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Wits geneticists and partners have published an innovative study informing the history of the African population, environmental adaptation and susceptibility to disease. More than three million new genetic variants have been discovered in one of the most extensive studies of highly sequenced African genomes reported to date. Photo: front page of NATURE magazine
One of the largest genomic studies ever conducted on African populations uncovered 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 entire genomes of 426 people from 13 African countries were analyzed. Their ancestors represent 50 ethnolinguistic groups from across the continent.
Prof. Michèle Ramsay, director of the Sydney Brenner Institute for Molecular Bioscience at Wits University’s Faculty of Health Sciences, explained the importance of discovering three million new genetic variants for Citizen MaverickWhat is remarkable is that every time we study African genomes we discover many new variants, even though the databases keep track of all known variants from research conducted around the world. European populations are well studied, but they actually have much less genetic variation and have been studied more frequently, so the detectability of 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” took place, only small groups of people left the continent.
It is important to study genetic variation for two main reasons, firstly it can be relevant to health and disease susceptibility, and secondly, it can reveal fascinating historical links between people and groups.
“We can observe deep ancestral relationships between populations that we were not aware of,” says Ramsay, “as well as historical interactions and migratory events across Africa.”
One of the interesting findings is diversity across Africa, with some variations 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 from 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 ancestors – notably Nilo-Saharan from Chad – in a Nigerian ethnolinguistic group. central, the Berom. It was not previously known that they had ever had contact.
Ramsay said genetic information on populations could highlight information about past encounters. “It’s 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 conducted by Prof Zané Lombard of the Human Genetics Division of the University of the Witwatersrand (Wits) and under the aegis of Human Heredity and 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, in the course of evolution and its natural selection mechanism, people have tried to survive for hundreds of thousands of years. The environment, diet, infections and migration influenced how and who survived. Each generation has carried their genetic material to the next, and within this myriad of sequences are genes that have given people some advantages.
“These genes have selection signals that we can pick up by looking at the genomes of people living today. They indicate large-scale adaptations in specific areas and specific groups have different natural selection patterns; 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 further research; for example, in those genes associated with immunity. “
The team is just starting to unravel the secrets of these new variants. It showed that these signals were significantly different when geographic areas were compared. When people migrated, large-scale adaptations took place and today this can be seen in the 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 conducted in other populations, but this is slowly changing, years after the first complete human genome was sequenced and published in 2003.
The authors wrote in the paper: “The African continent is considered the birthplace 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 examined.
Advances in genomics have allowed for interrogation of the human genome among global populations, with the resulting studies showing that Africa is home to the greatest genetic variation and diversity. To date, only a limited number of the approximately 2,000 African ethnolinguistic groups have been genetically characterized “.
The H3Africa Consortium supports 48 genomic projects and seeks to remedy the lack of information by studying the genomes of peoples across the breadth of Africa to understand the population demographics of human diseases.
“This is very important to us, to show that in Africa we have the ability to do this work,” Lombard noted. “It is a milestone that so many African researchers, representing more than 24 African research institutes across the continent, contributed, for the main article in Nature.
“The addition of genomic data from all global populations, including Africa, is essential to ensure that everyone can benefit from the health advances offered by precision medicine.”
Precision medicine – or “personalized medicine” – refers to disease treatment and prevention that takes into account the individual variability in each person’s genes, environment and lifestyle, “he explained. DM / MC
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