Noninvasive Prenatal Diagnosis Of Trisomy Research Articles

Noninvasive Prenatal Diagnosis from Maternal Blood: Finally Available after 20 Years of Research

ABSTRACT Since all prenatal invasive procedures, such as amniocentesis and chorionic villus sampling carry a small risk for the pregnant woman and a risk to induce the loss of a pregnancy of up to 1%, there have been efforts now for at least a quarter of a century to develop a noninvasive method from the blood of pregnant women. First there was a considerable effort to isolate fetal cells from maternal circulation, and these techniques were carefully evaluated in a NIH-sponsored study of a few US American centers and ours in Basel/Switzerland. It turned out; however, that interphase fluorescence to identify fetal aneuploidies from these isolated cells was not reliable enough for clinical use. The breakthrough came with the recognition of the group by D Lo et al; who showed for the first time that cell-free fetal DNA in maternal plasma and serum can be used reliably for prenatal diagnosis. One of the first successful applications was the detection of the fetal Rhesus factor around 11 weeks of gestation in pregnancies of Rhesus-negative mothers. The Sequenom Company in San Diego, USA, which acquired the patent of D Lo et al on the use of cell free DNA and ours on size separation of fetal vs maternal DNA subsequently showed in large series that the noninvasive prenatal diagnosis of fetal trisomy 21 from maternal blood by massive parallel sequencing has an accuracy around 99%, and currently up to 100,000 cases have been investigated already in different laboratories. Also the noninvasive prenatal diagnosis of trisomies 18 and 13 is possible, and an increasing amount of single gene anomalies will be diagnosable in the future noninvasively. The whole development of noninvasive prenatal diagnosis is appositive example that long-term research pays-off to bring a concept from the first steps finally into clinical use. How to cite this article Holzgreve W. Noninvasive Prenatal Diagnosis from Maternal Blood: Finally Available after 20 Years of Research. Donald School J Ultrasound Obstet Gynecol 2013;7(4):440-442.

Development of noninvasive prenatal diagnosis of trisomy 21 by RT-MLPA with a new set of SNP markers

Placental mRNA can now be detected in maternal whole blood, raising the possibility of using maternal blood for noninvasive prenatal diagnosis (NIPD) of trisomy 21. We aimed to identify new mRNA-single nucleotide polymorphism (mRNA-SNP) markers suitable for use in reverse-transcriptase multiplex ligation-dependent probe amplification (RT-MLPA) to develop a more reliable diagnostic method for trisomy 21 in Chinese subjects. Using sequencing, we determined the status of SNPs in genes expressed in the placenta and calculated their heterozygote frequencies to determine which loci were suitable for use in RT-MLPA. Cell-free fetal RNA was extracted from peripheral blood samples of 246 women at 12-24 weeks of pregnancy, and the SNP loci selected were analyzed by RT-MLPA, followed by capillary electrophoresis. Karyotype analyses were used to confirm the diagnosis of trisomy 21. As compared with karyotype analysis, the diagnostic sensitivity and specificity of RT-MLPA were excellent (95 and 100% in different gestational weeks). The RT-MLPA technique is a suitable and reliable method for the diagnosis of trisomy 21. Use of RT-MLPA with the SNP markers described here shows good specificity, high sensitivity, and high throughput potential, making this technique suitable for NIPD in clinical practice.

Noninvasive prenatal diagnosis of trisomy 21, 18 and 13 using cel – free fetal DNA

Trisomy 21, 18 and 13 are the most common trisomies diagnosed in newborns. Screening methods consist of ultrasound and maternal serum markers. High risk for fetal aneuploidies is an indication for routine karyotyping, which requires collection of fetal tissue through amniocentesis or chorionic villous sampling. They are invasive procedures and carry a potential risk of miscarriage. The discovery of cell free fetal DNA (cffDNA) in maternal blood offered new opportunities for noninvasive prenatal diagnosis. The fraction of cell-free fetal DNA in total pool of cell-free DNA in maternal plasma is very low, therefore the analysis of cffDNA is very challenging. The introduction of massive parallel sequencing has enabled the application of noninvasive prenatal testing in the clinical practice and a variety of recent studies have proven its high efficacy in diagnosing common aneuploidies.

