A Balance between Nuclear and Cytoplasmic Volumes Controls Spindle Length
Fig 2
Changes in nuclear to cytoplasmic ratio have impact on spindle length.
(A) Left panel: Blastomeres of mouse 2-cell embryos were microinjected with cRNAs encoding Histone-H2B fused to mCherry and Tubulin fused to EGFP. The following cells were used for experiments: intact two cell embryos (Intact), cells with double volume obtained by fusion of two blastomeres (2 fused), and cells with double volume of the cytoplasm and impaired nuclear to cytoplasmic ratio resulting from enucleation (2 fused enucleated). Right panel shows representative movie frames from time lapse imaging of each cell type in interphase and in mitosis; chromosomes are in red, spindle is in green, scale bar represents 10 μm. (B) The length of the spindle in 2 fused enucleated cells (42.91 ± 3.35 μm, n = 12) was significantly increased (p < 0.0001) in comparison to the length of the spindle in intact cells (32.83 ± 2.95 μm, n = 22) or 2 fused cells (34.96 ± 3.37 μm, n = 14). (C) Left panel: haploid embryos were produced by parthenogenetic activation of metaphase II eggs. Following activation, cells were microinjected with cRNAs encoding Histone-H2B fused to mCherry and Tubulin fused to EGFP together with blastomeres of 2-cell embryos. Right panel shows representative movie frames from time lapse imaging of each cell type in interphase and in mitosis; chromosomes are in red, spindle is in green, scale bar is 10 μm. (D) The length of the spindle in Unfertilized haploid cells (38.04 ± 4.06 μm, n = 37) was significantly increased (p < 0.0001) in comparison to the length of the spindle in intact cells (Fertilized) (31.18 ± 3.32 μm, n = 26).
