To the extent possible under law, AOP-Wiki has waived all copyright and related or neighboring rights to KE:720

Event: 720

Key Event Title

The KE title should describe a discrete biological change that can be measured. It should generally define the biological object or process being measured and whether it is increased, decreased, or otherwise definably altered relative to a control state. For example “enzyme activity, decreased”, “hormone concentration, increased”, or “growth rate, decreased”, where the specific enzyme or hormone being measured is defined. More help

Disruption, Microtubule dynamics

Short name
The KE short name should be a reasonable abbreviation of the KE title and is used in labelling this object throughout the AOP-Wiki. The short name should be less than 80 characters in length. More help
Disruption, Microtubule dynamics

Biological Context

Structured terms, selected from a drop-down menu, are used to identify the level of biological organization for each KE. Note, KEs should be defined within a particular level of biological organization. Only KERs should be used to transition from one level of organization to another. Selection of the level of biological organization defines which structured terms will be available to select when defining the Event Components (below). More help
Level of Biological Organization

Cell term

Further information on Event Components and Biological Context may be viewed on the attached pdf.The biological context describes the location/biological environment in which the event takes place.  For molecular/cellular events this would include the cellular context (if known), organ context, and species/life stage/sex for which the event is relevant. For tissue/organ events cellular context is not applicable.  For individual/population events, the organ context is not applicable. More help
Cell term
eukaryotic cell

Organ term

Further information on Event Components and Biological Context may be viewed on the attached pdf.The biological context describes the location/biological environment in which the event takes place.  For molecular/cellular events this would include the cellular context (if known), organ context, and species/life stage/sex for which the event is relevant. For tissue/organ events cellular context is not applicable.  For individual/population events, the organ context is not applicable. More help

Key Event Components

Further information on Event Components and Biological Context may be viewed on the attached pdf.Because one of the aims of the AOP-KB is to facilitate de facto construction of AOP networks through the use of shared KE and KER elements, authors are also asked to define their KEs using a set of structured ontology terms (Event Components). In the absence of structured terms, the same KE can readily be defined using a number of synonymous titles (read by a computer as character strings). In order to make these synonymous KEs more machine-readable, KEs should also be defined by one or more “event components” consisting of a biological process, object, and action with each term originating from one of 22 biological ontologies (Ives, et al., 2017; See List). Biological process describes dynamics of the underlying biological system (e.g., receptor signalling). The biological object is the subject of the perturbation (e.g., a specific biological receptor that is activated or inhibited). Action represents the direction of perturbation of this system (generally increased or decreased; e.g., ‘decreased’ in the case of a receptor that is inhibited to indicate a decrease in the signalling by that receptor).Note that when editing Event Components, clicking an existing Event Component from the Suggestions menu will autopopulate these fields, along with their source ID and description. To clear any fields before submitting the event component, use the 'Clear process,' 'Clear object,' or 'Clear action' buttons. If a desired term does not exist, a new term request may be made via Term Requests. Event components may not be edited; to edit an event component, remove the existing event component and create a new one using the terms that you wish to add. More help
Process Object Action
microtubule depolymerization microtubule increased

Key Event Overview

AOPs Including This Key Event

All of the AOPs that are linked to this KE will automatically be listed in this subsection. This table can be particularly useful for derivation of AOP networks including the KE. Clicking on the name of the AOP will bring you to the individual page for that AOP. More help
AOP Name Role of event in AOP Point of Contact Author Status OECD Status
Tubulin binding and aneuploidy KeyEvent Francesco Marchetti (send email) Open for citation & comment EAGMST Under Review


This is a structured field used to identify specific agents (generally chemicals) that can trigger the KE. Stressors identified in this field will be linked to the KE in a machine-readable manner, such that, for example, a stressor search would identify this as an event the stressor can trigger. NOTE: intermediate or downstream KEs in one AOP may function as MIEs in other AOPs, meaning that stressor information may be added to the KE description, even if it is a downstream KE in the pathway currently under development.Information concerning the stressors that may trigger an MIE can be defined using a combination of structured and unstructured (free-text) fields. For example, structured fields may be used to indicate specific chemicals for which there is evidence of an interaction relevant to this MIE. By linking the KE description to a structured chemical name, it will be increasingly possible to link the MIE to other sources of chemical data and information, enhancing searchability and inter-operability among different data-sources and knowledgebases. The free-text section “Evidence for perturbation of this MIE by stressor” can be used both to identify the supporting evidence for specific stressors triggering the MIE as well as to define broad chemical categories or other properties that classify the stressors able to trigger the MIE for which specific structured terms may not exist. More help

Taxonomic Applicability

Latin or common names of a species or broader taxonomic grouping (e.g., class, order, family) can be selected from an ontology. In many cases, individual species identified in these structured fields will be those for which the strongest evidence used in constructing the AOP was available in relation to this KE. More help
Term Scientific Term Evidence Link
mouse Mus musculus High NCBI
Homo sapiens Homo sapiens Moderate NCBI
Xenopus laevis Xenopus laevis Moderate NCBI