MeDIP real‐time qPCR of maternal peripheral blood reliably identifies trisomy 21

To reevaluate the efficiency of the 12 differentially methylated regions (DMRs) used in the methylated DNA immunoprecipitation (MeDIP) real-time quantitative polymerase chain reaction (real-time qPCR) based approach, develop an improved version of the diagnostic formula and perform a larger validation study. Twelve selected DMRs were checked for copy number variants in the Database of Genomic Variants. The DMRs located within copy number variants were excluded from the analysis. One hundred and seventy-five maternal peripheral blood samples were used to reconstruct and evaluate the new diagnostic formula and for a larger-scale blinded validation study using MeDIP real-time qPCR. Seven DMRs entered the final model of the prediction equation and a larger blinded validation study demonstrated 100% sensitivity and 99.2% specificity. No significant evidence for association was observed between cell free fetal DNA concentration and D value. The MeDIP real-time qPCR method for noninvasive prenatal diagnosis of trisomy 21 was confirmed and revalidated in 175 samples with satisfactory results demonstrating that it is accurate and reproducible. We are currently working towards simplification of the method to make it more robust and therefore easily, accurately, and rapidly reproduced and adopted by other laboratories. Nevertheless, larger scale validation studies are necessary before the MeDIP real-time qPCR-based method could be applied in clinical practice.

Digital PCR for Noninvasive Detection of Aneuploidy: Power Analysis Equations for Feasibility

Objective: To determine the feasibility of digital PCR analysis for noninvasive prenatal diagnosis of trisomy 21. Methods: Through power equations, we modeled the number of wells necessary to determine the feasibility of digital PCR as a practical method for trisomy 21 risk assessment. Results: The number of wells needed is a direct correlate of the ability to isolate free fetal DNA. If a 20% fetal DNA enhancement can be achieved, then 2,609 counts would be sufficient to achieve a 99% detection rate for a 1% false-positive rate and potentially feasible with readily available plates. However, if only a 2% increase is seen, then 220,816 counts will be necessary, and over 110,000 would be needed just to achieve 95% for a 5% false-positive rate – both far beyond current commercially available technology. Conclusion: There are several noninvasive prenatal diagnostic methods which may reach commercialization; all have differing potential advantages and disadvantages. Digital PCR is potentially a cheaper methodology for trisomy 21, but it is too early to determine the optimal method.

Noninvasive prenatal diagnosis of Down syndrome: current knowledge and novel insights

The noninvasive prenatal diagnosis of trisomy 21 (Down syndrome) is an actively researched area of prenatal medicine, as this is the most common aneuploidy compatible with life and a major cause of mental retardation. The isolation of intact fetal cells, and most importantly, the successful detection of fetal-origin nucleic acids (cell-free fetal DNA and RNA), in maternal plasma even from the early stages of pregnancy has inspired scientists to develop discriminative genetic markers for the prenatal detection of aneuploidy. In the near future, the development of epigenetic fetal-specific markers will possibly allow the universal application of a cell-free fetal DNA-based diagnostic test regardless of the gender of the fetus or its polymorphic status. Other promising approaches rely upon the detection of free placentally derived RNA transcribed from genes located on chromosome 21 and the application of highly sensitive techniques, such as digital polymerase chain reaction and high-throughput shotgun sequencing. However, irrespective of which strategy is selected for isolating or distinguishing fetal genetic material in maternal plasma, the small quantity of fetal origin nucleic acids poses severe technical challenges. In this review article, we present an overview of the current knowledge in the field of noninvasive prenatal assessment of fetuses with Down syndrome and the future perspectives regarding new fetal markers and novel molecular techniques that may eventually be applied in the clinical setting as a valid and safe option for women who opt for noninvasive accurate prenatal diagnosis.

703: Non-invasive prenatal diagnosis of trisomy 21: replacing invasive testing or replacing screening?

703: Non-invasive prenatal diagnosis of trisomy 21: replacing invasive testing or replacing screening?

Non-invasive prenatal diagnosis of trisomy 21 by dosage ratio of fetal chromosome-specific epigenetic markers in maternal plasma

This study examined the methylation difference in AIRE and RASSF1A between maternal and placental DNA, and the implication of this difference in the identification of free fetal DNA in maternal plasma and in prenatal diagnosis of trisomy 21. Maternal plasma samples were collected from 388 singleton pregnancies, and placental or chorionic villus tissues from 112 of them. Methylation-specific PCR (MSP) and methylation-sensitive restriction enzyme digestion followed by fluorescent quantitative PCR (MSRE + PCR) were employed to detect the maternal-fetal methylation difference in AIRE and RASSF1A. Diagnosis of trisomy 21 was established according to the ratio of fetal-specific AIRE to RASSF1A in maternal plasma. Both methods confirmed that AIRE and RASSF1A were hypomethylated in maternal blood cells but hypermethylated in placental or chorionic villus tissues. Moreover, the differential methylation for each locus could be seen during the whole pregnant period. The positive rates of fetal AIRE and RASSF1A in maternal plasma were found to be 78.1% and 82.1% by MSP and 94.8% and 96.9% by MSRE + PCR. MSRE + PCR was superior to MSP in the identification of fetal-specific hypermethylated sequences (P<0.05). Based on the data from 266 euploidy pregnancies, the 95% reference interval of the fetal AIRE/RASSF1A ratio in maternal plasma was 0.33-1.77, which was taken as the reference value for determining the numbers of fetal chromosome 21 in 102 pregnancies. The accuracy rate in 98 euploidy pregnancies was 96.9% (95/98). Three of the four trisomy 21 pregnancies were confirmed with this method. It was concluded that hypermethylated AIRE and RASSF1A may serve as fetal-specific markers for the identification of fetal DNA in maternal plasma and may be used for noninvasive prenatal diagnosis of trisomy 21.

