BRCA1 and breast cancer: Murine Brca1-BRCT domain mutations (analogous to M1775R, S1655F in human, identified in familial breast cancers) abrogate not only binding of the A, B, C complexes to the BRCT domain, but also the BRCT-Wwox interaction, i.e., MEFs expressing the Brca1 S1598F mutation, are defective in HR repair and the homozygous mutant mice are highly susceptible to tumor development [40].