Mesostoma ehrenbergii have a unique male meiosis: their spermatocytes have three large bivalents that oscillate for 1-2 h before entering into anaphase without having formed a metaphase plate, have a precocious ('pre-anaphase') cleavage furrow, and have four univalents that segregate between spindle poles without physical interaction between them, that is via 'distance segregation'. These unique and unconventional features make Mesostoma spermatocytes an ideal organism for studying the force produced by the spindle to move chromosomes, and to study cleavage furrow control and 'distance segregation'. We review the literature on meiosis in Mesostoma spermatocytes and describe our current research with Mesostoma spermatocytes, rearing the animals in the laboratory using methods that described in our companion article [Hoang et al. (2013); Cell Biol Int].
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Evidence of Non-microtubule Spindle Forces in Spermatocytes.
Front Mol Biosci
November 2020
Department of Biology, York University, Toronto, ON, Canada.
We tested conclusions reached in previous experiments in which spermatocyte chromosomes moved rapidly to a pole in the absence of microtubules: after 10 μM nocodazole (NOC) depolymerized metaphase spindle microtubules, kinetochores from each of the 3 bivalents detached from the same pole and rapidly moved to the other pole, at speeds averaging 37.7 μm/min. with some as high as 100 μm/min.
View Article and Find Full Text PDFPrecocious cleavage furrows simultaneously move and ingress when kinetochore microtubules are depolymerized in Mesostoma ehrenbergii spermatocytes.
Protoplasma
September 2018
Department of Biology, York University, 4700 Keele St, Toronto, ON, M3J 1P3, Canada.
A "precocious" cleavage furrow develops and ingresses during early prometaphase in Mesostoma ehrenbergii spermatocytes (Forer and Pickett-Heaps Eur J Cell Biol 89:607-618, 2010). In response to chromosome movements which regularly occur during prometaphase and that alter the balance of chromosomes in the two half-spindles, the precocious furrow shifts its position along the cell, moving 2-3 μm towards the half cell with fewer chromosomes (Ferraro-Gideon et al. Cell Biol Int 37:892-898, 2013).
View Article and Find Full Text PDFChromosomes selectively detach at one pole and quickly move towards the opposite pole when kinetochore microtubules are depolymerized in Mesostoma ehrenbergii spermatocytes.
Protoplasma
July 2018
Department of Biology, York University, 4700 Keele St, Toronto, ON, M3J 1P3, Canada.
In a typical cell division, chromosomes align at the metaphase plate before anaphase commences. This is not the case in Mesostoma spermatocytes. Throughout prometaphase, the three bivalents persistently oscillate towards and away from either pole, at average speeds of 5-6 μm/min, without ever aligning at a metaphase plate.
View Article and Find Full Text PDFMeiosis-I in Mesostoma ehrenbergii spermatocytes includes distance segregation and inter-polar movements of univalents, and vigorous oscillations of bivalents.
Protoplasma
January 2014
Department of Biology, York University, 4700 Keele St, Toronto, ON, M3J 1P3, Canada,
In this article, we describe meiosis-I in spermatocytes of the free-living freshwater flatworm Mesostoma ehrenbergii. The original observations of Oakley (1983, 1985) and Fuge (Eur J Cell Biol 44:294-298, 1987, Cell Motil Cytoskeleton 13:212-220, 1989, Protoplasma 160:39-48, 1991), the first to describe these cells, challenge our understanding of cell division, and we have expanded on these descriptions with the aim of laying the framework for further experimental work. These cells contain three bivalents and four univalent chromosomes (two pairs).
View Article and Find Full Text PDFMesostoma ehrenbergii spermatocytes--a unique and advantageous cell for studying meiosis.
Cell Biol Int
September 2013
Department of Biology, York University, 4700 Keele St., Toronto, Canada ON M3J 1P3.
Mesostoma ehrenbergii have a unique male meiosis: their spermatocytes have three large bivalents that oscillate for 1-2 h before entering into anaphase without having formed a metaphase plate, have a precocious ('pre-anaphase') cleavage furrow, and have four univalents that segregate between spindle poles without physical interaction between them, that is via 'distance segregation'. These unique and unconventional features make Mesostoma spermatocytes an ideal organism for studying the force produced by the spindle to move chromosomes, and to study cleavage furrow control and 'distance segregation'. We review the literature on meiosis in Mesostoma spermatocytes and describe our current research with Mesostoma spermatocytes, rearing the animals in the laboratory using methods that described in our companion article [Hoang et al.
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