A Roberts Syndrome individual with differential genotoxin sensitivity and a DNA damage response defect.

Abstract

Roberts Syndrome (RBS) is a rare recessively-transmitted developmental disorder characterized by growth retardation, craniofacial abnormalities and truncation of limbs. All affected individuals to date have mutations in the ESCO2 (Establishment of cohesion 2) gene, a key regulator of the cohesin complex, which is involved in sister chromatid cohesion and DNA double-strand break (dsb) repair. Here we characterize DNA damage responses (DDRs) for the first time in a RBS-affected family. Lymphoblastoid cell lines (LCLs) were established from an RBS family, including the proband, and parents carrying ESCO2 mutations. Various DDR assays were performed on these cells, including clonogenic, chromosome break and apoptosis assays, checkpoint activation indicators and measures of DNA breakage and repair. Cells derived from the RBS-affected individual showed sensitivity to ionizing radiation (IR) and Mitomycin C (MMC) -induced DNA damage. In this ESCO2 compound heterozygote, other DNA damage responses were also defective, including enhanced IR-induced clastogenicity and apoptosis, increased DNA dsb induction and a reduced capacity for repairing IR -induced DNA dsbs as measured by γ-H2AX foci and the comet assay. in addition to its developmental features, RBS can be, like ataxia telangiectasia, considered a DNA damage response-defective syndrome, which contributes to its cellular, molecular and clinical phenotype.