三個爹娘試管嬰兒 mtDNA

2015.03.13

 三個爹娘試管嬰兒 mtDNA

今天是試管嬰兒一個重要里程碑的一天，
英國國會下議院在2/3表決通過重大法案，以382票贊成、128票反對，通過允許透過試管嬰兒製造擁有三個爸媽DNA的試管寶寶，
以防止母親經由有缺陷的粒線體DNA將重大的疾病傳染給下一代，
一旦再經過上議院通過，
英國將成為世界第一個擁有三個爹娘DNA合法國家，這使得美國有一定的壓力，在這一期的TIME雜誌提到：
美國人也應該得到三個爹娘的試管嬰兒技術並從中得到幫助病人好處，
粒線體是我們人體的能量來源，我們通常稱它為細胞的發電機，在人類所有的細胞內都有粒線體，
一旦基因缺陷它可能會產生一些能量的缺陷，
例如：肌肉萎縮症，或腦部中樞產生癲癇、中風、或認知衰退、心臟衰竭。
 
這種粒線體的缺陷會代代相傳，但粒線體是在細胞質裡面，
這樣說好了，比如說一顆雞蛋，遺傳爸媽特質的是在雞蛋的蛋黃，而粒線體的DNA則是在蛋白、蛋清裡面。
 
三個爹娘試管嬰兒的作法是，擁有粒線體缺陷的母親的卵子與父親結合成為受精卵，成為雙原核2PN之後，將捐卵者所提供的卵子，挖空卵房後再將成為雙原核受精卵注射到卵子中，也就是受精卵租房子住，受精卵住到另一個卵子中，意思就是住到雞蛋的蛋黃裡面，但裡面原先的蛋黃要先挖空。
 
因為蛋白裡面有捐卵者的粒線體DNA，也因此受精卵同時擁有受精卵夫婦及捐卵者的粒線體DNA，所以才有「三個爸媽試管寶寶」的說法。
 
在台灣，如果立法院沒有通過 「三個爸媽試管寶寶」法案，而病人又有這樣的疾病該怎麼辦？
還是有解決辦法，
1.借卵生子，因為這個疾病是在母親這邊，所以只要換一批卵子即可，整批換成˙捐卵者的卵子。
2.使用次世代定序NGS做胚胎著床前基因診斷，這可以偵測到哪顆胚胎的粒線體DNA mtDNA有問題，而植入沒有問題的健康的試管寶寶。
 
也就是說，台灣即便沒有通過這樣的法案，仍然在法律上、在醫學上可以解決這種因為粒線體DNA疾病所產生的可能生下發病下一代的可能性。
 
其實在2000年英國新堡中心的藤布爾就是這方面的研究先趨，他先把有缺陷的不孕症夫妻所結合成的雙原核注射到捐卵者的卵子中，但首先要把捐卵者的卵去核，也就是所謂的細胞核轉植。
 
可能你會擔心說，如果有3個爸媽那是不是會有捐卵者的DNA？其實，99.9％的遺傳物質仍然來自於爸媽(蛋黃)，只有0.1％是來自於捐卵者的DNA（蛋白)，所以你不用太擔心，這個小孩的身高、體重、膚色、性格、聰明才智都不會有所改變。
 
現在台灣即便沒有這個法案通過，我相信我們的立法院大概也沒有時間通過這種有新聞議題的法案，還是有辦法解決：
1.借卵生子
2.透過胚胎著床前基因診斷，但是一定要用次世代定序NGS，才有辦法去偵測到粒線體DNA疾病這樣一個缺陷。
 
目前市面上所有的胚胎切片PGS，使用基因晶片也好、使用qPCR也好、使用SNP也好，都沒有辦法偵測這個疾病，但目前台灣有沒有NGS PGS呢？
 
是有，但是還在實驗階段，費用也十分昂貴，大約需要50～60萬新台幣。
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Feb. 3, 2015
 
