researchPublished 2006
Human migrations not traceable by JC Virus after all
Most of us contract JC virus (JCV) during childhood, from our parents. Only rarely does infection cause disease; mostly, it remains unnoticed, and we pass the virus on to our children in turn. JCV has at least 14 genetically distinct subtypes, some of which are associated with specific human populations — for example, type 7A predominates in Southeast Asians, types 3 and 6 in Africans, and types 1 and 4 in Europeans.
The parent-child transmisison route, together with the population specificity of particular subtypes, has led some researchers to use JCV as a genetic marker for tracing early human migration patterns. Furthermore, rates of JCV evolution have been inferred by assuming co-divergence with human populations over the last 200,000 years.
However, Laura Shackelton, Eddie Holmes and collaborators report that JCV and human evolution are not tightly coupled after all. When the researchers examined JCV from a variety of human populations worldwide, as well as mitochondrial genomes from the same set of human populations, they discovered that:
- JCV is evolving much faster than previously thought;
- Much of JCV's genetic variability stems from a population expansion starting around 350 years ago, much later than early human migrations;
- Evolutionary "trees" for JCV do not map at all closely onto the evolutionary history of humans inferred from mitochondrial sequences.
» Their findings are published in the Journal of Virology