Centriole as microtubule-organizing centers for marginal bands of molluscan erythrocytes

Abstract

The erythrocytes of blood clams (Arcidae) are flattened, elliptical, and nucleated. They contain elliptical marginal bands (MBs) of microtubules, each physically associated with a pair of centrioles (Cohen, W., and I. Nemhauser, 1980, J. Cell Biol., 86:286-291). The MBs were found to be cold labile in living cells, disappearing within 1-2 h at 0°C. After the cells had been rewarmed for 1-2 h, continuous MBs with associated centrioles were once again present. Time-course studies utilizing phase contrast, antitubulin immunofluorescence, and electron microscopy of cytoskeletons prepared during rewarming revealed structural evidence of centriole participation in MB reassembly. At the earliest stage of reassembly, a continuous MB was not present. Instead, relatively short and straight microtubules focused on a pointed centriolar "pole," and none were present elsewhere in the cytoskeleton. Thin continuous MBs then formed, still pointed in the centriolar region. Subsequently, the MBs regained ellipticity, with their thickness gradually increasing but not reaching that of controls even after several hours of rewarming. At these later time points, microtubules still radiated from the centrioles and joined the MBs some distance away. In the presence of 0.1 mM colchicine, MB reassembly was arrested at the pointed stage. Electron microscopic observations indicate that pericentriolar material is involved in microtubule nucleation in this system, rather than the centriolar triplets directly. The results suggest a model in which the centrioles and associated material nucleate assembly and growth of microtubules in diverging directions around the cell periphery. Microtubules of opposite polarity would then pass each other at the end of the cell distal to the centrioles, with continued elongation eventually closing the MB ellipse behind the centriole pair.Spatial and temporal control of microtubule (MT) assembly in living cells remains an area of critical importance for understanding cellular morphogenesis. In the case of cilia, flagella, mitotic spindles of animal cells, and cytoplasmic MT networks, centrioles and basal bodies are believed to function as MTorganizing centers (32), but the mechanisms involved are unknown. In many instances including both living cells and in vitro systems, centriole function appears to be indirect in that MT-organizing activity has been localized to pericentriolar material (10,22,35,38). Theoretical and experimental analysis of MT polarity supports the view that the "+", or assembly end, of the MT is distal to such centriole-containing organizing centers (9,15,24,26).The marginal band (MB) of nonmammalian vertebrate

Morphogenesis of filaments growing in flexible confinements

“…Our findings establish a paradigm for understanding morphogenesis of thin filaments in a multitude of biological mechanisms. Most importantly, we showed how nature may employ flexible envelopment and low frictional forces as a mechanical trick to realize spontaneous bundling and alignment of confined threads, as it is observed in giant vesicles [21,22], erythrocytes [19,20], hagfish cells [44] etc., without need for filament interlinking. On the technological side, the morphologies we discovered in flexible confinement should find direct impact in nanorobotics and nanomotors, for which the reported folding of elastic rings provides a new method to stably store and deploy mechanical work in tightly confined spaces.…”

“…Detachable platinum coils for example, which have revolutionized the surgical treatment of saccular cerebral aneurysms [15], are many orders of magnitude stiffer than the arterial walls they are fed into [16]. Microtubules confined in lipid bilayer membranes [17,18] and erythrocytes [19,20] as well as actin/filamin networks in vesicles [21,22] are able to deform their weak confinements significantly. In turn, such cavities force the contained filaments to buckle and reorder if their persistence length grows large enough.…”

Development of a differentiated microtubule structure: formation of the chicken erythrocyte marginal band in vivo.

“…3 b) shows a dark structure at precisely the position of the immunofluorescent focal point. A correspondence between fluorescence pattern and pairs of phase-dense structures has been used as evidence for MTOCs in studies by others (Nemhauser et al, 1983). (Similar dark bodies can also be seen in mature chicken erythrocytes, although their identification as MTOCs is not supported by staining with anti-tubulin [Pillus, L., unpublished observations]).…”

Structure and composition of the cytoskeleton of nucleated erythrocytes: III. Organization of the cytoskeleton of Bufo marinus erythrocytes as revealed by freeze‐dried platinum‐carbon replicas and immunofluorescence microscopy

“…Thus, the cytoskeleton of the neuron may be similar to that of the erythrocyte in that the stability of each cytoskeleton may be due, in part, to microtubule attachments to a spectrin-like protein of the SAC. The presence of a specific protein that links the microtubules of the MB to the SAC would explain the ability of the microtubules in some erythrocytes to be depolymerized by cold or drug treatments and then repolymerize in the same position when the destabilizing conditions are reversed [Nemhauser, Joseph-Silverstein, and Cohen, 1983;Miller and Solomon, 19841. Some molecule is needed to specify Fig.…”