Wednesday, September 05, 2007

conservation != importance

A paper in PLOS has shown that ultraconserved elements, these stretches on hundreds of base pairs that are perfectly conserved between mice, rats and humans, can be deleted without any ill effect on the mice. evolution works in mysterious ways...
"It is widely believed that the most evolutionarily conserved DNA sequences in the human genome have been preserved because of their functional importance and that their removal would thus have a devastating effect on the organism. To ascertain this we removed from the mouse genome four ultraconserved elements—sequences of 200 base pairs or longer that are 100% identical among human, mouse, and rat. To our surprise, we found that the mice lacking these elements are viable, fertile, and show no apparent abnormalities. This completely unexpected finding indicates that extreme levels of DNA sequence conservation are not necessarily indicative of an indispensable functional nature."


rob said...

I considered posting this also.
I guess the question is then 'what is the purpose of these conserved regions?' I'll take a stab at it. Is it possible they are related to some pathogen? This would not come up in the laboratory environment. It would have to be a pathogen that can infect mice, rats and humans.
Or perhaps the sequences themselves are structured in such a way that they are always replicated with extremely high fidelity and therefore once established never go away?
Any other interesting guesses?

Bayman said...

Resistance to radiation?

Bayman said...

From nature news article:

But so far there has been just one report on the origin of some ultraconserved DNA (G. Bejerano et al. Nature 441, 87–90; 2006). A team from the University of California, Santa Cruz, traced the origins of one ultraconserved region back to a group of ancient fishes, including the coelacanth. This was only possible because another group of researchers had previously opted to sequence a few segments of coelacanth DNA. As Gill Bejerano, a former member of the Santa Cruz team, says: "If the coelacanth people hadn't been interested in that puny 1% of the genome we would not have the answer. Who knows what other information is out there?"