Another piece has been added to the puzzle about the role of ancestry in the South African Coloured population's susceptibility to tuberculosis (TB).
This population is the result of the African click-speaking, African Bantu speaking, European, South Asian and East Asian populations coming together a few generations ago.
"Such admixture is a well-known confounder in genetic association studies, and should be considered in statistical models," explains Dr Michelle Daya, who completed her PhD in biomedical sciences under supervision of Prof Eileen Hoal and Prof Lize van der Merwe.
When genome-wide data is not available, researchers use ancestry informative markers (AIMs) to take admixture into account. Using the large genotypic data sets collected over many years by the DST-NRF Centre for Biomedical TB Research, Daya developed a small set of AIMs specifically for the South African Coloured population. These now make it easier to distinguish the genetic influences of its five ancestral source populations.
"This cost-effective method helps researchers who study tuberculosis and other diseases in this population to correct for ancestry, knowing that their findings are valid," she hopes.
A further admixture mapping study identified genetic regions where ancestry between TB cases and healthy controls differ markedly. Immune-related genes, as well as ones associated with anaemia, glucose metabolism and developing diabetes are found in these regions.
"Iron is essential in the growth and metabolism of Mycobacterium tuberculosis, and diabetes is a risk factor for developing TB ," explains Daya. "The admixture mapping study may provide direction to investigate how these factors influence the development of TB , based on the genetics underpinning them."
Researchers argue that some people's susceptibility to recurrent TB infections cannot simply be overcome with current medications and vaccines.
"Insight into the genetic mechanisms driving this susceptibility is important for the effective development of drugs and vaccines for the South African Coloured community, as well as many affected communities worldwide," believes Daya.
This article appeared in the Faculty of Medicine and Health Sciences' annual publication. Visit www.sun.ac.za/FMHSpublications to subscribe.
