多重定量荧光PCR快速检测染色体非整倍体疾病

目的 探讨多重定量荧光PCR快速检测染色体非整倍体标本疾病的价值.方法 利用21,18,13号及X染色体上15个STR(短串联重复序列)位点进行多重PCR扩增,在24 h内快速检测染色体非整倍体标本.通过建立两个多重PCR体系,对921例临床标本(包括外周血、绒毛膜及羊水标本)进行检测.结果 921例标本中915例结果 与染色体核型结果 相符,其中2例45,X外周血标本,2例21-三体综合征标本、1例46,XX标本未检出,1例羊水标本分析失败,与传统染色体核型分析方法 相比,其灵敏度及特异度分别为97.64%、99.85%.结论 多重定量荧光PCR技术可用于快速诊断非整倍体疾病.     

QF-PCR在5358例地中海贫血产前诊断中对常见染色体病的诊断价值

目的:研究荧光定量PCR(Quantitative Fluorescent Polymerase Chain Reaction,QF-PCR)技术在地中海贫血(简称地贫)产前诊断病例中对常见非整倍体染色体的检测作用,了解此方法的运用对地中海贫血产前诊断,同时快速排除胎儿常见染色体病的诊断价值。方法:回顾分析2015年1月~2017年1月因夫妇双方为同型地贫在我院医学遗传中心行介入性产前诊断(取样标本包括绒毛、羊水与脐血)检测胎儿地贫基因,同时行QF-PCR快速诊断常见染色体数目异常的5 358例产前诊断结果。总结常见非整倍体染色体病在这组人群的检出率,QF-PCR异常而地贫基因正常或轻型的病例再次行胎儿染色体核型分析验证。结果:5 358例地贫产前诊断标本中,所有样本均同时行QF-PCR检测,选用STR(Short Tandem Repeat,STR)位点排查胎儿常见染色体非整倍体异常(13、18、21、X与Y染色体),共检测出染色体异常占0.47%(25/5 358),其中4例合并重型地贫,胎儿引产未行染色体核型分析,其余21例均行染色体核型分析确诊结果一致。结论:QF-PCR技术定量分析STR多态性位点能准确、快速诊断常见非整倍体染色体病,是产前诊断中不可缺少的重要检验方法,在常规地贫产前诊断病例中运用能避免漏诊染色体异常胎儿。     

Use of the quantitative fluorescent-PCR assay in the study of fetal DNA from micromanipulated transcervical samples.

AIM: The purpose of this study was to evaluate the validity of the combined use of micromanipulation and quantitative fluorescent (QF)-PCR assay for the identification of fetal elements in transcervical cell (TCC) samples collected in early pregnancy. METHODS: TCC samples were obtained by intrauterine lavage (IUL) in 113 pregnant women who were between 7 and 12 weeks pregnant before termination of pregnancy. All IUL samples were screened under an inverted microscope, at which time the isolation of fetal cells by micromanipulation was attempted. QF-PCR assay, using 9 small tandem repeat (STR) markers for chromosomes 13, 18, 21, X, and Y, was performed in all specimens to identify fetal cells in TCC samples and the corresponding placental tissue and blood specimens. TCC samples from male fetuses in which either the micromanipulation or QF-PCR analysis were unsuccessful, were studied with fluorescent in situ hybridization (FISH), using probes for X and Y chromosomes. RESULTS: Isolation of supposed fetal material from IUL samples was carried out by means of micromanipulation in 93 cases (82.3%), where discernible chorionic villous filaments or cell clumps of probable trophoblastic origin were present. The QF-PCR analysis was performed in all 93 IUL samples and paternal peaks could be documented in 88 cases (94.6%) thus confirming the presence of fetal cells. Thirteen cases negative to micromanipulation and derived from male fetuses and four male cases not informative with QF-PCR analysis, after micromanipulation, were then tested with FISH assay using probes for sexual chromosomes. In six samples, rare (2-3%) male fetal cells were detected. Considering the combined results obtained from QF-PCR and FISH assays, the overall fetal sexing was correct in 83.2% of cases (94 of 113). CONCLUSION: This study provides evidence that fetal cells are present in a high proportion of IUL samples. Micromanipulation appears to be an extremely efficient method for the isolation of trophoblastic elements. This study also confirms the potential of IUL as a possible alternative to the traditional prenatal diagnostic procedures for the recovery of fetal cells in precocious stage of gestation, and validates the combination of the isolation of such fetal elements by means of micromanipulation and analysis with the QF-PCR assay for the identification of the most frequent prenatal chromosomal aneuploidies.     

