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ABSTRACT: Abstract The collection of fetal genetic materials is required for the prenatal diagnosis of fetal genetic diseases. The conventional methods for sampling fetal genetic materials, such as amniocentesis and chorionic villus sampling, are invasive in nature and are associated with a risk of fetal miscarriage. For decades, scientists had been pursuing studies with goals to develop non-invasive methods for prenatal diagnosis. In 1997, the existence of fetal derived cell-free DNA molecules in plasma of pregnant women was first demonstrated. This finding provided a new source of fetal genetic material that could be obtained safely through the collection of a maternal blood sample and provided a new avenue for the development of non-invasive prenatal diagnostic tests. Now 15 years later, the diagnostic potential of circulating fetal DNA analysis has been realized. Fruitful research efforts have resulted in the clinical implementation of a number of non-invasive prenatal tests based on maternal plasma DNA analysis and included tests for fetal sex assessment, fetal rhesus D blood group genotyping and fetal chromosomal aneuploidy detection. Most recently, research groups have succeeded in decoding the entire fetal genome from maternal plasma DNA analysis which paved the way for the achievement of non-invasive prenatal diagnosis of many single gene diseases. A paradigm shift in the practice of prenatal diagnosis has begun.
Clinical Chemistry and Laboratory Medicine 10/2012; · 2.15 Impact Factor
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Nature medicine 09/2012; 18(9):1327-8. · 27.14 Impact Factor
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ABSTRACT: The 15 years since the discovery of fetal DNA in maternal plasma have witnessed remarkable developments in noninvasive prenatal diagnosis. An understanding of biological parameters governing this phenomenon, such as the concentration and molecular size of circulating fetal DNA, has guided its diagnostic applications. Early efforts focused on the detection of paternally inherited sequences, which were absent in the maternal genome, in maternal plasma. Recent developments in precise measurement technologies such as digital polymerase chain reaction (PCR) have allowed the detection of minute allelic imbalances in plasma and have catalyzed analysis of single-gene disorders such as the hemoglobinopathies and hemophilia. The advent of massively parallel sequencing has enabled the robust detection of fetal trisomies in maternal plasma. Recent proof-of-concept studies have detected a chromosomal translocation and a microdeletion and have deduced a genome-wide genetic map of a fetus from maternal plasma. Understanding the ethical, legal, and social aspects in light of such rapid developments is thus a priority for future research.
Annual review of genomics and human genetics 05/2012; 13:285-306. · 11.57 Impact Factor
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ABSTRACT: Fetal DNA is present in the plasma of pregnant women. A fetus with trisomy of a chromosome will release an increased amount of DNA from that chromosome into maternal plasma. Such an increase has previously been measured using methods that allow individual DNA molecules to be counted. One such method involves the use of random massively parallel sequencing of maternal plasma DNA. As the sequencing process is random, sequence tags from a potentially aneuploid chromosome only represent a fraction of the sequencing data. The performance of selective amplification and sequencing of specific genomic regions is a recently reported approach for focusing the sequencing power onto genomic regions of diagnostic interest. This article provides a critical analysis of this approach and puts this method in the perspective of other recent works in the field.
Expert Review of Molecular Diagnostics 05/2012; 12(4):329-31. · 4.86 Impact Factor
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Yuk Ming Dennis Lo
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ABSTRACT: Fetal DNA is present at an approximate mean fractional concentration of 10% in the plasma of pregnant women. The detection of paternally-inherited DNA sequences that are absent in the maternal genome, e.g., Y chromosomal sequences for fetal sexing and the RHD gene for blood group genotyping, is well established. The recent emergence of single molecule counting technologies, such as digital polymerase chain reaction and massively parallel sequencing has allowed circulating fetal DNA to be used for the non-invasive prenatal diagnosis of fetal chromosomal aneuploidies and monogenic diseases. With large scale clinical validation and further reduction in costs, it is expected that the analysis of circulating fetal DNA will play an increasingly important role in the future practice of prenatal diagnosis.
Clinical Chemistry and Laboratory Medicine 10/2011; 50(6):995-8. · 2.15 Impact Factor
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Pak Cheung Ng,
Irene Ling Ang,
Rossa Wai Kwun Chiu,
Karen Li,
Hugh Simon Lam,
Raymond Pui On Wong,
Kit Man Chui,
Hon Ming Cheung,
Eddy Wing Yin Ng,
Tai Fai Fok,
Joseph Jao Yiu Sung, Yuk Ming Dennis Lo,
Terence Chuen Wai Poon
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ABSTRACT: Preterm infants are highly susceptible to life-threatening infections that are clinically difficult to detect, such as late-onset septicemia and necrotizing enterocolitis (NEC). Here, we used a proteomic approach to identify biomarkers for diagnosis of these devastating conditions. In a case-control study comprising 77 sepsis/NEC and 77 nonsepsis cases (10 in each group being monitored longitudinally), plasma samples collected at clinical presentation were assessed in the biomarker discovery and independent validation phases. We validated the discovered biomarkers in a prospective cohort study with 104 consecutively suspected sepsis/NEC episodes. Proapolipoprotein CII (Pro-apoC2) and a des-arginine variant of serum amyloid A (SAA) were identified as the most promising biomarkers. The ApoSAA score computed from plasma apoC2 and SAA concentrations was effective in identifying sepsis/NEC cases in the case-control and cohort studies. Stratification of infants into different risk categories by the ApoSAA score enabled neonatologists to withhold treatment in 45% and enact early stoppage of antibiotics in 16% of nonsepsis infants. The negative predictive value of this antibiotic policy was 100%. The ApoSAA score could potentially allow early and accurate diagnosis of sepsis/NEC. Upon confirmation by further multicenter trials, the score would facilitate rational prescription of antibiotics and target infants who require urgent treatment.
