Primate Stem Cell Barrier Broken

Primate Stem Cell Barrier Broken

Embryonic stem cells derived from adult primate cells suggest humans may get their turn yet

 
THE RHESUS MONKEY has become the first primate to have adult cells cloned into embryonic stem cells.

Researchers report they have generated the first confirmed embryonic stem cells from an adult primate, suggesting that it may be only a matter of time (and eggs) before they perfect the same technique on humans.

Using a process called somatic cell nuclear transfer (SCNT), a team from Oregon Health & Science University (O.H.S.U.) in Portland implanted the contents of individual skin cells from adult male rhesus macaques into each of 304 macaque egg cells stripped of their genetic material. In two cases, according to the study, the hijacked eggs grew into early-stage embryos that yielded embryonic stem cell lines, indicating that the hosts successfully reprogrammed the skin cell DNA into an embryonic state.

The journal Nature published the findings online today, along with a separate genetic analysis corroborating the cloned nature of the cells.

"This unequivocally shows you can generate stem cells from primates, and we're primates," says stem cell biologist Robert Lanza, chief scientific officer of the Worcester, Mass., company Advanced Cell Technology, who was not involved in the research.

"It's a giant step toward showing that human therapeutic cloning is possible," he added, referring to the concept of creating stem cells matched to an individual's immune system to repair tissue damaged in spinal cord injuries and by diseases such as diabetes, Parkinson's and Alzheimer's.

Senior study author Shoukhrat Mitalipov calls the result a proof of concept. "I'm quite sure it will work in humans," he says, but notes that the process is still very inefficient. "Basically it comes [down] to how many eggs you would need to derive one embryonic stem cell line." (In this case, 152.)

Mitalipov says his goal is to engineer better primate models of human disease by cloning adult rhesus monkey cells that have been genetically altered to mimic neurological and other disorders that are otherwise difficult to study in living humans or other animals. He says that his team has yet to try to impregnate female monkeys with embryos derived using the new method.

A group from O.H.S.U. reported in 2000 that it had achieved a kind of primate cloning by splitting an eight-cell monkey embryo into four two-cell embryos, only one of which came to term. But researchers have struggled to clone nonhuman primates by SCNT, used in the 1997 cloning of Dolly the sheep.

After two earlier published attempts that led to early-stage embryos but not confirmed embryonic stem cells, Mitalipov and colleagues took steps to preserve a protein complex believed to help primate eggs restructure transplanted DNA, and employed a new imaging system to observe the egg's chromosomes directly instead of by staining them or using ultraviolet light, which might damage DNA.

The two newly reported cell lines developed into several types of tissue in culture dishes, including heart and brain, and when injected into mice generated teratomas (tumors made of the three embryonic tissue types). The cells had the genetic markers of clones, not of fertilized embryos or parthenotes, the latter of which derive only from the egg, according to the genetic analysis by researchers at Monash University in Australia.

Three teams of scientists reported earlier this year that they had directly reprogrammed adult mouse skin cells into embryonic cells, although the process involved viruses and cancer-causing genes.

In a commentary accompanying the new study, Dolly cloner Ian Wilmut and his co-worker Jane Taylor of the University of Edinburgh in Scotland wrote that "a modified approach to direct reprogramming…is likely to be the ultimate method of choice for producing human stem cells."

Lanza agrees but says that in the meantime SCNT remains a viable approach—although limited by the number of women willing to donate eggs to research.

Some scientists had proposed that SCNT might have hit a wall with primates, but Lanza says the new result shows that "primates are no different than other species. You just need to work out the unique biology and physiology." Meaning that humans could be next. 

Small planets forming in the Pleiades: astronomers

Small planets forming in the Pleiades: astronomers

Small planets forming in the Pleiades: astronomers An artist's rendering of what the environment around Pleiades star HD 23514 might look like as two planets collide. Small, rocky planets that could resemble the Earth or Mars may be forming around a star in the Pleiades star cluster, astronomers reported on Wednesday. REUTERS/ Gemini Observatory/Lynette R. Cook

WASHINGTON (Reuters) - Small, rocky planets that could resemble the Earth or Mars may be forming around a star in the Pleiades star cluster, astronomers reported on Wednesday.

One of the stars in the cluster, also known as the Seven Sisters, is surrounded by an extraordinary number of hot dust particles that could be the "building blocks of planets" said Inseok Song, a staff scientist at NASA's Spitzer Science Center at the California Institute of Technology.

