Malorientation and abnormal segregation of chromosomes during recovery from Colcemid and Nocodazole

Abstract

Reversal of meiotic arrest in crane-fly spermatocytes by U. V. irradiation of Colcemid-arrested cells or by rinsing Nocodazole-arrested cells in fresh buffer results in the induction of chromosome malorientation. Malorientations observed among Colcemid-recovering and Nocodazole-recovering spermatocytes at frequencies higher than normally observed in untreated cells included associations of sister kinetochores of half-bivalents with both spindle poles (amphitely), in contrast with associations of sisters with only one pole (syntely) as is usually found during the first meiotic division. In several cases, prior to anaphase onset, maloriented bivalents appeared unusually tilted with respect to the spindle axis, and during anaphase they gave rise to laggard half-bivalents that did not segregate during anaphase along with half-bivalents having proper syntelic orientation. The results parallel previous findings obtained during cold recovery, and the properties of the drugs used here suggest that their action on microtubules, although reversible, induces malorientation during recovery from meiotic arrest.

Checkpoint control in crane-fly spermatocytes: unattached chromosomes induced by cytochalasin D or latrunculin treatment do not prevent or delay the start of anaphase

“…One reason we believe that the bivalents we described as "unattached" are indeed unattached is that when a variety of treatments of crane-fly spermatocytes induce maloriented bivalents (including partial merotely -individual half-bivalent kinetochores being oriented to both poles), the maloriented bivalents become aligned at the equator at metaphase; unlike those described herein, the maloriented bivalents remain in the spindle and do not move to the poles or into the cytoplasm (Janicke and LaFountain 1982, 1984, 1986Ladrach and LaFountain 1986;LaFountain 1985a, b). Another reason is that it is difficult to imagine how bivalents situated partially (Fig.…”

Characterization of HCP-6, a C. elegans protein required to prevent chromosome twisting and merotelic attachment

“…However, one question that remains unaddressed in these experiments is the mechanism by which merotelic chromosomes naturally arise. They are observed with an increased frequency following treatment with colcemid or nocadazole (Ladrach and LaFountain 1986;Cimini et al 2001), which seem to bring about structural changes in the kinetochores, causing them to adopt a curled, crescent-like morphology and promoting merotelic attachment (Cimini et al 2001). This observation is analogous to our results describing how the decondensed chromosomes of hcp-6 are more flexible, which leads to a failure in bipolar attachment.…”

“…Defects of this nature are referred to as merotelically oriented chromosomes and lead to lagging anaphase chromosomes. The occurrence of these chromosomes can be enhanced by treatment with colcemid or nocodazole, which seem to induce morphological changes in the kinetochore, making them appear stretched or curled (Ladrach and LaFountain 1986;Cimini et al 2001). This suggests that alterations in kinetochore structure and flexibility can prevent the establishment and maintenance of bipolar attachment.…”

Merotelic kinetochore orientation occurs frequently during early mitosis in mammalian tissue cells and error correction is achieved by two different mechanisms

“…Another major question is why transient spindle disassembly is such a potent promoter of lagging chromosomes (Cimini et al, 2002;Cimini et al, 2001). Upon spindle reassembly and progression into anaphase the frequency of cells with merotelically oriented lagging chromosomes is substantially increased to 8-30% (Cimini et al, 2002;Cimini et al, 2001;Ladrach and LaFountain, 1986).…”