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Event: 1972

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

Increased, Steroidogenic acute regulatory protein (StAR)

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
Increased, Steroidogenic acute regulatory protein (StAR)

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
steroid hormone secreting 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
Organ term
reproductive organ

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
increased luteinizing hormone level StAR-related lipid transfer protein 3 increased
increased luteinizing hormone level StAR-related lipid transfer protein 4 increased
increased luteinizing hormone level StAR-related lipid transfer protein 5 increased
increased luteinizing hormone level StAR-related lipid transfer protein 6 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
Hypothalamic estrogen receptors inhibition leading to ovarian cancer KeyEvent Kalyan Gayen (send email) Under development: Not open for comment. Do not cite


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
human Homo sapiens High NCBI
mice Mus sp. High NCBI
rat Rattus norvegicus High NCBI
Monkey Monkey Low 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
Adult, reproductively mature 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
Female High
Male Low

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

Biological state: Steroidogenic acute regulatory protein (StAR) plays important role in luteal steroidogenesis(Christenson and Devoto, 2003). Steroidogenic acute regulatory protein (StAR) controls the transport of cholesterol from the outer to inner mitochondrial membrane(Stocco, 2000). There are several pathways involved for the transport of cholesterol from different subcellular pools into the inner mitochondria(Martin et al., 2016).

Biological compartments: Cholesterol is one type of lipid which is crystalline solid with yellow colour.  It is biosynthesized by animal cells and is an essential structural component of animal cell membranes (Hanukoglu, 1992). It is the precursor molecule for the synthesis all steroid hormones(Payne and Hales, 2004).  Cytochrome P450 enzymes are present in most tissues of the body, and play important roles in hormone synthesis in mitochondria using cholesterol as precursor(Poderoso et al., 2013).

General role in biology:  It is been reported that high  in cholesterol levels in mitochondrial resulted several diseases like cancer, neurodegenerative diseases, steatohepatitis ischemia, and influence disease (Martin et al., 2016). The alteration in mitochondrial cholesterol import may change the cholesterol concentrations that may lead to proper mitochondrial function along with biophysical properties of mitochondrial membranes. In absence of StAR protein, cholesterol transport into the mitochondria did not occurs leading to  no conversion of progesterone from cholesterol precursors doesn’t occur(Kiriakidou et al., 1996; Pescador et al., 1996). All Steroidogenic acute regulatory protein (StAR) promoters contain steroidogenic factor 1 binding sites which is responsible for sex hormones regulation(Manna et al., 2002).

One of the important function of the steroid hormones is maintaining reproductive capacity. For this purpose, steroidogenic cells must move large amounts of cholesterol from the outer mitochondrial membrane to the inner membrane. In the granulosa cells, this cholesterol is ultimately converted to progesterone. The initial transport of cholesterol across the mitochondrial membrane requires Steroidogenic Acute Regulatory (StAR) protein. Expression of StAR protein in preovulatory cells of the developing follicle is low. The dramatic upregulation of StAR protein expression within the dominant follicle is found after the luteinizing hormone (LH) surge. This upregulation allows the corpus luteum to produce substantial amounts of progesterone to maintain the reproductive capacity in human/animal (Men et al., 2017; Stocco, 2000).

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). ?

StAR protein is measure by quantitative real time PCR (qRT-PCR):

For qRT-PCR analyses, cDNA is synthesized using reagent kit in a 20-μl reaction containing 0.5 μg of total RNA collected from human ovarian granulosa tumor cell line ( KGN cells ), mouse Leydig cells. qPCR is performed in a 25-μl reaction containing 0.5 to 1.5 μl of cDNA using fluorescein in real-time PCR detection systems. PCR was performed by initial denaturation at 95°C for 5 minutes, followed by 40 cycles of 30 seconds at 95°C, 30 seconds at 60°C, and 30 seconds at 72°C. The threshold cycle values of each sample are used to calculate mRNA levels. The PCR primers for the indicated human and mouse genes are as follows (Men et al., 2017).







