Gene chips for testing embryos

BioNews reporting from ESHRE conference, Berlin:
Couples at risk of having a child affected by a genetic disease could benefit from new, faster tests to detect gene mutations in IVF embryos, Australian scientists say. The research shows that 'gene chips' can be used to carry out PGD (preimplantation genetic diagnosis) for cystic fibrosis (CF). But, say the researchers, who are based at Monash University in Melbourne, the technique is only effective if carried out on embryos grown for between five to six days in the laboratory. Currently, most PGD tests are done a single cell taken from a three-day old embryos, which are made up of just eight cells.

Cystic fibrosis, a severe disease that affects the lungs and digestive system, is one of the most prevalent inherited conditions. According to study author, Chelsea Salvado, the identification of embryos free from CF is one of the most common reasons for couples to request PGD. By using PGD, couples at risk of having a child with CF can undergo IVF, and then implant only unaffected embryos. People are born with CF if they inherit two faulty CF genes, one from each parent. Eighty per cent of these CF gene mutations are a type called delta 508, but there are at least another nine CF mutations found in the Australian population. Testing for each mutation separately would be a time-consuming approach.

The new method uses microarray (gene chip) technology, in which many different gene mutations can be analysed at the same time. The Australian team has developed a way of amplifying the DNA from ten cells taken from a blastocyst embryo grown to the 100 cell stage of development, which usually takes five to six days. However, the method was not reliable when carried out on one cell taken from an eight cell stage, which is when most PGD tests are currently performed. The scientists hope their method will lead to new, faster PGD tests for many genetic diseases in the future. 'Microarray technology will lead to semi-automated genetic testing for PGD and prenatal diagnosis, providing a rapid diagnosis, thus reducing the stress of couples waiting for a result', said Salvado.