Expression of constitutively active MPS1 (TT675/6DD) results in extended mitotic duration. (A) Cells expressing GFP-MPS1 variants as indicated were filmed passing through mitosis. GFP-MPS1 (cyan and lefthand insert) and DNA (red and righthand insert) are shown. 0 min, nuclear envelope breakdown (NEBD). Anaphase DNA bridges and unaligned chromosomes are indicated by arrows and arrowheads, respectively. See also Videos 1, 2, 3, and 4, showing cells expressing the different GFP-MPS1 mutants progressing through the cell cycle. (B) Cell lysates from cells in A were Western blotted for MPS1 and actin (loading control). (C–E) Cumulative mitotic exit (C), nuclear envelope breakdown–anaphase duration (D), and proportion of mitotic cells with unaligned chromosomes (E) were plotted over time. In D, each point represents an individual cell with mean ± SD. Nuclear envelope breakdown–anaphase time shown as bars. Data are from two independent experiments with 35 (WT), 27 (KD), 42 (AA), and 28 (DD) cells measured.