One cell at a time
The new testing method allows you to determine the genetic abnormalities of the fetus in the womb by the DNA of a single cell
Polina Gershberg, Naked Science
In an article published in The Journal of Molecular Diagnostics (Sato et al., Direct Assessment of Single-Cell DNA Using Crudely Purified Live Cells: A Proof of Concept for Noninvasive Prenatal Definitive Diagnosis), a new method of noninvasive prenatal tests (NPT) is described, which can detect genetic abnormalities in the fetus without causing harm to either the pregnant woman or her unborn child. This method allows the evaluation of genetic data based on a single cell.
A population of embryonic cells obtained from a maternal blood sample (figure from the article by Sato et al.).
Screening of genetic abnormalities of the fetus is necessary to exclude possible severe genetic diseases of the unborn child. The methods by which such screenings are carried out are divided into non-invasive (for them, a blood test is simply taken from the mother) and invasive (in this case, material taken from the fetus itself is needed). Invasive techniques are more accurate, but they increase the risk of miscarriage, and non-invasive ones do not threaten the child, but due to the indirection of the material provided, they sin with insufficient information content.
The new technique is based on the combined use of NPT in combination with drip digital PCR (an ultra-precise and well-reproducible method of DNA determination). Thanks to her, scientists were able to conduct a study of the genetic material of embryonic cells that circulate in very small quantities in the peripheral blood of the expectant mother.
The testing method described in the article allows obtaining information about the DNA of a single cell without the stages of cell fixation, cell staining and amplification of the entire genome. Usually, drip-digital PCR normally works only for well-washed cells or for labeled with fluorescent probes and sorted by glow. The scientists modified the technique in such a way that PCR gave good results even in roughly purified samples.
The new technique made it possible to detect male DNA samples in the blood of three women who were carrying male children. Due to the high sensitivity of the test in PCR, it was possible to identify the SRY gene, which determines the development of the body according to the male type. The blood of 10 women pregnant with girls, in all cases, gave a negative result for the presence of SRY.
"Since NPTs are now analyzing small fragments of DNA, it can be difficult to determine whether the fragment was obtained from the mother or from the fetus," says Kenichiro Hata, lead author of the study. – In some cases, the results of the NPT do not correspond to the genetic information about the fetus, which was reported [by invasive methods]. This study serves as proof of the operability of non-invasive prenatal diagnostics using circulating fetal cells without any strict cell purification."
Scientists intend to further improve their methodology. A modified diagnostic scheme using digital drip PCR can be a real breakthrough in genetic analysis.
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