An example is the role of a sialylated GPI side-chain in prion protein: It was shown by in vitro studies that lack of Sia in the GPI side-chain of PrPc slowed generation of pathogenic PrPsc after infection of cultured cells, suggesting involvement of the sialylated GPI side-chain in conversion of PrPc to PrPsc6. This evidence concerns the gene PRNP and infection.