Fibroblasts from PCNT knockout mice show loss of astral microtubules and spindle misorientation. Top (a and c) and side (b and d) views of three-dimensional reconstructed immunofluorescence images of mitotic spindle stained for α-tubulin (green), γ-tubulin (red), and kinetochore (CREST, blue). Mitotic spindles are misoriented in PCNT−/− (b) versus wild-type cells (d). α, metaphase spindle angle relative to the bottom of the dish. Astral microtubules in the wild-type cell (a, arrow) are lost in PCNT−/− cells (b, arrow with broken line). MEF, mouse embryonic fibroblast. Images provided by S. Doxsey and G. Zheng (University of Massachusetts Medical School, Worcester MA).