody stain; and 2) a partial defect exists, such as a segmental deletion of the C-terminal portion of dystrophin. Dystrophin study in muscle diseases is a helpful tool for the following reasons: 1) it improves diagnostic accuracy and helps to differentiate variant types of muscle disorders; 2) it makes an early diagnosis possible before the onset of the symptoms of DMD/BMD; and 3) it detects nonsymptomatic carriers of DMD/BMD. However, without the aid of a genetic study, dystrophin antibody stains cannot absolutely rule out the diagnosis of carriers.     

荧光原位杂交与染色体核型分析应用于自然流产病因学诊断的比较研究

目的:分析并比较荧光原位杂交技术(fluorescence in situ hybridization,FISH)及普通染色体核型分析技术在自然流产中的诊断意义。方法:以早孕自然流产的患者为研究对象,共201例。将同一孕周的患者随机分为A组和B组,A组(n=100)进行绒毛培养加染色体核型分析,B组(n=101)进行FISH分析,另在A、B组孕6~11周患者中每一孕周各随机选取1例,每组6例,共12例同时进行2种技术分析,并比较结果。结果:染色体核型分析成功率为66%,其中核型异常率为30.3%;FISH成功率为100%,其中核型异常率为46.5%;2种检测技术检测出的异常核型率比较有统计学差异(P=0.036)。结论:2种分析技术对异常核型的检出率有明显的差异,FISH更容易成功,更能反应胚胎的染色体数目;染色体核型分析结合FISH技术能有效诊断自然流产的染色体异常。     

FISH快速检测自然流产绒毛染色体非整倍体异常的临床价值

目的:探讨应用荧光原位杂交技术(FISH)对早期自然流产绒毛染色体非整倍体检测的临床价值。方法:对30例因自然流产行清宫术的绒毛组织行FISH分析,使用7种探针对13、16、18、21、22号和X、Y染色体进行了检测,并对这30例流产夫妇行外周血淋巴细胞染色体常规核型分析。结果:FISH分析的30例自然流产的绒毛组织中,有17例检测出了异常信号,检出率为57%,其中8例16-三体、2例22-三体、2例13-三体和5例三倍体。30例自然流产夫妇外周血淋巴细胞染色体核型未见异常。结论:FISH技术可以快速、简便地检测出流产物绒毛组织染色体非整倍体的异常,FISH技术的应用可以为自然流产夫妇遗传咨询提供重要的信息。     

Prenatal diagnosis of Charcot-Marie-Tooth disease type 1A by interphase fluorescence in situ hybridization.

Charcot-Marie-Tooth Disease (CMT) is the most common cause of peripheral neuropathy, with an incidence of 1:2500 persons affected. Previously, we reported the use of fluorescence in situ hybridization (FISH) to detect the common submicroscopic duplication of 17p12 found in more than 98 per cent of individuals with CMT1A. We found that FISH is a reliable means for the diagnosis of the duplication of 17p12 in peripheral blood and reported the validation of the FISH assay for amniotic fluid specimens. Herein, we report the validation of the FISH assay for use on chorionic villus samples (CVS) to prenatally diagnose CMT1A duplications and the testing of 17 prenatal specimens. Seven fetuses were found to carry the duplication and are predicted to be affected. FISH is a rapid assay in prenatal specimens, with a 9.3 day average turn-around time. Limited follow-up on pregnancies indicates that the duplication found in CMT1A is reliably diagnosed in the fetus, using FISH on either amniotic fluid specimens or CVS.