African human genomes decoded

[Image] The genomes of members of Namiba’s
Ju/’hoansi tribe, as well as that of Desmond
Tutu, have been decoded by a group
of scientists from institutions around
the world.
(Image: Stephan C. Schuster)
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Janine Erasmus

An international group of scientists have decoded the entire genome of Archbishop Emeritus Desmond Tutu and an indigenous Namibian, and partially decoded three others, in the hope that it will pave the way for personalised medicine in developing nations.

Until the ground-breaking study, genomic decoding focused mostly on the Western world.

The 50-strong team, comprising researchers from Australia, Namibia and South Africa, was supported by Pennsylvania State University.

The group was co-led by biochemistry and molecular biology professor Stephan Schuster of Penn State’s Eberly College of Science, and Vanessa Hayes of the University of New South Wales.

Hayes also works at the Children’s Cancer Institute Australia. She expressed her pleasure at the addition of Tutu to the test line-up, saying that the distinguished Nobel laureate was an ideal representative for a large group of Southern Africans because of his Nguni and Tswana heritage.

The findings were published in the 18 February issue of the scientific journal Nature.

Controversial issues

The project is not without its controversy, however. The availability of genetic information raises the question of who should be able to access it, and why?

Only a small number of genomes have ever been published – one of them is that of James Watson who, together with his colleague Francis Crick, determined the double helix structure of DNA in 1953, earning themselves a Nobel prize in the process.

Employees could find themselves the victims of genetic discrimination in the workplace, while insurance companies could structure an individual’s premium or limit the amount of cover, based on the client’s genetic information. There are even more sinister possibilities, such as the development of chemical weapons based on ethnicity.

But genetic testing also has many positive implications. The more that is known about human genetics, the more likely it is that researchers will develop life-saving therapy for any number of hereditary diseases.

Genetic testing will also increase the chances of detecting serious problems at an early age – or even before birth – to prevent the need for expensive treatment later on.

The team hope that the participation of Tutu – known and admired throughout the world not only for his anti-apartheid activism but also for his battle against prostate cancer, polio and tuberculosis – will inspire others to do the same.

Potential for better health

Genomic decoding potentially offers tremendous benefits for human health, and holds implications for the way doctors will treat their patients in the future. Now that the new information has been added to current databases, medical research will include Southern Africans, who have not featured prominently in studies to date.

“Southern Africans will immediately be included in genome-wide disease association studies as a result of this project,” said Hayes, “increasing our ability to examine regionally significant diseases.”

The genome is defined as all DNA carried within a living organism, of which genes are just one component. DNA determines everything about the organism – whether it is plant or animal, its species, and all its biological characteristics.

DNA molecules are made of the same four chemicals, or nucleotides, in all living creatures – but the sequence of nucleotides is crucial. Nucleotides occur in pairs, and the human genome has about 3-billion pairs that occur in a sequence unique to each person.

Because of this fundamental relationship between living organisms, the comparative study of non-human genomes provides valuable insights into human biology and complex biological systems.

The US-based Human Genomic Project was launched in 1990 and ran for 13 years. The project’s goals were to identify all human genes, establish the sequence of all 3-billion DNA pairs, and make the information accessible to scientists for further research while addressing the legal and ethical implications.

The full potential of this enormous scientific accomplishment has not been realised yet. Some of the data still to be revealed by researchers in the coming decades include a deeper study of proteins, whose function is regulated by the genes; and the use of genetic variation to predict susceptibility to disease.

Ancient people

The new study involved three new DNA sequencing techniques, which are significantly faster and more economical than existing technologies. “Human genomics is becoming a realistic and powerful medical resource that will gain momentum in 2010,” said Schuster.

The study of how the effectiveness of medicines is influenced by genetic makeup is known as pharmocogenomics, and it is a growing field of research. For example, anti-HIV drugs are known to be less effective in Africans than in Europeans – a problem that could be solved by tweaking the formulation appropriately.

The test group consisted of Tutu and four members of the Ju/’hoansi tribe, who live along the border between Namibia and Botswana. !Gubi is the name of the other man whose genome was fully decoded.

The indigenous people of Southern Africa, known as San Bushmen, belong to the oldest known lineage of humankind. The San have roamed the Kalahari Desert for many thousands of years in small, mobile groups.

“We sequenced the personal genomes of four Bushmen participants who are tribal leaders from their communities and are at least 80 years of age,” said Schuster, “and from one Bantu participant who is in his late 70s,” referring to Tutu. The word “Bantu” is used to refer to the indigenous peoples of Central and Southern Africa who belong to the Niger-Congo language subfamily that includes kiSwahili, isiXhosa, and isiZulu

The study revealed that the people of Southern Africa are distinctly different genetically from those in Asia, Europe and even West Africa. About 1.3-million genetic variants were discovered which will help drug developers to more accurately tailor medications to a specific people, increasing their efficacy.

The test group was found to be extremely diverse in genetic terms, with the number of genetic differences exceeding those found to exist between Asians and Europeans.

“To know how genes affect health, we need to see the full range of human genetic variation,” said biology professor and study participant Webb Miller of Penn State, “and Southern Africa is the place to look.”

A surprise outcome of the study showed that Tutu was genetically related to the Bushmen through his mother. “The fact that the test found that I am related to these wise people who paint rocks makes me feel very privileged and blessed,” said the Archbishop, talking to BBC News.

The study also revealed genetic factors such as intolerance to a high-fat diet in the San Bushmen, who still practice their age-old hunter-gatherer lifestyle, making them poorly suited to an agricultural way of life. Other factors, such as their advanced senses and superior physical abilities, explain why their current lifestyle suits them so perfectly.

Miller added that the data is freely available on Penn State’s internet servers.