Preimplantation genetic testing for the breast cancer gene

PGD-embryo-pivfThe use of Preimplantation Genetic Testing (PGD) enables fertility doctors to screen embryos for genetic diseases such as Cystic Fibrosis or Sickle Cell Anemia, permitting couples at high risk to avoid transmitting these diseases onto their children. PGD is done as part of an IVF cycle. A biopsy is taken when the embryo reaches the 8 cell or the blastocyst stage, and tested for the specific gene we are concerned about. This same technology can also be used to test for genes that do not necessarily cause a disease but put an individual at risk for other serious diseases. One such genetic mutation, called the BRCA 1 and 2 gene, puts affected women at very high risk for developing breast and ovarian cancer. The risk of developing these cancers in affected women is so high that many women (such as Angelina Jolie) chose to have their breasts and/or ovaries surgically removed just to prevent cancer. Since we know the genetic sequence of the BRCA mutation, it is possible to screen embryos for it, and prevent transmitting the gene onto one’s daughters. This article in the Wall Street Journal tells the story of a family who decided to go that route.

Do embryos and the uterus talk to each other?

blastocyst-embryo-pivfWe know that in normal fertile couples it takes an average of 3 months to conceive.  We also know that in successful IVF programs, most embryos will never implant.  Even when genetic testing is performed on the embryos to eliminate the most common cause of IVF failure, 30% of embryos will still not stick. So, is the embryo sending some sort of message to the uterus that is OK to allow implantation or not? Researchers from the UK, discovered that embryos produce an enzyme called trypsin that facilitates the implantation process, but that embryos which are genetically abnormal produce less trypsin. This may be a way that embryos tells the uterus whether it ok to allow implantation. Perhaps a better understanding of this process may help develop ways to make IVF more successful.

Time lapse video: from egg to blastocyst

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Did you ever wonder what happens from conception until implantation? This video from the NIH website shows a time lapse video of the egg and embryo as it moves from the pronuclear stage, to the cleavage stage, to the morula stage and finally to a blastocyst, ready to implant in the uterus. Click here to view the video.