Chromosome attachment to the spindle in crane-fly spermatocytes requires actin and is necessary to initiate the anaphase-onset checkpoint

Silverman-Gavrila, Rosalind V.; Forer, Arthur

doi:10.1007/bf01279347

Cited by 7 publications

(1 citation statement)

References 64 publications

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“…Inhibitors of myosin (and actin) blocked the poleward flux of tubulin along kinetochore spindle fibres [Silverman-Gavrila and Forer, 2000a], and the same myosin (and actin) inhibitors blocked or slowed anaphase chromosome movements [Silverman-Gavrila and Forer, 2001;Forer and Pickett-Heaps, 1998]. When myosin (and actin) inhibitors were applied around the time of nuclear membrane breakdown, chromosomes were unable to attach to the spindle [Silverman-Gavrila and Forer, 2000b;Forer and Pickett-Heaps, 1998]. Thus, myosin (and actin) are implicated in chromosome movement and other spindle functions in crane-fly spermatocytes.…”

Section: Introductionmentioning

confidence: 99%

Myosin localization during meiosis I of crane‐fly spermatocytes gives indications about its role in division

Silverman-Gavrila¹,

Forer²

2003

Cell Motil. Cytoskeleton

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We showed previously that in crane-fly spermatocytes myosin is required for tubulin flux [Silverman-Gavrila and Forer, 2000a: J Cell Sci 113:597-609], and for normal anaphase chromosome movement and contractile ring contraction [Silverman-Gavrila and Forer, 2001: Cell Motil Cytoskeleton 50:180-197]. Neither the identity nor the distribution of myosin(s) were known. In the present work, we used immunofluorescence and confocal microscopy to study myosin during meiosis-I of crane-fly spermatocytes compared to tubulin, actin, and skeletor, a spindle matrix protein, in order to further understand how myosin might function during cell division. Antibodies to myosin II regulatory light chain and myosin II heavy chain gave similar staining patterns, both dependent on stage: myosin is associated with nuclei, asters, centrosomes, chromosomes, spindle microtubules, midbody microtubules, and contractile rings. Myosin and actin colocalization along kinetochore fibers from prometaphase to anaphase are consistent with suggestions that acto-myosin forces in these stages propel kinetochore fibres poleward and trigger tubulin flux in kinetochore fibres, contributing in this way to poleward chromosome movement. Myosin and actin colocalization at the cell equator in cytokinesis, similar to studies in other cells [e.g., Fujiwara and Pollard, 1978: J Cell Biol 77:182-195], supports a role of actin-myosin interactions in contractile ring function. Myosin and skeletor colocalization in prometaphase spindles is consistent with a role of these proteins in spindle formation. After microtubules or actin were disrupted, myosin remained in spindles and contractile rings, suggesting that the presence of myosin in these structures does not require the continued presence of microtubules or actin. BDM (2,3 butanedione, 2 monoxime) treatment that inhibits chromosome movement and cytokinesis also altered myosin distributions in anaphase spindles and contractile rings, consistent with the physiological effects, suggesting also that myosin needs to be active in order to be properly distributed.

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Section: Introductionmentioning

confidence: 99%

Myosin localization during meiosis I of crane‐fly spermatocytes gives indications about its role in division

Silverman-Gavrila¹,

Forer²

2003

Cell Motil. Cytoskeleton

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Effects of anti‐myosin drugs on anaphase chromosome movement and cytokinesis in crane‐fly primary spermatocytes

Silverman-Gavrila

Forer

2001

Cell Motil. Cytoskeleton

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To investigate whether myosin is involved in crane-fly primary spermatocyte division, we studied the effects of myosin inhibitors on chromosome movement and on cytokinesis. With respect to chromosome movement, the myosin ATPase inhibitor 2,3-butanedione 2-monoxime (BDM) added during autosomal anaphase reversibly perturbed the movements of all autosomes: autosomes stopped, slowed, or moved backwards during treatment. BDM added before anaphase onset altered chromosome movement less than when BDM was added during anaphase: chromosome movements only rarely were stopped. They often were normal initially and then, if altered at all, were slowed. To confirm that the effects of BDM were due to myosin inhibition, we treated cells with ML-7, a drug that inhibits myosin light chain kinase (MLCK), an enzyme necessary to activate myosin. ML-7 affected anaphase movement only when added in early prometaphase: this treatment prevented chromosome attachment to the spindle. We treated cells with H-7 as a control for possible non-myosin effects of ML-7. H-7, which has a lower affinity than ML-7 for MLCK but a higher affinity than ML-7 for other potential targets, had no effect. These data confirm that the BDM effect is on myosin and indicate that the myosin used for chromosome movement is activated near the start of prometaphase. With respect to cytokinesis, BDM did not block furrow initiation but did block subsequent contraction of the contractile ring. When BDM was added after initiation of the furrow, the contractile ring either stalled or relaxed. ML-7 blocked contractile ring contraction when added at all stages after autosomal anaphase onset, including when added during cytokinesis. H-7 had no effect. These results confirm that the effects of BDM are on myosin and indicate that the myosin used for cytokinesis is activated starting from autosomal anaphase and continuing throughout cytokinesis.

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Possible roles of actin and myosin during anaphase chromosome movements in locust spermatocytes

Fabian

Forer

2007

Protoplasma

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We tested whether the mechanisms of chromosome movement during anaphase in locust (Locusta migratoria L.) spermatocytes might be similar to those described for crane-fly spermatocytes. Actin and myosin have been implicated in anaphase chromosome movements in crane-fly spermatocytes, as indicated by the effects of inhibitors and by the localisations of actin and myosin in spindles. In this study, we tested whether locust spermatocyte spindles also utilise actin and myosin, and whether actin is involved in microtubule flux. Living locust spermatocytes were treated with inhibitors of actin (latrunculin B and cytochalasin D), myosin (BDM), or myosin phosphorylation (Y-27632 and ML-7). We added drugs (individually) during anaphase. Actin inhibitors alter anaphase: chromosomes either completely stop moving, slow, or sometimes accelerate. The myosin inhibitor, BDM, also alters anaphase: in most cases, the chromosomes drastically slow or stop. ML-7, an inhibitor of MLCK, causes chromosomes to stop, slow, or sometimes accelerate, similar to actin inhibitors. Y-27632, an inhibitor of Rho-kinase, drastically slows or stops anaphase chromosome movements. The effects of the drugs on anaphase movement are reversible: most of the half-bivalents resumed movement at normal speed after these drugs were washed out. Actin and myosin were present in the spindles in locations consistent with their possible involvement in force production. Microtubule flux along kinetochore fibres is an actin-dependent process, since LatB completely removes or drastically reduces the gap in microtubule acetylation at the kinetochore. These results suggest that actin and myosin are involved in anaphase chromosome movements in locust spermatocytes.

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Chromosome attachment to the spindle in crane-fly spermatocytes requires actin and is necessary to initiate the anaphase-onset checkpoint

Cited by 7 publications

References 64 publications

Myosin localization during meiosis I of crane‐fly spermatocytes gives indications about its role in division

Myosin localization during meiosis I of crane‐fly spermatocytes gives indications about its role in division

Effects of anti‐myosin drugs on anaphase chromosome movement and cytokinesis in crane‐fly primary spermatocytes

Possible roles of actin and myosin during anaphase chromosome movements in locust spermatocytes

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