Horizontal gene transfer in vertebrates

[Moontanman]

Horizontal gene transfer between higher animals has been thought to be rare, i remember reading someplace many years ago about turtle and rabbit genes being mixed by gene transfer, the kicker was of course the tale of the race between the tortoise and the hare. This article would at least seem to indicate that such gene transfer is not quite as rare as first assumed. i thought the transfer between cow and snake genomes was particularly interesting since one of the tales i grew up with involved snakes milking cows.

 

http://www.the-scientist.com//?articles.view/articleNo/33829/title/DNA-Jumps-Between-Vertebrates/

[CarbonCopy]

How does gene transfer work ?

[Moontanman]

How does gene transfer work ?

 

 

I am not sure, the article negated to lay out a possible method of this occurring. Some sort of Virus transfer is the first thing that comes to my mind....

[overtone]

Clearly most snake and cow genes do not jump around like that. So one of the lessons, if this checks out, is that code set up to jump more easily may be significantly more likely to jump spontaneously than the calculated average stretch of code - i.e. it may actually happen, on a human life scale.

[imatfaal]

Clearly most snake and cow genes do not jump around like that. So one of the lessons, if this checks out, is that code set up to jump more easily may be significantly more likely to jump spontaneously than the calculated average stretch of code - i.e. it may actually happen, on a human life scale.

Although an alternative is that all sections can jump around - but other areas are necessarily highly preserved and a horizontal transfer will be weeded out at some point from the rna transcriptase nuclear level to the non-viability of offspring

[CharonY]

The article describes retrotransposons as a source of horizontal gene transfer, something that has e.g. also been described in Drosophila. The actual mechanism is still unknown, but hypotheses include parasites as vectors (including e.g. bacteria). Wolbachia is an example (again, with Drosophila).

 

Retroviral transfer is a more classic route (though not the subject of the paper in question), but would not be considered terribly novel, I would think.

Edited January 4, 2013 by CharonY

[imatfaal]

The abstract mentions parasitic tics as a vector - but I assumed there had to be a further mechanism ie retrovirus within the matter transferred by the tics.

[CharonY]

Yes, something else is likely to be needed, but not necessarily of viral origin. I was thinking if intracellular parasites in general. Bacteria are an interesting example (think in terms of mitochondrial-nuclear gene transfer). The precise mechanisms are afaik unknown, however.

[Moontanman]

I wonder how much of an influence on vertebrate evolution such gene transfers have....

[Arete]

Around 8% of the human genome is viral in origin: http://www.sciencedaily.com/releases/2010/01/100107103621.htm and these genes can have a profound influence on the evolution of vertebrates. Carl Zimmer wrote a pretty cool article on it: http://blogs.discovermagazine.com/loom/2012/06/14/we-are-viral-from-the-beginning/#.UOn883d1NSI

[Moontanman]

Very cool Arete, I have read of some of this before. makes you wonder if visiting another planet with it's own viruses would be such a good idea down the line...

[CharonY]

Well, the question is what the physiological consequences of these are. Large genomes offer an enormous "habitat" for mobile genetic elements (or, one could argue that they became so large because of them). As the size and structure are somewhat less under selective pressure than in bacteria they may offer quite a different landscape for evolutionary changes.

Early analyses of the human genome estimated something close to 45% of the human genome consist of transposable elements (and much higher levels were found in plants).

 

However, their mechanism of replication is quite specific and chances are that an alien virus would not be able to do much.

Edited January 7, 2013 by CharonY

[Arete]

I totally didn't mean to imply that because a gene of viral/prokaryote origin finds its way into a human genome, it immediately generates a functional difference. I have first hand experience with the Wolbachia/Glossina quagmire and trying to figure out which organism all these damn non-functional/fragmented paralogs came from and how the hell they got there...

 

All having a virus gene in a human genome does is provide recombining processes/mutation/evolution some novel raw material to work with. The vast majority of horizontally transferred genes in eukaryotic genomes do nothing. However it does look like some of these genes of novel origin have played an important role in eukaryotic evolution.

 

The whole shrinking endosymbiont genome phenomenon, with the transfer of the symbiont's genes to the host genome and subsequent taking over of essential functions for the symbiont by the host is really interesting - it kind of pushes the boundaries of the definitions we use for "life" and provides pretty good evidence for the posed mechanism for the origins of mitochondria and chloroplasts.

 

http://www.pnas.org/content/106/22/9063.short

http://www.sciencemag.org/content/317/5845/1753.short

Edited January 7, 2013 by Arete

[CharonY]

Indeed. Although I do think that they may actually have physiological consequences of sorts. For example, such stretches may affect DNA dynamics and in a subtle way alter gene expression strengths. Although this is more likely of relevance for single-celled organisms and the evolutionary consequences are likely to be of more relevance.

[pantheory]

This seems like a big evolution news to me. Another mechanism that can cause evolution. Like the article says, such a mechanism has been known to exist for a long time, but only fairly recently was it shown to exist as a cross over between two highly complex animals, and only until now has it been realized that it is not as rare as once thought.

 

I'm still waiting for the "dat" or "cog," genetic manipulations resulting in a cross between a dog and a cat

[overtone]

Although an alternative is that all sections can jump around - but other areas are necessarily highly preserved

The jumping code is not necessarily or usually replacing, but augmenting, in most cases - it seems unlikely, especially given the ease with which engineers can insert big and varaiable blocks of code, that entire genomes are so tightly preserved in their exact current relationships.

 

It seems more likely, off hand, that certain stretches of code jump more easily than others - as if made for horizontal transfer, in a sense.

 

Which has implications for the code that is in fact made for horizontal transfer.

[Moontanman]

This seems like a big evolution news to me. Another mechanism that can cause evolution. Like the article says, such a mechanism has been known to exist for a long time, but only fairly recently was it shown to exist as a cross over between two highly complex animals, and only until now has it been realized that it is not as rare as once thought.

 

I'm still waiting for the "dat" or "cog," genetic manipulations resulting in a cross between a dog and a cat

 

 

I want a elephant the size of a dog... or a centaur! Genetic engineering gives me goose bumps...

[overtone]

I want a elephant the size of a dog

It would need thick fur and smaller ears, smaller bones and different teeth, and modified digestion etc - also, the trunk would probably have to be elimiinated. You'd get much the same animal in a miniature goat, one of the hornless types - and probably less pugnacious, less apt to bite. Elephants derive much of their estimation of safety etc from their automatic comparison of size - this is likely to be a fearful and high-strung little guy.

 

The book Jurassic Park recounts a toy sized elephant created by the genetic engineers, used in sales pitches to raise investment money. It had behavioral problems - Crichton did get some of the science down plausibly.

[Moontanman]

Spoil sport... so I don't get to be transferred into a centaurs brain either?