Meiotic spindles

Mailer Why do you say that the first spindle poles are made of PCM Is there some reason to think that PCM is needed without a centrosome In Nenopus, I have never heard anyone argue that there is PCM organizing the meiotic spindles. If you look at the /-tubulin staining pattern, it is totally different in a meiotic spindle than in a mitotic spindle. 

Brunet S, Polanski Z, Verlhac M-H, Kubiak JZ, Maro B 1998 Bipolar meiotic spindle formation... 

Hunt All I know is what happens in clams, because I have seen it with my own eyes you do not duplicate the spindle pole if you inhibit protein synthesis, so you get a monopolar second meiotic spindle, which causes chaos. 

Cullen CF, Brittle AL, Ito T, Ohkura H (2005) The conserved kinase NHK-1 is essential for mitotic progression and unifying acentrosomal meiotic spindles in Drosophila melanogaster. J Cell Biol 171(4) 593-602... 

The dynamic features listed above are often combined in many types of supramolecular structure. The mitotic and meiotic spindles are excellent examples. The spindles are built for the purpose of separating the chromosomes to the daughter cells of a dividing cell and are then dismantled. The separation of chromosomes, of course, requires mechanical work and the expenditure of energy by components in the spindle. 

Since the discovery 117) of its action on tubulin 118) (the protein which, in the form of microtubules, constitutes the mitotic spindle), taxol has been of great utility to biologists. Numerous publications, not all of which need be cited here, describe the use of taxol for the isolation of tubulin from cellular preparations in which the concentration of this protein is too low to permit its polymerization, as in the pancreas 119) or the vegetal domain 120). Taxol has permitted not only the discovery of new microtubules in the Xenopus oocyte cortex 121) but also the study of the role of microtubules in certain cellular processes owing to its lack of destructive effects, in contrast to other known spindle poisons such as colchicine or vinblastine (722). Among other problems, taxol has helped in studies of the influence of the tubulin-microtubule equilibrium on the fluidity of platelet membranes 123) and of the function of the meiotic spindle in spermatocytes 124). 

Theurkauf, W. E., and Hawley, R. S. (1992). Meiotic spindle assembly in Drosophila females Behavior of nonexchange chromosomes and the effects of mutations in the nod kinesin-like protein. J. Cell Biol. 116, 1167-1180. 

Baluch DP, Koeneman BA, Hatch KR, McGaughey RW, Capco DG. 2004. PKC isotypes in post-activated and fertilized mouse eggs association with the meiotic spindle. Dev Biol 274(l) 45-55. 

Mohammadi Roushandeh A, Habibi Roudkenar M. 2009. The influence of meiotic spindle configuration by cysteamine during in vitro maturation of mouse oocytes. Iran BiomedJ13(2) 73-78. 

Szczepanska K, Maleszewski M. 2005. LKB1/PAR4 protein is asymmetrically localized in mouse oocytes and associates with meiotic spindle. Gene Expr Patterns 6(l) 86-93. 

Yuan J, Li M, Wei L, Yin S, Xiong B, Li S, Lin SL, Schatten H, Sun QY. 2009. Astrin regulates meiotic spindle organization, spindle pole tethering and cell cycle progression in mouse oocytes. Cell Cycle 8(20) 3384-3395. 

Microtubules are polymers of the protein tubulin which, in vivo, are probably always associated with other proteins, the Microtubule Associated Proteins (MAPs). Microtubules are the main structural components of mitotic and meiotic spindles, and of cilia and flagella in axons and dendrites, they serve as cables along which organelles are moved by kinesin and the retrograde translocator [R.D.Vale et al. Cell 43 (1986) 623-632]. Depending on the function of the microtubules, they are associated with different... 

Much has been learned about Drosophila meiosis by immunocytochemical studies of whole-mount oocytes lacking functional meiotic proteins and by localization of some of the relevant proteins (McKim et al. 1993 White-Cooper et al. 1993 Afshar et al. 1995 Endow and Komma 1996 Matthies et al. 1996 Moore et al. 1998). However, none of these classic methods easily point out kinetic problems, nor are the earliest points of deviation always readily obvious by static methods. For these reasons, and because the behavior of the highly dynamic components of the meiotic spindle may be perturbed in meiotic mutants, methods have been developed to directly observe the cytoskeleton and chromosomes in living egg chambers (Theurkauf 1994a Endow and Komma 1996 Matthies et al. 1996). 

Around stage 13, the oocyte nuclear envelope breaks down and the meiotic spindle assembles around the chromatin. The meiotic spindle arrests at metaphase I until fertilization. The metaphase I spindle is highly tapered and lacks astral microtubules. The chromatin is stretched on the spindle but is held together by chiasmata. The always nonexchange fourth chromosomes are found adjacent to the main mass that contains the exchange chromosomes. 

Matthies H.J., McDonald H.B., Goldstein L.S., and Theurkauf W.E. 1996. Anastral meiotic spindle morphogenesis Role of the non-claret disjunctional kinesin-Hke protein. /. Cell Biol. 134 455—464. 

Casal J., Gonzalez C., Wandosell E, Avila J., and Ripoll P. 1990. Abnormal meiotic spindles cause a cascade of defects during spermatogenesis in asp males of Drosophila. Development 108 251-260. 

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