Identification of the DNA repair defects in a case of Dubowitz syndrome.
Dubowitz Syndrome is an autosomal recessive disorder with a unique set of clinical features including microcephaly and susceptibility to tumor formation. Although more than 140 cases of Dubowitz syndrome have been reported since 1965, the genetic defects of this disease has not been identified. In this study, we systematically analyzed the DNA damage response and repair capability of fibroblasts established from a Dubowitz Syndrome patient. Dubowitz syndrome fibroblasts are hypersensitive to ionizing radiation, bleomycin, and doxorubicin. However, they have relatively normal sensitivities to mitomycin-C, cisplatin, and camptothecin. Dubowitz syndrome fibroblasts also have normal DNA damage signaling and cell cycle checkpoint activations after DNA damage. These data implicate a defect in repair of DNA double strand break (DSB) likely due to defective non-homologous end joining (NHEJ). We further sequenced several genes involved in NHEJ, and identified a pair of novel compound mutations in the DNA Ligase IV gene. Furthermore, expression of wild type DNA ligase IV completely complement the DNA repair defects in Dubowitz syndrome fibroblasts, suggesting that the DNA ligase IV mutation is solely responsible for the DNA repair defects. These data suggests that at least subset of Dubowitz syndrome can be attributed to DNA ligase IV mutations.
The Cancer Institute of New Jersey, Robert Wood Johnson Medical School, New Brunswick, New Jersey, United States of America.
Jingyin
J
Yue
Huimei
H
Lu
Shijie
S
Lan
Jingmei
J
Liu
Mark N
MN
Stein
Bruce G
BG
Haffty
Zhiyuan
Z
Shen
D000328:Adult; D000970:Antineoplastic Agents / Q000494:pharmacology; D053903:DNA Breaks, Double-Stranded; D004249:DNA Damage; D000072481:DNA Ligase ATP; D011088:DNA Ligases / Q000235:genetics*; D004260:DNA Repair; D004485:Eczema / Q000235:genetics* / Q000473:pathology / Q000532:radiotherapy; D019066:Facies; D017809:Fatal Outcome; D005260:Female; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism / Q000473:pathology / Q000528:radiation effects; D005720:Gamma Rays; D006130:Growth Disorders / Q000235:genetics* / Q000473:pathology / Q000532:radiotherapy; D006801:Humans; D008607:Intellectual Disability / Q000235:genetics* / Q000473:pathology / Q000532:radiotherapy; D008831:Microcephaly / Q000235:genetics* / Q000473:pathology / Q000532:radiotherapy; D009154:Mutation; D011836:Radiation Tolerance
D000970:Antineoplastic Agents; C000607893:LIG4 protein, human; D011088:DNA Ligases; D000072481:DNA Ligase ATP