RESORPTION OF PRIMARY CILIA DURING MITOSIS IN A VERTEBRATE (PTK1) CELL-LINE

A high-voltage electron microscope (HVEM) was used to investigate the fate of primary cilia during late interphase and mitosis in a ciliated subline of PtK1 (Potorous tridactylis). The results provide direct evidence that PtK1 cells which possess primary cilia resorb their cilia during the early stages of spindle formation and subsequently complete a normal mitotic division. During late interphase the single diplosome with its attached cilium replicates to form two diplosomes, only one of which has an associated cilium. It was found that during the early stages of spindle formation (i.e., during prophase to prometaphase) the primary cilium is progressively resorbed so that by metaphase each spindle pole contains two normal centrioles. During resorption the axoneme with its attached centriole is incorporated into the cytoplasm where it is gradually disorganized from its distal end. The resorption of cilia during the early stages of mitosis suggests that this organelle is part of the cytoplasmic microtubule complex (CMTC). This report constitutes the first documentation of ciliary resorption during mitosis in a vertebrate cell. © 1979 Academic Press, Inc.