"This is the first clear evidence for planet formation in the Pleiades, and the results we are presenting may well be the first observational evidence that terrestrial planets like those in our solar system are quite common," said Joseph Rhee of the University of California Los Angeles, who led the study.

There is "hundreds of thousands of times as much dust as around our sun," said Benjamin Zuckerman, a UCLA professor of physics and astronomy. "The dust must be the debris from a monster collision, a cosmic catastrophe."

The team used two telescopes to spot the dust, and report their findings in Astrophysical Journal.

Located about 400 light years away in the constellation of Taurus, the Pleiades is one of the best known star clusters and among the closest to Earth. A light-year is the distance light travels in a year, about 5.8 trillion miles.

"The cluster actually contains some 1,400 stars," said Song.

Song said the dust can accumulate into comets and small asteroid-size bodies, and then clump together to form planetary embryos, and finally full-fledged planets.

"In the process of creating rocky, terrestrial planets, some objects collide and grow into planets, while others shatter into dust; we are seeing that dust," Song said.

"Our observations indicate that terrestrial planets similar to those in our solar system are probably quite common," Zuckerman added.

Researchers have observed about 200 planets around stars outside our solar system but none are as small as Earth and just one, spotted earlier this year, appears potentially capable of supporting life.

Naked Trees Dominated Early Forests

Naked Trees Dominated Early Forests

Analysis of 385-million year-old fossils from upstate New York paint picture of Earth's first trees 

LEAFLESS CROWN: A reconstruction of an ancient tree from one of Earth's first forests reveals that the plants were topped with fronds and not leaves.

The crown of a prehistoric tree found in a sandstone quarry in Gilboa, N.Y., has shed light on the look of the world's earliest forests believed to have thrived during the Devonian period between 360 million and 397 million years ago.

The 2004 discovery of this 380-million year-old, six-foot uppermost portion of an ancient tree trunk allowed paleobotanists to create a composite picture of the entire plant when they put it together with fragments of a trunk found a the same site a year later and with tree stumps recovered more than 130 years ago in another rock quarry 10 miles away. The remains have been widely touted as "evidence of the Earth's oldest forest," according to a report published in this week's Nature.

"The basic point of this paper is, well, two things," says lead author William Stein, a biologist at the Binghamton University in New York State. "We now have clear evidence what these stumps really were," part of the class Cladoxylopsida believed to be related to modern-day ferns, and we also have "real strong evidence of the morphology of these forms."

From the fossil reconstruction, the team of scientists determined that a tree comprising all these parts could grow about 30 feet tall. According to Stein, the base would have been massive—on the order of 2.5 feet in diameter—with a large, single trunk and longitudinal ridges (probably part of the tree's vascular system), topped by a leafless crown of a material resembling fronds on ferns and palms. These fronds apparently had a structure somewhat similar to fingers protruding from the palm of a hand, with multiple branches that split into thinner branchlets. These wispy appendages would have done the work of photosynthesis for the tree and also have borne the spores with which the plant reproduced.

The researchers, including Christopher Berry, a geoscientist from Cardiff University in Wales, and paleontologists from the New York State Museum were able to classify the tree crown into the genus Wattieza, Berry says, "because the very small leaflike appendages have distinctive characteristic recurved tips," meaning they flop back toward the trunk of the tree. Berry has studied other ancient specimens from this genus in Belgium and Venezuela. Stein says the team is "sticking with just the genus," as far as classification goes, because "we can't distinguish species from genera with the fragments we have."

By piecing together the fragments, the team was able to get an idea of what a forest ecosystem might have looked like 360 million years ago. Stein estimates these Wattieza trees would have been "fairly closely spaced," about three to 16 feet apart, and that they would have dropped a load of litter from their branches onto the forest floor. Amongst these trees were likely smaller plants and shrubs and, by the late Devonian, precursors of modern-day conifers called Archaeopteris, as well. Arthropods, which live on detritus, such as millipedes, centipedes and now-extinct spiderlike organisms, may have lived below these trees, which likely let more sunlight through than modern-day counterparts, because their branch structures did not fan out as far and were ascendant, forming a gobletlike shape.

In an editorial that accompanied the paper, Brigitte Meyer-Berthaud and Anne-Laure Decombeix, paleobotanists at the French Agricultural Research Center for International Development and the University of Montpellier in France, respectively, note that the Gilboa tree seemed to be constructed to optimize "mechanical stability and reproduction." In contrast to modern-day trees, which require more complex vascular systems to grow to more hulking sizes, they write: "The Gilboa tree represents an economical alternative where, beyond the necessary investment in spores to ensure reproduction, the products of photosynthesis were mainly devoted to vertical growth of the trunk."

