Cytoplasmic Microtubules and Their Functions

Porter, Keith R.

doi:10.1002/9780470719442.ch13

Cited by 162 publications

(10 citation statements)

References 51 publications

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“…By the mid 1960's, microtubules, which earlier had not been seen in the spindle region, were clearly visualized by electron microscopy using improved, osmium-and glutaraldehyde-containing fixatives (Harris, 1962; reviewed by Porter, 1966). The distribution and behavior of the microtubules closely paralleled those of the birefringent fibrils that had been described earlier within the spindle fibers.…”

Section: Early History: the Dynamic Equilibrium Modelmentioning

confidence: 65%

Force Generation by Microtubule Assembly/Disassembly in Mitosis and Related Movements

Inoué¹,

Salmon²

2008

Collected Works of Shinya Inoué

116

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In this article, we review the dynamic nature of the filaments (microtubules) that make up the labile fibers of the mitotic spindle and asters, we discuss the roles that assembly and disassembly of microtubules play in mitosis, and we consider how such assembling and disassembling polymer filaments can generate forces that are utilized by the living cell in mitosis and related movements. EARLY HISTORY: THE DYNAMIC EQUILIBRIUM MODELThe orderly segregation of chromosomes at every cell division, and the placement of the resulting daughter nuclei into appropriate cytoplasmic environments, are essential for the normal development of an organism, the generation of functional tissues and gametes, and indeed for the continuity of life itself. Such bipolar segregation of chromosomes in mitosis, and the movement of centrosomes that position the daughter nuclei into appropriately partitioned regions of the cytoplasm in animal cells are accomplished by a bipolar mitotic spindle and its associated astral rays.Although the significance of the spindle and astral rays for mitosis and for the coordination of mitosis with cell cleavage were well recognized by the early cytologists, much controversy abounded in the first half of this century regarding the actual nature of the mitotic spindle fibers (Wilson, 1928;Schrader, 1953). Although visible in cells exposed to acidic or proteinprecipitating fixatives, the fibers were not visible by bright field or phase contrast microscopy in most living cells and were absent in cells observed by light or electron microscopy after fixation with what were considered to be better structure-preserving reagents. There were indications that the fibers would disappear reversibly in cells treated with low temperature or with ethyl ether, and that they were so labile that chromosomes having to traverse laterally to accom- ' Corresponding author. plish their anaphase separation could even cut right through the fibers (Ostergren, 1949). Yet without the bipolar fibrous organization, what would move or guide the chromosomes to the spindle poles?The reality in living cells of spindle fibers, and the fibrils that as a bundle made up the fibers, were established by Inoue by observing a variety of living, animal and plant cells in division with a sensitive polarized light microscope (Inoue, 1951(Inoue, -1953(Inoue, , 1964. The birefringence of the fibers measured and photographed through the sensitive polarizing microscope depicted the distribution, concentration, and appearance and disappearance of oriented fibrils in the spindle fibers in living cells. In addition to the dynamic formation, fluctuation, and disappearance of these fibers and fibrils during the normal course of cell division, the birefringence revealed the labile nature of the fibrous spindle elements in cells exposed to cold or to a mitosis-inhibiting alkaloid, colchicine (Inoue, 1952(Inoue, , 1964. From these findings, Inoue postulated that the spindle fibers and fibrils were made up of a loosely coupled, linear chain of protein molecu...

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Section: Early History: the Dynamic Equilibrium Modelmentioning

confidence: 65%

Force Generation by Microtubule Assembly/Disassembly in Mitosis and Related Movements

Inoué¹,

Salmon²

2008

Collected Works of Shinya Inoué

116

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“…The spindle microtubules play essential roles in chromosome movement toward the equatorial plane in prometaphase, and in poleward movement in anaphase. In an earlier microtubule study, Porter (1966) postulated the existence of cytoplasmic foci, or centers, that function in controlling microtubule distribution and changes in microtubule distribution. Such a structure was found and named the microtubule organizing center (MTOC) by PickettHeaps (1969).…”

Section: Spindles In Land Plantsmentioning

confidence: 99%

Plant microtubule studies: past and present

Mineyuki

2007

J Plant Res

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Here, I briefly review historical and morphological aspects of plant microtubule studies in land plants. Microtubules are formed from tubulins, and the polymeric configurations appear as singlet, doublet, and triplet microtubules. Doublet microtubules occur in the axoneme of cilia and flagella, and triplet microtubules occur in the basal bodies and centrosomes. Doublet and triplet microtubules are lost in all angiosperms and some gymnosperms that do not possess flagellated sperm. In land plants with flagellated sperm, centriolar centrosomes transform into basal bodies during spermatogenesis. In flowering plants, however, most male gametes (sperm) are conveyed to eggs without the benefit of cilia or flagella; thus, higher plants lack centriolar centrosome and doublet and triplet microtubules. The loss of centriolar centrosomes from the life cycle of flowering plants may have influenced the evolution of the plant microtubule system. Comparison of mitotic apparatuses in basal land plants and flowering plants illuminates the evolutionary transition from the centriolar microtubule system to the acentriolar microtubule system.

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“…Early electron microscopy revealed distinct subcellular sites from which microtubules appeared to emanate which were named ‘microtubule-organizing centres’ (MTOCs) [1,2]. Since then, the exact nature of MTOCs has remained somewhat nebulous.…”

Section: Introductionmentioning

confidence: 99%

Microtubule-organizing centers: from the centrosome to non-centrosomal sites

Sanchez

Feldman

2017

Current Opinion in Cell Biology

250

289

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The process of cellular differentiation requires the distinct spatial organization of the microtubule cytoskeleton, the arrangement of which is specific to cell type. Microtubule patterning does not occur randomly, but is imparted by distinct subcellular sites called microtubule-organizing centers (MTOCs). Since the discovery of MTOCs fifty years ago, their study has largely focused on the centrosome. All animal cells use centrosomes as MTOCs during mitosis. However in many differentiated cells, MTOC function is reassigned to non-centrosomal sites to generate non-radial microtubule organization better suited for new cell functions, such as mechanical support or intracellular transport. Here, we review the current understanding of non-centrosomal MTOCs (ncMTOCs) and the mechanisms by which they form in differentiating animal cells.

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Cytoplasmic Microtubules and Their Functions

Cited by 162 publications

References 51 publications

Force Generation by Microtubule Assembly/Disassembly in Mitosis and Related Movements

Force Generation by Microtubule Assembly/Disassembly in Mitosis and Related Movements

Plant microtubule studies: past and present

Microtubule-organizing centers: from the centrosome to non-centrosomal sites

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