Centre for Research into Circulating Fetal Nucleic Acids, Department of Chemical Pathology, Li Ka Shing Institute of Health Sciences, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong SAR, China.
PLoS One. 2012;7(10):e48319. doi: 10.1371/journal.pone.0048319. Epub 2012 Oct 31.
Fetal DNA in maternal urine, if present, would be a valuable source of fetal genetic material for noninvasive prenatal diagnosis. However, the existence of fetal DNA in maternal urine has remained controversial. The issue is due to the lack of appropriate technology to robustly detect the potentially highly degraded fetal DNA in maternal urine.
We have used massively parallel paired-end sequencing to investigate cell-free DNA molecules in maternal urine. Catheterized urine samples were collected from seven pregnant women during the third trimester of pregnancies. We detected fetal DNA by identifying sequenced reads that contained fetal-specific alleles of the single nucleotide polymorphisms. The sizes of individual urinary DNA fragments were deduced from the alignment positions of the paired reads. We measured the fractional fetal DNA concentration as well as the size distributions of fetal and maternal DNA in maternal urine.
Cell-free fetal DNA was detected in five of the seven maternal urine samples, with the fractional fetal DNA concentrations ranged from 1.92% to 4.73%. Fetal DNA became undetectable in maternal urine after delivery. The total urinary cell-free DNA molecules were less intact when compared with plasma DNA. Urinary fetal DNA fragments were very short, and the most dominant fetal sequences were between 29 bp and 45 bp in length.
With the use of massively parallel sequencing, we have confirmed the existence of transrenal fetal DNA in maternal urine, and have shown that urinary fetal DNA was heavily degraded.
如果存在于母体尿液中的胎儿 DNA 将是一种有价值的非侵入性产前诊断的胎儿遗传物质来源。然而，母体尿液中是否存在胎儿 DNA 一直存在争议。这个问题是由于缺乏适当的技术来稳健地检测母体尿液中潜在的高度降解的胎儿 DNA。
我们使用大规模平行配对末端测序来研究母体尿液中的游离 DNA 分子。在妊娠晚期，从 7 名孕妇的导尿管尿液样本中收集样本。通过识别包含单核苷酸多态性的胎儿特异性等位基因的测序读段，我们检测到了胎儿 DNA。从配对读段的对齐位置推断出单个尿液 DNA 片段的大小。我们测量了母体尿液中胎儿 DNA 的分数浓度以及胎儿和母体 DNA 的大小分布。
在 7 个母体尿液样本中的 5 个中检测到了游离的胎儿 DNA，胎儿 DNA 的分数浓度范围从 1.92%到 4.73%。分娩后，母体尿液中的胎儿 DNA 无法检测到。与血浆 DNA 相比，总尿液游离 DNA 分子完整性较低。尿液中的胎儿 DNA 片段非常短，最主要的胎儿序列长度在 29 个碱基对和 45 个碱基对之间。
我们使用大规模平行测序证实了母体尿液中转肾胎儿 DNA 的存在，并表明尿液中的胎儿 DNA 严重降解。
