The evolution of the anti-viral OAS1 gene in mice and primates

The interaction between host defense genes and virulent pathogens is of great concern for both medical and evolutionary research. I analyzed the variation in the oligoadenylate synthetase (OAS) gene family in both mice and primates. The OAS family of genes is part of the innate cellular response to viral infection and is found in all mammals, as well as some lower invertebrates. In both populations of the house mouse (Mus musculus) and chimpanzees (Pan troglodytes) I identified divergent alleles of the OAS family evolving under balancing selection. I analyzed three different mouse Oas1 genes and found different levels of variation for each gene within populations of M. musculus. Using molecular clocks I identified the age of alleles for Oas1b (> 3 million years old), Oas1g (between 1.5 and 2.8 million years old), and Oas1e (< 0.5 million years old). In chimp populations we identified two divergent alleles of Oas1 which were calculated to be over 9 million years old. Further functional analysis of the chimp alleles determined that the proteins had varying abilities to bind to viral RNA. This identifies viral RNA as the selective pressure within chimp populations and is a likely candidate for retaining alleles in mouse populations as well.