Heterozygous germline mutations in BRCA2 are associated with an increased risk of developing breast and ovarian cancers. BRCA2 is thought to be important for genome stability owing to its involvement in DNA-repair pathways; in addition, previous work has suggested that BRCA2 might regulate cytokinesis, the final step of cell division. Mark Petronczki and colleagues now provide data that disprove this latter hypothesis (p. ). Using time-lapse imaging of HeLa cells, the authors show that depletion of BRCA2 abrogates its function in DNA repair but has no effect on cytokinesis. In addition, a diffusion-based assay that precisely discerns the timing of abscission and cell separation shows that BRCA2 does not have a role in these final stages of cytokinesis. Furthermore, DLD1 colon cancer cells in which both BRCA2 alleles are disrupted successfully complete cytokinesis. Finally, the authors show that, in contrast to results from a previous study, BRCA2 does not localise to the spindle midzone or midbody, two structures of the mitotic spindle that play important roles during cytokinesis. Together, these data indicate that BRCA2 does not regulate cytokinesis in human cells, which is a finding of crucial importance for understanding cancers with which BRCA2 mutations are associated.