Noninvasive Prenatal Diagnosis of Fetal Trisomy 18 and Trisomy 13 by Maternal Plasma DNA Sequencing

Massively parallel sequencing of DNA molecules in the plasma of pregnant women has been shown to allow accurate and noninvasive prenatal detection of fetal trisomy 21. However, whether the sequencing approach is as accurate for the noninvasive prenatal diagnosis of trisomy 13 and 18 is unclear due to the lack of data from a large sample set. We studied 392 pregnancies, among which 25 involved a trisomy 13 fetus and 37 involved a trisomy 18 fetus, by massively parallel sequencing. By using our previously reported standard z-score approach, we demonstrated that this approach could identify 36.0% and 73.0% of trisomy 13 and 18 at specificities of 92.4% and 97.2%, respectively. We aimed to improve the detection of trisomy 13 and 18 by using a non-repeat-masked reference human genome instead of a repeat-masked one to increase the number of aligned sequence reads for each sample. We then applied a bioinformatics approach to correct GC content bias in the sequencing data. With these measures, we detected all (25 out of 25) trisomy 13 fetuses at a specificity of 98.9% (261 out of 264 non-trisomy 13 cases), and 91.9% (34 out of 37) of the trisomy 18 fetuses at 98.0% specificity (247 out of 252 non-trisomy 18 cases). These data indicate that with appropriate bioinformatics analysis, noninvasive prenatal diagnosis of trisomy 13 and trisomy 18 by maternal plasma DNA sequencing is achievable.

Fetal-Specific DNA Methylation Ratio Permits Noninvasive Prenatal Diagnosis of Trisomy 21

The standard procedures for prenatal genetic diagnosis of trisomy 21 (or Down syndrome) are invasive techniques based on cytogenetic or DNA analyses. Fetal genetic material with these techniques is obtained by amniocentesis, chorionic villus sampling, or cordocentesis, and there is significant risk of miscarriages of normal pregnancies. Safer alternatives investigated include a promising test for noninvasive prenatal diagnosis of trisomy 21 that can detect methylation differences (differentially methylated regions) between the free-fetal DNA in the maternal circulation among cases with and without trisomy 21. The test combines methylated DNA immunoprecipitation (MeDIP) methodology with real-time quantitative PCR to distinguish fetal DNA of trisomy 21 cases from normal cases. Worldwide trials have demonstrated that this test (called MeDIP) has considerable medical and commercial potential for noninvasive prenatal diagnosis of trisomy 21 as an alternative to invasive diagnostic procedures. The aim of this study was to demonstrate the efficacy of this test to discriminate between trisomy 21 and normal cases among blind samples. DNA methylation ratio values were determined for 40 blind and 40 known samples of free fetal DNA obtained from normal and trisomy 21 cases. The test correctly identified all 40 blind samples of the fetal-specific differentially methylated regions. There were 14 cases of trisomy 21 and 26 normal cases. These findings demonstrate that application of MeDIP in combination with real-time quantitative PCR is an accurate procedure for noninvasive prenatal detection of trisomy 21 and has future potential for routine testing of all pregnancies.

Noninvasive prenatal tests for Down syndrome are near

Noninvasive prenatal tests for Down syndrome are near

Fetal DNA: A Needle in the Haystack

A fetal epigenetic footprint in mothers’ blood paves the way for noninvasively diagnosing Down’s syndrome.