Glutathione peroxidase activity, lipid peroxides and selenium status in blood in patients with Down's syndrome

The concentrations of selenium and lipid peroxides and the catalytic activity of glutathione peroxidase were measured in the blood of 6 children (6-16 years of age) and 8 adults (17-27 years old) with Down's syndrome (trisomy 21). The values were compared with those for a control group of age-matched normal people. The selenium concentration in whole blood, erythrocytes and plasma was significantly lower in trisomy 21 patients than in normal subjects (p less than 0.001) in both age groups. No statistically significant differences were observed in selenium concentration in whole blood, erythrocytes and plasma between children and adults in the Down's syndrome group. Glutathione peroxidase catalytic activity in erythrocytes was significantly higher in Down's syndrome children than in healthy children (p less than 0.001). Plasma glutathione peroxidase catalytic activity in both investigated age groups was statistically considerably lower in the Down's syndrome patient group. The concentration of lipid peroxides, expressed as the malondialdehyde concentration, is lower in Down's syndrome patients. No correlation between selenium concentration, glutathione peroxidase catalytic activity and amount of lipid peroxides was found in the trisomy 21 patient group.     

The alpha adrenergic response of Down's syndrome platelets

The alpha adrenergic responsiveness and pharmacological characteristics of alpha adrenergic receptors were examined using platelets from normal diploid and Down's syndrome (trisomy 21) individuals. Lower than normal doses of epinephrine were required to aggregate Down's syndrome platelets and promote ATP secretion. The concentrations of other platelet aggregating agents (ADP or thrombin) did not distinguish normal from Down's syndrome. Analysis of the alpha adrenergic receptor density and ligand affinity using the radioligand dihydroergocryptine indicated that the Down's syndrome platelets were not significantly different from normal. Likewise, the biochemical characteristics of the adenylate cyclase enzyme, e.g., its sensitivity to stimulation by prostaglandin E1 or inhibition by epinephrine, were not different when comparing Down's syndrome with normal platelet membranes. These data suggest that the enhanced epinephrine sensitivity of Down's syndrome platelets is independent of any change in the alpha adrenergic receptor or the adenylate cyclase enzyme complex.     

Determination of sensitivity and specificity of a novel gene dosage assay for prenatal screening of trisomy 21 syndrome

ObjectiveTo compare the gene dosage results achieved by a novel multiplex quantitative assay with cytogenetic and quantitative fluorescent polymerase chain reaction (QF-PCR) analysis for prenatal screening of trisomy 21 syndrome on corresponding fetal samples.Design and methodsFetal samples (n = 134) were collected from pregnant women considered high risk for having trisomy 21 affected fetus. Cytogenetic analysis and QF-PCR were performed. Then, the relative gene dosage of DSCAM and DYRK1A2 genes was determined on corresponding samples using comparative delta cycle of threshold (ΔC_T) method.ResultsThe mean gene dosage ratio was 1.55 ± 0.11 (95% CI:1.51–1.58) in trisomy 21 cases and 1.01 ± 0.12 (95% CI:0.98–1.03) in normal samples (p value < 0.001). The results were in agreement to the results of cytogenetic and QF-PCR analysis with the overall specificity of 0.96 (95% CI:0.91–0.98) and the sensitivity of 0.80 (95% CI:0.49–0.94).ConclusionsThis gene dosage assay is appropriate for the screening of high risk pregnant women and is readily amenable to automation.     

