Researchers studying the biological basis of mental illness conducted the first genomic analysis of schizophrenia in Africa and identified multiple rare mutations that are more common in people with the disorder. Mutations have mostly been found in genes that are important for the development of the brain and brain synapses - tiny structures that coordinate communication between neurons. The genes found correspond to genes identified in other similar studies of schizophrenia, however, almost all previous studies have been conducted in European or Asian countries. The work was published in the journal Science.
Why Africa?
The results of the study are consistent with current hypotheses about the biological origin of schizophrenia, which can cause a range of symptoms such as hallucinations, delusions and disordered thinking. The researchers believe that each mutation may make a small contribution to the overall risk of developing the disease, and the disruption of synapses may be critical to the development of the disease.
Because genome sequencing research has flourished in recent decades, making it possible to detect many diseases. However, researchers have often been criticized for failing to select different populations, largely neglecting Africans. About 80% of all genetic research participants are of European descent, and less than 3% are African. This bias means that diagnostic tests and treatments based on narrow research may not work in certain populations. For example, a 2016 study found that genetic tests that calculate the risk of fatal cardiovascular disease were often misdiagnosed. This happened because the genes on which it was based were identified in research,which did not involve people from Africa, who, as a rule, have many different gene variants that affect the risk of developing diseases.
Research in different populations also allows scientists to develop a more complete picture of disease. In particular, some Africans have a more diverse genome than other populations. Moreover, it contains a large number of unique gene variants. The researchers explain this by the fact that the greatest period of human evolution took place in Africa, where modern Homo sapiens originated. It is believed that people left Africa 50,000-100,000 years ago and only a relatively small number of people migrated to Europe and Asia. As a result, genetic diversity in these regions is much more modest.
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Does the severity of schizophrenia affect the study results?
The latest study, conducted by scientists in South Africa and the United States, looked at about 900 people with schizophrenia and a similar number who did not have the disorder. All participants identified themselves as Xhosa, a large ethnic group living in South Africa.
The researchers sequenced part of the subjects' genome in search of mutations that damage the genes. They found that such mutations were much more common in people with schizophrenia than in control subjects, and were concentrated in genes that are highly expressed in the brain or involved in synaptic function. The team compared their findings with those from a large Swedish study on schizophrenia that used the same methods. Studies have identified similar genes, but the density of mutations in the gene tended to be more common among South Africans.
Lyubov Sokovikova