Functional characterization of the Caenorhabditis elegans gene fcd-2 during meiosis and in maintenance of genomic stability

Fanconi anemia (FA) is a complex cancer susceptibility disorder associated with defects in the repair of DNA interstrand cross-links (ICLs) resulting in occasional developmental defects and in ICL hypersensitivity of patient cells, yet the precise role of the FA proteins during DNA repair has remained unclear. I will present evidence that FA counteracts illegitimate repair of DNA lesions by non-homologous end joining (NHEJ). FCD-2 has proven to be involved in the choice of repair pathways: 1) fcd-2 mutants show an increase in spo-11 dependent RAD-51 foci and in germline apoptosis, 2) in genetic backgrounds where chiasma formation is abrogated (such as msh-4 and syp-2) resolves in less than the expected 12 DAPI stained bodies at diakinesis, such bodies are the results of chromosome fusions also involving non-homologous chromosomes (as demonstrated by FISH), 4) in the contemporary absence of FCD-2 protein, crossovers and NHEJ (i.e. in the triple mutants fcd-2; syp-2;lig-4 and fcd-2; msh-4;lig-4) we observe more than 12 DAPI stained bodies at diakinesis, a phenotype reminiscent of what observed in brc-1;syp-2 and brc-1;msh-4 double mutants (brc-1 being the ortholog of human BRCA1, see Adamo et al. 2008 enclosed). Furthermore, other fcd-2 mutant phenotypes such as interstrand cross-linking sensitivity and hypermutation are due to promiscuous use of NHEJ.