Figure 3.

Chromosome condensation behavior and cell cycle distribution in response to IR. (A) LCLs derived from two MCPH1 patients with homozygous truncating mutations were irradiated with 0.5 Gy, 1 Gy or 2 Gy, and cytogenetic slides were prepared at varying times following IR as indicated. The fractions of mitotic and prophase-like cells were determined by counting 1,000 cells per time point. (B) Immunofluorescence micrographs showing 53BP1 IRIF (red) in fibroblasts from an MCPH1 patient with hypercondensed, prophase-like chromatin morphology. Nuclei were counterstained with DAPI (blue). Scale bar = 5 µm. (C) Cell cycle distribution of MCPH1 patient and control LCLs at varying times after 1 Gy IR as determined by flow cytometry. Error bars indicate SD. (D) Determination of the proportion of cells with a prophase-like appearance in the same experiment.