建議通過(guò)植入前基因檢測(cè)來(lái)預(yù)測(cè)常見疾病的風(fēng)險(xiǎn)

　　Preimplantation genetic testing proposed to predict risk of common diseases

　　一項(xiàng)新的研究聲稱已經(jīng)繪制了IVF產(chǎn)生的胚胎基因組圖，并表明所使用的相同技術(shù)也可用于實(shí)現(xiàn)植入前基因檢測(cè)(PGT)。

　　該論文發(fā)表在《自然醫(yī)學(xué)》雜志上，概述了使用微量遺傳物質(zhì)推斷3天和5天大的體外胚胎全基因組序列的分子和統(tǒng)計(jì)技術(shù)。作者認(rèn)為，這使得預(yù)測(cè)患癌癥和糖尿病等受許多不同基因影響的常見疾病的風(fēng)險(xiǎn)成為可能。這種理解許多基因的綜合影響的方法稱為多基因風(fēng)險(xiǎn)評(píng)分（PRS）。

　　來(lái)自加利福尼亞基因組學(xué)公司MyOme的作者寫道：“我們的方法能夠預(yù)測(cè)胚胎基因組中罕見和常見的變異?！薄拔覀兊难芯拷Y(jié)果可能會(huì)為討論基于基因組的PGT在臨床實(shí)踐中的效用和實(shí)施提供信息。”

　　為了構(gòu)建100多個(gè)胚胎的基因組，研究人員在稱為基因分型的過(guò)程中分析了整個(gè)基因組中的數(shù)十萬(wàn)個(gè)特定位點(diǎn)。他們用來(lái)自未來(lái)父母的基因序列填補(bǔ)了基因組的空白，并將他們預(yù)測(cè)的基因組與出生的孩子的基因組進(jìn)行了比較。

　　作者發(fā)現(xiàn)，他們能夠以97-99%的準(zhǔn)確率推斷出用于計(jì)算12種醫(yī)療狀況的PRS的站點(diǎn)的正確序列。他們說(shuō)這可以為胚胎創(chuàng)建PRS。

　　雖然組裝胚胎基因組的方法引起了科學(xué)界的興趣，但所謂的“PGT-P”（涉及PGS的PGT）的預(yù)測(cè)價(jià)值和倫理意義是有爭(zhēng)議的。除論文外，《自然醫(yī)學(xué)》發(fā)表評(píng)論指出PGT-P存在的許多科學(xué)和倫理問(wèn)題，同時(shí)在《自然》雜志上發(fā)表了類似的批評(píng)性社論。

　　“需要強(qiáng)調(diào)的是，這項(xiàng)研究并未闡明使用PRS進(jìn)行IVF胚胎選擇的最重要方面，其中存在PRS在這種情況下的統(tǒng)計(jì)有效性以及程序的倫理適當(dāng)性的基本問(wèn)題'，沒有參與這項(xiàng)研究的歐洲分子生物學(xué)實(shí)驗(yàn)室副主任Ewan Birney教授說(shuō)。

　　在英國(guó)，僅允許有可能生育患有嚴(yán)重遺傳疾?。ㄈ绾嗤㈩D病或囊性纖維化）孩子的夫婦根據(jù)其攜帶的基因選擇胚胎。人類受精和胚胎學(xué)管理局最近表示，在英國(guó)使用PGT-P進(jìn)行胚胎選擇是不合法的。

　　A new study claims to have mapped the genomes of embryos created by IVF,and suggests that the same techniques used could also be used to enable preimplantation genetic testing(PGT).

　　The paper,published in Nature Medicine,outlines molecular and statistical techniques for inferring the whole genome sequence of three-and five-day-old in vitro embryos using tiny amounts of genetic material.The authors believe that this makes it possible to forecast the risk of developing common diseases,such as cancer and diabetes,that are affected by many different genes.Such an approach to understanding the combined effects of many genes is called a polygenic risk score(PRS).

　　'Our approach enabled the prediction of both rare and common variants in embryo genomes'wrote the authors,from genomics company MyOme in California.'Our findings may inform the discussion of utility and implementation of genome-based PGT in clinical practice.'

　　To construct the genomes of more than 100 embryos,the researchers analysed hundreds of thousands of specific sites across the genome,in a process called genotyping.They filled in the gaps in the genomes with genetic sequences from the prospective parents,and compared their predicted genome to that of the born child.

　　The authors found that they were able,with 97-99 percent accuracy,to infer the correct sequence at sites used to calculate PRSs for 12 medical conditions.They say that this could enable the creation of PRSs for embryos.

　　While the method for assembling the genomes of embryos is of interest to the scientific community,the predictive value and ethical implications of so-called'PGT-P'(PGT that involves PGSs)are controversial.Alongside the paper,Nature Medicine published commentaries pointing to the many scientific and ethical problems with PGT-P,while a similarly critical editorial on the matter was published in Nature proper.

　　'It is important to stress that this study does not shed light on the most important aspect of using PRSs for embryo selection from IVF,where there are fundamental questions of both the statistical validity of the PRS in this setting and also the ethical appropriateness of procedure',said Professor Ewan Birney,deputy director of the European Molecular Biology Laboratory,who was not involved in the study.

　　In the UK,selecting an embryo based on the genes it carries is only permitted for couples who are at risk of having a child with a serious genetic condition,such as Huntington's disease or cystic fibrosis.The Human Fertilisation and Embryology Authority has recently stated that it would not be legal to use PGT-P for embryo selection in the UK.