Life Stages

The structured ontology terms for life-stage are more comprehensive than those for taxa, but may still require further description/development and explanation in the free text section. More help
Life stage Evidence
All life stages High

Sex Applicability

The authors must select from one of the following: Male, female, mixed, asexual, third gender, hermaphrodite, or unspecific. More help
Term Evidence
Mixed High

Key Event Description

A description of the biological state being observed or measured, the biological compartment in which it is measured, and its general role in the biology should be provided. For example, the biological state being measured could be the activity of an enzyme, the expression of a gene or abundance of an mRNA transcript, the concentration of a hormone or protein, neuronal activity, heart rate, etc. The biological compartment may be a particular cell type, tissue, organ, fluid (e.g., plasma, cerebrospinal fluid), etc. The role in the biology could describe the reaction that an enzyme catalyses and the role of that reaction within a given metabolic pathway; the protein that a gene or mRNA transcript codes for and the function of that protein; the function of a hormone in a given target tissue, physiological function of an organ, etc. Careful attention should be taken to avoid reference to other KEs, KERs or AOPs. Only describe this KE as a single isolated measurable event/state. This will ensure that the KE is modular and can be used by other AOPs, thereby facilitating construction of AOP networks. More help

Microtubules are polar structures, and in each filament, subunits are added to one extremity (the plus end) and removed from the other one (the minus end) [reviewed in Marchetti et al. 2016]. Microtubules are dynamic structures characterized by features such as dynamic instability and treadmilling. Dynamic instability defines the ability of microtubules to grow or shorten [Mitchison & Kirschner, 1984; Wade and Hyman, 1997]; the process is based on a multitude of events regulating the assembly/disassembly of the subunits. Treadmilling is the process by which, in the presence of an active loss of subunits (at the minus end) and acquisition of subunits (at the plus end), a steady-state is maintained, and the length of the microtubule remains unchanged [Waterman-Sloter and Salmon, 1997]. Microtubule dynamics can be affected as a result of microtubule depolymerization or microtubule stabilization.

How It Is Measured or Detected

One of the primary considerations in evaluating AOPs is the relevance and reliability of the methods with which the KEs can be measured. The aim of this section of the KE description is not to provide detailed protocols, but rather to capture, in a sentence or two, per method, the type(s) of measurements that can be employed to evaluate the KE and the relative level of scientific confidence in those measurements. Methods that can be used to detect or measure the biological state represented in the KE should be briefly described and/or cited. These can range from citation of specific validated test guidelines, citation of specific methods published in the peer reviewed literature, or outlines of a general protocol or approach (e.g., a protein may be measured by ELISA).Key considerations regarding scientific confidence in the measurement approach include whether the assay is fit for purpose, whether it provides a direct or indirect measure of the biological state in question, whether it is repeatable and reproducible, and the extent to which it is accepted in the scientific and/or regulatory community. Information can be obtained from the OECD Test Guidelines website and the EURL ECVAM Database Service on Alternative Methods to Animal Experimentation (DB-ALM). ?

Microtubule depolymerization is generally assessed by an acellular tubulin polymerization assay [Salmon et al., 1984; Wilson et al., 1984; Wallin and Hartley-Asp, 1993; Ibanez et al., 2003; Liu et al., 2010]. A reaction mixture containing tubulin and a test agent, after preincubation, is chilled on ice. GTP is added, and turbidity development is followed at 350 nm in a temperature-controlled recording spectrophotometer. The extent of the reaction is then measured and the area under the curve is used to determine the concentration that inhibited tubulin polymerization by 50% (IC50) [Hamel, 2003]. A concentration of 2.5 μM of colchicine is needed to inhibit microtubule polymerization by 50% [Zavala et al., 1980] and the ability of new chemicals to induce this effect is benchmarked against this value (e.g., combretastatin A-4 IC50 is 1.2 μM [Pettit et al., 1998]).

Domain of Applicability

This free text section should be used to elaborate on the scientific basis for the indicated domains of applicability and the WoE calls (if provided). While structured terms may be selected to define the taxonomic, life stage and sex applicability (see structured applicability terms, above) of the KE, the structured terms may not adequately reflect or capture the overall biological applicability domain (particularly with regard to taxa). Likewise, the structured terms do not provide an explanation or rationale for the selection. The free-text section on evidence for taxonomic, life stage, and sex applicability can be used to elaborate on why the specific structured terms were selected, and provide supporting references and background information.  More help

Depolymerization of microtubules has been measured in many somatic cell types, in addition to frog and mouse eggs, and in human cells, including eggs, in culture [Salmon et al. 1984; Wilson et al., 1984; Ibanez et al., 2003; Liu et al., 2010]. Quantitative cell-based assays for assessing microtubule activities of compounds are achieved by measuring the indirect effects on cell cycle which result from a disruption of microtubule networks. These methods utilize either fluorescent microscopy or cell cycle analysis. In fluorescent microscopic studies, either the α- or β-tubulin can be labeled directly with a tubulin antibody-conjugated fluorescent probe, or indirectly via a secondary antibody [Zhou et al., 2009]. Tubulin stabilizers and destabilizers cause cell cycle arrest at the G2/M phase [Bhalla, 2003], and therefore measurement of the percentage of cells arrested in G2/M phase is used as a surrogate endpoint for microtubule activity.

