The primary risk factors for high-grade serous ovarian carcinoma are mutations in BRCA1/2, which are members of the Fanconi Anemia (FA) pathway and have key roles in homology directed DNA repair (HDR). FA pathway members recognize interstrand crosslinks (ICLs), which can result in double-strand DNA breaks. Loss of FA Complementation group I, FANCI, results in failure to activate the FA pathway, with ensuing hypersensitivity to ICLs. Recently, the FANCI L605F variant (L604F in mouse) was identified in a French-Canadian family lacking BRCA1/2 mutations, implicating FANCI as a new ovarian cancer-predisposing gene. Biochemical studies point towards the variant being hypomorphic. Unlike the effects observed with BRCA1/2 studies, mutations in FANCI result in insensitivity to PARP inhibition, suggesting its functional point may not reside in HDR. Interestingly, FANCI has been shown to independently of the FA pathway play a role in both the resolution of transcription-replication conflicts (TRCs) as well as modulating dormant origin firing.

We have established two mouse lines carrying the L604F variant or a KO allele. KO mice are infertile in both sexes, consistent with published studies, while the L604F mice have female-specific infertility. Interestingly, the phenotype resembles Mcm9 KO mice. L604F females present with premature age-associated vacuolization of the oviduct, which is linked to cellular stress, and spontaneously form ovarian neoplasias. Using in vivo oviduct electroporation, we are currently introducing oncogenes/disrupting p53 in L604F females and assessing time to tumor-formation. DNA repair capacity, TRC resolution and origin firing is being assessed in vitro. Our preliminary data indicate that the L604F variant may have a unique functional point different from HDR and that the mutation affects processes crucial both in the context of cancer and fertility.