TPX2–Eg5 interaction is required for kinetochore fiber formation but not microtubule nucleation near chromosomes. (A and B) Parental cells and cells expressing either no transgene (none) or the indicated transgene and treated with pig TPX2 siRNA. Cells were stained for Hec1 and α-tubulin. (A) Cold-stable microtubules are observed in parental cells and cells expressing mTPX2^LAP and depleted of pTPX2 (bottom two rows) but not after depletion of pTPX2 from parental cells or cells expressing mTPX2-710^LAP. (B) After release from nocodazole, microtubules form at centrosomes and near kinetochores in parental cells and cells expressing mTPX2^LAP or mTPX2-710^LAP and depleted of endogenous TPX2 (bottom two rows) but not in parental cells depleted of TPX2. Bars, 5 µm.