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Relationship: 2683

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

dimerization, AHR/ARNT leads to Increase, slincR expression

Upstream event

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

dimerization, AHR/ARNT

Downstream event

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

Increase, slincR expression

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
Aryl hydrocarbon receptor activation leading to early life stage mortality via sox9 repression induced impeded craniofacial development	adjacent	Moderate	Moderate	Agnes Aggy (send email)	Under development: Not open for comment. Do not cite	Under Review
Aryl hydrocarbon receptor activation leading to early life stage mortality via sox9 repression induced cardiovascular toxicity	adjacent	Moderate	Moderate	Allie Always (send email)	Under development: Not open for comment. Do not cite	Under Review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
zebrafish	Danio rerio	High	NCBI
mouse	Mus musculus	High	NCBI
human	Homo sapiens	Moderate	NCBI

Sex Applicability

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

Sex	Evidence
Unspecific	High

Life Stage Applicability

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

Term	Evidence
Embryo	High
Development	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

Dimerization of Ahr/ARNT take place when the ligand-activated Ahr translocates to the nucleus from the cytoplasm.
The Ahr/ARNT heterodimer can recognize aryl hydrocarbon response elements (AHREs), also known as xenobiotic response elements (XREs) or dioxin response elements (DREs), in the promoter region of downstream genes to regulate gene expression (Schmidt and Bradfield 1996). The target genes can either increase or decrease in their expression.
slincR expression significantly increases when zebrafish are exposed to TCDD, and the slincR promoter includes the core AHRE (5’-T/GCGTG-3’) in multiple locations (Garcia et al., 2017), suggesting that slincR is a direct downstream target of the Ahr/ARNT heterodimer.

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 gathered for this KER is primarily from two main studies, (Garcia et al., 2017) and (Garcia et al., 2018), that discovered and described slincR in zebrafish.

Evidence Supporting this KER

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

Biological Plausibility

Addresses the biological rationale for a connection between KEupstream and KEdownstream. This field can also incorporate additional mechanistic details that help inform the relationship between KEs, this is useful when it is not practical/pragmatic to represent these details as separate KEs due to the difficulty or relative infrequency with which it is likely to be measured. More help

Eight putative AHREs have been identified in the slincR promoter of the zebrafish gene (Garcia et al., 2017).
The potential orthologs of slincR in the mouse and human genomes also have conserved AHREs (Garcia et al., 2018).

Empirical Evidence

Provides specific (citable) evidence that supports the idea of a change in the upstream KE (KEupstream) leading to, or being associated with, a subsequent change in the downstream KE (KEdownstream), assuming the perturbation of KEupstream is sufficient. More help

Empirical evidence and essentiality of KE_up for KE_downto occur

Expression of slincR is significantly increased when zebrafish are exposed to TCDD (Garcia et al., 2017). TCDD is a strong Ahr activating ligand that causes the dimerization of Ahr and ARNT, and ARNT1 in zebrafish has been shown to be required for TCDD-induced toxicity (Prasch et al., 2006).
When AHR2-null zebrafish generated using CRISPR-Cas9 are exposed to TCDD, slincR expression at 48 hours post fertilization (hpf) is significantly lower than wildtype zebrafish exposed to TCDD (Garcia et al., 2017).
slincR expression is significantly induced upon exposure to several polycyclic aromatic hydrocarbons (PAHs), many of whom are Ahr activating chemicals (Garcia et al., 2018). The PAHs that induce slincR expression are retene, benzo[j]fluoranthene, benzo[k]fluoranthene, dibenzo[a,h]pyrene, dibenzo[a,i]pyrene, and benzo[b]fluoranthene.
TCDD-exposed embryonic mouse urogenital tissue samples showed significant increase in expression of the mouse slincR ortholog (2610035D17Rik) compared to the vehicle control, DMSO (Garcia et al., 2018).

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

Certain PAHs, such as fluoranthene, phenanthrene, and 9-methylanthracene that significantly induce cyp1a greater than log₂FC = 2, indicating that Ahr has been activated, do not induce slincR expression in zebrafish (Garcia et al., 2018).

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

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

A TCDD dose-response experiment was conducted measuring gene expression changes of slincR and cyp1a (biomarker for Ahr activation) in 48 hpf zebrafish. While cyp1a expression was always higher than slincR, the expression of the two genes increased in parallel, with significant slincR expression being identified at and above 0.0625 ng/mL TCDD exposure concentration (Garcia et al., 2018).
slincR expression increases in parallel with cyp1a when zebrafish are also exposed individually to several PAHs. Data come from a study that created a gene co-expression network and found that cyp1a and slincR expression were highly correlated with each other across multiple PAH treatments (Shankar et al., 2021).

Response-response Relationship

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

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

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

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

Ahr activation (and thus, the dimerization of Ahr/ARNT) resulting in significant slincR induction of expression has only been investigated in zebrafish and mice (Garcia et al., 2017; Garcia et al., 2018).

References

List of the literature that was cited for this KER description. More help

Garcia GR, Goodale BC, Wiley MW, La Du JK, Hendrix DA, Tanguay RL. 2017. In vivo characterization of an ahr-dependent long noncoding rna required for proper sox9b expression. Mol Pharmacol. 91(6):609-619.

Garcia GR, Shankar P, Dunham CL, Garcia A, La Du JK, Truong L, Tilton SC, Tanguay RL. 2018. Signaling events downstream of ahr activation that contribute to toxic responses: The functional role of an ahr-dependent long noncoding rna (slincr) using the zebrafish model. Environ Health Perspect. 126(11):117002.

Prasch AL, Tanguay RL, Mehta V, Heideman W, Peterson RE. 2006. Identification of zebrafish arnt1 homologs: 2,3,7,8-tetrachlorodibenzo-p-dioxin toxicity in the developing zebrafish requires arnt1. Mol Pharmacol. 69(3):776-787.

Schmidt JV, Bradfield CA. 1996. Ah receptor signaling pathways. Annu Rev Cell Dev Biol. 12:55-89.

Shankar P, McClure RS, Waters KM, Tanguay RL. 2021. Gene co-expression network analysis in zebrafish reveals chemical class specific modules. BMC Genomics. 22(1):658.