The populations of the Amazon suffered a natural selection due to the Chagas pathogen and their genetics adapted until they had a resistant variant of this diseaseaccording to a study co-led by the Institute of Evolutionary Biology (IBE-CSIC-UPF) and the University of Sao Paulo (Brazil).
The work, which was published this Wednesday by the magazine Science Advanceshas been led by the IBE researcher Tábita Hünemeier, has combined the genomic analysis of 118 people from 19 populations of the Amazon with laboratory studies. His main discovery is that Amazonian populations have a high frequency of a variant of the PPP3CA gene that reduces the risk of Chagas infection.
Chagas diseasean infection also called ‘American Trypanosomiasis’, is caused by the parasite Trypanosoma cruzi (T.cruzi) and affects approximately 6 million people in Latin America alone. It is one of the leading causes of death in this region.
However, despite being in contact with the parasite, Amazonian populations hardly suffer from the infection of Chagas and therefore the aim of the study was to find out why.
Researchers already knew that tuberculosis and Chagas were in the Amazon before the arrival of Europeansbut there were no studies on the genetic adaptations of Amazonian populations to survive in this environment.
genetic adaptations
This study has revealed for the first time that these populations acquired genetic adaptations that gave them resistance to infectious diseases, such as that produced by the Chagas pathogen, and allowed them to adapt to their lifestyle in the jungle.
“We focused on finding evidence of positive natural selection related to tropical diseases in the Americas,” explained Hünemeier.
Analyzing the genomes, the study found a variant of the PPP3CA gene at high frequency in the inhabitants of Amazonia that could be responsible for this resistance and to verify if this was the case, they subjected it to tests in the laboratory, where they discovered that the variant of the PPP3CA gene reduces the risk of infection with the Chagas pathogen.
The researchers found that the PPP3CA gene codes for a key protein that activates innate immune cells and the internalization of the T.cruzi parasite in human cells and that it’s genderwhich is expressed in heart tissue and immune cells, It is very abundant in Amazon populations.
“The presence of the PPP3CA gene variant could be the cause of milder disease or less infection in these populations“, has summarized the professor of Biology at the UPF and researcher at the IBE-CSIC-UPF David Comas.
The study has estimated that this natural selection for greater resistance to Chagas disease began 7,500 years agoafter the populations of the Amazon separated from the populations of the Andes and the Pacific coast.
Supported by previous studies with 9,000-year-old samples, the research has concluded that epidemics would have positively selected for humans with higher resistance to tropical diseaseslike Chagas, generating a unique resistance in this population.
Research has also found genetic adaptations associated with behavioral traits such as “Novelty-seeking behaviors” or “Novelty-seeking behavior,” a genetic trait that determines behavior that actively seeks new experiences.
The study concludes thatThis trait may have been important to the hunter-gatherer lifestyle. of the Amazon populations in the past, as it would have helped them to explore new territories and search for resources.
They have also detected cardiovascular and metabolic traits that are consistent with the genetic predominance observed in previous research, since it had already been detected a rate of obesity, diabetes and coronary diseases of 66% in some Amazonian populations.