 This syndrome is characterized by cellular radiation sensitivity, growth retardation, developmental delay, microcephaly, facial dysmorphisms, increased disposition to leukemia, variable degrees of immunodeficiency and reduced number of blood cells.Accumulation of DNA damage leading to stem cell exhaustion is regarded as an important aspect of aging.Deficiency of lig4 in pluripotent stem cells impairs Non-homologous end joining (NHEJ) and results in accumulation of DNA double-strand breaks and enhanced apoptosis.