Radiation-induced delayed cell death in a hypomorphic Artemis cell line.
Null mutations in Artemis confer a condition described as RS-SCID, in which patients display radiosensitivity combined with severe combined immunodeficiency. Here, we characterize the defect in Artemis in a patient who displayed progressive combined immunodeficiency (CID) and elevated lymphocyte apoptosis. The patient is a compound heterozygote with novel mutations in both alleles, resulting in Artemis proteins with either L70 deletion or G126D substitution. Both mutational changes impact upon Artemis function and a fibroblast cell line derived from the patient (F96-224) has greatly reduced Artemis protein. In contrast to Artemis null cell lines, which fail to repair a subset of DNA double strand breaks (DSBs) induced by ionizing radiation, F96-224 cells show slow but residual DSB rejoining. Despite showing intermediate cellular and clinical features, F96-224 cells are as radiosensitive as Artemis null cell lines. We developed a FACS-based assay to examine cell division and cellular characteristics for 10 days following exposure to ionizing radiation (2 and 4 Gy). This analysis demonstrated that F96-224 cells show delayed cell death when compared with rapid growth arrest of an Artemis null cell line, and the emergence of a cycling population shown by a control line. F96-224 cells also display elevated chromosome aberrations when compared with control cells. F96-224 therefore represents a novel phenotype for a hypomorphic cell line. We suggest that delayed cell death contributes to the progressive CID phenotype of the Artemis patient.
Institute of Child Health, University College London, 30 Guilford Street, London WC1N 1EH, UK.
Paul M
PM
Evans
Lisa
L
Woodbine
Enriquetta
E
Riballo
Andrew R
AR
Gennery
Michael
M
Hubank
Penny A
PA
Jeggo
D016923:Cell Death / Q000528:radiation effects*; D002455:Cell Division / Q000187:drug effects; D002460:Cell Line; D004249:DNA Damage / Q000528:radiation effects; D004260:DNA Repair; D004268:DNA-Binding Proteins; D004720:Endonucleases; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism; D006579:Heterozygote; D006801:Humans; D007700:Kinetics; D009154:Mutation; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D016511:Severe Combined Immunodeficiency / Q000378:metabolism; D045567:VDJ Recombinases / Q000378:metabolism
D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D045567:VDJ Recombinases; C426344:DCLRE1C protein, human; D004720:Endonucleases