Abstract
The study of genetic syndromes characterized by sensitivity to DNA damaging agents has provided important insights into the mechanisms that maintain genome stability and identified novel targets for cancer therapies. Here, we used exome sequencing to study 51 unrelated individuals with previously reported hypersensitivity to ionizing radiation as well as a range of neurologic, immunologic, and developmental features, but who did not clearly fit any previously defined genetic syndrome. Based on the combination of variant identification, computational evidence of deleteriousness, and functional screening, we identified three groups of subjects. Two subjects carried the bi-allelic loss of function variants in causative genes for known DNA damage response syndromes. Eight subjects carried the single loss of function variants in causative genes for DNA damage response syndromes, six of whom also carried predicted deleterious variants in other genes with DNA damage-related functions. Three subjects carried deleterious mutations in genes without obvious roles in DNA damage responses. However, treatment of U2OS cells with small interfering RNA targeting these genes resulted in significantly increased radiation sensitivity. Our results suggest that gene-gene interaction may contribute to ionizing radiation sensitivity as well as highlighting possible roles for several genes not obviously involved in the response to DNA damage.