Fetal-specific DNA methylation ratio permits noninvasive prenatal diagnosis of trisomy 21

The trials performed worldwide toward noninvasive prenatal diagnosis (NIPD) of Down's syndrome (or trisomy 21) have shown the commercial and medical potential of NIPD compared to the currently used invasive prenatal diagnostic procedures. Extensive investigation of methylation differences between the mother and the fetus has led to the identification of differentially methylated regions (DMRs). In this study, we present a strategy using the methylated DNA immunoprecipitation (MeDiP) methodology in combination with real-time quantitative PCR (qPCR) to achieve fetal chromosome dosage assessment, which can be performed noninvasively through the analysis of fetal-specific DMRs. We achieved noninvasive prenatal detection of trisomy 21 by determining the methylation ratio of normal and trisomy 21 cases for each tested fetal-specific DMR present in maternal peripheral blood, followed by further statistical analysis. The application of this fetal-specific methylation ratio approach provided correct diagnosis of 14 trisomy 21 and 26 normal cases.

Non-invasive prenatal diagnosis of trisomy 21 by reverse transcriptase multiplex ligation-dependent probe amplification

Obtaining fetal DNA or RNA by either chorionic villus sampling (CVS) or amniocentesis is currently, the gold standard prenatal diagnosis. However, these invasive procedures carry risk of miscarriage. A reliable method for non-invasive prenatal diagnosis (NIPD) has long been sought to reduce the risk of miscarriage. Cell-free fetal RNA was extracted from the plasma of peripheral blood from 121 women 9-20 weeks of pregnancy. Five single nucleotide polymorphism (SNP) loci in PLAC4 gene were analyzed by reverse transcriptase multiplex ligation-dependent probe amplification (RT-MLPA), followed by capillary electrophoresis. Karyotype analysis was used for confirmation of prenatal diagnosis of trisomy 21. Of 121 samples, 23 were diagnosed with trisomy 21, 87 with normal ploidy, nine had all five SNP loci homozygous and two had one heterozygous SNP locus. Comparing with karyotype analysis, the diagnostic sensitivity and specificity of RT-MLPA were 92% and 100%, respectively. RT-MLPA is a convenient and reliable method for the diagnosis of trisomy 21. We have shown that this method has good specificity, high sensitivity, and high throughput, making this technique applicable for NIPD in clinical practice.

Maternal Plasma DNA Analysis with Massively Parallel Sequencing by Ligation for Noninvasive Prenatal Diagnosis of Trisomy 21

Noninvasive prenatal diagnosis of trisomy 21 (T21) has recently been shown to be achievable by massively parallel sequencing of maternal plasma on a sequencing-by-synthesis platform. The quantification of several other human chromosomes, including chromosomes 18 and 13, has been shown to be less precise, however, with quantitative biases related to the chromosomal GC content. Maternal plasma DNA from 10 euploid and 5 T21 pregnancies was sequenced with a sequencing-by-ligation approach. We calculated the genomic representations (GRs) of sequenced reads from each chromosome and their associated measurement CVs and compared the GRs of chromosome 21 (chr21) for the euploid and T21 pregnancies. We obtained a median of 12 x 10(6) unique reads (21% of the total reads) per sample. The GRs deviated from those expected for some chromosomes but in a manner different from that previously reported for the sequencing-by-synthesis approach. Measurements of the GRs for chromosomes 18 and 13 were less precise than for chr21. z Scores of the GR of chr21 were increased in the T21 pregnancies, compared with the euploid pregnancies. Massively parallel sequencing-by-ligation of maternal plasma DNA was effective in identifying T21 fetuses noninvasively. The quantitative biases observed among the GRs of certain chromosomes were more likely based on analytical factors than biological factors. Further research is needed to enhance the precision for measuring for the representations of chromosomes 18 and 13.

Noninvasive Prenatal Detection of Trisomy 21 by an Epigenetic–Genetic Chromosome-Dosage Approach

The use of fetal DNA in maternal plasma for noninvasive prenatal diagnosis of trisomy 21 (T21) is an actively researched area. We propose a novel method of T21 detection that combines fetal-specific epigenetic and genetic markers. We used combined bisulfite restriction analysis to search for fetal DNA markers on chromosome 21 that were differentially methylated in the placenta and maternal blood cells and confirmed any target locus with bisulfite sequencing. We then used methylation-sensitive restriction endonuclease digestion followed by microfluidics digital PCR analysis to investigate the identified marker. Chromosome-dosage analysis was performed by comparing the dosage of this epigenetic marker with that of the ZFY (zinc finger protein, Y-linked) gene on chromosome Y. The putative promoter of the HLCS (holocarboxylase synthetase) gene was hypermethylated in the placenta and hypomethylated in maternal blood cells. A chromosome-dosage comparison of the hypermethylated HLCS and ZFY loci could distinguish samples of T21 and euploid placental DNA. Twenty-four maternal plasma samples from euploid pregnancies and 5 maternal plasma samples from T21 pregnancies were analyzed. All but 1 of the euploid samples were correctly classified. The epigenetic-genetic chromosome-dosage approach is a new method for noninvasive prenatal detection of T21. The epigenetic part of the analysis can be applied to all pregnancies. Because the genetic part of the analysis uses paternally inherited, fetal-specific genetic markers that are abundant in the genome, broad population coverage should be readily achievable. This approach has the potential to become a generally usable technique for noninvasive prenatal diagnosis.

