Increased risks of genetic diseases in cloned embryos

5 July 2005

Researchers from Cornell University in the US have reported findings on the risk of genetic disorders in children born following assisted reproduction. Concerns have arisen over the safety of assisted reproductive techniques, due to the higher incidence of genetic imprinting disorders among children born following such procedures. Imprinting is a process of differential expression of certain genes in the foetus based on whether they are present on the paternal or maternal alleles. Imprinting disorders can lead to abnormal foetal development and diseases in humans such as Angelman's and Beckwith-Wiedemann's syndromes. Speaking at the Annual Meeting of the European Society of Human Reproduction and Embryology (ESHRE) held in Berlin last week, Takumi Takeuchi and Gianpiero Palermo said that they had investigated mouse embryos created from a total of 68 mouse eggs by three different methods of assisted reproduction: intracytoplasmic sperm injection (ICSI); parthenogenesis and somatic cell nuclear transfer (cloning). The embryos were grown for 3-5 days, to the blastocyst stage of development (16 cells).

They found no evidence of defects in mouse embryos created by the first two of these techniques in terms of decreased survival rate of embryos compared with naturally conceived embryos, whereas only 30% of the cloned embryos survived to the 16-cell stage. This was proposed to be the result of abnormal gene expression in cloned embryos. On further investigation, the researchers found that the histones (DNA binding proteins) in the cloned embryos had been altered to show a pattern of imprinting similar to that seen in a mature egg cell. No such alterations were observed in the other embryos studied. Commenting on their findings, Dr Takumi Takeuchi said:

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