title: Rad51C is essential for embryonic development and haploinsufficiency causes increased DNA damage sensitivity and genomic instability.
abstract: Homologous recombination is essential for repair of DNA interstrand cross-links and double-strand breaks. The Rad51C protein is one of the five Rad51 paralogs in vertebrates implicated in homologous recombination. A previously described hamster cell mutant defective in Rad51C (CL-V4B) showed increased sensitivity to DNA damaging agents and displayed genomic instability. Here, we identified a splice donor mutation at position +5 of intron 5 of the Rad51C gene in this mutant, and generated mice harboring an analogous base pair alteration. Rad51C(splice) heterozygous animals are viable and do not display any phenotypic abnormalities, however homozygous Rad51C(splice) embryos die during early development (E8.5). Detailed analysis of two CL-V4B revertants, V4B-MR1 and V4B-MR2, that have reduced levels of full-length Rad51C transcript when compared to wild type hamster cells, showed increased sensitivity to mitomycin C (MMC) in clonogenic survival, suggesting haploinsufficiency of Rad51C. Similarly, mouse Rad51C(splice/neo) heterozygous ES cells also displayed increased MMC sensitivity. Moreover, in both hamster revertants, Rad51C haploinsufficiency gives rise to increased frequencies of spontaneous and MMC-induced chromosomal aberrations, impaired sister chromatid cohesion and reduced cloning efficiency. These results imply that adequate expression of Rad51C in mammalian cells is essential for maintaining genomic stability and sister chromatid cohesion to prevent malignant transformation.
authors.affiliation: Department of Toxicogenetics, Leiden University Medical Center, Leiden, Postal Zone S-4-P, P.O. Box 9600, 2300 RC Leiden, The Netherlands.
authors.forename: Godelieve
authors.initials: G
authors.lastname: Smeenk
authors.forename: Anton J L
authors.initials: AJ
authors.lastname: de Groot
authors.forename: Ron J
authors.initials: RJ
authors.lastname: Romeijn
authors.forename: Paul P W
authors.initials: PP
authors.lastname: van Buul
authors.forename: Malgorzata Z
authors.initials: MZ
authors.lastname: Zdzienicka
authors.forename: Leon H F
authors.initials: LH
authors.lastname: Mullenders
authors.forename: Albert
authors.initials: A
authors.lastname: Pastink
authors.forename: Barbara C
authors.initials: BC
authors.lastname: Godthelp
mesh_terms: D000818:Animals; D002869:Chromosome Aberrations; D006224:Cricetinae; D003412:Cricetulus; D004249:DNA Damage; D004268:DNA-Binding Proteins / Q000235:genetics*; D047108:Embryonic Development / Q000235:genetics*; D005260:Female; D042822:Genomic Instability; D006238:Haploidy; D051379:Mice; D008810:Mice, Inbred C57BL; D016685:Mitomycin / Q000494:pharmacology; D009154:Mutation; D011247:Pregnancy; D012854:Sister Chromatid Exchange
chemical_list: D004268:DNA-Binding Proteins; C448305:RAD51C protein, human; D016685:Mitomycin