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Relationship: 2665


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

Activation, estrogen receptor alpha leads to Increased, Kisspeptin signalling

Upstream event
The causing Key Event (KE) in a Key Event Relationship (KER). More help
Downstream event
The responding Key Event (KE) in a Key Event Relationship (KER). More help

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
Estrogen Receptor Alpha Agonism leads to Impaired Reproduction adjacent High Moderate John Hoang (send email) Under development: Not open for comment. Do not cite

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
rodents rodents High NCBI
mammals mammals High NCBI
fish fish Low NCBI

Sex Applicability

An indication of the the relevant sex for this KER. More help
Sex Evidence
Male High
Female High

Life Stage Applicability

An indication of the the relevant life stage(s) for this KER.  More help
Term Evidence
Adult, reproductively mature 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

Estrogen receptor alpha (ERα) is a nuclear receptor that can be activated by estrogens, a group of hormones involved in reproductive development. Activation of ERα promotes the transcription and regulation of physiological processes involved with the endocrine system(Christian and Moenter, 2007). Kisspeptins are a family of peptide hormones with varying amino acid lengths derived from the KISS1 gene & neurons (Nejad et al., 2017). Breakthrough research in the 2000s has shown that kisspeptins play a large role in the hypothalamic-pituitary-gonadal axis with gonadotropin circulation(Alcin et al., 2013). In particular, more recent research has shown kisspeptin neurons contain large populations of estrogen receptors, particularly ERα.

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

The majority of papers used in evidence supporting the key event relationship were found through AbstractSifter, a Microsoft Excel-based application that extracts papers from PubMed. AbstractSifter ranks abstracts based on their relevance through key search and filter terms. Initial papers were found through the search engine, Google Scholar, utilizing the search terms “Kisspeptin” and “estrogen”. This search yielded 11600 search results but only papers found on the first page of results were further examined. These papers were used to help curate search and filter terms used in Abstract Sifter. An additional search using CSU Long Beach’s One Search engine with key terms “GPR54” and “Kisspeptin” was also done in support of further curating search and filter terms for Abstractsifter. In this search, 3395 papers were initially found and only papers on the first page of the search were initially read. In AbstractSifter, 2 different searches were done to curate a subset of 71 papers. Search terms for the 2 searches included “kisspeptin AND GPR54” and “danio rerio AND kisspeptin” which yielded an initial set of 521 and 60 results respectively. Filter terms for the 2 searches included “estr AND LH” and “estr” which yielded 58 and 13 papers. Additional sources used towards the weight of evidence were found through sources in papers curated in the AbstractSifter search.

Evidence Supporting this KER

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

Concordance Table available here: ERalpha_Kisspeptin_CT

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

Previous studies have shown that estrogen exposures to organisms have caused increases in gonadotropin levels despite gonadotropin-releasing hormone neurons not expressing estrogen receptors. Recent studies have shown kisspeptin neurons located within the hypothalamus to express estrogen, androgen, and progesterone receptors(Clarkson et al., 2008). Fluorescence-activated cell sorting in mice found 99% and 70% of KISS1 neurons in the arcuate and anteroventral periventricular regions of the hypothalamus express ERα receptors (Smith et al., 2005). Estrogen exposures thereby should elicit an increase in kisspeptin expression.

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

When young female rhesus macaques were exposed to estradiol and ovariectomized, there was not a significant change in Kiss-1 expression (Eghlidi et al., 2010).

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

Modulating factors haven’t been evaluated yet.

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

Dose concordance evidence above demonstrates a response-response relationship where lower doses of estradiol don’t elicit changes in kisspeptin levels.

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

5 hours after an estrogen exposure, there is evidence of a change in kisspeptin expression (Adachi et al., 2007).

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

ERα and kisspeptins are involved with gonadotropin circulation within the body. It is well known that gonadotropins have both a negative and positive feedback loop depending on the circumstances. In females under proper reproductive conditions, estrogen induces positive feedback for ovulation. Under all other circumstances in females and males, estrogen induces negative feedback action to regulate levels of gonadotropins.

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
  • Taxonomic Applicability:

    • The understanding of kisspeptins on the hypothalamus-gonadotropin- pituitary axis comes largely from rodent and mammal studies. However, there have been more studies recently in other species such as fish to determine if applicability is present which it has shown.

  • Sex Applicability:  

    • Estrogen is present in both males and females. There is sexual dimorphism in the expression of kisspeptin neurons within the hypothalamus due to the positive feedback actions present in females particularly with reproduction. .

  • Life Stage Applicability: 

    • Kisspeptin plays a role in gonadotropin circulation. As a result of gonadotropins’ role in reproduction, the applicability can be directed towards reproductively mature organisms and developing organisms.


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