The Journal of clinical investigation 08/2010; 120(8):2989-3000. · 15.39 Impact Factor
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ABSTRACT: In recent years, the application of circulating nucleic acids as a clinical diagnostic tool has aroused the interest of many
clinicians and biomedical scientists. Circulating nucleic acids refer to the DNA and RNA species that are present in the plasma
or serum portion of a blood sample. Although the existence of circulating nucleic acids was described more than half a century
ago, the potential clinical implication of circulating nucleic acid analysis has only been realized by the global scientific
community in the past 5 yr. In this chapter, current developments of circulating DNA analysis will be discussed. The clinical
applications of circulating Epstein-Barr virus (EBV) DNA in cancer detection and monitoring will be discussed in detail to
illustrate the important technical issues of performing circulating DNA analysis.
01/2008: pages 217-236;
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Clinical Chemistry 11/2007; 53(10):1874-6. · 7.91 Impact Factor
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Nature Genetics 07/2007; 39(6):691-2; author reply 694-6. · 35.53 Impact Factor
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ABSTRACT: T-box expressed in T cells (T-bet) and GATA-binding protein 3 (GATA-3) are transcriptional factors that play a crucial role in Th1 and Th2 development. We investigated the immunomodulatory roles of T-bet and GATA-3 and Th1/Th2 related cytokines in the pathogenesis of systemic lupus erythematosus (SLE) and their association with disease activity.
Gene expressions of T-bet, GATA-3, interferon-gamma (IFN-gamma), and interleukin 4 (IL-4) in peripheral blood mononuclear cells, and plasma concentrations of the Th1/Th2 cytokines IFN-gamma, IL-18, and IL-4, were assayed in 80 patients with SLE and 40 sex and age matched healthy subjects by real-time quantitative polymerase chain reaction and ELISA.
The mRNA levels of T-bet and IFN-gamma and the relative expression levels of T-bet/GATA-3 and IFN-gamma/IL-4 were significantly higher, in contrast to the lower expressions of GATA-3 and IL-4, in SLE patients than controls (all p < 0.05). In all SLE patients, there were significant correlations in mRNA expression of T-bet with IFN-gamma (r = 0.590, p < 0.0001), and of GATA-3 with IL-4 (r = 0.245, p = 0.029). The relative expressions of T-bet/GATA-3 and IFN-gamma/IL-4 correlated with lupus disease activity (r = 0.229, p = 0.042; r = 0.231, p = 0.040, respectively). Plasma IL-18 concentration was increased significantly in all SLE patients (p < 0.05). The elevated plasma Th1/Th2 cytokine ratio IL-18/IL-4 correlated positively with disease activity in all SLE patients (r = 0.250, p = 0.025).
There is an association between expression of Th1/Th2 transcription factors and cytokines in SLE. The elevated gene expressions of Th1/Th2 transcription factors and cytokines should provide a useful tool for assessing the functional status of T-helper lymphocytes in SLE disease development.
The Journal of Rheumatology 01/2007; 34(1):89-96. · 3.69 Impact Factor
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ABSTRACT: Cell-free fetal DNA and RNA released into the maternal circulation offer new opportunities to study fetal and pregnancy-associated abnormalities. Similarly, tumor cells can release cell-free DNA and RNA into the peripheral circulation, and these cell-free DNA and RNA can be used for cancer diagnosis, monitoring, and prognosis. However, these DNA and RNA often exist at very low concentrations (for fetal DNA, approximately 20 genome-equivalents (G.E.)/mL of plasma in the first trimester). The analysis is further complicated by the predominant amount of blood cell-derived DNA and RNA. MALDI-TOF mass spectrometry can provide quantitative, specific, and sensitive analysis of DNA and RNA, and thus may be a useful technology for the field.
Annals of the New York Academy of Sciences 10/2006; 1075:282-7. · 3.15 Impact Factor
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ABSTRACT: Successful detection of circulating nucleic acids has opened up new possibilities in cancer testing and prenatal diagnosis. Circulating DNA markers are useful in cancer detection, prognostication and monitoring. Cancer-associated molecular changes which can be detected include gene mutations, chromosomal rearrangements, microsatellite alterations, viral sequences, and, to be discussed in more detailed, gene promoter hypermethylation. Methylation analysis is commonly performed by DNA digestion with methylation-sensitive restriction endonucleases followed by polymerase chain reaction (PCR), or bisulfite modification followed by methylation-specific PCR (MSP). The detection of fetal DNA in maternal plasma has opened up new possibilities for noninvasive prenatal diagnosis. However, circulating fetal DNA detection has been based on exploiting gender and polymorphic differences between the fetus and mother. The recent discovery of epigenetic differences between the maternal and the fetal DNA detectable in maternal plasma has launched a hunt for fetal-derived epigenetic markers in maternal plasma. It is hoped that this type of universally applicable markers would be made available in a clinical diagnostic setting in the near future.
Frontiers in Bioscience 02/2006; 11:2647-56. · 3.52 Impact Factor
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Methods in molecular medicine 02/2004; 97:217-36.
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Yuk-Ming Dennis. Lo
