Penn researchers show new evidence of genetic 'arms race' against malaria

PHILADELPHIA — For tens of thousands of years, the genomes of malaria parasites and humans have been at war with one another. Now, University of Pennsylvania geneticists, in collaboration with an international team of scientists, have developed a new picture of one way that the human genome has fought back.

The international team was led by Sarah Tishkoff, a Penn Integrates Knowledge professor with appointments in the genetics department in Penn's Perelman School of Medicine and the biology department of biology in the School of Arts and Sciences, and Wen-Ya Ko, a postdoctoral fellow in the genetics department at the medical school. They performed a genetic analysis of 15 ethnic groups across Africa, looking for gene variants that could explain differing local susceptibility to malaria.

Their research will be published online in the journal American Journal of Human Genetics on June 2.

Malaria remains one of the deadliest diseases on the planet, annually killing about a million people, 90% of whom live in Africa. Different populations show different responses to the parasites that cause malaria; the team conducted the largest cross-population comparison ever on a pair of genes related to malaria's ability to enter red blood cells.

"When you try to identify the variants that are associated with disease susceptibility, it's important to do a very fine scale study," Ko said. "Different populations evolve independently, to a certain degree, so different populations can come up with unique mutations."

The life cycle of malaria depends on infecting red blood cells by binding to their surfaces, which is why mutations, such as sickle cell anemia, that change the overall shape of those cells are thought to have experienced positive selection.

"Both host and the parasite try to fight back with mutations; it's a co-evolution arms-race that leaves a signature of selection on the genes," Ko said. "We've identified several single-nucleotide polymorphisms that are candidates for that signature."

Across the 15 population sets, the researchers focused on polymorphisms in a pair of genes that code for proteins called glycophorin A and glycophorin B. These proteins exist on the surface of red blood cells, and changes to their shape affect the ability of the parasite causing malaria to bind to them and to infect the cells.

There are, however, two conflicting theories of why changes to glycophorin shape influence rates of malaria. One theory suggests that glycophorin A acts as a decoy, making itself more attractive to binding so that pathogens don't infect more vulnerable cells. Another theory suggests that glycophorin A mutates so that malaria parasites can't bind at all.

Does Race Exist? | 8Questions | 8Asians.com

I’ve spent the last year writing about Asian stereotypes on the Internet. In one of my recent articles, I asked the question: “ Are Asians the Smartest Race? ” As I was researching this question, I kept reading that race doesn’t really exist and that it is just a social construct.

Could this be true? Is race really something that WE created to separate ourselves from each other? Or is race real? Are there biological differences between Asian, Africans, Europeans, and others?  Needless to say, I’m not qualified to answer this question and for once I decided not to Google it. Instead, I went out and found someone who is qualified.

Professor Clark Barrett is an Associate Professor of Anthropology at UCLA. Professor Barrett  received his BA in Biology at Harvard and his PhD in Anthropology at UCSB. He conducts research among the Shuar, an indigenous Amazonian society in Ecuador. His research uses cross-cultural comparisons to examine universals and variation in human cognitive development.

I was lucky enough to ask Professor Barrett a few questions…

What does a biological anthropologist (like yourself) do/study?

Biological anthropologists generally agree that races as discrete categories — Black, White, Asian, etc. — are cultural constructs. However, this does not mean that there is not variation among humans in both appearance and many other traits. This variation is, in part,  caused by genetic variation. However, human genetic variation is a continuum, without discrete boundaries. Because racial categories are just that — categories — they impose boundaries where in fact there are none. Genes do not cluster in ways that map onto cultural racial categories.

Some people confuse it for the claim that people do not differ in appearance in different parts of the world. That part is obviously true. However, any trait that you could use to classify people, such as skin color, is in fact a continuum. People are often surprised to discover, for example, that if you were to assemble all the shades of skin color of people who are classified by the American folk racial category “black,” that set of skin colors would in fact overlap every other folk racial category (White, Asian, etc).

Not if it sorts people into categories. People are individuals, both genetically and culturally. It’s accurate to say what part of the world a particular ancestor of a person, e.g., your grandmother, came from. However, the set of all ancestors is also a continuum which, for all of us, stretches back to Africa sometime around 50,000 years ago.

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