Figure 2.Degree of genomic instability in Lmna^Δ9/Δ9 MEFs. (A) Genomic instability was monitored in wild-type and Lmna^Δ9/Δ9 MEFs by counting percentage of metaphase spreads showing single telomere losses (STL), chromosome end-to-end fusions, chromosome and chromatid breaks, and other complex aberrations. Images show examples of chromosomal aberrations. Note that Lmna^Δ9/Δ9 fibroblasts do not show a marked increase in genomic instability. (B) Quantitation of percentage of cells presenting with basal levels of DNA damage, as assessed by the presence of >5 γH2AX foci by immunofluorescence. n, total number of cells analyzed. (C) Neutral comet assays were performed in wild-type and Lmna^Δ9/Δ9 MEFs at different times (0‒150 min) post-irradiation with 8 Gy, to compare kinetics of DNA DSB repair. Average “olive moment,” a measure or unrepaired DNA damage, was calculated in 3 independent experiments with 25‒30 measurements per condition. Bars represent standard deviation. (D) Quantitation of CTSL, 53BP1, BRCA1, and RAD51 transcripts levels by qRT-PCR in wild-type and Lmna^Δ9/Δ9 MEFs. (E) Western blots to monitor levels of 53BP1, BRCA1, RAD51, and CTSL proteins in MEFs from Lmna^{Δ8–11/Δ8–11}, Lmna^Δ9/Δ9 and their corresponding wild-type littermates. β-Tubulin was used as loading control.