WRN and Werner syndrome: Although murine models have been described which show some WS-like features on mutation of the WRN helicase alone or with co-mutation of either telomerase or PARP (Lebel, 2002; Lebel et al., 2003; Chang et al., 2004; Massip et al., 2006), the relatively long lifespan and complexity of genetic intervention pose severe limitations on their exploitation.