Indirect immunohistochemistry for the detection of Steroidogenic Acute Regulatory Protein (StAR):

Ovarian or peritoneal tissues from the human patients are collected. Ovarian or peritoneal tissues from the patient are fixed using 10% paraformaldehyde. Tissues are embedded in paraffin. Serial sections of 5 µm are made using microtome. Tissue sections are prepared by microwave heating in 10× citrate buffer, pH 6.0, for 10 min. Tissues are rinsed three times in 20 mM phosphate buffered saline (PBS), pH 7.2, for 10 min each, before incubation with 1:200 dilutions of polyclonal anti-human StAR antibodies at 37°C for 60 min. Tissue sections were washed three times in 20 mM PBS, pH 7.2, for 2 min each, before incubation with a 1:1000 dilution of secondary mouse– anti-rabbit antibody at 37°C for 30 min. Indirect immunohistochemistry kits were used according to the manufacturer’s instructions to visualize StAR protein stained tissue under microscope and image collected. A pathological image analysis system is used to measure mean optical density (MOD) analysis under high-magnification (×400) microscopy. The MOD, which reflected the positive staining intensity, and the positive staining ratio (area %) of every positively stained area, are measured. The area % is calculated as ([the area of positive staining]/[total nuclear area in the field of view]) × 100. The MOD and area % are used to calculate the expression index, EI (%) = MOD × area %(Tian et al., 2009).

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

In Granulosa cells


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

Baker, B. Y., Epand, R. F., Epand, R. M., & Miller, W. L. (2007). Cholesterol binding does not predict activity of the steroidogenic acute regulatory protein, StAR. J Biol Chem, 282(14), 10223-32. doi:S0021-9258(19)57693-1 [pii]

Chaffin, C., Dissen, G., & Stouffer, R. (2000). Hormonal regulation of steroidogenic enzyme expression in granulosa cells during the peri-ovulatory interval in monkeys. Molecular human reproduction, 6(1), 11-18.

Christenson, L. K., & Devoto, L. (2003). Cholesterol transport and steroidogenesis by the corpus luteum. Reproductive Biology and Endocrinology, 1(1), 1-9.

Hanukoglu, I. (1992). Steroidogenic enzymes: structure, function, and role in regulation of steroid hormone biosynthesis. The Journal of steroid biochemistry and molecular biology, 43(8), 779-804.

Hasegawa, T., Zhao, L., Caron, K. M., Majdic, G., Suzuki, T., Shizawa, S., et al. (2000). Developmental roles of the steroidogenic acute regulatory protein (StAR) as revealed by StAR knockout mice. Mol Endocrinol, 14(9), 1462-71. doi:10.1210/mend.14.9.0515.

Kiriakidou, M., Mcallister, J. M., Sugawara, T., & Strauss 3rd, J. (1996). Expression of steroidogenic acute regulatory protein (StAR) in the human ovary. The Journal of Clinical Endocrinology & Metabolism, 81(11), 4122-4128.

Manna, P. R., Dyson, M. T., Eubank, D. W., Clark, B. J., Lalli, E., Sassone-Corsi, P., et al. (2002). Regulation of steroidogenesis and the steroidogenic acute regulatory protein by a member of the cAMP response-element binding protein family. Molecular Endocrinology, 16(1), 184-199.

Martin, L. A., Kennedy, B. E., & Karten, B. (2016). Mitochondrial cholesterol: mechanisms of import and effects on mitochondrial function. Journal of bioenergetics and biomembranes, 48(2), 137-151.

Men, Y., Fan, Y., Shen, Y., Lu, L., & Kallen, A. N. (2017). The Steroidogenic Acute Regulatory Protein (StAR) Is Regulated by the H19/let-7 Axis. Endocrinology, 158(2), 402-409. doi:10.1210/en.2016-1340.

Payne, A. H., & Hales, D. B. (2004). Overview of steroidogenic enzymes in the pathway from cholesterol to active steroid hormones. Endocrine reviews, 25(6), 947-970.

Pescador, N., Soumano, K., Stocco, D. M., Price, C. A., & Murphy, B. D. (1996). Steroidogenic acute regulatory protein in bovine corpora lutea. Biology of reproduction, 55(2), 485-491.

Poderoso, C., Duarte, A., Cooke, M., Orlando, U., Gottifredi, V., Solano, A. R., et al. (2013). The spatial and temporal regulation of the hormonal signal. Role of mitochondria in the formation of a protein complex required for the activation of cholesterol transport and steroids synthesis. Molecular and cellular endocrinology, 371(1-2), 26-33.

Sreerangaraja Urs, D. B., Wu, W.-H., Komrskova, K., Postlerova, P., Lin, Y.-F., Tzeng, C.-R., et al. (2020). Mitochondrial function in modulating human granulosa cell steroidogenesis and female fertility. International journal of molecular sciences, 21(10), 3592.

Stocco, D. (2000). The role of the StAR protein in steroidogenesis: challenges for the future. Journal of Endocrinology, 164(3), 247-253.

Tian, Y., Kong, B., Zhu, W., Su, S., & Kan, Y. (2009). Expression of steroidogenic factor 1 (SF-1) and steroidogenic acute regulatory protein (StAR) in endometriosis is associated with endometriosis severity. J Int Med Res, 37(5), 1389-95. doi:10.1177/147323000903700513.