Effects of ultraviolet-microbeam irradiation of kinetochores in crane-fly spermatocytes

Ilagan, Arlene; Forer, Arthur

doi:10.1002/(sici)1097-0169(1997)36:3<266::aid-cm7>3.0.co;2-5

Cited by 16 publications

(9 citation statements)

References 32 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Backward chromosome movements in anaphase have been seen previously in crane-fly spermatocytes, but only rarely and only when the poleward force was blocked by UV microbeam irradiation [101,102]. However, chromosome arms, severed with a laser beam, regularly moved backwards [95].…”

Section: Discussionmentioning

confidence: 93%

“…In grasshopper spermatocytes [104] there are fast backwards movements after UV irradiation of the kinetochore in early anaphase. Ilagan and Forer [101], LaFountain et al [95] and Wong and Forer [102] all considered that there are mechanical connections between the arms of separating half-bivalents in crane-fly spermatocytes and that these connections, or "tethers"[95], elastically cause the backwards movements. Even though the tethers act on both partner half-bivalents, the backwards movements need not be symmetric, with both partners moving equally, because in all previous observations only one chromosome (or arm) moved, the one no longer attached to the pole.…”

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Calyculin A, an enhancer of myosin, speeds up anaphase chromosome movement

2007

View full text Add to dashboard Cite

Actin and myosin inhibitors often blocked anaphase movements in insect spermatocytes in previous experiments. Here we treat cells with an enhancer of myosin, Calyculin A, which inhibits myosinlight-chain phosphatase from dephosphorylating myosin; myosin thus is hyperactivated. Calyculin A causes anaphase crane-fly spermatocyte chromosomes to accelerate poleward; after they reach the poles they often move back toward the equator. When added during metaphase, chromosomes at anaphase move faster than normal. Calyculin A causes prometaphase chromosomes to move rapidly up and back along the spindle axis, and to rotate. Immunofluorescence staining with an antibody against phosphorylated myosin regulatory light chain (p-squash) indicated increased phosphorylation of cleavage furrow myosin compared to control cells, indicating that calyculin A indeed increased myosin phosphorylation. To test whether the Calyculin A effects are due to myosin phosphatase or to type 2 phosphatases, we treated cells with okadaic acid, which inhibits protein phosphatase 2A at concentrations similar to Calyculin A but requires much higher concentrations to inhibit myosin phosphatase. Okadaic acid had no effect on chromosome movement. Backward movements did not require myosin or actin since they were not affected by 2,3-butanedione monoxime or LatruculinB. Calyculin A affects the distribution and organization of spindle microtubules, spindle actin, cortical actin and putative spindle matrix proteins skeletor and titin, as visualized using immunofluorescence. We discuss how accelerated and backwards movements might arise.

show abstract

Section: Discussionmentioning

confidence: 93%

Section: Discussionmentioning

confidence: 99%

Calyculin A, an enhancer of myosin, speeds up anaphase chromosome movement

2007

View full text Add to dashboard Cite

show abstract

“…Therefore, tethers are responsible for, or at least are required for, regulating the speeds of separating partner chromosomes. Extending this conclusion, we assume that when both partners stop moving after UV microbeam irradiation of only one kinetochore fibre (Figure 1; Forer, 1966;Sillers and Forer, 1981a,b;Adames and Forer, 1996;Yin and Forer, 1996;Ilagan and Forer, 1997) the stoppage of the partner chromosome (moving to the opposite pole) is due to tethers. Consistent with this is that UV microbeam irradiation of the interzone uncouples the movements of the separating anaphase chromosomes: after first irradiating the interzone, the chromosome associated with the irradiated kinetochore spindle fibre stops moving -the partner moves normally (Yin and Forer, 1996).…”

Section: Discussionmentioning

confidence: 90%

“…When irradiation of one kinetochore fibre stopped the anaphase movement of the associated chromosome, the partner chromosome moving to the opposite pole also stopped moving (Forer, 1966;Sillers and Forer, 1981a,b;Adames and Forer, 1996;Yin and Forer, 1996;Ilagan and Forer, 1997); the other chromosomes were not affected, as illustrated in Figure 1. UV microbeam irradiation of the interzone uncoupled the separating chromosomes in that only the chromosome attached to the irradiated spindle fibre stopped moving, not its partner (Yin and Forer, 1996).…”

Section: Introductionmentioning

confidence: 95%

Elastic Tethers Between Separating Anaphase Chromosomes Regulate the Poleward Speeds of the Attached Chromosomes in Crane-Fly Spermatocytes

Forer

Berns

2020

Front. Mol. Biosci.

