In situ hybridization of Aurora-B/AIM-1 mRNA. In situ hybridization was performed to examine the message level of Aurora-B/AIM-1 in transgenic megakaryocytes. Microscopic images shown here demonstrate that morphologically recognizable large megakaryocytes⁴  (identified by arrows) in the spleen of transgenic mice (TG 58 or TG 74) have elevated levels of the Aurora-B/AIM-1 message compared with control wild-type (WT) counterparts of similar cell size. Some small-diameter cells showed a strong positive signal in the wild-type or transgenic samples (not shown). Approximately 30 polyploid megakaryocytes of similar diameter were surveyed in each preparation. Original magnification, × 200.