Assessment of QF-PCR as the first approach in prenatal diagnosis

Quantitative fluorescent PCR (QF-PCR) has been used by many laboratories for prenatal diagnosis of the most common aneuploidies. QF-PCR is rapid, cost-effective, and suitable for automation and can detect most abnormalities diagnosed by conventional karyotyping. Whether QF-PCR should be used alone in most of the samples and in which karyotyping should also be offered is currently a topic of debate. We evaluated and compared the results obtained from 7679 prenatal samples in which conventional karyotype and QF-PCR had been performed, including 1243 chorionic villi and 6436 amniotic fluid samples. Concordant QF-PCR and karyotype results were obtained in 98.75% of the samples. An abnormal karyotype associated with adverse clinical outcome undetected by QF-PCR was found in 0.05% of samples. Therefore, QF-PCR can be used alone in a large number of samples studied in a prenatal laboratory, thereby reducing both the workload in cytogenetic laboratories and parental anxiety when awaiting results.     

Noninvasive determination of acetaminophen disposition in Down's syndrome

In this study we evaluated subjects with Down's syndrome for the possibility that direct or indirect gene dosage effects of trisomy 21 alter the fate of acetaminophen. We also investigated the usefulness of noninvasive sampling techniques to obtain parameter estimates for drug disposition in these developmentally disabled individuals. After administration of 5 mg/kg and 20 mg/kg oral doses of acetaminophen, subjects with Down's syndrome resembled control subjects in most pharmacokinetic and metabolic parameters, including apparent half-life, volume of distribution per kilogram body mass, total body clearance per kilogram of body mass, extrapolated saliva concentration at time zero, and the urinary excretion of acetaminophen glucuronide and sulfate conjugates. Glutathione conjugation tended to increase and sulfate conjugation tended to decrease in all subjects as the acetaminophen dose increased from 5 mg/kg to 20 mg/kg. Results based on these samples of very limited size also suggest that acetaminophen metabolism to glutathione-derived conjugates may have been increased in subjects with Down's syndrome. The similarity of estimates of acetaminophen pharmacokinetics and data on metabolic fate between subjects with Down's syndrome and normal volunteers indicates that large effects of trisomy 21 on these processes are unlikely. Also, these results were in agreement with extensive data obtained with invasive techniques, indicating that simple noninvasive methodologies appear to be well suited for studying acetaminophen disposition in populations of developmentally disabled individuals.     

Hypoplasia of the middle phalanx of the fifth digit. A feature of the second trimester fetus with Down's syndrome

It has been established that 60% of infants with Down's syndrome have hypoplasia of the middle phalanx of the fifth digit. To determine whether this would be a useful prenatal sonographic sign for Down's syndrome, we measured the middle phalanx of the fifth and fourth digits in 1,032 fetuses between 15 and 20 weeks gestational age at the time of amniocentesis, prior to any knowledge of the karyotypes. A ratio of the middle phalanx of the fifth digit over the middle phalanx of the fourth digit was calculated, and the median ratio for the 1,024 normal fetuses was 0.85. There were eight fetuses who had trisomy 21 by karyotype and their median ratio was 0.59 (P = .04). Of the eight fetuses with Down's syndrome, seven had ratios below the normal population median. If an arbitrary cut-off point is used at a ratio of 0.70, 6/8 (75%) of those with Down's syndrome would be identified, as well as 18% of normal fetuses (positive predictive value = 3.2% in this group). Although we do not suggest that this ratio be used alone as a screening test for Down's syndrome, these findings confirm the presence of a small middle phalanx in fetuses with trisomy 21 as early as 15 to 16 weeks and may be a useful adjunct to the several already reported sonographic signs in the fetus at risk for Down's syndrome.     

DNA polymerase activity as an index of lymphocyte stimulation: studies in Down''s syndrome

The ability of peripheral blood lymphocytes to respond to phytohemagglutinin (PHA) in vitro was studied in patients with Down's syndrome. The response was measured by the increase in DNA polymerase activity and the rate of incorporation of tritiated thymidine by the cultured lymphocytes. These activities were significantly lower in PHA-stimulated lymphocytes from patients with Down's syndrome compared with age- and sex-matched, mentally retarded patients without Down's syndrome from the same institution and the normal healthy volunteers. The impairment in response to PHA does not seem to be related to the presence of Australia antigen in patients with Down's syndrome or to institutionalization itself. In contrast to DNA polymerase activity and thymidine-(3)H uptake, there was no significant difference in the percentage of blast transformation in the three groups studied. The poor response of the lymphocytes from patients with Down's syndrome to a mitogenic stimulus could reflect an impairment of cellular immune functions in these patients which may be one of the factors contributing to the vulnerability of these patients to repeated or persistent infections.     

