New genetics research reveals how Africans are protected from diseases and viruses
New research by African geneticists has given them a peek into how migration has changed DNA and protected Africans from diseases and viruses.
Researchers have identified around 62 previously unreported genes associated with viral immunity, DNA repair and metabolism in Bantu-speaking populations.
The study analysed whole genomes of 426 individuals from 13 African countries, whose ancestries represent 50 ethnolinguistic groups from across the continent. It was published as a cover story in the journal Nature.
The study was led by Wits University’s Division of Human Genetics Professor Zané Lombard under the auspices of the Human Heredity and Health in Africa (H3Africa) Consortium in association with Dr Neil Hanchard and Dr Adebowale Adeyemo. Members of the H3Africa Consortiums who contributed to this work include researchers from 24 institutions across Africa, including the Sydney Brenner Institute for Molecular Bioscience (SBIMB) in the Faculty of Health Sciences at Wits University.
They observed complex patterns of ancestral mixing within and between populations, alongside evidence that Zambia was a likely intermediate site along the routes during migrations over 2000 years ago.
“We know that populations many thousands of years ago moved from West Africa - the Chad, Nigeria region - into East, Central and Southern Africa. What this data is showing us now is that most probably based on signatures we see in different people who are living in these countries now is that that movement probably happened via Zambia.
“One of the things we know is that there is a big rainforest that separates West Africa from the southern part. Moving and migration through that area wasn’t always clear and this genetic data is showing us similarities between the different groups that are currently living in West Africa and those in Zambia,” Lombard said.
They also found genomes that might be helping Africans fight off disease. Dr Dhriti Sengupta of the SBIMB and one of the lead analysts said they found more than 100 areas of the genome that had probably been under natural selection; a sizeable proportion of which were associated with immunity related genes.
“While genes involved in resistance to insect-transmitted diseases like malaria and sleeping sickness have long been known to be positively selected, our study shows that viral infections could have also helped to shape genomic differences between people and groups by altering the frequency of genes that affect individuals’ disease susceptibility.
“There were noticeable variations in selection signals between different parts of the continent, indicating that large-scale local-adaptations might have accompanied the migration of populations to new geographies, and consequent exposure to new diets and pathogens,” Sengupta said.
Lombard said more research still needs to be done on the genomes. “We haven’t been able to link them to specific disease or outbreaks. What we can see is that they are linked to genes that influence the way we metabolise food. What we are thinking is that those people migrated out of specific regions and their diets might have changed. They might have gone from being hunter gatherers to domesticating animals.
“We need to explore the immunity factor more. What we can do now is go back to communities and research the history and start looking at the genes and link them to epidemics and viral infections that happened in the history of that country and start learning what genes are important for immunity and resistance,” Lombard said.
She said the research being done by geneticists on the continent was important to remove historical bias. “Africa is the continent with greatest genetic diversity and this study shows the importance of African genomic data for taking science and health research forward. It is an important step in redressing existing biases in available data for research, which hamper the study of African health problems and narrows global research,” she said.