Yeast estrogen screen (YES) and Yeast androgen screen (YAS) are ''

in vitro ''In vitro'' (meaning ''in glass'', or ''in the glass'') Research, studies are performed with Cell (biology), cells or biological molecules outside their normal biological context. Colloquially called "test-tube experiments", these studies in ...

'' screens that have been developed in order to detect

estrogen Estrogen (also spelled oestrogen in British English; see spelling differences) is a category of sex hormone responsible for the development and regulation of the female reproductive system and secondary sex characteristics. There are three ...

ic and

androgen An androgen (from Greek ''andr-'', the stem of the word meaning ) is any natural or synthetic steroid hormone that regulates the development and maintenance of male characteristics in vertebrates by binding to androgen receptors. This includes ...

ic activities, respectively, of natural and synthetic compounds, mixtures and environmental samples. The test is based on genetically modified

yeast cell Yeasts are eukaryotic, single-celled microorganisms classified as members of the fungus kingdom. The first yeast originated hundreds of millions of years ago, and at least 1,500 species are currently recognized. They are estimated to constitu ...

s (''

Saccharomyces cerevisiae ''Saccharomyces cerevisiae'' () (brewer's yeast or baker's yeast) is a species of yeast (single-celled fungal microorganisms). The species has been instrumental in winemaking, baking, and brewing since ancient times. It is believed to have be ...

''), which contain the gene for the human estrogen or androgen receptor coupled to a reporter gene (e.g. lacZ). Activation of the receptor initiates a cascade of events leading to the expression of the reporter gene product (e.g. β-galctosidase) which converts a substrate (e.g. CPRG) which leads to a measurable color change from yellow to red in the medium.Routledge, E.J. and Sumpter, J.P. (1996). Environ. Toxicol. Chem. 15(3): 241-248.Sohoni, P. and Sumpter, J.P. (1998). Endocrinol. 158, 327-339 Alternative systems are based on the generation of a luminescence signal. Activating (agonistic) samples can be measured directly; inhibiting (antagonistic) activities are measured as the reduction of color development in the presence of a known activating substance.

Assay format

The YES/YAS assay is performed in 96-well microtiter plates. Total assay time is usually 2–3 days, but faster protocols (18 hrs. exposure time) using induced cell lysis have been developed.Schultis T. and Metzger J.W., 2004. Chemosphere 57, 1649-1655 Several yeast cell lines have been developed for the YES and YAS assay, both proprietary and publicly available. Commercial kits with all necessary ingredients and detailed instructions are also available.Xenometrix AG, Allschwil, Switzerland.

Relevance

Substances with an activating or inhibitory effect on the estrogen and/or androgen receptor of organisms may interfere with reproduction, affect the metabolism and immune system and induce the formation of tumors. This assay is suitable for detecting numerous natural and synthetic hormonally active substances such as environmental toxins from everyday products, e.g.

birth control pill The combined oral contraceptive pill (COCP), often referred to as the birth control pill or colloquially as "the pill", is a type of birth control that is designed to be taken orally by women. It is the oral form of combined hormonal contra ...

ingredients ( 17α-ethinylestradiol), synthetic materials (

bisphenol A Bisphenol A (BPA) is a chemical compound primarily used in the manufacturing of various plastics. It is a colourless solid which is Solubility, soluble in most common organic solvents, but has very poor solubility in water. BPA is produced on a ...

phthalates Phthalates ( ), or phthalate esters, are esters of phthalic acid. They are mainly used as plasticizers, i.e., substances added to plastics to increase their flexibility, transparency, durability, and longevity. They are used primarily to soften ...

), pesticides ( methoxychlorine) and non-ionic surfactants (

alkylphenol Alkylphenols are a family of organic compounds obtained by the alkylation of phenols. The term is usually reserved for commercially important propylphenol, butylphenol, amylphenol, heptylphenol, octylphenol, nonylphenol, dodecylphenol and related ...

s). The test has a good reproducibility and concordance with literature data of ''

in vivo Studies that are ''in vivo'' (Latin for "within the living"; often not italicized in English) are those in which the effects of various biological entities are tested on whole, living organisms or cells, usually animals, including humans, an ...

'' or ''

'' data. Kolle, S.N., Kamp H.G., Huener H.A., Knickel J., Verlohner A., Woitkowiak C., Landsiedel R., van Ravenzwaay B. (2010). Toxicol. In vitro 24(7): 2030-2040

Advantages

The assay has a very good sensitivity (detection limit for 17β-estradiol in the YES assay about 5 x 10⁻¹² M or 1.4 ng/L), and the microplate format requires only small amounts of sample. Analysis of native aqueous samples, concentrated environmental samples and chemicals or mixtures in solvents like ethanol or DMSO is possible. Results can be obtained as quickly as after an overnight exposure. The handling of yeast cells is generally less demanding than mammalian cell culture.

Guidelines and literature

No international standards are available to date. An

ISO The International Organization for Standardization (ISO ; ; ) is an independent, non-governmental, international standard development organization composed of representatives from the national standards organizations of member countries. Me ...

guideline for the YES assay is under preparation.

References

{{Reflist Medical tests Sex hormones

Assay format

Relevance

Advantages

Guidelines and literature

See also

References