Importin-β mutants cause distinct mitotic abnormalities in fixed HeLa cells. (A) Mitotic cells transfected with pEGFP vector, or with GFP-tagged or untagged importin-β mutants, fixed and stained for either α-tubulin and DAPI, or for TPX2 to stain MTs; in that case chromosomes are visualized by H2B-GFP incorporation. Misaligned chromosomes in apparently normal bipolar mitoses are arrowed. Bars, 10 µm. (B) Quantification of mitotic defects induced by importin-β mutants in fixed cells. Means and standard deviations were calculated from 1,000–1,800 cells for most samples (5 to 10 experiments) and 500 cells for RCC1 (4 experiments). *, significant (P < 0.05); **, highly significant (P < 0.01) differences relative to vector (χ2 test) are shown in purple (spindle pole defects) and green (misaligned chromosomes), respectively.
