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Endogenous NuMA protein is delocalized to the cytoplasm. This is the same intracellular localization pattern observed for the APL-associated chimeric RAR protein, NuMA-RAR. Using immuno-fluorescent confocal microscopy, analysis of COS cells stably expressing NuMA-RAR revealed that NuMA and NuMA-RAR co-localize in the cytoplasm (yellow/orange immunostaining). Adjacent cells that do not express NuMA-RAR retain typical NuMA localization patterns (red immunostaining). These are seen as being strongly associated with the spindle poles in mitotic cells, and dispersed throughout the nucleus (excluding the nucleolus) in interphase cells. COS cells were dually immunostained with primary antibodies specific to NuMA-RAR and NuMA, then visualized with FITC (green) and Rhodamine (red) conjugated secondary antibodies, respectively. For details, see the article by J.L. Hummel et al. in this issue.