Figure 1: BRCA1^mut/+ HMECs exhibit increased genomic instability and telomere dysfunction.

(a) Representative images of immunofluorescence (IF) staining for phospho-ATM/ATR substrates, γH2AX foci, p53BP1 foci in proliferating (Prolif) WT and BRCA1^mut/+ HMECs. Bar graphs under the images show the percent of cells positive for phospho-ATM/ATR substrates; the average number of γH2AX foci per field (avg number of cells per field WT=278, BRCA1=182); and the average number of p53BP1 foci per field (avg number of cells per field WT=262, BRCA1=187). (b) Representative images and summary table of significant genetic and chromosomal events determined by karyotype analysis in Prolif WT and BRCA1^mut/+ HMECs. (c) Telomere erosion rate in WT (n=4) and BRCA1^mut/+ (n=4) HMECs. Telomere length was determined by qPCR in Prolif and agonescent/senescent WT and BRCA1^mut/+ HMECs. The telomere erosion rate was calculated by the formula: TER=Δtelomere length/ΔPDs. (d) Representative images and the mean telomere lengths (kb) determined using quantitative fluorescent in situ hybridization (qFISH) in WT lobules (n=762 cells) and BRCA1^mut/+ lobules (n=800 cells). Student’s two-tailed t-test was used to calculate P values. (*) indicates P value within the 0.05 level of significance. Error bar, s.e. Scale bar, 10 μm.