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Relationship: 714

Title

A descriptive phrase which clearly defines the two KEs being considered and the sequential relationship between them (i.e., which is upstream, and which is downstream). More help

Binding, Tubulin leads to Disruption, Microtubule dynamics

Upstream event

The causing Key Event (KE) in a Key Event Relationship (KER). More help

Binding, Tubulin

Downstream event

The responding Key Event (KE) in a Key Event Relationship (KER). More help

Disruption, Microtubule dynamics

Key Event Relationship Overview

The utility of AOPs for regulatory application is defined, to a large extent, by the confidence and precision with which they facilitate extrapolation of data measured at low levels of biological organisation to predicted outcomes at higher levels of organisation and the extent to which they can link biological effect measurements to their specific causes.Within the AOP framework, the predictive relationships that facilitate extrapolation are represented by the KERs. Consequently, the overall WoE for an AOP is a reflection in part, of the level of confidence in the underlying series of KERs it encompasses. Therefore, describing the KERs in an AOP involves assembling and organising the types of information and evidence that defines the scientific basis for inferring the probable change in, or state of, a downstream KE from the known or measured state of an upstream KE. More help

AOPs Referencing Relationship

AOP Name	Adjacency	Weight of Evidence	Quantitative Understanding	Point of Contact	Author Status	OECD Status
Chemical binding to tubulin in oocytes leading to aneuploid offspring	adjacent	High		Cataia Ives (send email)	Open for citation & comment	EAGMST Under Review

Taxonomic Applicability

Latin or common names of a species or broader taxonomic grouping (e.g., class, order, family) that help to define the biological applicability domain of the KER.In general, this will be dictated by the more restrictive of the two KEs being linked together by the KER. More help

Term	Scientific Term	Evidence	Link
Homo sapiens	Homo sapiens	Moderate	NCBI
mouse	Mus musculus	High	NCBI
Xenopus laevis	Xenopus laevis	Low	NCBI

Sex Applicability

An indication of the the relevant sex for this KER. More help

Sex	Evidence
Mixed	High

Life Stage Applicability

An indication of the the relevant life stage(s) for this KER. More help

Term	Evidence
All life stages	High

Key Event Relationship Description

Provides a concise overview of the information given below as well as addressing details that aren’t inherent in the description of the KEs themselves. More help

Chemicals that bind to tubulin on colchicine or vinca domain directly interfere with the addition of new tubulin dimers to the microtubules. The result of this process is a net loss of microtubules (i.e., microtubule depolymerization).

Evidence Collection Strategy

Include a description of the approach for identification and assembly of the evidence base for the KER. For evidence identification, include, for example, a description of the sources and dates of information consulted including expert knowledge, databases searched and associated search terms/strings. Include also a description of study screening criteria and methodology, study quality assessment considerations, the data extraction strategy and links to any repositories/databases of relevant references.Tabular summaries and links to relevant supporting documentation are encouraged, wherever possible. More help

Evidence Map 2.0

ID	Experimental Design	Species	Upstream Observation	Downstream Observation	Citation (first author, year)	Notes

Evidence Map

Addresses the scientific evidence supporting KERs in an AOP setting the stage for overall assessment of the AOP. More help

Title	First Author	Biological Plausibility	Dose Concordance	Temporal Concordance	Incidence Concordance

Biological Plausibility

Dose Concordance Evidence

Temporal Concordance Evidence

Incidence Concordance Evidence

Uncertainties and Inconsistencies

Addresses inconsistencies or uncertainties in the relationship including the identification of experimental details that may explain apparent deviations from the expected patterns of concordance. More help

No apparent uncertainties or inconsistencies. This KER is biologically plausible and broadly accepted. Indeed, in vitro assays to measure tubulin depolymerization are well standardized and represent the gold standard to determine whether a chemical is binding to tubulin.

Known modulating factors

This table captures specific information on the MF, its properties, how it affects the KER and respective references.1.) What is the modulating factor? Name the factor for which solid evidence exists that it influences this KER. Examples: age, sex, genotype, diet 2.) Details of this modulating factor. Specify which features of this MF are relevant for this KER. Examples: a specific age range or a specific biological age (defined by...); a specific gene mutation or variant, a specific nutrient (deficit or surplus); a sex-specific homone; a certain threshold value (e.g. serum levels of a chemical above...) 3.) Description of how this modulating factor affects this KER. Describe the provable modification of the KER (also quantitatively, if known). Examples: increase or decrease of the magnitude of effect (by a factor of...); change of the time-course of the effect (onset delay by...); alteration of the probability of the effect; increase or decrease of the sensitivity of the downstream effect (by a factor of...) 4.) Provision of supporting scientific evidence for an effect of this MF on this KER. Give a list of references. More help

Microtubules assembled in vitro contain several minor protein components that have been referred to as microtubule-associated proteins (MAPs). Several of these proteins are believed to play a role in the microtubule assembly process [Kakiu & Sato, 2016]. MAPs have been shown to inhibit colchicine binding to tubulin in a competitive manner. In contrast, Mg²⁺, which also induces microtubule assembly in vitro, had no effect on colchicine binding to tubulin [Nunez J et al. 1978].

Quantitative Understanding of the Linkage

Captures information that helps to define how much change in the upstream KE, and/or for how long, is needed to elicit a detectable and defined change in the downstream KE. More help

As described above, the quantitative relationship is well established for colchicine, and other chemicals are benchmarked against this chemical [Brunner et al., 1991]. Microtubule assembly is inhibited by approximately 50% when half of the tubulin dimers are bound by colchicine [Margolis et al., 1980], and a concentration of 2.5 μM of colchicine is needed to inhibit microtubule polymerization by 50% [Zavala et al., 1980].

Response-response Relationship

Provides sources of data that define the response-response relationships between the KEs. More help

Microtubule assembly is inhibited by approximately 50% when half of the tubulin dimers are bound by colchicine [Margolis et al., 1980], and a concentration of 2.5 μM of colchicine is needed to inhibit microtubule polymerization by 50% [Zavala et al., 1980].

Time-scale

Information regarding the approximate time-scale of the changes in KEdownstream relative to changes in KEupstream (i.e., do effects on KEdownstream lag those on KEupstream by seconds, minutes, hours, or days?). More help

Colchicine binds slowly to tubulin, in contrast to Combretastatin A4, which binds in a relatively fast, temperature-dependent manner. The rate of Colchicine binding has a rate constant of ~10² M^-1 s^-1 as determined by an isotopic labeling technique [Gaarland D.L. 1978]. Hovever, colchicine dissociates from tubulin over 100 times slower than combretastatin A-4, with a half.life of 405 min at 37 °C, compared to 3.6 min of CA4 [Lin et al. 1989].

Known Feedforward/Feedback loops influencing this KER

Define whether there are known positive or negative feedback mechanisms involved and what is understood about their time-course and homeostatic limits. More help

To our knowledge, there are no feedback loops influencing this KER.

Domain of Applicability

A free-text section of the KER description that the developers can use to explain their rationale for the taxonomic, life stage, or sex applicability structured terms. More help

This KER has been demonstrated in multiple species including sea urchins, frogs, mice, rats, cows, and human cells in culture.