Scientists Discover Mechanism That Gives Shape to Life

First time accepted submitter mcswell writes "Daniël Noordermeer and Denis Duboule, two researchers at Ecole Polytechnique Fédérale de Lausanne and the University of Geneva claim to have discovered how vertebrae get built in sequence in embryos (and by extension, how ribs, arms and so forth wind up in the right place). The story is that the DNA strands contain a linear series of HOX genes, and that the strands slowly unwind over a period of two days, successively exposing each HOX gene, thereby allowing it to be transcribed to form the segments of the vertebra. Snakes, it seems, have a defect that causes the system not to shut down; eventually it 'runs out of steam.' The same process is said to apply in many invertebrates, including worms (presumably segmented worms) and insects."

Comments

For the non-molecular biologist among us

[GreatBunzinni]

What a Hox gene might be

Re:Precision like a Swiss watch...

[morgaen]

A watchmaker made of tides and magnets?

Re:What the HOX?

[maxwell demon]

Now if only we can find the gene that causes ignorance.

I think that's related to the HOAX gene. :-)

Re:Precision like a Swiss watch...

[Teun]

It can also point to a system where from many divergences the slight failures land by the wayside and the successful evolve to sustainable species.

I think I'll call it Evolution.

Hox genes are the basic sequence of embryogenesis

[wombatmobile]

TFA is saying that organisms are built in slices, from the tip of the head down to the tip of the tail. These slices are activated in order, from first to last. It is the same in fruit flies, worms, whales, dogs, monkeys, deer and humans. The HOX genes control the basic sequence, like a player piano roll or a series of punch cards.

The reason we get so many different organisms, like whales, fruit flies and elephants, is evolution.

Procrastination gene

[mrops]

The gene that controls procrastination

Re:

[taiwanjohn]

No, it merely affirms that all the other less precise mechanisms did not survive.

It's in Science 'cuz now we can SEE it?

[enderwig]

A caveat as I write this critique, I have only read the linked article and the abstract of the original scientific article, not the full Science article.
Also, I'm a Ph.D. in Developmental Biology from 2000.

If unwinding the super-coiled DNA is considered the chronometer for embryonic segmentation, what makes the DNA unwind at such a specific time? I'm not sure how much new light is shed by this work. We've known for >20 years that transcription factors help "open" DNA for the transcription process. We've also known for >20 years that HOX genes in their clusters are the masters of structural differentiation. Put these two facts together and we can see it should be obvious that the HOX genes need to be "opened" sequentially.

  In the end, we are left with the still burning question of "What controls the HOX genes and their clusters?"

Re:It's in Science 'cuz now we can SEE it?

[Suiggy]

According to a purvey of information posted on Wikipedia, Hox transcription factor proteins produced from the expression of the Hox genes activate the transcription of specific genes while at the same repressing the expression of other genes. Hox proteins are themselves regulated by other genes, such as gap genes and pair-rule genes, and there's a transcription factor cascade which controls the whole process for each stage, which has been explored in depth. Apparently, there's been a lot of work in this field since 2000.

http://en.wikipedia.org/wiki/HOX_genes

Re:It's in Science 'cuz now we can SEE it?

[Samantha Wright]

That may sound novel and exciting, but what you've described is how every transcription factor works. enderwig was making a point about the timing mechanism. If you leave a transcription-driven genetic circuit to keep its own clock without any assistance, it generally does a pretty bad job. There has to be something fairly elaborate guiding the chromatin unwinding.

Re:Precision like a Swiss watch...

[Anonymous Coward]

Something this complex can't just "happen by accident"

If there's an omnipotent, omniscient creator of the world, then nothing can "happen by accident." Ergo, in such a universe you would have no means to distinguish accident from non-accident.

Snakes

[TeknoHog]

The sinuous body of the snake is a perfect illustration. A few years ago, Duboule discovered in these animals a defect in the Hox gene that normally stops the vertebrae-making process. “Now we know what’s happening. The process doesn’t stop, and the snake embryo just keeps on making vertebrae, all identical, until the process just runs out of steam.”

Looks more like a feature than a bug to me. Another fine example of evolution by mutations.

Re:Snakes

[Anonymous Coward]

The real amazing discovery is that snakes run on steam!

Re:Snakes

[Arancaytar]

They can't. You're probably thinking of worms.

The only vertebrate with a (very limited) form of limb regeneration is the salamander, and that's an amphibian, not a reptile like the snake.

Re:Macro and micro

[Samantha Wright]

That excuse falls down fast when you look at the genomes themselves. It's very obvious where and how the DNA has mutated, even over hundreds of millions of years. I don't mean to pick on you so much as give you ammunition with which to fire back.

Re:HOTAIR?

[Samantha Wright]

Absurd names are common in molecular biology. Here is the usual example.

Re:Snake?

[Samantha Wright]

It would either be short and fat, or dead because there wouldn't be enough room for its organs to grow. Either way, it wouldn't slither very well, and would be at something of a disadvantage.

The use of the word "defect," as you can probably already imagine, is a very biased way of looking at things and will probably do more harm than good. Although, of course, at the time the mutation first appeared, when snakes still had non-vestigial limbs, it probably was at least partially something of an inconvenience.