Scientists Take Step Toward Creating Artificial Embryos
Experts said the results suggested human embryos could be created in a similar way in future — a step that would allow scientists to use artificial embryos rather than real ones to research the very earliest stages of human development
An international team of scientists has moved closer to creating artificial embryos after using mouse stem cells to make structures capable of taking a crucial step in the development of life.
Experts said the results suggested human embryos could be created in a similar way in future — a step that would allow scientists to use artificial embryos rather than real ones to research the very earliest stages of human development.
The team, led by Magdalena Zernicka-Goetz, a professor at Britain’s Cambridge University, had previously created a simpler structure resembling a mouse embryo in a lab dish. That work involved two types of stem cells and a three-dimensional scaffold on which they could grow.
But in new work published Monday in the journal Nature Cell Biology, the scientists developed the structures further — using three types of stem cells — enabling a process called gastrulation, an essential step in which embryonic cells begin self-organizing into a correct structure for an embryo to form.
“Our artificial embryos underwent the most important event in life in the culture dish,” Zernicka-Goetz said in a statement about the work. “They are now extremely close to real embryos.”
She said the team should now be better able to understand how the three stem cell types interact to enable embryo development. And by experimentally altering biological pathways in one cell type, they should be able to see how this affects the behavior of the other cell types.
“The early stages of embryo development are when a large proportion of pregnancies are lost and yet it is a stage that we know very little about,” said Zernicka-Goetz.
“Now we have a way of simulating embryonic development in the culture dish, so it should be possible to understand exactly what is going on during this remarkable period in an embryo’s life, and why sometimes this process fails.”
Christophe Galichet, a senior research scientist at Britain’s Francis Crick Institute who was not directly involved in this work, agreed that the results held promise.
“While [this study] did not use human stem cells, it is not too far-fetched to think the technique could one day be applied to studying early human embryos,” he said in an emailed comment. “These self-assembled human embryos would be an invaluable tool to understand early human development.” (VOA)
Off the shores of Newfoundland, Canada, an ecosystem is unraveling at the hands (or pincers) of an invasive crab.
Some 1,500 kilometers (930 miles) to the south, the same invasive crab — the European green crab — is helping New England marshes rebuild.
Both cases are featured in a new study that shows how the impacts of these alien invaders are not always straightforward.
Around the world, invasive species are a major threat to many coastal ecosystems and the benefits they provide, from food to clean water. Attitudes among scientists are evolving, however, as more research demonstrates that they occasionally carry a hidden upside.
“It’s complicated,” said Christina Simkanin, a biologist at the Smithsonian Environmental Research Center, “which isn’t a super-satisfying answer if you want a direct, should we keep it or should we not? But it’s the reality.”
Simkanin co-authored a new study showing that on the whole, coastal ecosystems store more carbon when they are overrun by invasive species.
Good news, crab news
Take the contradictory case of the European green crab. These invaders were first spotted in Newfoundland in 2007. Since then, they have devastated eelgrass habitats, digging up native vegetation as they burrow for shelter or dig for prey. Eelgrass is down 50 percent in places the crabs have moved into. Some sites have suffered total collapse.
That’s been devastating for fish that spend their juvenile days among the seagrass. Where the invasive crabs have moved in, the total weight of fish is down tenfold.
The loss of eelgrass also means these underwater meadows soak up less planet-warming carbon dioxide from the atmosphere.
In Cape Cod, Massachusetts, the same crab is having the opposite impact.
Off the coast of New England, fishermen have caught too many striped bass and blue crabs. These species used to keep native crab populations in check. Without predators to hold them back, native crabs are devouring the marshes.
But the invasive European green crab pushes native crabs out of their burrows. Under pressure from the invader, native crabs are eating less marsh grass. Marshes are recovering, and their carbon storage capacity is growing with them.
Simkanin and colleagues compiled these studies and more than 100 others to see whether the net impact on carbon storage has been positive or negative.
They found that the ones overtaken by invasive species held about 40 percent more carbon than intact habitats.
They were taken by surprise, she said, because “non-native species are thought of as being negative so often. And they do have detrimental impacts. But in this case, they seem to be storing carbon quicker.”
At the Smithsonian Environmental Research Center where she works, the invasive reed Phragmites has been steadily overtaking a marsh scientists are studying.
Phragmites grows much taller, denser and with deeper roots than the native marsh grass it overruns.
But those same traits that make it a powerful invader also mean it stores more carbon than native species.
“Phragmites has been referred to as a Jekyll and Hyde species,” she said.
Not all invaded ecosystems stored more carbon. Invaded seagrass habitats generally lost carbon, and mangroves were basically unchanged. But on balance, gains from marsh invaders outweighed the others.
Not a lot of generalities
To be clear, Simkanin said the study is not suggesting it’s always better to let the invaders take over; but, it reflects an active debate among biologists about the role of invasive species in a changing world.
“One of the difficult things in the field of invasion biology is, there aren’t a lot of generalities,” said Brown University conservation biologist Dov Sax, who was not involved with the research. “There’s a lot of nuance.”
The prevailing view among biologists is that non-native species should be presumed to be destructive unless proven otherwise.
When 19 biologists wrote an article in 2011 challenging that view, titled, “Don’t judge species on their origins,” it drew a forceful rebuke from 141 other experts.
Sax said the argument is likely to become more complicated in the future.
“In a changing world, with a rapidly changing climate, we do expect there to be lots of cases where natives will no longer be as successful in a region. And some of the non-natives might actually step in and play some of those ecosystem services roles that we might want,” he said.
“In that context, what do we do? I definitely don’t have all the answers.” (VOA)