Doctors at University College London (UCL) used preimplantation genetic diagnosis (PGD) to check embryos for the presence of a mutation in the RB1 gene that can lead to the development of the eye cancer retinoblastoma. PGD enables the identification and selection of embryos created by IVF to implant in the mother that are free of an undesirable mutation.
Mutations in the RB1 gene are inherited in an autosomal dominant manner, and so the naturally conceived child of a parent who carries the mutation has a 50 per cent chance of inheriting the gene. Retinoblastoma tumours can be successfully treated if detected early enough, but the required chemotherapy and surgery can result in blindness.
The UCL team was granted the licence to test for retinoblastoma by the Human Fertilisation and Embryology Authority (HFEA) last year (see HFEA news story, 3 October 2005 ), and this is the first child to be conceived under that licence. Other hereditary cancers that have been licensed for PGD by the HFEA include familial adenomatous polyposis coli (FAP) and Li-Fraumeni syndrome, but no pregnancies have been reported thus far from PGD for those conditions in the UK.
It should be emphasised that the current case is not connected to the draft recommendations that the HFEA announced on 9 May 2006 , following a 2005 consultation, to use PGD for mutations that increase susceptibility to both breast and colon cancer. Unlike those conditions, retinoblastoma usually develops in early childhood, and the mutation is almost fully penetrant – about 90 per cent of those who inherit the variant going on to develop the condition.
Nevertheless, because retinoblastoma is potentially treatable, this case is seen by some critics as a worrying extension of the use of PGD technology. Supporters, however, welcomed the news as offering greater choice and reassurance for parents who have suffered from the condition themselves and who want to ensure that they do not pass it on to their children.
Article courtesy of the Public Health Genetics Unit .