Knockdown of SSX2IP compromises mitotic MT nucleation and dynamics, and delays mitotic progression. Mitotic progression of HeLa cells stably expressing Histone 2B was analyzed by time-lapse recording. (A) Experimental setup. (B) Analysis using the CellCognition (Held et al., 2010) image recognition software. An early mitotic index (prometaphase, metaphase) was determined via automatic annotation; one representative analysis (out of at least four analyses) for the indicated situations is shown. (C) Histone 2B still images (20-min intervals) in cells progressing through mitosis in control situations, or after knockdown of SSX2IP. Arrowheads indicate nonaligned chromosomes; see also Videos 4 and 5. Bar, 10 µm. (D and E) Quantification of mitotic timing (D: overall duration; E: single mitotic phases; PRO, prophase; PM, prometaphase; M, metaphase; A, early anaphase; TELO, late anaphase and telophase) in control and SSX2IP knockdown cells that were analyzed by manual tracking for all conditions (n ≥ 34, in 4/5 independent experiments). The graphs represent mean values ± SD. The significance was scored by a two-tailed Student’s t test and scored as **, P < 0.01; ***, P < 0.001.