N-acetylator variability in Down's syndrome: characterization with caffeine

Little is known regarding the biotransformation of drugs in Down's syndrome. In particular, there are no published studies that examine metabolic pathways such as N-acetylation, which can exhibit genetically-determined variability. The objective of the present investigation was to compare the acetylator phenotypes of white subjects with Down's syndrome with age-matched control subjects, with use of caffeine as the pharmacologic probe. After the ingestion of caffeine-containing beverages, spot urine collections were obtained at 2 and 4 hours in 22 subjects with Down's syndrome and in 22 control subjects (age range of 4 to 49 years). The urinary excretion ratios of 5-acetylamino-6-amino-3-methyluracil (AAMU) to 1-methylxanthine (1X) determined in these 2-hour and 4-hour samples were highly correlated (r = 0.82; p less than 0.001). In addition, more extensive urinary excretion studies performed for an 8-hour period in three subjects with Down's syndrome demonstrated that the coefficient of variability for the ratio of AAMU/1X ranged from 10.1% to 14.2%, which is similar to the reproducibility previously reported for control subjects. A trimodal distribution of acetylator phenotypes was observed, with no differences in average or frequency distribution of ratio values between the subjects with Down's syndrome and the control subjects. This study demonstrates that polymorphic N-acetylator status, as assessed by caffeine metabolism, is similar in subjects with Down's syndrome and in control subjects.     

Microsatellite markers within --SEA breakpoints for prenatal diagnosis of HbBarts hydrops fetalis

BACKGROUND: We sought to develop a rapid prenatal diagnostic test for simultaneous detection of HbBarts hydrops fetalis and exclusion of maternal contamination. METHODS: We developed a multiplex quantitative fluorescent PCR (QF-PCR) test that detects the presence/ absence of 2 microsatellite markers (16PTEL05/16PTEL06) located within breakpoints of the Southeast Asia ((-SEA)) deletion. HbBarts hydrops fetalis ((-SEA/-SEA)) is diagnosed by absence of both markers, and maternal contamination of fetal DNA is excluded by absence of noninherited maternal alleles. Fetal and parental DNA samples from 50 families were analyzed in a blinded clinical validation study, and QF-PCR results were compared with their respective molecular genotypes. RESULTS: The multiplex QF-PCR results included correct diagnoses of HbBarts hydrops fetalis in 11 of the fetuses tested, correct verification as unaffected in 20 fetuses, and correct identification as either carriers (alphaalpha/(-SEA)) or unaffected homozygotes in 18. Misidentification as unaffected occurred for 1 carrier. Sensitivity for diagnosis of HbBarts hydrops fetalis was 100% [lower 95% confidence interval, 76.2%], and specificity was 100% (lower 95% confidence interval, 92.6%). None of the samples tested showed any traces of noninherited maternal alleles; thus false-positives because of maternal contamination were eliminated. CONCLUSIONS: In this QF-PCR method, detection of maternally and paternally inherited fetal alleles allowed diagnosis of the double-deletion syndrome, and the ability to differentiate between these alleles allowed simultaneous exclusion of maternal contamination of the fetal genetic material. This novel strategy using cell-free fetal DNA in maternal plasma could form the basis for noninvasive testing for HbBarts hydrops fetalis.     

Lipid peroxides in blood plasma and enzymatic antioxidative defence of erythrocytes in Down's syndrome

The level of lipid peroxides was significantly increased in the blood of patients with Down's syndrome. In erythrocytes increased activities of superoxide dismutase and glutathione peroxidase were confirmed while catalase activity was similar to that of healthy controls. The concentration of selenium in erythrocytes of Down's syndrome patients was reduced, in spite of increased glutathione peroxidase activity. These results confirm the hypothesis of an altered oxidative metabolism in Down's syndrome.     