Berry notes that the rise of forests with trees like the Gilboa caused the removal of carbon dioxide from the air and temperatures to drop, creating climates like those experienced today. The drop in carbon dioxide levels, he surmises, likely led to the evolution of flat leaves on trees to attract and retain more of the gas, which plants need for photosynthesis. Up next, he says: research will focus on "the internal structure of the plants to work out how they grew" as well as "how they functioned physiologically, particularly the relationship with atmospheric carbon dioxide." 

Methane-Guzzling Bacteria Thrive in Bubbling Mud Pots

Methane-Guzzling Bacteria Thrive in Bubbling Mud Pots

Tiny bacteria hiding out in a witches' brew of bubbling mud not only thrive in the searing-hot slurry but also chow down on its methane.

Two papers published online this week in the journal Nature describe these mud-loving microbes, the hardiest bacteria identified to date. Found living in mud volcanoes and other geothermal hideouts, the bacteria feast on methane, considered the second most abundant greenhouse gas behind carbon dioxide. While carbon dioxide makes up the majority of greenhouse gases in the atmosphere, methane traps about 20 times more heat and so is a critical global warmer.

And so in addition to expanding the conditions where one might find extremophiles, the discovies have implications for the global methane cycle. These specialized bacteria could help to suck up methane from the Earth's crust that would otherwise spew into the atmosphere.

Mud pits

The hellish temperature and pressure conditions beneath the Earth's surface can turn rock into goopy mud, which along with a soup of gases (including methane) and other chemicals, can stream gently (or eject violently) from surface vents called fumaroles. These "mud volcanoes" support a range of conditions, with some areas reaching temperatures of 158 degrees Fahrenheit (70 degrees Celsius) and pH's close to that of battery acid.

Mike Jetten of Radboud University Nijmegen in the Netherlands and his colleagues discovered a bacterium dubbed Acidimethylosilex fumarolicum in a fuming vent in the Solfatara volcanic area near Naples, Italy.

Lab experiments revealed A. fumarolicum could grow at a very acidic pH, as low as 0.8, and at a temperature of about 130 degrees F (55 degrees C), consuming methane for energy. (The pH scale ranges from 0 to 14, from acidic to basic. Water has a neutral pH of 7; battery acid and hydrochloric acid have pH's below 1, and the pH of household bleach can reach about 12.5.)

The bacteria can use oxygen too, but their muddy habitat is nearly devoid of such luxuries, making for a stressful life.

"The only oxygen the bacteria get is from the bubbling of the volcano, which puts air into the liquid," Jetten told LiveScience. "They are always stressed for air, so they're always living under oxygen limitation. The ecosystems themselves are completely devoid of oxygen, so every molecule that enters is immediately consumed."

Another extreme-loving methane consumer was discovered at Hell's Gate (Tikitere) in New Zealand. Peter Dunfield of GNS Science, a New Zealand government-owned research organization, and his colleagues found that Methylokorus infernorum could thrive at a pH as low as 1.5 and temperatures of about 140 degrees F (60 degrees C).

Methane munchers

Both bacterial finds top the hardiest methane munchers identified to date. Until now, the lowest pH found to support "methanothrophs" was in peat bogs, where bacteria thrived down to a pH of about 4.

How exactly the bacteria are able to withstand the harsh habitats while consuming methane is still a bit of a mystery. Genetics do play a role. The research teams analyzed the genomes for the two bacterial species, finding some novel systems that likely allow the methane-consuming microbes to thrive in harsh conditions.

"The new bacterium has a completely new repertoire of genetic elements to do this job," Jetten said of A. fumarolicum. "And it's also quite different from the known methane-oxidizing bacteria." 

Newborns Can Bond to a "Mother" from a Different Species

Newborns Can Bond to a "Mother" from a Different Species

Often all you need to do is stick around to convince a baby animal that you are its mother

 
WHO'S YOUR MOMMA?: Lacking an appropriate mother figure, animals like ducks, pigs and even potentially humans can bond to a parent from an entirely different species.

If you saw Winged Migration or Fly Away Home, which delivered the first true bird's-eye views of the world, you may have wondered how they got those wild geese to wear tiny camcorders on their heads. In fact, the cameras were in ultralight aircraft, which the birds accompanied—by choice. The crafty filmmakers took advantage of one of Mother Nature's tricks called imprinting: If you had grown up thinking your mom was inside that noisy plane—or was that noisy plane—you'd have gladly tolerated it, too.

