PGD Update, November 2006

Preimplantation genetic diagnosis, or PGD, has been successfuly used for a decade, but its potential is still developing. Some of the latest developments to unfold have done so through research by IntegraMed network researchers.

The purpose of PGD is genetic screening of IVF-created embryos, performed before they are transferred to the mother's uterus. The use of PGD has virtually eliminated the familial transmission of some genetic conditions, such as chromosome disorders (aneuploidy and / or structural chromosome abnormalities) or single gene disorders (i.e. Tay Sach's disease,) and is helping to increase the use of single embryo transfer to prevent multiple pregnancies.

Expanding beyond the technology's limitations is a constant work in progress. Most recently, Dr. William G. Kearns, geneticist and director of the Shady Grove Center for Preimplantation Genetics, unveiled an upgrade that allows optimized and enhanced DNA extraction / amplification employing a modified microarray platform. What this means to patients who use PGD is that the test can reveal far more aberrant genetic situations than ever before, allowing IVF users more assuredness that the embryos they select for transferring will be free of numerous genetic conditions.

Some of the new opportunities Dr. Kearns describes as presented by the new PGD technology include:

  • a complete molecular karyotype for all 23 chromosome pairs
  • identification of structural chromosome abnormalities (translocations and inversions)
  • identification of genetic imbalances caused by duplications or microdeletions
  • determining which partner provided an extra chromosome in aneuploid embryos
  • determine what embryo implanted
  • selection of best embryo for single embryo transfer
  • correlate embryo genotype with embryo grading and implantation
  • optimization of in vitro embryo growth and development
  • identify epigenetic changes
  • identification of pathways causing infertility
  • identify single gene disorders
  • identify affected embryos of a segregating genetic disorder in a family with a no known mutation

Another developing use of PGD with tremendous potential was presented at the October 2006 meeting of the American Society for Reproductive Medicine by Kearns and co-researchers from Colorado Center for Reproductive Medicine, headed by Dr. M.G. Katz-Jaffe with Drs. David Gardner and John Stevens, and reproductive endocrinologist Dr. William Schoolcraft. The team presented results from the first study to investigate PGD screening performed by looking at the proteins that embryos produce and secrete, called secretome.

What the study authors found is very encouraging toward finding new and less invasive ways to examine the genetic condition of an embryo. Rather than utilizing biopsy techniques, in which a cell or two is removed from the embryo to analyze, this latest study concluded that analysis of an embryo's secretome may reveal whether or not the embryo is normal or aneuploid.

Amazing scientific breakthroughs are fortunately common in reproductive medicine. Technological innovation that answers to the needs of society and patients alike is remarkable. For more information on PGD, please see "PGD: The Best Choice for Some Parents" here on the IntegraMed website.