ERCC1- and XPF-deficient mice are not viable or undergo early postnatal death depending on the genetic background while in humans, mutations affecting these genes have been linked to some severe diseases, including the skin cancer-prone disease xeroderma pigmentosum (XP), a progeroid syndrome of accelerated aging (XFE), and cerebro-oculo-facio-skeletal syndrome (COFS)45. This evidence concerns the gene ERCC4 and COFS syndrome.