View full text Add to dashboard Cite

Elastic “tethers” connect separating anaphase chromosomes in most (or all) animal cells. We tested whether tethers are involved in coordinating movements of separating anaphase chromosomes in crane-fly spermatocytes. In these cells the coupled movements of separating chromosomes become uncoupled after the tethers are severed by laser microbeam irradiation of the interzone region between the chromosomes ( Sheykhani et al., 2017 ). While this strongly suggests that tethers are involved with coordinating the poleward chromosome movements, the experiments are open to another interpretation: laser irradiations that cut the tethers also might damage something else in the interzone, and those non-tether components might regulate chromosome movements. In the experiments reported herein we distinguish between those two possibilities by disabling the tethers without cutting the interzone. We cut the arms from individual chromosomes, thereby severing the mechanical connection between separating chromosomes, disconnecting them, without damaging components in the interzone. Disabling tethers in this way uncoupled the movements of the separating chromosomes. We thus conclude that tethers are involved in regulating the speeds of separating anaphase chromosomes in crane-fly spermatocytes.

show abstract

“…We also often have followed several spermatocytes consecutively from metaphase through anaphase, or prometaphase through anaphase, with no apparent deleterious changes in the later cells. Crane-fly spermatocytes in clots act the same as spermatocytes smeared under oil using every criterion we have looked at, namely time intervals between nuclear membrane breakdown and anaphase (Forer and Pickett-Heaps, 1998b;LaFountain et al, 2001;Silverman-Gavrila and Forer, 2001), velocities of autosome movements during anaphase (Forer, 1965;Schaap and Forer, 1979;Yin and Forer, 1996;Ilagan and Forer, 1997;LaFountain et al, 2001;Forer, 2003, spermatocytes under oil, compared with Forer andPickett-Heaps, 1998b;Silverman-Gavrila and Forer, 2001;, spermatocytes in clots), time intervals between onset of autosomal anaphase and subsequent sexchromosome anaphase (Schaap andForer, 1979, under oil, compared with Forer andPickett-Heaps, 1998b;Silverman-Gavrila and Forer, 2001, in clots), behaviours of severed spindle fibres and associated chromosomes after ultraviolet microbeam irradiation of spindle fibres (Forer, 1965(Forer, , 1966Wilson and Forer, 1988;Spurck et al, 1997, under oil, compared with Forer et al, 2003, and general appearances of cells and chromosomes. Nor does periodic flow of solution past the cells seem to harm the cells: anaphase velocities are not perturbed by flow of Ringer's solution or DMSO (Forer and Pickett-Heaps, 1998a, b).…”

Section: Discussionmentioning

confidence: 99%

Fibrin clots keep non-adhering living cells in place on glass for perfusion or fixation

Forer

Pickett‐Heaps

2005

Cell Biology International

View full text Add to dashboard Cite

We describe a method to hold living cells in place that ordinarily do not adhere to glass coverslips. The method, developed for insect spermatocytes but with application to other cell types, consists of embedding cells in a fibrin clot that forms after the enzyme thrombin cleaves the blood protein fibrinogen. The method permits continuous observation of living cells as they are treated with and recover from drug or other treatments: when held in the clot the living cells remain in place and keep their shapes when perfused with drugs that ordinarily cause drastic shape changes, and they remain in place and keep their shapes through lysis/fixation procedures. We describe how to place live cells in a fibrin clot and how subsequently to perfuse them.

show abstract

Effects of ultraviolet-microbeam irradiation of kinetochores in crane-fly spermatocytes

Cited by 16 publications

References 32 publications

Calyculin A, an enhancer of myosin, speeds up anaphase chromosome movement

Calyculin A, an enhancer of myosin, speeds up anaphase chromosome movement

Elastic Tethers Between Separating Anaphase Chromosomes Regulate the Poleward Speeds of the Attached Chromosomes in Crane-Fly Spermatocytes

Fibrin clots keep non-adhering living cells in place on glass for perfusion or fixation

Contact Info

Product

Resources

About