Preimplantation genetic diagnosis (PGD) technologies allow identification of genetic disorders in human preimplantation embryos after in vitro fertilization (IVF) and before the embryo is transferred back to the patient. This technique allows couples with a high risk of passing on inherited diseases, to increase their chances of having a healthy baby. Despite the theoretical benefits of PGD, clinical outcomes using these technologies vary, possibly because of the need to remove one or more cells from the embryo using biopsy. In a study published on March 13, 2013 in Reproductive Biomedicine Online, a group of researchers from Italy and the United Kingdom sought to achieve diagnosis of genetic disease in embryonic DNA without the use of a biopsy. By extracting fluid from human embryos at the blastocyst stage they found that it contains DNA from the embryo. Blastocysts are 5- or 6-day-old embryos and are at the last free-living stage that can be studied in the laboratory prior to transfer into the uterus. Blastocysts contain between 50 and 300 cells that surround a fluid-filled cavity called the blastocoel.. The researchers carefully removed fluid from the blastocoel, leaving the cells intact. The sampled blastocysts were subsequently cryopreserved. This study employed real-time PCR to show that genomic DNA was present in about 90% of blastocoele fluid samples harvested. Moreover, the potential for determining embryo sex directly from blastocoele fluid was demonstrated by amplifying the multicopy genes TSPY1 (on the Y chromosome) and TBC1D3 (on chromosome 17). The authors said this opens up the possibility of screening embryos from couples carrying an X-linked disorder to identify male embryos at high risk of disease.
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