All new fertility methods sound crazy at first
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In a historic vote that rocked the world of fertility medicine Tuesday, British lawmakersapproved the use of a controversial IVF practice that would take genetic material from three people to create a single embryo.
The promising technique, which involves replacing the defective cellular material of a woman’s eggs with that from a healthy donor, aims to prevent patients from passing down crippling genetic diseases to their offspring. It also might hold the key to other groundbreaking applications, such as extending women’s fertility by rehabilitating old eggs.
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The decision is inspiring because members of Parliament chose science over a firestorm of often ill-informed debate questioning whether we’ve gone too far in experimenting with genetic engineering. Hopefully, they will motivate the U.S. Food and Drug Administration, which held public hearings on the topic last year but declined to move forward with human trials citing lack of safety data, to follow suit. New research published in the New England Journal of Medicine estimated that more than 12,000 women in the U. S. of childbearing age risk passing down such mitochondrial diseases, which have been linked to everything from poor growth, blindness, neurological problems and heart and kidney problems.
The world is right to be cautious about this latest mind-boggling advance in reproductive medicine. It does sound like science fiction: If you’re a woman who suffers from a mutation in her mitochondrial DNA—the part of our cells that generate energy—scientists can take your egg, extract the nucleus—the part containing your most important genetic instructions, such as hair and eye color—and insert it into a new egg that has been provided by another woman. (The nucleus would have already been removed from the donor egg.) This newly renovated egg is then fertilized by your partner’s sperm and implanted into your uterus. You carry on with your pregnancy, just like billions of women before you. (Another version of the technique switches out the nucleus of a newly fertilized egg.)
Have we pushed the boundaries too far in innovative baby-making? Think back to when critics charged that the inventors of in-vitro fertilization recklessly “played God” by daring to combine a sperm and an egg in a lab to create Louise Brown in 1978. Now some 5 million of the world’s babies have been conceived via IVF. But it’s one thing to get used to combining reproductive parts in a lab; it’s a lot less comfortable to imagine tinkering with those parts beforehand. In an open letter to the U.K. Parliament, Paul Knoepfler, stem cell and developmental biology researcher at the University of California Davis School of Medicine, warned that supporters “could well find themselves on the wrong side of history … with horrible consequences.”
 
Yet it’s important to understand that mitochondrial replacement isn’t genetic engineering run amok, cautions Debra Mathews of the Berman Institute of Bioethics at Johns Hopkins University. The mitochondrial energy-making material of an egg accounts for a mere 37 genes, compared to the nucleus, which contains about 23,000 genes. “No one is messing directly with genes,” she says. “Scientists are replacing damaged mitochondria with healthy mitochondria. It’s a specific technology for a specific application. We’re modifying eggs to avoid serious diseases.” So far, researchers haven’t attempted a pregnancy using the technique, but a studypublished in 2012 in Nature found that resulting embryos appeared to develop normally with the nucleus intact and did not contain any of the mutated mitochondria from patients’ previous eggs. And scientists at Oregon Health and Science University transferred the mitochondria between rhesus-monkey eggs and created four healthy monkey babies.
Yet determining when a technology is “safe” is especially challenging in fertility medicine because the only way to find out is to create another human. The FDA’s prudence is a welcome change from the early “wild west” days of reproductive medicine when many scientists “implanted and prayed” that their experiments wouldn’t lead to the “horrible consequences” Knoepfler is warning against. So far, we’ve been incredibly lucky.
We don’t want to risk holding up progress by being too cautious, especially when some 1,000 to 4,000 babies are estimated to be born every year with mitochondrial disease, according to the United Mitochondrial Disease Foundation.
Yet what should the threshold be? The FDA shut down other suchresearch being done more than a decade ago. Scientists at several fertility clinics were responsible for 30 pregnancies from eggs that had been injected with donor cytoplasm that contained mitochondria. The kids haven’t been tracked over the long term, and it’s unknown whether the procedure contributed to two cases of chromosomal abnormalities that resulted in one miscarriage and one abortion. And researchers at New York University’s Langone Medical Center tried a similar mitochondrial transfer techniqueusing younger eggs for three women in their 40s suffering from age-related infertility. Although the embryos developed naturally, none got pregnant. A Chinese team later used the NYU method to achieve a triplet pregnancy, but the patient lost the entire pregnancy after she tried to abort one fetus to give the other two a better chance of survival.
Let’s follow the British example and find the right balance between prudence and progress. “We’re at a stage when we can use these technologies to help all kinds of patients, and we have enough reassuring evidence that it’s safe,” says NYU’s Jamie Grifo, and author of the The Whole Life Fertility Plan. “It shouldn’t be taking this long to move forward.”