Maternal Plasma DNA Analysis with Massively Parallel Sequencing by Ligation for Noninvasive Prenatal Diagnosis of Trisomy 21

Maternal Plasma DNA Analysis with Massively Parallel Sequencing by Ligation for Noninvasive Prenatal Diagnosis of Trisomy 21

Sites of Differential DNA Methylation between Placenta and Peripheral Blood: Molecular Markers for Noninvasive Prenatal Diagnosis of Aneuploidies

The use of epigenetic differences between maternal whole blood and fetal (placental) DNA is one of the main areas of interest for the development of noninvasive prenatal diagnosis of aneuploidies. However, the lack of detailed chromosome-wide identification of differentially methylated sites has limited the application of this approach. In this study, we describe an analysis of chromosome-wide methylation status using methylation DNA immunoprecipitation coupled with high-resolution tiling oligonucleotide array analysis specific for chromosomes 21, 18, 13, X, and Y using female whole blood and placental DNA. We identified more than 2000 regions of differential methylation between female whole blood and placental DNA on each of the chromosomes tested. A subset of the differentially methylated regions identified was validated by real-time quantitative polymerase chain reaction. Additionally, correlation of these regions with CpG islands, genes, and promoter regions was investigated. Between 56 to 83% of the regions were located within nongenic regions whereas only 1 to 11% of the regions overlapped with CpG islands; of these, up to 65% were found in promoter regions. In summary, we identified a large number of previously unreported fetal epigenetic molecular markers that have the potential to be developed into targets for noninvasive prenatal diagnosis of trisomy 21 and other common aneuploidies. In addition, we demonstrated the effectiveness of the methylation DNA immunoprecipitation approach in the enrichment of hypermethylated fetal DNA.

44 Single-Nucleotide Polymorphisms Expressed by Placental RNA: Assessment for Use in Noninvasive Prenatal Diagnosis of Trisomy 21

For noninvasive prenatal diagnosis, markers that directly reflect changes in chromosome dosage are preferred over indirect markers that are associated with epiphenomena(1)(2). The RNA:single-nucleotide polymorphism (SNP) allelic ratio strategy was described recently as a means to directly assess fetal chromosome dosage in maternal plasma(2). Quantitive comparison of the allelic expression ratios of a placentally expressed, chromosome 21–encoded gene, placenta-specific 4 ( PLAC4 ), enabled detection in maternal plasma of the differences between 2 (normal) or 3 copies of chromosome 21(2). The RNA:SNP ratio strategy is currently limited to a subset of the population with heterozygosity of the SNP used. Theoretically, an increase in population coverage can be obtained by inclusion of additional SNPs within PLAC4 or other chromosome 21–encoded transcripts with placental expression and detectability in maternal plasma(2). We therefore tested 44 SNPs expressed by 7 chromosome 21–encoded, placentally expressed genes(2), PLAC4 , collagen, type VI, alpha 2 ( COL6A2 ), collagen, type VI, alpha 1 ( COL6A1 ), BTG family, member 3 ( BTG3 ), ADAM metallopeptidase with thrombospondin type 1 motif, 1 ( ADAMTS1 ), chromosome 21 open reading frame 105 ( C21orf105 ), and amyloid …

Prenatal diagnosis of trisomy 13 on fetal cells obtained from maternal blood after minor enrichment

In a pilot study to establish fetal nucleated red blood cell (NRBC) detection in maternal blood, trisomy 13 was diagnosed by FISH analysis at 11 weeks' gestation. The NRBCs were detected after a single-step ficoll density gradient enrichment. In blood samples taken both before and after CVS, 52 and 80 NRBCs, respectively, were found to be positive for fetal haemoglobin. In 47 per cent of these cells, FISH analysis for X and Y chromosomes confirmed the fetal sex. Moreover, 48 per cent of these NRBCs showed three fluorescent signals for a chromosome 13 probe, which confirmed the diagnosis of trisomy 13, previously detected at CVS karyotyping. This is the first report of non-invasive prenatal diagnosis of trisomy 13, i.e., pre-CVS, in the first trimester. The high number of fetal NRBCs detected indicates a connection with aneuploidy, probably due to early impairment of the feto-maternal barrier.