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Wits geneticists and partners published a groundbreaking study reporting on the history of the African population, environmental adaptation and susceptibility to disease. More than three million new genetic variants were discovered in one of the largest studies of high-depth sequenced African genomes reported to date. Photo: Cover of NATURE magazine
One of the most extensive genomic studies ever conducted in African populations has discovered three million new genetic variants, revealing new insights into the diversity and history of the continent and its people.
In a new study published Wednesday afternoon in Nature The complete genomes of 426 people from 13 African countries were analyzed. Their ancestors represent 50 ethnolinguistic groups from across the continent.
Professor Michèle Ramsay, Director of the Sydney Brenner Institute for Molecular Bioscience at Wits University’s School of Health Sciences, explained the importance of discovering three million novel genetic variants to Rogue citizen: “What is remarkable is that every time we study African genomes we discover many new variants, despite the fact that databases keep track of all known variants from research conducted around the world. European populations are well studied, but in fact they have much less genetic variation and have been studied more frequently, so the chance of discovering new findings is much lower. There is much more to explore in the genetic makeup of Africans. “
African populations have much greater genetic variation because they are much older and because, when migrations “out of Africa” occurred, only small groups of people left the continent.
Studying genetic variation is important for two main reasons: first, it may be relevant to health and susceptibility to disease, and second, it can reveal fascinating historical links between peoples and groups.
“We can observe deep ancestral relationships between populations that we did not know,” says Ramsay, “such as historical interactions and migratory events in Africa.”
One of the interesting findings is the diversity in Africa, with some variants much more common in specific regions. For example, people who are carriers of sickle cell anemia are more likely to be in areas where malaria is hyperendemic, because this variant protects them against severe malaria. This is an evolutionary adaptation to the environment.
The work revealed evidence supporting the movement from East Africa to central Nigeria between 1,500 and 2,000 years ago through the identification of a substantial amount of East African descent, particularly Nilo-Saharan Chad, in a central Nigerian ethnolinguistic group, the Berom. It was not previously known if they had ever had contact.
Ramsay said genetic information about populations could highlight information about past encounters. “It is a biological reflection of history. Much of human evolution has no written history, but genomes are a permanent record. It tells the story of us, of humans. “
The study was led by Professor Zané Lombard in the Division of Human Genetics at the University of the Witwatersrand (Wits) and under the auspices of Heredity and Human Health in Africa (H3Africa).
The researchers found more than 100 areas of the genome that had been under natural selection, and of these 62 genes had not been seen before.
Lombard explained that, during the course of evolution and its mechanism of natural selection, people tried to survive for hundreds of thousands of years. The environment, diet, infections and migration influenced how and who survived. Each generation carried its genetic material to the next and within this myriad of sequences are genes that gave people some advantages.
“These genes have selection signals that we can pick up when we look at the genomes of people living today. They indicate large-scale adaptations in specific areas and specific groups have different patterns of natural selection; 62 of these selection signals are seen for the first time in this group of individuals from Africa. This gives us clues as to where to do more research; for example, in those genes associated with immunity ”.
The team is beginning to unravel the secrets of these new variants. It has shown that these signals were markedly different when geographical areas were compared. When people migrated, large-scale adaptations occurred and today that can be seen in genomes.
Despite Africa’s central role in the origin of modern humans, knowledge of genetic diversity in African populations has been poor. Most genomic studies have been done in other populations, but this is slowly changing, years after the sequencing and publication of the first complete human genome in 2003.
The authors wrote in the article: “The African continent is considered the cradle of modern humans and African genomes contain more genetic variation than those of any other continent, but only a fraction of the genetic diversity among African individuals has been studied.
“Advances in genomics have enabled the interrogation of the human genome in global populations, and the resulting studies show that Africa is home to the greatest genetic variation and diversity. To date, only a limited number of the around 2,000 African ethnolinguistic groups have been genetically characterized. “
The H3Africa Consortium supports 48 genomic projects and seeks to correct the information gap by studying the genomes of people throughout Africa, to understand population demographics of human disease.
“This is very important to us, to show that we have the capacity in Africa to do this job,” Lombard said. “It is a milestone that so many African researchers, representing more than 24 African research institutions across the continent, contributed to the lead article in Nature.
“Aggregating genomic data from all global populations, including Africa, is essential to ensure that everyone can benefit from the advances in health that precision medicine offers.”
Precision medicine, or “personalized” medicine, refers to treatment and prevention of diseases that take into account individual variability in genes, environment and lifestyle of each person ”, he explained. DM / MC
