The BBC News has a good popular science article on the enhanced regenerative capabilities of MRL mice - something that has impressed scientists for a while now: "The MRL mouse has been used in research for years - mostly as a model for autoimmune diseases because the genetic mutations they carry mean they have a lupus-like disease. ... This animal has an unusual ability to show cell proliferation and lack of scarring which I think are two key elements to why we don't regenerate. ... She believes that one of the factors that blocks regeneration in most mammals is a membrane that forms as the body starts to repair itself. ... When the team looked at the formation of the membrane in the ears of MRL mice, they found that it did form initially, but disappeared soon after and then cell growth begins. ... [the researchers] are now looking to see if they can breed mice have the regenerative capabilities but do not carry autoimmune disease."