“Welcome back home!” ” Welcome to the house. The theme of the 14th International Congress of Human Genetics (ICHG), held every five years, was not chosen at random: for the first time, the conferences of specialists in this young discipline, held at the end of February, were linked in Africa, in Cape Town. A strong symbol and “a way of remembering that we are all African”, explains Professor Ambroise Wonkam, world-renowned specialist and president of the African Society of Human Genetics (SAfGH), organizer of the event.
Yet since the publication of the first complete sequencing of a human genome twenty-two years ago, less than 2% of all genomes listed have come from people of African descent. A paradox, when “the vast majority of human genetic diversity has remained on the continent, specifies the Cameroonian researcher, who also heads the department of genetic medicine at Johns-Hopkins University in Baltimore, United States (Maryland ). It is estimated that each African genome has five times more variations than a Caucasian genome. With the exodus of Homo sapiens from Africa 50,000 to 60,000 years ago, only a small sample of genetic diversity has spread across the globe.
The vast majority of research carried out over the past two decades has been carried out by European and American teams. “Researchers worked with genomes that were most easily accessible, therefore mainly from populations of European descent. But the genomes of African populations show a much greater diversity than that which exists among Caucasian genomes,” adds Hugues Abriel, professor of molecular medicine at the University of Bern, Switzerland.
If, in recent years, the interest of researchers has extended to Asian populations, Africans remain the forgotten ones. With very concrete consequences for improving the diagnosis and management of genetic diseases on the continent. “As a medical geneticist, when I sequence the genome of a sick child, if I find an abnormality, the available databases do not help me, because they only contain information from populations of European descent says Shahida Moosa, head of the genetic medicine department at Tygerberg Hospital and professor at Stellenbosch University in Cape Town. There is therefore an urgent need to sequence DNA on the continent in order to develop an African genomic library.
A scientific necessity, an equity issue
Because a genetic variant can change the symptoms of a disease, sometimes for the same disease, it is a gene different from that known in the Caucasian genomes which is in question. “A mutation very frequently found in Western babies who are born deaf is almost never present in Africa, illustrates Ambroise Wonkam. On the other hand, we have identified in Ghana seven new genes involved in deafness. »
Identifying these variations and improving knowledge of the genomes and genetic diseases of African populations is therefore not only a scientific necessity, but also an equity issue. “When I started my project on cystic fibrosis, I discovered that in the Democratic Republic of Congo, out of 100 million inhabitants, not a single case is officially recorded!, Reports Professor Hugues Abriel, who collaborates to several projects on the continent. However, we know, through small cohorts, that this disease also exists in Africa. »
When she applies for funding, Shahida Moosa is still often told that rare diseases and human genetics projects are not a priority in Africa. “Yes, HIV, TB and malaria are scourges here, but we have to stop working in silos and pitting the issues against each other,” she says. Knowing more about the human genetics of African populations will have benefits far beyond rare diseases! Genetics has made it possible to progress on many diseases, infectious and chronic in particular. »
To support his colleague’s point, Ambroise Wonkam recalls that the latest drugs developed to treat excess cholesterol, and mainly used in high-income countries, come from studies carried out on a variant of the PCSK9 gene very present in certain populations. African, but rare among populations of European origin.
Increase local search capabilities
The experts interviewed therefore insist on the universality of the benefits to be derived from a better knowledge of African genetics, but also on the need for research carried out locally. “We no longer want ‘helicopter research’ done by experts who come to the continent for a few months and leave,” insists Shahida Moosa. Researchers from here have been used by certain foreign colleagues and retain a mistrust of this which today harms collaborations between African teams. However, we must network if we want to move forward. »
Le projet Human Heredity
For several years now, African and European universities have forged close ties to ensure an increase in local research capacities. For example, the collaboration between The Guild of Research and the African Research Universities Alliance (ARUA), which seeks to translate this work into “African clusters of excellence”, explains Hugues Abriel, member of the Guild. As Ambroise Wonkam explained in a recent column published in Nature, to create a library with well-stocked shelves, it will be necessary to sequence some 3 million genomes in the next ten years. An ambition that requires 450 million dollars a year.
