Development and characterization of immortalized fibroblastoid cell lines from an FA(C) mouse model

Fanconi anemia (FA) is an autosomal recessive disorder, characterised by multiple congenital malformations, bone marrow failure and a predisposition to developing malignancies, especially leukemia. FA cells show increased levels of spontaneous chromosomal aberrations and a hypersensitivity to DNA cross-linking agents such as mitomycin C (MMC) and diepoxybutane (DEB). There are at least eight complementation groups involved in FA, and the genes for two of these groups, FA(A) and FA(C), have been isolated and cloned. Mouse models for FA(C) have been developed by replacing exon 8 or exon 9 of Fac with the neo gene. Mice homozygous for Fac mutations show reduced fertility and hypersensitivity to induction of chromosomal aberrations by MMC and DEB. To facilitate the study of cellular defects in vitro, transformed mouse fibroblast cell lines were established. Cell-killing experiments and cytogenetic analyses were performed on these cells following treatment with MMC and DEB. Fac-/- showed significant hypersensitivity to MMC and DEB as compared with Fac+/+ and +/- for both cellular phenotypes. This is consistent with results obtained from similar studies on human fibroblasts and lymphoblastoid cell lines. Therefore, these isogenic transformed mouse fibroblasts provide as in vitro model for further investigation of the hypersensitivity of Fanconi anemia cells to DNA cross-linking agents.