Immortalization and characterization of Nijmegen Breakage Syndrome fibroblasts

Nijmegen Breakage Syndrome (NBS) is a very rare autosomal recessive chromos omal instability disorder characterized by microcephaly, growth retardation , immunodeficiency and a high incidence of malignancies. Cells from NBS pat ients are hypersensitive to ionizing radiation (IR) and display radioresist ant DNA synthesis (RDS). NBS is caused by mutations in the NBS1 gene on chr omosome 8q21 encoding a protein called nibrin. This protein is a component of the hMre11/hRad50 protein complex, suggesting a defect in DNA double-str and break (DSB) repair and/or cell cycle checkpoint function in NBS cells. We established SV40 transformed, immortal NBS fibroblasts, from primary cel ls derived from a Polish patient, carrying the common founder mutation 657d el5, Immortalized NBS cells, like primary cells, are X-ray sensitive (2-fol d) and display RDS following IR. They show an increased sensitivity to bleo mycin (3.5-fold), etoposide (2.5-fold), camptothecin (3-fold) and mitomycin C (1.5-fold), but normal sensitivity towards UV-C, Despite the clear hyper sensitivity towards DSB-inducing agents, the overall rates of DSB-rejoining in NBS cells as measured by pulsed field gel electrophoresis were found to be very similar to those of wild type cells. This indicates that the X-ray sensitivity of NBS cells is not directly caused by an overt defect in DSB repair. (C) 1999 Elsevier Science B.V. AU rights reserved.