一些私人生育診所正在宣傳和銷售使用多基因風險評分(PRS)來選擇胚胎。

　　這些診所聲稱，胚胎的PRS可以幫助預測未來孩子發(fā)展某些條件或復雜性狀的可能性，而這些條件或復雜性狀被認為受到多種不同基因的影響。然而，發(fā)表在《歐洲人類遺傳學雜志》上的一篇論文指出，沒有證據(jù)表明PRS可以以這種方式可靠地預測個體的特征。該論文認為，使用PRS來選擇胚胎既未經(jīng)證實也不道德。

　　“許多情況是由遺傳和環(huán)境共同造成的，而PRS只能捕獲任何相關遺傳成分的一部分，這本身可能非常復雜且難以分析，”第一作者Francesca Forzano博士說歐洲人類遺傳學會(ESHG)公共和專業(yè)政策委員會主席。“此外，雖然PRS可以識別普通人群中存在特定疾病風險的個體（遺傳變異性非常廣泛），但沒有證據(jù)表明它們可以幫助一對夫婦確定選擇一個胚胎而不是另一個胚胎，因為單個家庭內(nèi)的遺傳變異性是有限的。

　　個體具有特定基因的不同變體。PRSs著眼于跨多個基因的變異，這些變異可以影響疾病或性狀的發(fā)展。某些變體可能會增加發(fā)展特定性狀的可能性，而其他變體可能會降低可能性。

　　針對特定個體的特定性狀的PRS采用我們目前對特定人群中遺傳變異的了解，然后預測個體在整個人群的性狀分布中可能落在哪里。（例如，如果所討論的特征是身高，PRS可能會預測個人是否可能是人口中最高的20%、人口中最短的20%或中間的某個地方。）

　　英國的生育監(jiān)管機構——人類受精和胚胎管理局（HFEA）告訴《泰晤士報》：“在英國，目前在植入前基因檢測中使用PRS是非法的。胚胎選擇僅在英國是合法的，以避免嚴重的遺傳性疾病。

　　出版BioNews的慈善機構Progress Educational Trust的負責人Sarah Norcross呼吁監(jiān)管機構密切關注這些測試在英國的營銷情況?！皣L試使用PRS選擇胚胎在科學上和倫理上都不合法，”她說?！凹词埂獮榱藸幷摚M管完全缺乏臨床證據(jù)——PRS可以有意義地預測某些胚胎的某些事情，但使用該測試所需的胚胎數(shù)量無法在臨床環(huán)境。在生育治療的背景下，可供選擇的胚胎很少，因此選擇一個胚胎而不是另一個胚胎的原因必須基于明確的證據(jù)。

　　原文如下：

　　The use of polygenic risk scores(PRSs)to select embryos is being advertised and sold by some private fertility clinics.

　　Such clinics have claimed that PRSs for an embryo can help to predict the likelihood of the future child developing certain conditions or complex traits,when these are thought to be influenced by multiple different genes.However,a paper published in the European Journal of Human Genetics states that there is no evidence that PRSs can reliably anticipate an individual's characteristics in this way.The paper argues that the use of PRSs to select embryos is both unproven and unethical.

　　'Many conditions are caused by a combination of genetics and environment,and PRSs are only able to capture parts of any of the relevant genetic component,which is itself likely to be highly complex and difficult to analyse,'said Dr Francesca Forzano,first author of the paper and chair of the European Society of Human Genetics(ESHG)'s Public and Professional Policy Committee.'In addition,while PRSs may identify individuals at risk of a given disease in the general population(where the genetic variability is very wide)there is no evidence that they can be useful for a couple in determining the choice of one embryo over another,as the genetic variability within an individual family is limited.'

　　Individuals have different variants of particular genes.PRSs looks at variants,across multiple genes,which can influence the development of a disease or trait.Certain variants may increase the likelihood of developing a particular trait,while others may decrease the likelihood.

　　A PRS for a particular trait in a particular individual takes what we currently know about genetic variants in a particular population of people,and then predicts where the individual is likely to fall in the distribution of the trait across the entire population.(For example,if the trait in question is height,the PRS might predict whether the individual is likely to be among the tallest 20 percent of the population,the shortest 20 percent of the population,or somewhere in the middle.)

　　The UK's fertility regulator-the Human Fertilisation and Embryology Authority(HFEA)–told the Times:'The use of PRSs in pre-implantation genetic testing is currently illegal in the UK.Embryo selection is only legal in the UK to avoid serious inherited illnesses.'

　　Sarah Norcross,director of the charity Progress Educational Trust,which publishes BioNews,called for regulators to keep a careful eye on the marketing of these tests in the UK.'It is neither scientifically nor ethically legitimate to try to select embryos using PRSs,'she said.'Even if–for the sake of argument,and despite a complete lack of clinical evidence–a PRS could meaningfully predict certain things about certain embryos,the sheer number of embryos that would be needed to make use of this test could not be achieved in a clinical setting.There are precious few embryos to choose from in a fertility treatment context,and so reasons for preferring one embryo over another must be grounded in clear evidence.'