Hannah Devlin “Woolly mammoth on verge of resurrection, scientists reveal” https://www.theguardian.com/science/2017/feb/16/woolly-mammoth-resurrection-scientists
約4000年前に絶滅したされるケナガマンモス*1を「遺伝子編集」技術によって復活させるというハーヴァード大学のプロジェクト。正確に言えば、長い毛、小さな耳、寒さに適合した血液などのケナガマンモスの特徴を有した亜細亜象。２年以内に可能なのだという。
Speaking ahead of the American Association for the Advancement of Science (AAAS) annual meeting in Boston this week, the scientist leading the “de-extinction” effort said the Harvard team is just two years away from creating a hybrid embryo, in which mammoth traits would be programmed into an Asian elephant.“Our aim is to produce a hybrid elephant-mammoth embryo,” said Prof George Church*2. “Actually, it would be more like an elephant with a number of mammoth traits. We’re not there yet, but it could happen in a couple of years.”
The creature, sometimes referred to as a “mammophant”, would be partly elephant, but with features such as small ears, subcutaneous fat, long shaggy hair and cold-adapted blood. The mammoth genes for these traits are spliced into the elephant DNA using the powerful gene-editing tool, Crispr.
Until now, the team have stopped at the cell stage, but are now moving towards creating embryos – although, they said that it would be many years before any serious attempt at producing a living creature.
“We’re working on ways to evaluate the impact of all these edits and basically trying to establish embryogenesis in the lab,” said Church.
Since starting the project in 2015 the researchers have increased the number of “edits” where mammoth DNA has been spliced into the elephant genome from 15 to 45.
“We already know about ones to do with small ears, subcutaneous fat, hair and blood, but there are others that seem to be positively selected,” he said.
このプロジェクトの前提としての「遺伝子編集」技術の発展；
The woolly mammoth roamed across Europe, Asia, Africa and North America during the last Ice Age and vanished about 4,000 years ago, probably due to a combination of climate change and hunting by humans.
Their closest living relative is the Asian, not the African, elephant.
このプロジェクトに対する「倫理的懸念」；
“De-extincting” the mammoth has become a realistic prospect because of revolutionary gene editing techniques that allow the precise selection and insertion of DNA from specimens frozen over millennia in Siberian ice.Church helped develop the most widely used technique, known as Crispr/Cas9, that has transformed genetic engineering since it was first demonstrated in 2012. Derived from a defence system bacteria use to fend off viruses, it allows the “cut and paste” manipulation of strands of DNA with a precision not seen before.
プロジェクトに対する他の懐疑的な見解としては、
Matthew Cobb*3, professor of zoology at the University of Manchester, said: “The proposed ‘de-extinction’ of mammoths raises a massive ethical issue – the mammoth was not simply a set of genes, it was a social animal, as is the modern Asian elephant. What will happen when the elephant-mammoth hybrid is born? How will it be greeted by elephants?”Church also outlined plans to grow the hybrid animal within an artificial womb rather than recruit a female elephant as a surrogate mother - a plan which some believe will not be achievable within the next decade.
“We hope to do the entire procedure ex-vivo (outside a living body),” he said. “It would be unreasonable to put female reproduction at risk in an endangered species.”
He added that his lab is already capable of growing a mouse embryo in an artificial womb for 10 days - halfway through its gestation period.
“We’re testing the growth of mice ex-vivo. There are experiments in the literature from the 1980s but there hasn’t been much interest for a while,” he said. “Today we’ve got a whole new set of technology and we’re taking a fresh look at it.”
“Church’s team is proposing to rear the embryo in an ‘artificial womb’ which seems ambitious to say the least – the resultant animal would have been deprived of all the pre-birth interactions with its mother,” said Cobb.
Tori Herridge*4 “Mammoths are a huge part of my life. But cloning them is wrong” https://www.theguardian.com/commentisfree/2014/nov/18/mammoth-cloning-wrong-save-endangered-elephants
彼女は倫敦自然史博物館*5の古生物学者。パラグラフをひとつ切り取っておく；
さて、この報告が行われた米国科学振興協会（AAAS）*6の年次総会の周辺では、20日にはトランプ政権の科学政策に反対する、AAASのCEOも参加しての科学者たちによるデモが行われたのだった；
Because by bringing back the woolly mammoth, we could restore the ecosystem of the mammoth steppe and potentially stabilise the tundra terrain in the high Arctic? The idea being that this would mitigate the risk of permafrost melt, and the release of huge amounts of methane gas stored there, which would be bad news for our already warming planet. The problem here is that we don’t yet fully understand the role of the woolly mammoth as an ecosystem engineer, and it is unclear still whether the mammoth steppe disappeared as a result of the loss of the mammoth or whether the mammoth disappeared because its habitat was lost, along with its ice age world. It’s a big gamble to put your climate-change mitigation hopes on a herd of woolly mammoths – and if it did work, it would require numbers in the hundreds of thousands to have an effect. That’s going to take a long time, and a lot of surrogate elephant mums, to achieve. And have you seen the rate at which climate change seems to be progressing?
Hannah Devlin and Alan Yuhas “'Science for the people': researchers challenge Trump outside US conference” https://www.theguardian.com/us-news/2017/feb/19/epa-trump-boston-science-protest
*1:See eg. 「ケナガマンモス」http://www.zetsumetsudoubutsu.com/woolly_mammoth.php 東海大学自然史博物館「展示解説：ケナガマンモス」http://www.sizen.muse-tokai.jp/collect/2002/e_2f/mmmth.html https://en.wikipedia.org/wiki/Woolly_mammoth
*2:http://arep.med.harvard.edu/gmc See eg. https://en.wikipedia.org/wiki/George_M._Church
*3:See eg. https://www.research.manchester.ac.uk/portal/cobb.htmlhttps://www.research.manchester.ac.uk/portal/cobb.html
*5:https://www.theguardian.com/culture/natural-history-museum
*6:http://www.aaas.org/ See eg. https://en.wikipedia.org/wiki/American_Association_for_the_Advancement_of_Science https://ja.wikipedia.org/wiki/%E3%82%A2%E3%83%A1%E3%83%AA%E3%82%AB%E7%A7%91%E5%AD%A6%E6%8C%AF%E8%88%88%E5%8D%94%E4%BC%9A
