Defective DNA double-strand break repair in pediatric systemic lupus erythematosus

• Published in: Arthritis & rheumatology (Hoboken, N.J.) Vol. 64; no. 2; pp. 568 - 578
• Main Authors: Davies, Robert C., Pettijohn, Kelly, Fike, Francesca, Wang, Jiexi, Nahas, Shareef A., Tunuguntla, Rashmi, Hu, Hailiang, Gatti, Richard A., McCurdy, Deborah
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc., A Wiley Company 01-02-2012; Wiley; Wiley Subscription Services, Inc
• Subjects: Adolescent; Autoimmune diseases; Biological and medical sciences; Cell Line; Child; Deoxyribonucleic acid; Diseases of the osteoarticular system; DNA; DNA Breaks, Double-Stranded; DNA Repair; Female; Humans; Injuries of the limb. Injuries of the spine; Lupus; Lupus Erythematosus, Systemic - genetics; Male; Medical research; Medical sciences; Pediatrics; Phosphorylation; Protein expression; Proteins; S Phase Cell Cycle Checkpoints; Sarcoidosis. Granulomatous diseases of unproved etiology. Connective tissue diseases. Elastic tissue diseases. Vasculitis; Traumas. Diseases due to physical agents; Young Adult; Human; Immunopathology; Connective tissue disease; Pediatrics; Skin disease; Rheumatology; Break; Autoimmune disease; Systemic lupus erythematosus; DNA; Systemic disease; Repair; Child
• ISSN: 0004-3591; 2326-5191; 1529-0131; 2326-5205
• DOI: 10.1002/art.33334

Objective
Previous reports of cells from patients with systemic lupus erythematosus (SLE) note that repair of single‐strand breaks is delayed, and these lesions may be converted to double‐strand breaks (DSBs) at DNA replication forks. We undertook this study to assess the integrity of DSB recognition, signaling, and repair mechanisms in B lymphoblastoid cell lines derived from patients with pediatric SLE.
Methods
Nine assays were used to interrogate DSB repair and recognition in lymphoblastoid cell lines from patients with pediatric SLE, including the neutral comet assay (NCA), colony survival assay (CSA), irradiation‐induced foci formation for γ‐H2AX and 53BP1 proteins, kinetics of phosphorylation of structural maintenance of chromosomes protein 1 (SMC1), postirradiation bromodeoxyuridine incorporation to evaluate S phase checkpoint integrity, monoubiquitination of Fanconi protein D2, ATM protein expression, and non‐homologous DNA end joining protein expression and function.
Results
Three of the 9 assays revealed abnormal patterns of response to irradiation‐induced DNA damage. The NCA and CSA yielded aberrant results in the majority of SLE lymphoblastoid cell lines. Abnormal prolongation of SMC1 phosphorylation was also noted in 2 of 16 SLE lymphoblastoid cell lines.
Conclusion
Our data suggest that DSB repair is defective in some lymphoblastoid cell lines from pediatric patients with SLE, especially when assessed by both NCA and CSA. Since these studies are nonspecific, further studies of DNA repair and kinetics are indicated to further delineate the underlying pathogenesis of SLE and possibly identify therapeutic targets.