By Erica Bellman
If you’re familiar with 23andMe’s products, you know there are currently two options for how customers can receive results: Ancestry only, or
both Ancestry and Health. On the surface, these two categories might seem unrelated, but when it comes to the science, ancestry and health are intrinsically linked, and knowledge of one may provide vital information about the other.
A recent article in Nature illuminates this connection. The piece looks at how recent studies of certain South Asian populations’ ancestral origins have spurred important insights about recessive heritable disorders.
To understand why the South Asian studies could be so fruitful for genetic health research, it’s crucial to understand the so-called “founder effect.” In essence, the founder effect is the loss of genetic variation that occurs when a new population emerges from a very small number of individuals (or founders) — who are isolated by geography or culture, for example — from a larger population.
Throughout South Asia’s “mosaic” of populations, a prominent demographic pattern has been for individuals to marry within their communities. One of the results of this pattern is the higher-than-typical frequency of certain of genetic variants that can cause recessive disorders, which in turn makes those variants easier to detect, screen for, and ultimately prevent.
It’s important to note that this certainly isn’t the first time scientists have identified health implications for a population descended from founders. For example, individuals of Ashkenazi Jewish ancestry were vital in improving our understanding of Tay-Sachs disease. The Finnish people have been studied due to their genetic uniformity and the occurrence of hereditary diseases such as congenital nephrosis, a kidney disease.
By continuing to study recessive disorders in founder populations, geneticists will be able to identify variants in the same deleterious gene in other populations. This helps to better understand the biology of the conditions, and develop potential treatments.
“If we know people of a certain ancestry have the same disease, we’re able to locate the regions of their genome where their ancestral background may overlap,” said Kimberly McManus, a population geneticist on 23andMe’s Research and Development team. “These sites can be informative, because they’re potential segments that may be causing or influencing the disease.”
Right now, one of the biggest hurdles to advancement in ancestry-inspired health research is the relative lack of genetic samples obtained from founder populations. Populations in South Asia, Africa and East Asia hold some of the richest genetic diversity in the world. However, they’ve historically been the least studied.
“Until a few years ago, more than 90% of genetic studies were based on individuals of European descent,” Kimberly said. “(This was) primarily due to the lack of available data from diverse populations.”
But some research-driven organizations are implementing programs that could significantly increase the diversity of the data available for study.
For 23andMe’s African Genetics Project, the company distributed free kits to people of underrepresented populations in Sub-Saharan Africa. The aim is to better serve those communities and customers who might have ancestral ties there.
“The benefits of increasing our sample sizes from these populations will be twofold,” Kimberly said. “It will allow people from these populations to better understand their ancestry. And it will allow researchers to investigate genetic health risks in these populations, as the genetics may be slightly different than in other populations.”
These new horizons for research and increased diversity of genetic samples. They present exciting possibilities for health breakthroughs. However, genetic similarities between populations around the world far outweigh the differences.
“Ancestry-inspired health is very important,” Kimberly said. “But it’s also important to remember that the vast, vast majority of variants are shared between all populations. Sequencing genomes of understudied groups can just be useful in better understanding some of the health traits shared among these populations.”