Diagnosis of trisomy 21 in fetal nucleated erythrocytes from maternal blood by use of short tandem repeat sequences

BACKGROUND: The purpose of this study was to determine whether aneuploid fetal nucleated erythrocytes (NRBCs) could be detected in maternal blood through the use of fluorescent PCR amplification with polymorphic short tandem repeat (STR) markers as an alternative or complementary method to analysis by fluorescent in situ hybridization (FISH). METHODS: Peripheral blood samples were obtained from women who had just undergone termination of pregnancy because of fetal trisomy 21 (three cases, 47,XY,+21; four cases, 47,XX,+21). Candidate fetal cells were isolated by flow-sorting by antibodies to the gamma chain of fetal hemoglobin and Hoechst 33342. FISH analysis was performed by the use of chromosome-specific probes for X, Y, and 21. Fetal NRBCs, as defined by the presence of gamma staining, characteristic morphology, and three chromosome 21 signals, along with maternal leukocytes, defined as gamma negative and two chromosome 21 signals, were micromanipulated separately and subjected to fluorescent PCR amplification of chromosome 21 STR markers (D21S11, D21S1411, and/or D21S1412). RESULTS: In five of seven cases analyzed, fetal NRBCs were aneuploid, as determined by the presence of triallelic or diallelic peaks of chromosome 21 sequences when compared with sequences from the maternal leukocytes. CONCLUSIONS: Fluorescent PCR amplification of STRs can detect fetal aneuploidy and may be useful in the setting of poor hybridization efficiency with FISH analysis. These results suggest that combined fetal aneuploidy and single-gene diagnoses by the use of DNA microarrays may be feasible in the near future.     

Fetal hyperechogenic bowel and Down's syndrome.

Hyperechogenic bowel was identified among 55 of 6781 (0.81%) fetuses prior to second-trimester genetic amniocentesis. Trisomy 21 was found in eight of the 55 (14.5%) fetuses identified with hyperechogenic bowel compared to 60 of 6726 (0.89%) fetuses with normal bowel echogenicity (p < 0.001). Hyperechogenic bowel carried a 16-fold greater risk for Down's syndrome than normal bowel echogenicity (relative risk 16.8, 95% confidence intervals 8.2-32.5). Chromosome abnormalities other than trisomy 21 were found in four additional fetuses with hyperechogenic bowel (two triploid and one each with 47,XXX; 45,X/47,XXX mosaicisim). Combining these four cases with the eight fetuses having trisomy 21, 21.8% (12 of 55) of fetuses with hyperechogenic bowel proved to have a chromosome abnormality. We conclude that hyperechogenic bowel is associated with chromosome abnormalities, particularly Down's syndrome, when detected during the second trimester.     

Diagnosis of transfusion-associated graft-vs.-host disease: the importance of short tandem repeat analysis

Transfusion-associated graft-vs.-host disease (TA-GvHD) can occur following transfusion of blood products containing immunocompetent lymphocytes, usually from HLA homozygous donors, into immunocompromised patients sharing one HLA haplotype with the donor. The diagnosis of TA-GvHD may be delayed due to the initial nonspecific clinical features involved. Investigations to detect the presence of donor-derived cells in the blood and/or affected tissues of the recipient are essential to confirm the diagnosis. We report the investigation of suspected TA-GvHD using short tandem repeat (STR) analysis, to detect the presence of donor cells (chimerism), in an immunocompetent patient admitted for coronary artery bypass surgery. Peripheral blood and skin biopsies (from affected and nonaffected sites) from the patient and peripheral blood samples from the implicated donors were taken for HLA typing and STR analysis. STR analysis revealed the presence of donor material in the patient's peripheral blood sample and in DNA extracted from the affected skin biopsy but not the unaffected biopsy, suggesting lymphocytes from this donor were responsible for the development of TA-GvHD. Furthermore, HLA typing results supported the diagnosis of TA-GvHD. These data demonstrate the use of STR and HLA analysis as effective tools in the diagnosis of TA-GvHD.     

