Recruitment: The ins and outs of spindle pole formation

Abstract

A striking feature of microtubule-based structures is the regular forms they take, forms that are reproduced from generation to generation and clearly bear on the function of cells. The primary determinants of form in microtubule structures are cytoplasmic organelles, generically called microtubule organizing centers (MTOCs) [Pickett-Heaps, 19691, which direct microtubules into specific patterns by binding their minus ends. Not surprisingly, the dramatic change in microtubule distribution from cytoplasmic asters to mitotic spindles during the transition from interphase to mitosis is preceded by many changes in MTOCs. MTOCS ARE INTERRELATEDWe routinely distinguish between different MTOCs such as centrosomes and basal bodies or even basal bodies and centrioles, but it is clear that these structures are closely related to each other. For example, in sea urchin embryos, the sperm basal body becomes a part of the interphase centrosome, and the centrosome then gives rise to spindle poles. At the core of these structures are centrioles, which Sluder and coworkers propose contain the reproductive capacity of sea urchin MTOCs [Sluder and Rieder, 198.51. One telling observation that illustrates the relatedness of different MTOCs is the de novo synthesis of basal bodies at spindle poles in centric diatoms [Manton et al., 19701. Centric diatoms are not normally ciliated or flagellated but depend on environmental factors such as sea currents for dispersion. The MTOCs of these organisms normally are not associated with centrioles, and no basal bodies are found in the cytoplasm. However, during the second meiotic division, basal bodies appear de novo at the spindle poles of cells destined to be sperm and immediately organize flagellar axonemes. The ability of spindle poles to direct the synthesis of basal bodies not only establishes a relationship between basal bodies 0 1990 Wiley-Liss, Inc. and spindle poles but, relative to the Sluder and Rieder observations, suggests that the reproductive capacity for these structures is contained in a subcomponent common to both spindle poles and basal bodies. The basal-body DNA discovered in Chlamydomonas reinhardtii [Hall et al., 19891 is an attractive candidate for such a shared subcomponent, but there is no evidence linking it to spindle pole formation. SPINDLE POLES ARE DISTINCT FROM CENTROSOMESThe most frequently presented view of spindle pole formation is that spindle poles are simply replicate centrosomes separated by the growth of spindle microtubules during prophase; however, considerable evidence suggests that spindle MTOCs are very different from their interphase counterparts. The differences include morphological changes in MTOCs during mitosis, posttranslational modification of centrosomal proteins during prophase, de novo synthesis of spindle poles, and the recruitment of new proteins into spindle poles during prophase.The obvious differences in morphology of spindles and interphase asters have been correlated with changes in the shape of their organizing centers. Spin...

Hyaluronic acid stimulates human fibroblast proliferation within a collagen matrix

“…Microtubules are also critical for cells passing through by centrifugation, resuspended in 1 ml of complete DMEM, and counted with a hemocytometer. the cell cycle (Leslie, 1990). We find that added HA increases the expression of tubulin in primary human Thymidine labeling fibroblast lines and speculate that increasing intracellular tubulin pools advances cells through the cell cycle Cell uptake of [ 3 H]-thymidine was determined in both FPCLs and monolayer cultures by adding 40 ml of as proposed by John (1984).…”

In vitro microtubule-nucleating activity of spindle pole bodies in fission yeast Schizosaccharomyces pombe: cell cycle-dependent activation in xenopus cell-free extracts

“…The amount of PCM surrounding centrioles increases at the onset of mitosis (reviewed in Mazia, 1984;Leslie, 1990), and mitotic centrosomes in vitro are capable of nucleating more MTs than interphase centrosomes (Snyder and McIntosh, 1975;Kuriyama and Borisy, 1981). The MT-nucleating activity of centrosomes is also regulated during cell differentiation (reviewed in Karsenti and Maro, 1986).…”

Cold-treated centrosome: Isolation of centrosomes from mitotic sea urchin eggs, production of an anticentrosomal antibody, and novel ultrastructural imaging

“…Given the known chemical and physical changes which occur in the transition from interphase to mitosis in the centrosome [reviewed in Leslie, 1990;Kuriyama and Nislow , 19921 an improved isolated protocol of the spindle pole is of interest. Sea urchin eggs provide a good system from which to isolate mitotic centrosomes, since they are very synchronous and large amounts of cells can be obtained for biochemical analysis.…”