Human Genome Project Helps Child Birth Defects

Professor Peter Scambler at the Institute of Child Health in London takes a professional interest in several medical conditions that children are born with. The effects vary from restricted growth and limb development problems to heart defects, mental retardation and behavioural difficulties. The syndromes or conditions are different but the common thread is that they are all linked to defective genes.

Pinpointing the 'bad' genes that lead to illness, deformity or a failure to develop normally, coupled with an understanding of how they work, has been facilitated by the Human Genome Project which is identifying the entire genetic code. Using this information, scientists like Professor Scambler are able to carry out what is known as 'database mining'. In effect, they look through the sequence data as soon as it becomes available to try and identify the genes that may play a role in certain diseases. All of the sequence data emanating from the international Human Genome Project is deposited free of charge or any restriction into publicly accessible databases within 24 hours of it being available.

Peter Scambler is currently on such a hunt for genes implicated in three conditions: 3M Syndrome, which results in short stature; Fraser Syndrome which causes mental retardation, kidney cysts and a failure of the eyelids to open, and Congenital Tufting Enteropathy, an extremely rare condition, affecting only a handful of cases worldwide, in which the gut refuses to work.

In the case of birth defects, where the damage has already been done, it is not always feasible to talk in terms of cures but there are other options. "Once we have the sequence for specific genes, it makes diagnosis easier. We can carry out ante-natal tests to see whether the embryo or foetus may be affected," Peter Scambler explains.

Knowing whether or not a child may be affected gives parents an opportunity to make choices about whether to continue with the pregnancy or to plan provision for a child likely to be born with a deformity or medical condition that may need long term specialist treatment.

Isolating a gene responsible for, or linked to, a specific condition, also enables scientists to compare data with other researchers who may have isolated the same gene but for a different condition. Once a gene has been identified, the next stage is to see whether it codes for a protein, what this might be and what it might do in the body. All of this provides greater insight into the way that cells develop.

Professor Scambler explains: "We'll also use genomic data to help search for polymorphic sequence - that is compare sequences from different sources to detect any variations; also to compare human sequence with that of different organisms such as the mouse, fruit fly and yeast to identify the differences and what those might mean."

Adding value to data in this way and depositing it back into databanks for other researchers to use is not uncommon in the scientific community.

As Peter Scambler postulates : It may be at this stage that a drug company identifies a promising line of research for a potential new drug treatment. For many of the conditions I am working on, this is unlikely to be a cure but it may able to control or alleviate some of the symptoms."

One condition where the genes responsible have already been sequenced is Di George or Velo-Cardio Facial Syndrome. This is a potential fatal heart condition that affects 1 child in every 4,000 and may also result in mental retardation or behavioural problems. It is linked to a deficiency of genes from part of chromosome 22. "Now that we know the chromosome defect, we can build up a picture about prognosis. Parents want to have all the information that there is available, so that they know what to expect, even if there is no possibility of a cure," says Scambler.

These sentiments are echoed by Julie Wootton who lost her four-month old son Max to complications arising from a gene deletion on chromosome 22. She now runs the DiGeorge Syndrome Support Group. "Knowledge of the missing genes and thus a prediction of the type of congenital abnormalities to occur coupled with the appropriate medical intervention available from the instant of birth would possibly be the only way to prevent a baby like Max from dying.

"Further research is required to provide a safe and generally available prenatal testing system. Thus, we are very enthusiastic about the progress the Human Genome Project is making."

Professor Scambler is also supportive of the outcomes that the Human Genome Project is providing. "The availability of DNA sequence data has enabled me to work across a whole range of conditions instead of being limited to just one. If there was no Human Genome Project, we would have invented one but it would be being carried out by a network of researchers and the progress would be painfully slow."

Notes to editors:

  1. Photographs of Dr. Scambler are available from the Press Office.

  2. DiGeorge Syndrome Support Group: Mrs Julie Wooton, Lansdowne House, 13 Meriden Avenue, Wollaston, Stourbridge, West Midlands, DY8 4QN.

Completion of draft human genome:

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