In the mid 1930s German ethologist Konrad Lorenz popularized filial imprinting, the process by which a newborn animal learns to recognize the unique characteristics of its parent, typically its mother. This phenomenon was termed imprinting (translated from the German word prägung) by Lorenz's mentor, Oskar Heinroth, who believed that the sensory stimulus encountered by the hatchling was immediately, and irreversibly, "stamped" onto the animal's brain. Lorenz demonstrated this with his famous goslings, which had spent their first hours of life with him and subsequently followed him everywhere; as adults they preferred the company of humans over fellow avians.

Lorenz's little geese are the most well-known example of cross-species imprinting, but it can occur between other species, too. Any animal born relatively independent—not entirely relying on a parent to provide food or protection, so-called precocial species—needs to be able to discriminate between its parents and other members of its (or other) species, lest they get lost or attacked. A gosling, or other precocial animal, accomplishes this with an instinct to approach and follow a moving target after birth as well as a vague preference for objects that have particular features, such as a head and neck. In the wild, this guides a gosling to favor its mother.

In the absence of an appropriate stimulus, however, practically any object can become a source of comfort to the newborn. After one to two hours of exposure to the target, a gosling will have formed a strong preference, avoiding novel objects and showing signs of distress when the "imprinted" object is removed.

No explicit reward, such as food or warmth, is needed. In fact, some research suggests that aspects of the object itself—its shape or movements, for example—may have the capacity to stimulate endogenous opioid (endorphin) production in a newborn's brain: hence, instant comfort.

"There have been a lot of questions about whether [precocial birds] actually do have a naive preference for their own species," explains Utrecht University zoologist Johan Bolhuis. "They probably don't."

This may be true for humans as well. Cognitive neuroscientist Mark Johnson of Birkbeck, University of London, who worked with Bolhuis on chick imprinting and now studies this phenomenon in human infants, found that within minutes of birth babies show a preference for facelike over nonfacelike stimuli. And, after visual exposure to their own mothers, newborns show a strong preference for their moms' faces, likely reinforced by the flurry of activity, including protein synthesis and changes in synaptic transmission, that occurs in the brain during imprinting, as shown by University of Cambridge neuroscientist Gabriel Horn.

Because recognizing and bonding with a parent are more dependent on exposure and learning than on a genetically programmed response, it's conceivable that any animal exposed exclusively to a member of a different species might happily call it mom—witness the children purportedly raised by wolves in India and the orphaned chipmunk adopted by Buffy the Chihuahua as well as a tiger in Thailand's Sriracha Tiger Zoo suckling piglets—after being suckled as a cub herself by, naturally, a pig. Without such a promiscuous capacity for trust, an infant whose mother abandoned it or died shortly after its birth would face certain doom if it were unable to swap preferences for an adoptive parent.

Despite its initial survival value, however, imprinting on something other than your kind can become problematic when you reach sexual maturity. Though it operates by different mechanisms, sexual imprinting—the process by which an animal learns to recognize an appropriate mate—is also strongly linked to early parental experience.

In 1976 there were about 100 whooping cranes (Grus americana), the tallest North American bird, left in the world. Conservationists tried to forestall their extinction by breeding cranes in captivity and reintroducing them into the wild, relying on one adult female to continue her rare genetic lineage. Hatched and hand-reared in the San Antonio Zoo, "Tex" wanted nothing to do with the handsome male whoopers she later met; she performed her elaborate mating dance solely for her human keepers. Only after George Archibald, one of the world's leading crane experts, literally moved in with Tex for several months, formed a pair-bond with her, and joined her repeatedly in the species-specific courting ritual, did she lay the first egg of her life at age 10.

Such sexual confusion also shows up in sheep and goats, which are, along with most ungulates, precocial species. When Keith Kendrick of the Babraham Institute in Cambridge, England, and his colleagues cross-fostered newborn kids and lambs with mothers from the other species, the infants formed strong bonds with their foster moms. The goats grew up thinking they were sheep, and vice versa.

And even though mammals are thought to exhibit more behavioral flexibility than geese, when two same-species siblings were raised together by a mother of the other species, the offspring's sexual preference in adulthood was for their foster mother's species. Further, males that had been cross-fostered preferred to mate with females of their moms' species even after living exclusively with their genetic species for three years.

Nevertheless, it remains unclear whether all parents (or foster parents) become "imprinted" on their infants' brains in a manner similar to that seen in precocial birds. In the meantime, try to avoid newly hatched chicks—unless you're ready to take on the responsibilities of motherhood.