As normal tissues frequently experience DNA double-strand breaks (DSBs), we asked how tissue architecture might participate in the DNA damage response. DSB repair activity is usually higher in basally polarized tissues, regardless of the malignant status of cells, and is controlled by hemidesmosomal integrin signaling. In the absence of glandular morphogenesis, in 2D flat monolayer cultures, basal polarity does not affect DNA repair activity but enhances H2AX phosphorylation, an early chromatin response to DNA damage. The nuclear mitotic apparatus protein 1 (NuMA), which controls breast glandular morphogenesis by acting on the organization of chromatin, displays a polarity-dependent pattern and redistributes in the cell nucleus of basally polarized cells upon the induction of DSBs. This is shown using high-content analysis of nuclear morphometric descriptors. Furthermore, silencing NuMA impairs H2AX phosphorylation C thus, tissue polarity and NuMA cooperate to maintain genome integrity. might have altered the percentage of cells in the cell cycle, which might in turn have influenced the H2AX response. However, comparable percentages of Ki67-positive cells were measured in cells transfected with siRNAs targeting NuMA or with nontargeting siRNA (34.34.2 vs 39.64.4, respectively). Moreover, the fact that Ki67 staining was either present or absent in individual cells did not seem to correlate with the striking changes observed in NuMA expression (Fig. 6D). To examine further the role of NuMA in H2AX phosphorylation, we used a cell-based system, in which DSBs can be induced at defined genomic sites (Fig. 6ECH). These human osteosarcoma cells contain stable genomic integrations of the I-values in the physique legends. A value of 0.05 was considered significant. For comet assays, grading results from different replicate experiments were summed and NCR1 arranged in contingency tables. Statistical significance was assessed using the Chi-square test. Supplementary Material BA-53038B Supplementary Material: BA-53038B Click here to view. Acknowledgements We thank Jun Xie for guidance regarding statistical analysis, Jeffrey A. Nickerson for providing antibodies against NuMA, Sloan McCormick Sypher for technical assistance, members of the Laboratory for Computational Imaging at Rutgers University for guidance, and Tom Misteli, Ourania Andrisani and Jo?lle K. Muhlemann for useful comments around the manuscript. Footnotes Funding This work was funded by the National Institutes of Health [grant numbers R01CA112017; to S.A.L., P41EB001046 NIBIB-funded RESBIO (Integrated Technology Resource for Polymeric Biomaterials) to P.V.M.]; the Bay Area Physical Sciences-Oncology Center, University of California, Berkeley, BA-53038B California [grant numbers R37CA064786;, U54CA126552;, R01CA057621;, U54CA112970;, U01CA143233; and U54CA143836 to M.J.B.]; the U.S. Department of Energy, Office of Biological and Environmental Research and Low Dose Radiation Program (contract no. DE-AC02-05CH1123 to M.J.B.); the US Department of Defense [grant number W81XWH0810736 to M.J.B.]; and postdoctoral fellowships from the Novartis Foundation and the Swiss National Science Foundation [grant number PBNEAC116967 to BA-53038B P.A.V.]. This research was also supported in part by the Intramural Research Program of the NIH, the National Cancer Institute and the Purdue University Center for Cancer Research. Deposited in BA-53038B PMC for release after 12 months. Supplementary material available online at http://jcs.biologists.org/lookup/suppl/doi:10.1242/jcs.089177/-/DC1.