Postrotary nystagmus response in children with Down's syndrome

The purpose of this study was to investigate the nystagmus response in school-age children with Down's syndrome. The 35 subjects were between 5 and 9 years of age and were enrolled in public school programs for the educable and trainable mentally retarded in the northern metropolitan areas of Utah. The Southern California Postrotary Nystagmus Test (SCPNT) was administered with slightly modified verbal instructions. Durations of nystagmus for the subjects with Down's syndrome were compared with Ayres' normative data from the SCPNT using a t-test for two independent means. Results indicated there was a significant reduction in the duration of nystagmus in the children with Down's syndrome when compared to Ayres' sample of normal children; however, there was no significant difference between males and females with Down's syndrome in duration of postrotary nystagmus.     

Lecithin: cholesterol acyltransferase in Down's syndrome

Based on earlier reports indicating that Down's syndrome may represent an atheroma-free human model, two groups of institutionalized subjects were compared with respect to various parameters of their plasma lipid transport system. One group of subjects was comprised of Down's syndrome subjects and the second, a group of mentally retarded individuals. Parameters measured included plasma cholesterol, triglyceride, HDL-cholesterol, apolipoprotein levels (A-I, B, C-III, and E), lecithin:cholesterol acyltransferase (LCAT) activity, body mass and blood pressure. Statistical analyses indicated no significant differences between the two groups except for the lower fractional rate of cholesterol esterification (% cholesterol esterified per hour, p = 0.0049) in the Down's syndrome subjects. Adjustment for the effects of body mass and age revealed no other significant differences between the two groups except for a lower molar rate of esterification (nmol cholesterol esterified X h-1 X ml-1, p less than 0.0063) in the Down's syndrome subjects. Additional differences between the two groups were revealed by partial correlational analyses of LCAT activity with the measured parameters or ratios of these parameters which suggests that the composition and/or metabolism of lipoproteins may differ between these two groups. Whether the lower LCAT activity and the other differences reflected by the correlational analyses contribute to the decreased incidence of atherosclerotic lesions in Down's syndrome remains to be elucidated.     

Gene dosage and down-regulation of the alpha-interferon receptor.

The gene coding for the alpha,beta-interferon (alpha,beta-IFN) receptor is localized to chromosome 21. Cells from patients with Down's syndrome (trisomy 21) contain an extra chromosome 21, which results in a 1.5 times increase of dosage for the genes localized to this chromosome. Trisomy 21 cells express more cell-surface alpha-IFN receptors, consistent with the increased gene dosage. Down-regulation of the alpha-IFN receptors in trisomy 21 and normal cells was studied by incubating the cells with alpha-IFN. The alpha-IFN-induced effects showed 1.6 times more internalized cell-surface alpha-IFN receptors in trisomy 21 cells compared with normal cells, but no statistically significant change in the dissociation constants. A close relationship was found between the alpha-IFN receptor number and the biological response expressed as 2',5'-oligoadenylate synthetase activity.     

Evaluation of an assay of the free beta-subunit of choriogonadotropin and its potential value in screening for Down's syndrome.

In this study I investigated the analytical and clinical performance of the measurement of the free beta-subunit of choriogonadotropin (hCG) in normal pregnancies and in pregnancies affected by Down's syndrome. Free beta-hCG in maternal serum has been shown to be increased in Down's syndrome-affected pregnancies and is proportionally increased in more cases than is total hCG. This study confirms previous findings of low concentrations of unconjugated estriol and alpha-fetoprotein in maternal serum in Down's syndrome-affected pregnancies. Using a multivariate risk analysis of maternal age and concentrations of alpha-fetoprotein, unconjugated estriol, and hCG in maternal serum, I determined that, at a risk cutoff value of 1 in 300, 52% of Down's cases could be detected with total hCG in the calculation, compared with 66% with the free beta-hCG concentration. The false-positive rate was 5.9% in both cases. Therefore, free beta-hCG can be used effectively in a screening program for Down's syndrome; however, further studies are required to ascertain whether the measurement of free beta-hCG has any advantages over the use of total hCG for detecting Down's syndrome.