Re: Chicken embryo grows dino-snout

[Jura <pristichampsus@yahoo.com>]

Newscientist apparently want to be annoying and insist on registration just to 
read their articles. It's free, but pointless. Below is the article in its 
entirety:

*crosses fingers and hopes the truncation demon is sleeping*

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Reverse evolution: Chicken revisits its dinosaur past 17 August 2011 by Sujata 
Gupta


Evolution has been rewound to create a "snouted" chicken. That means we might 
also be able to fast-forward it to create the animals of the future ARHAT 
ABZHANOV cuts a square hole in  the shell of a chicken egg, drops in a small 
gelatinous bead and watches the embryo develop. By day 14, the chick has formed 
not a beak but something more snoutish - a feature, he says, "modern birds have 
not seen since the Cretaceous". Abzhanov has rewound evolution. Chickens share 
a common ancestor with alligators and are descended from dinosaurs, raising the 
question of how they and other birds switched from snouts to beaks. Because 
chick and gator embryos start out looking strikingly similar, Abzhanov, an 
evolutionary biologist at Harvard University, suspected the key might be found 
in developing embryos. In his open-egg experiment he tweaked a few of the 
embryo's genes to make them behave more like identical genes do in an alligator 
embryo.

If rewinding evolution has a certain Frankenstein-esque quality, the opposite 
is even more intriguing. Fast-forwarding evolution to create the chickens of 
the future may also lie within grasp. And that, in theory, could lead to the 
creation of species better equipped to handle a changing climate.Mounting 
evidence shows that small modifications in when and where genes are switched on 
are all that's necessary to trigger dramatic shifts in anatomy. These changes 
can lead to the appearance of beaks, turtle shells and jaws (see "Qucks and 
duails"). Generally, the genes that control these major anatomical changes 
produce signalling molecules. In a developing embryo, these switch on genes 
controlling the forma
 limbs, organs and facial features. Other genes dictate where the molecules are 
produced and therefore where they take effect, ensuring that embryos don't grow 
digits in the wrong places, misshapen bones or an extra pair of
 eyes.Abzhanov's "snouted" chicken provides a striking demonstration of just 
how easy it can be to provoke major evolutionary changes, says Craig Albertson, 
a developmental biologist at the University of Massachusetts in Amherst. Before 
such experiments were possible, explanations for how creatures evolved "relied 
on the fossil record, which is incomplete, and mathematical modelling, which is 
boring".

So how did he do it? Abzhanov started by trying to pinpoint the gene changes 
that led to the myriad beak shapes of Galapagos finches. In 2004, he showed 
that all the finches share a handful of genes crucial to beak development, but 
instructions for the signalling molecules they control vary from bird to bird 
(Science, vol 305, p 1462). Abzhanov realised that a similar process might 
underlie the much bigger evolutionary shift from snouts to beaks.The tip of an 
alligator snout is made of a separate set of paired bones called the 
premaxillary, but in birds, these have fused with the main of the upper jaw to 
form a single, sharp bone.
Abzhanov scanned signalling molecules in alligator and chick embryos and found 
that two of them - known as sonic hedgehog and fibroblast growth factor 8 - 
show up before the snout and beak form. In gators, however, the molecules were 
only present along the sides of the face. Chicks express them both at the sides 
and centre of the developing face. What would happen, he wondered, if he turned 
that central expression off?

He developed a gel bead full of proteins that stick to the signalling molecules 
and deactivate them. As the molecules arrived at the centre of the embryonic 
chick face - around day 5 - Abzhanov added his bead to the mix. Sure enough, 
the chicks developed paired bones. "It looks exactly like a snout looks in an 
alligator [at this stage]," says Abzhanov, who presented his findings on 23 
July at the Jackson Laboratory in Bar Harbor, Maine. Ethics regulations mean no 
such eggs can be hatched.

Long term Abzhanov, dreams of turning chickens back into Maniraptora, small 
dinosaur
10,000 species of birds around today. Others have similar musings. 
Palaeontologist Jack Horner described the basic principles in a book he 
co-wrote with James Gorman, How to Build a Dinosaur (Dutton Books, 2009), and 
regularly speaks of a future "chickenosaurus". "We are interested in finding a 
way to extend the tail and create a hand in the chicken," Horner told New 
Scientist, but would not elaborate.The realisation that all it takes to create 
novel traits is a little genetic fine-tuning raises the possibility of 
engineering those shifts ourselves. Could we build the creatures of the future?

To a degree, we are already doing that, says Albertson. He and others are 
crossing closely related species - those that could conceivably pair on their 
own - and studying the resulting genetic changes. Sometimes those crosses 
result in novel creatures. For instance, Albertson crossed blue cichlid fish 
from neighbouring but separate populations and was surprised to find some of 
the offspring were red. He is trying to identify the genes and molecules 
involved, and says there is a possible advantage to the change. Some lakes that 
are home to cichlids are becoming increasingly murky, making it difficult for 
males to attract females with their colourful scales. Could it be that the 
bright red fish might have the edge, allowing the species to survive a more 
polluted world?

Amplifying the changes in the lab to create say, a fluorescent fish, may still 
be some way off, says Richard Schneider, of the University of California at San 
Francisco. So far, there are no ways to turn signalling pathways on; we can 
only rewind, not fast-forward evolution.Understanding these subtleties could 
have a huge impact on medicine. Many developmental abnormalities - cleft palate 
for instance - arise from changes in gene signalling. Could we tweak them in a 
developing embryo? "I can envision a day when we eliminate such defects in the 
womb," says Jill Helms, a stem cell biologist at Stanford University in 
Califorina.


Qucks and duails
______________
ecies as dissimilar as flies and humans share most of the same DNA. What could 
possibly trigger the huge differences in body structures? The first real clue 
emerged in the late 1970s, when Edward Lewis and colleagues discovered genes in 
the fruit fly that are now known to control development in all animals. 
Specifically, Lewis found that genes in the "bithorax complex" give rise to 
flies' body segments. By tweaking them, Lewis grew a mutant fruit fly with an 
extra segment - giving them an extra pair of wings. Since then, Richard 
Schneider and Jill Helms have crossed quails and ducks to isolate the genes 
responsible for developing the beak. When they transplanted the cells that give 
rise to beaks from one bird to the other, they swapped beaks. Quails grew wide 
bills and ducks grew pointy little quail beaks - the team had made qucks and 
duails. That suggested the cells were pre-programmed to build a specific beak 
and were
 simply following instructions in the host body. This led to the realisation 
that key evolutionary stages may have happened when changes in existing genes 
switched on new pathways - a theory Scott Gilbert, an evolutionary 
developmental biologist at Swarthmore College in Pennsylvania, all but 
confirmed with his work in turtles. Gilbert showed that turtles had tapped into 
an ancient evolutionary pathway that directed the fgf10 molecule - which helps 
form limbs in other animals - to their skin. In effect, turtles flipped their 
ribcage inside out to produce a shell. "A small gene change," says Gilbert, 
"can give you birth defects or evolution."