Physiological mechanism of Chinese researchers proved IVF gender imbalance

Xinhua News Agency, Washington D.C., March 7 (reporter Lin Xiaochun)-Gospel of IVF for many infertile couples, but the use of such technology babies born is highly concerned about the boys than girls. Chinese researchers found in a mouse experiment, the problem may be related to x-inactivation mechanism weakened.

Results of this research published 7th in new issue of United States National Academy of Sciences. Study of Professor Tian Jianhui, China Agricultural University, told Xinhua, since the first test-tube baby was born in 1978, in vitro fertilization are widely used in human fertility problems, there are 5.4 million test-tube baby was born and growing at a rate of 350,000 cases a year. With in vitro fertilization, a growing group, gender imbalances will become more and more prominent. However, the specific cause and still no clear idea of how to prevent.

In 2011, the Tian Jianhui found that mice also using in vitro fertilization to cultivate gender imbalances. Further studies have shown that IVF embryos exist issue of insufficient inactivation of the x chromosome, they concluded that this may be a major cause of gender imbalance.

Tian Jianhui explained that the x chromosome inactivation in female embryos early in development is through epigenetic modifications of events. If this mechanism is weakened, can result in female embryos developed abnormally, leading to a gender imbalance.

After a series of studies, they found that the x chromosome inactivation mechanisms associated with two gene Xist and Rnf12. Functional compensation on the basis of this experiment, researchers successful in vitro fertilization in mice at birth males from 57. 17% correction to 51. 92%, close to the normal range.

Tian Jianhui, said: "our research not only reveals the inner mechanism of the unbalanced sex ratio at birth, and through targeted adjustment of the cultivation system of in vitro fertilization, and address gender imbalances in vitro fertilization. ”

Tian Jianhui said there by in vitro fertilization miscarriages, low birth weight, birth defects, risk, their study also revealed the molecular mechanism of these problems and provides important guidelines for prevention.

Prior to this, pigs, cows, and other animals studies have repeatedly confirmed that IVF gender imbalances. In recent years, some studies have shown that human IVF also has this problem. For example, Australia and New Zealand an investigation shows that in vitro fertilization ratio of women to men is 1. 17:1, United Kingdom a survey of 1 per cent. 28:1. Gender imbalance means that embryonic defects on the one hand, on the other hand will have consequences on society. (End)

(Editor: Li UN659)
2016-03-08 10:00:41
Xinhua News Agency

中国研究人员探明试管婴儿性别失衡的生理机制

　　新华社华盛顿3月7日电（记者林小春）试管婴儿技术为许多不孕不育夫妇带来福音，但利用这种技术诞生的婴儿中男孩多于女孩的问题也引起高度关注。中国研究人员从一项小鼠实验中发现，这个问题可能与X染色体失活机制被削弱有关。

　　这项研究结果7日发表在新一期美国《国家科学院学报》上。负责研究的中国农业大学教授田见晖告诉新华社记者，自1978年第一例试管婴儿出生以来，体外受精被广泛应用于解决人类不育问题，目前已有540万例试管婴儿出生，并且以每年35万例的速度增长。随着试管婴儿这一群体越来越大，性别失衡问题也会越来越凸显。但是，其具体成因及如何预防仍没有明确的思路。

　　2011年，田见晖等人发现利用体外受精技术培育的小鼠也存在性别失衡问题。进一步研究显示，体外受精胚胎存在X染色体失活不足问题，他们推断这可能是导致性别失衡的主要原因。

　　田见晖解释说，X染色体失活是雌性胚胎在早期发育中经历的表观修饰事件。如果这一机制被削弱，会导致雌性胚胎发育异常，进而导致性别失衡。

　　经过一系列研究，他们发现，X染色体失活机制与两个基因Xist和Rnf12有关。在此基础上进行功能性补偿实验，研究人员成功将体外受精小鼠出生时的雄性比例由57．17％校正到51．92％，接近正常范围。

　　田见晖说：“我们的研究不仅揭示了出生性别比例失衡的内在机制，并且通过针对性地调整体外受精的培养体系，解决了体外受精性别失衡问题。”

　　田见晖表示，体外受精技术还存在流产、低出生体重、出生缺陷等风险，他们的研究也为揭示这些问题的分子机制并进行预防提供了重要指引。

　　此前，猪牛等动物研究反复证实体外受精存在性别失衡问题。近年来，一些研究显示人类试管婴儿也存在这一问题。比如，澳大利亚和新西兰一项调查显示试管婴儿的男女比例为1．17：1，英国一项调查显示的比例为1．28：1。性别失衡一方面意味着胚胎发育存在缺陷，另一方面会对社会产生一系列影响。（完）

(责任编辑：李辉 UN659)
2016-03-08 10:00:41
新华社