June 09, 2005

Schizophrenia, Embryo Controversy

Read more... Schizophrenia Biology

Barriers to embryo testing go down

The New Scientist Magazine reported this week that "TWO million babies worldwide have been born following in vitro fertilisation, and the embryos of at least 1000 of these were screened for genetic diseases before implantation." This, however, "is only the beginning: in the future more and more clinics will be offering pre-implantation genetic diagnosis (PGD) for an ever-growing range of diseases."

It may soon be possible to screen embryos for a class of genetic mutations called copy number polymorphisms (CNPs), caused by the deletion or duplication of segments of DNA. Until recently, these have been difficult to detect, but a team led by Michael Wigler of Cold Spring Harbor Laboratory in New York state has developed a DNA chip that can spot thousands of different CNPs.

But what does this ease in detection really mean for families with a history of schizophrenia? This is where the controversy comes in. Schizophrenia has been genetic basis, but with a very strong environmental factor also involved in the causation. The result is that while pre-implantation genetic diagnosis (PGD) might allow the identification of the genetic risk of getting schizophrenia (for a given embryo), it can't tell the environmental risk that the embryo, or child will face during his or her lifetime (so it will be only a very rough estimate of the risk of schizophrenia).

James Watson, co-discoverer of the double helix and president of the laboratory, has predicted that "In five years' time the method could be used to screen embryos for autism and possibly also for diseases such as schizophrenia."

He stated, "We should work as hard as possible to rid these diseases from families." But extending PGD to autism and other mental conditions is likely to prove controversial because the gene variants that contribute to these disorders might also contribute to desirable traits such as creativity.

Provided By: New Scientist


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