However, as much of a boon as PGD is, babies conceived in this manner are still exposed to other genetic risks, says Brezina, the most common being the gain or loss of chromosomes, a condition called aneuploidy. Aneuploidy can cause several diseases, the most commonly known of which is Down syndrome.
Brezina and Kearns applied their new modified multiple displacement technique to screen embryos from a couple where both parents were carriers for GM1 gangliosidosis, a potentially lethal disease that can cause seizures, bone malformations and mental disabilities; the couple already had one child with the disease and the mother was older and had a prior history of miscarriage. Brezina and Kearns amplified the DNA from the couple's embryos and sent some of the amplified DNA to their collaborators at the Reproductive Genetics Institute in Chicago for PGD testing for GM1 gangliosidosis. They had enough DNA leftover to test it for aneuploidy using a test called 23-chromosome microarray on embryos, a test developed by Kearns.
Of the ten IVF embryos that they tested, they found that although only two were affected by GM1 gangliosidosis, an additional three were also aneuploid, leaving them with only five healthy embryos available for transfer into the uterus. One of the healthy embryos was transferred back into the mother, who subsequently became pregnant. "The strength of this technique lies not only in its ability to
|Contact: John Lazarou|
Johns Hopkins Medical Institutions