1. Cell-free DNA in maternal plasma and serum: A comparison of quantity, quality and tissue origin using genomic and epigenomic approaches
- Author
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K.C. Allen Chan, Rossa W.K. Chiu, Peiyong Jiang, Felix C.K. Wong, Tak Yeung Leung, Yuk Ming Dennis Lo, Yvonne Kwun Yue Cheng, and Kun Sun
- Subjects
0301 basic medicine ,Pregnancy Trimester, Third ,Clinical Biochemistry ,Bisulfite sequencing ,Biology ,Epigenesis, Genetic ,03 medical and health sciences ,chemistry.chemical_compound ,0302 clinical medicine ,Pregnancy ,Humans ,Digital polymerase chain reaction ,Epigenomics ,Fetus ,Cell-Free System ,DNA ,Genomics ,General Medicine ,Methylation ,DNA Methylation ,Molecular biology ,genomic DNA ,030104 developmental biology ,Cell-free fetal DNA ,chemistry ,030220 oncology & carcinogenesis ,Female - Abstract
Objectives The objectives of this study were to compare the concentrations, size profiles and major tissue contributors of cell-free DNA (cfDNA) in plasma and in serum. Design and methods Thirteen pregnant women in the third trimester were recruited for this study. We collected EDTA-plasma and serum samples using various collection tubes. We determined their cfDNA concentrations and fetal cfDNA fractions using a zinc-finger X (ZFX)/zinc-finger Y (ZFY) droplet digital polymerase chain reaction (ZFX/ZFY ddPCR) assay. We used paired-end massively parallel sequencing (MPS) to measure plasma and serum cfDNA sizes at single-base resolution. We deconvoluted the genome-wide bisulfite sequencing data with reference to the methylation profiles of different tissues. Results The concentrations of cfDNA collected in Sarstedt Serum Z tubes were found to be significantly higher than those in Greiner Bio-One Vacuette® Z Serum Separator Clot Activator tubes or Vacuette® Z Serum Clot Activator tubes. The concentrations of fetal cfDNA were significantly reduced in samples collected in the Vacuette® serum collection tubes. Fetal cfDNA fractions were significantly reduced in all sera compared to plasma. MPS of serum cfDNA revealed a right shift of the size distributions compared to plasma. Methylation-based tissue mapping of serum cfDNA revealed an increase of cfDNA from neutrophils and B cells but not T cells. Conclusions The use of different serum collection tubes has a significant impact on serum cfDNA concentrations. This effect is likely mediated through the combined effect of genomic DNA release from white blood cells and DNA degradation or removal.
- Published
- 2016