Take heart! - Gene testing for inherited diseases
Izelle Theunissen, MRC News
Gene research isn't science fiction. While gene therapy might still be some
way off in the future, gene testing for inherited diseases is a reality.
Scientists from the MRC's Cape Heart Group (in collaboration with a private firm
in Austria) have developed a cost-effective test kit to spot familial
hypercholesterolaemia - a common cause of heart attacks in South Africa.
Familial hypercholesterolaemia (FH) - or hereditary high cholesterol -
affects about 10 million people in the world. But the majority of cases go
unspotted and therefore remain untreated or poorly treated.
In South Africa, FH is a common cause of the high death rate from coronary
heart disease due to a 'founder effect'. This means that the incidence of
affected cases are exceptionally high in certain groups - in South Africa
Afrikaans speakers, Jewish and Indian people are known to have a high prevalence
of the disease.
But Dr Maritha Kotze (formerly a part-time professor of Human Genetics at the
University of Stellenbosch, team member in the MRC Cape Heart Group and now the
director of a company GeneCare) says cases are not only limited to these groups.
"Our team also demonstrated a relatively high frequency of an FH gene
defect among affected black people, which might increase their risk of heart
attacks with further westernisation."
The GeneCare team. Dr Rochelle Thiart (left) and Dr Charlotte Scholtz (right
are in front, while Nico de Villiers (left) and Dr Maritha Kotze are at the
back.
The test, which is a direct spin-off from the Human Genome Project, is based
on strip-assay technology. Testing for a range of gene defects that occur
commonly in the South African population can be done at the same time.
"This, of course, has brought down the cost of comprehensive DNA screening
significantly, because the test looks for a variety of defects simultaneously
and only needs to be done once in a lifetime. And accurate test results are
available in a matter of 6 hours from the time the blood reaches the
laboratory," says Dr Kotze.
Why is it necessary to know whether a person has FH instead of 'ordinary'
high cholesterol? Dr Kotze explains: "This is because the risk of fatal
heart disease is so much higher in people with FH. Men with FH usually die
around age 45. By age 60 a full 50% of the men have died already and 45% of the
women have serious heart problems. The earlier you spot the problem, the earlier
the treatment can begin and the better the prognosis for such a patient."
Commercialising research
This is a prime example of collaborative research being commercialised.
According to Dr Nico Walters (Executive Director of Technology and Business
Development at the MRC) the MRC, in collaboration with Dr Kotze, has patented
the technology. "Further commercialisation involving the total spectrum of
tests is currently being implemented in partnership with a pharmaceutical
company. The final product is a comprehensive diagnostic procedure with export
potential," says Dr Walters.
She also says that once a person has been diagnosed with FH, their family can
also be screened. In addition, parents with FH can have their unborn babies
screened. "Any child of theirs would have a 25% chance of inheriting two
copies of the 'bad' gene, making them especially vulnerable to early, serious
heart disease. So we can start treatment very early to prevent problems,"
she explains.
Treatment varies according to the type of mutation found in a patient. For
people with FH (they have mutations in the LDL receptor gene), lifelong
medication is necessary, supplemented with changes in their diet and lifestyle.
Further testing can also differentiate people with mutations in their
apolipoprotein B or E gene - their cholesterol levels are usually not quite as
high and might easier be rectified with changes to diet and lifestyle only.
But up to 50% of people with cardiovascular disease don't have any of the
established risk factors such as elevated cholesterol, hypertension, smoking,
obesity and diabetes mellitus. "Based on the same technology, we've adapted
the test to look for elevated homocysteine or iron levels. If untreated, these
problems may eventually lead to heart failure or heart attack. But it is easily
rectified - people with elevated homocysteine levels can fix the problem by
taking regular folic acid and B vitamin supplements. And people with iron
overload should simply become regular blood donors," Dr Kotze says.
For more information about the test kit, please contact Dr Kotze at the
GeneCare laboratory at tel.: (021) 422-5538 or (021) 480-6503 or e-mail: mjk@genecare.co.za.
Visit their web site at http://www.genecare.co.za.
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