Evidence for Perturbation by Stressor


Colchicine interferes with microtubule dynamics at lower concentrations while it induces a net depolymerization at higher concentrations which is a consequence of the inability of further extending the microtubules [Stanton et al., 2011]. This dual action is in common with other spindle poisons (e.g. vinca derivatives) [Panda et al., 1996]. All microtubule-binding agents alter microtubule dynamics, engaging cell cycle surveillance mechanisms that arrest cell division in metaphase. This mitotic stall may then lead to various irremediable effects such as mitotic catastrophe, apoptosis or aneuploidy [Kops et al., 2005]. 

After addition of colchicine at concentrations of 0.1-3.0 mM, microtubule polymerization decreased rapidly and simultaneously thoughout the central spindle and aster (Salmon et al, 1984)


List of the literature that was cited for this KE description. Ideally, the list of references, should conform, to the extent possible, with the OECD Style Guide ( (OECD, 2015). More help

Bhalla KN. 2003. Microtubule-targeted anticancer agents and apoptosis. Oncogene 22:9075-9086.

Hamel E. 2003. Evaluation of antimitotic agents by quantitative comparisons of their effects on the polymerization of purified tubulin. Cell Biochem Biophys 38:1-22.

Ibanez E, Albertini DF, Overstrom EW. 2003. Demecolcine-induced oocyte enucleation for somatic cell cloning: coordination between cell-cycle egress, kinetics of cortical cytoskeletal interactions, and second polar body extrusion. Biol Reprod 68:1249-1258.

Kops GJ, Weaver BA, Cleveland DW. 2005. On the road to cancer: aneuploidy and the mitotic checkpoint. Nat Rev Cancer 5:773-785.

Lambrus BG, Holland AJ. 2017. A new mode of mitotic surveillance. Trends Cell Biol 27:314-321.

Liu S, Li Y, Feng HL, Yan JH, Li M, Ma SY, Chen ZJ. 2010. Dynamic modulation of cytoskeleton during in vitro maturation in human oocytes. Am J Obstet Gynecol 203:151.e151-157.

Mailhes JB, Carabatsos MJ, Young D, London SN, Bell M, Albertini DF. 1999. Taxol-induced meiotic maturation delay, spindle defects, and aneuploidy in mouse oocytes and zygotes. Mutat Res 423:79-90.

Marchetti F, Massarotti A, Yauk CL, Pacchierotti F, Russo A. 2016. The adverse outcome pathway (AOP) for chemical binding to tubulin in oocytes leading to aneuploid offspring. Environ Mol Mutagen 57:87-113.

Mitchison T, Kirschner M. 1984. Dynamic instability of microtubule growth. Nature. 312:237-242.

Panda D, Jordan MA, Chu KC, Wilson L. 1996. Differential effects of vinblastine on polymerization and dynamics at opposite microtubule ends. J Biol Chem 271:29807-29812.

Pettit GR, Toki B, Herald DL, Verdier-Pinard P, Boyd MR, Hamel E, Pettit RK. 1998. Antineoplastic agents. 379. Synthesis of phenstatin phosphate. J Med Chem 41:1688-1695.

Salmon ED, McKeel M, Hays T. 1984. Rapid rate of tubulin dissociation from microtubules in the mitotic spindle in vivo measured by blocking polymerization with colchicine. J Cell Biol 99:1066-1075.

Stanton RA, Gernert KM, Nettles JH, Aneja R. 2011. Drugs that target dynamic microtubules: a new molecular perspective. Med Res Rev 31:443-481.

Wade RH, Hyman AA. 1997. Microtubule structure and dynamics. Curr Opin Cell Biol 9:12-17.

Wallin M, Hartley-Asp B. 1993. Effects of potential aneuploidy inducing agents on microtubule assembly in vitro. Mutat Res 287:17-22.

Waterman-Sloter CM, Salmon ED. 1997. Microtubule dynamics: treadmilling comes around again. Curr Biol 7:R369-R372.

Wilson L, Miller HP, Pfeffer TA, Sullivan KF, Detrich HW, 3rd. 1984. Colchicine-binding activity distinguishes sea urchin egg and outer doublet tubulins. J Cell Biol 99:37-41.

Zavala F, Guenard D, Robin JP, Brown E. 1980. Structure--antitubulin activity relationship in steganacin congeners and analogues. Inhibition of tubulin polymerization in vitro by (+/-)-isodeoxypodophyllotoxin. J Med Chem 23:546-549.

Zhou YB, Feng X, Wang LN, Du JQ, Zhou YY, Yu HP, Zang Y, Li YJ, Li J. 2009. LGH00031, a novel ortho-quinonoid inhibitor of cell division cycle 25B, inhibits human cancer cells via ROS generation. Acta Pharmacol Sin 30;1359-1368.