Featured Research

from universities, journals, and other organizations

Genome Of Ancient Fish Could Reveal Evolutionary Mysteries, Stanford Scientists Say

Date:
November 25, 2004
Source:
Stanford University Medical Center
Summary:
A prehistoric fish that until 1938 was thought to be extinct has caught the eye of geneticists at the Stanford University School of Medicine who hope to sequence the ancient genome to learn how animals evolved to live on land.

STANFORD, Calif. – A prehistoric fish that until 1938 was thought to be extinct has caught the eye of geneticists at the Stanford University School of Medicine who hope to sequence the ancient genome to learn how animals evolved to live on land.

The 5-foot, 130-pound fish in question, called the coelacanth, ekes out an existence in cool, deep-water caves off the Comoro Islands in the Indian Ocean and northern Indonesia. Its lobed fins, skeleton structure and large, round scales are practically unchanged from its fossilized ancestors. This resemblance is what makes it an attractive target for sequencing, according to work published in this week's online issue of Genome Research.

Genetics professor Richard Myers, PhD, co-authored the paper, which makes the case for sequencing the coelacanth genome. "It's just making an argument that if we want to understand this level of evolution, this is what we need to do," he said. The next step is convincing a funding agency, such as the National Institutes of Health or the Department of Energy, to add the coelacanth to a list of high priority organisms to sequence.

Geneticists often compare gene sequences between species to learn how traits evolved. To learn what makes a mammal a mammal, for instance, they may compare a gene sequence in humans, mice, dogs, chickens and frogs to see what sequences the mammals share and that frogs and chickens lack. If all the mammals have one sequence in common, it is likely to be important for making milk, growing hair or other features unique to mammals.

This type of analysis has been all but impossible for learning how land animals crawled ashore and developed limbs and lungs. The problem is this: as fish evolved they went through a flurry of genetic alterations, making fish species almost as different from each other as they are from land animals. Given this vast diversity, a sequence in land animals that's missing in one of the fish species is not necessarily involved in land animal biology, according to James Noonan, PhD, who did the coelacanth work as a graduate student at Stanford with Myers, the Stanford W. Ascherman, MD, FACS Professor in Genetics. That genetic difference may just be the result of random changes in that particular fish.

In contrast, the coelacanth seems to have changed very little--physically or genetically--since one wayward branch of the fish family headed for land roughly 360 million years ago. Because it has changed so little the coelacanth is ideal for genetic comparisons. Any genetic feature found in all land animals but lacking in the coelacanth could represent a change that makes living on land possible.

Noonan said that coelacanth's close relative, the lungfish, could also fill in the genetic gap between land animals and fish, but the coelacanth has one practical advantage: "The lungfish genome is enormous," said Noonan, who is now a postdoctoral fellow at the Lawrence Berkeley National Laboratory. At 35 times the size of the human genome, sequencing the lungfish is an unlikely proposition. In contrast, the coelacanth genome is smaller than that of either humans or mice.

To make his case for the coelacanth, Noonan sequenced a group of coelacanth genes called the protocadherin gene cluster. He chose this region because it is extremely variable between different species, making it easy to see differences and similarities. This region has 54 genes in humans and 97 genes in the zebrafish, whose genome has been sequenced. He found that the coelacanth had 49 genes in the cluster, much like humans and other land animals. What's more, humans and coelacanths both have subgroups of these genes that zebrafish lack. "The coelacanth is evolving very slowly, that's what makes them interesting," Noonan said.

Although it isn't known why coelacanths evolve so slowly, Noonan suggested that their lifespan might be at issue. Where most fish reproduce quickly and have short generation times, the coelacanth reproduces slowly and gives birth to live young. This means that the coelacanth has had fewer generations of offspring to accumulate mutations.

The fact that coelacanth is available for sequencing is a lucky accident. They were thought to be extinct until 1938 when museum curator Marjorie Courtaney-Latimer discovered a specimen in a fisherman's catch near Cape Town, South Africa. In 1998 a honeymooning researcher found a second population off the coast of Indonesia.

Last year Myers and David Kingsley, PhD, professor of developmental biology, successfully recommended that a fish called the stickleback be added to the list of organisms to be sequenced by the National Human Genome Research Institute at the NIH. Myers said he, Noonan and other researchers who contributed to the article in Genome Research will be submitting the coelacanth for consideration soon.

Other Stanford researchers at the Stanford Human Genome Center who contributed to this work include Jane Grimswood, finishing group leader; Jeremy Schmutz, informatics group leader, and Mark Dickson, production sequence group leader.


Story Source:

The above story is based on materials provided by Stanford University Medical Center. Note: Materials may be edited for content and length.


Cite This Page:

Stanford University Medical Center. "Genome Of Ancient Fish Could Reveal Evolutionary Mysteries, Stanford Scientists Say." ScienceDaily. ScienceDaily, 25 November 2004. <www.sciencedaily.com/releases/2004/11/041123205008.htm>.
Stanford University Medical Center. (2004, November 25). Genome Of Ancient Fish Could Reveal Evolutionary Mysteries, Stanford Scientists Say. ScienceDaily. Retrieved August 27, 2014 from www.sciencedaily.com/releases/2004/11/041123205008.htm
Stanford University Medical Center. "Genome Of Ancient Fish Could Reveal Evolutionary Mysteries, Stanford Scientists Say." ScienceDaily. www.sciencedaily.com/releases/2004/11/041123205008.htm (accessed August 27, 2014).

Share This




More Plants & Animals News

Wednesday, August 27, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Raw: Firefighters Rescue Puppy Stuck in Tire

Raw: Firefighters Rescue Puppy Stuck in Tire

AP (Aug. 26, 2014) It took Houston firefighters more than an hour to free a puppy who got its head stuck in a tire. (Aug. 26) Video provided by AP
Powered by NewsLook.com
Have You Ever Been 'Sleep Drunk?' 1 in 7 Has

Have You Ever Been 'Sleep Drunk?' 1 in 7 Has

Newsy (Aug. 26, 2014) A study published in the journal "Neurology" interviewed more than 19,000 people and found 15 percent suffer from being "sleep drunk." Video provided by Newsy
Powered by NewsLook.com
Great White Shark Spotted Off Massachusetts Coast

Great White Shark Spotted Off Massachusetts Coast

Reuters - US Online Video (Aug. 26, 2014) A great white shark is spotted off the shore at Duxbury beach in Massachusetts forcing beach goers out of the water. Linda So reports. Video provided by Reuters
Powered by NewsLook.com
Raw: Elk Wanders Into German Office Building

Raw: Elk Wanders Into German Office Building

AP (Aug. 25, 2014) A young bull elk wandered inside the office building of a company in Dresden, Germany on Monday. The elk became trapped between a wall and glass windows while rescue workers tried to rescue him safely. (Aug. 25) Video provided by AP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins