PRESS-NEWS.org - Press Release Distribution
PRESS RELEASES DISTRIBUTION

Slow-evolving elephant shark genome is first to be sequenced from cartilaginous fish

SF State biology professor publishes findings in the journal Nature

2014-01-09
(Press-News.org) Contact information: Nan Broadbent
nbroadbe@sfsu.edu
415-338-7108
San Francisco State University
Slow-evolving elephant shark genome is first to be sequenced from cartilaginous fish SF State biology professor publishes findings in the journal Nature SAN FRANCISCO -- A team of researchers including SF State Assistant Professor of Biology Scott Roy has sequenced the entire genome of the elephant shark, uncovering several features that may shed light on the evolution of bony vertebrates.

The study is the first whole-genome analysis of a cartilaginous fish. Cartilaginous fishes include sharks, rays and skates. Together with bony fish, birds, reptiles, amphibians and mammals, they make up the branch of jawed vertebrates on life's family tree.

The elephant shark genome is relatively small, consisting of slightly fewer than a billion DNA base pairs compared with 3 billion base pairs in humans. But this spare sequence has yielded some intriguing details, the researchers write. For instance, the elephant shark lacks the genes for secreted phosphoproteins, which may explain why their cartilage is not converted into bone as in the other jawed vertebrates.

They also lack the genes for several key immune system cells and protein receptors in the adaptive immune system, which provides carefully targeted defenses against specific disease threats. This finding, say the researchers, may suggest that the adaptive immune system in jawed vertebrates gradually became more elaborate over time.

One of the most notable features of the elephant shark's genome is its incredibly slow rate of evolution, said Roy. Even slower than in "living fossils" such as the coelacanth, the elephant shark's genome has not changed substantially in hundreds of millions of years.

This slow rate of evolution was uncovered in part by Roy's analysis of the genome's introns. Introns are the part of the genetic sequence that "interrupts" genes, and must be spliced out before the gene can be expressed. In vertebrates, these introns can be thousands of DNA letters long and must include their own splicing instructions.

There have been very few intron changes in the elephant shark genome, but this isn't entirely surprising, noted Roy, who has studied intron organization across a variety of organisms, including humans. "It's pretty well established in vertebrates that very little of this intron loss and creation occurs."

"It would be a rare and weird physical event" for this many nucleotides to exactly appear or disappear in a genome, he added. "It's unlikely to have that big of a change exactly and all at once." The elephant shark genome helps to confirm that the lack of intron loss and gain is a general characteristic of vertebrates, Roy said. In close invertebrate relatives such as the tunicates (which include marine animals such as sea squirts), the rate of intron evolution is much faster. "Because vertebrate introns are very long, this may make it harder to create and delete them," Roy said. "In some tunicates, introns are about 40 nucleotides long, and this simply may make it easier for them to come and go over time."

The time between generations also tends to be much swifter in invertebrates than vertebrates, he noted, which may increase the opportunity for mutations to accumulate in invertebrate genomes. These slow-changing introns also helped Roy and his colleagues clarify the relationship between cartilaginous fish and other jawed vertebrates. These relationships can be determined by comparing gene sequences between organisms, and introns can be especially helpful in this analysis. "Because things are changing so slowly with [introns], the chance that two species will share a change is likely to be very small" unless they are closely related, Roy explained.

The researchers found "a very clear signal," Roy said, that bony fish and other bony vertebrates including mammals are all more closely related to each other than either group is to the cartilaginous fishes.

### The study "Elephant shark genome provides unique insights into gnathostome evolution" was published in the Jan. 9 issue of the journal Nature.


ELSE PRESS RELEASES FROM THIS DATE:

Higher risk of birth problems after assisted conception

2014-01-09
Higher risk of birth problems after assisted conception A University of Adelaide study has shown that the risk of serious complications such as stillbirth, preterm birth, low birth weight and neonatal death is around twice as high for babies conceived ...

Blood pressure study points to more equitable care in England than America

2014-01-09
Blood pressure study points to more equitable care in England than America In the US but not in England, patients on low incomes with high blood pressure have their condition managed poorly compared with those who earn more. A new study comparing blood pressure ...

Penn Medicine epidemiologists find bed bug hotspots in Philadelphia, identify seasonal trends

2014-01-09
Penn Medicine epidemiologists find bed bug hotspots in Philadelphia, identify seasonal trends Philadelphia infestations are increasing, with many reports in South Philadelphia PHILADELPHIA—A new study from Penn Medicine epidemiologists ...

Literary mood reflects the economic mood of past 10 years, study finds

2014-01-09
Literary mood reflects the economic mood of past 10 years, study finds The frequency of words expressing misery and unhappiness in books reflects the economic conditions in the 10 years prior to the work's composition, according to researchers in Bristol ...

Scientists unlock evolution of cholera, identify strain responsible for early pandemics

2014-01-09
Scientists unlock evolution of cholera, identify strain responsible for early pandemics Working with a nearly 200-year-old sample of preserved intestine, researchers at McMaster University and the University of Sydney have traced the bacterium behind a global ...

Organic mega flow battery promises breakthrough for renewable energy

2014-01-09
Organic mega flow battery promises breakthrough for renewable energy Harvard technology could economically store energy for use when the wind doesn't blow and the sun doesn't shine Cambridge, Mass. – January 8, 2014 – A team of Harvard scientists and engineers has demonstrated ...

Researchers unveil rich world of fish biofluorescence

2014-01-09
Researchers unveil rich world of fish biofluorescence Technology-driven study finds about 180 glowing species, highlights new potential source for biomedical fluorescent proteins A team of researchers led by scientists from the American Museum of Natural ...

Simple test can indicate cervical cancer

2014-01-09
Simple test can indicate cervical cancer LOUISVILLE, Ky. – Researchers at the University of Louisville have confirmed that using the heat profile from a person's blood, called a plasma thermogram, can serve as an indicator for the presence or absence of cervical ...

On-field blood test can diagnose sports concussions

2014-01-09
On-field blood test can diagnose sports concussions A brain protein, S100B, which may soon be detected by a simple finger-stick blood test, accurately distinguishes a sports-related concussion from sports exertion, according to a study of college ...

Fungi may determine the future of soil carbon

2014-01-09
Fungi may determine the future of soil carbon When scientists discuss global change, they often focus on the amount of carbon in the atmosphere and vegetation. But soil contains more carbon than air and plants combined. This means that even a minor ...

LAST 30 PRESS RELEASES:

Fentanyl detection through packaging

Prof. Eran Meshorer elected to EMBO for pioneering work in epigenetics

New 3D glacier visualizations provide insights into a hotter Earth

Creativity across disciplines

Consequences of low Antarctic sea ice

Hear here: How loudness and acoustic cues help us judge where a speaker is facing

A unique method of rare-earth recycling can strengthen the raw material independence of Europe and America

Epilepsy self-management program shows promise to control seizures, improve mood and quality of life

Fat may play an important role in brain metabolism

New study finds no lasting impact of pandemic pet ownership on human well-being

New insights on genetic damage of some chemotherapies could guide future treatments with less harmful side effects

Gut microbes could protect us from toxic ‘forever chemicals’

Novel modelling links sea ice loss to Antarctic ice shelf calving events

Scientists can tell how fast you're aging from a single brain scan

U.S. uterine cancer incidence and mortality rates expected to significantly increase by 2050

Public take the lead in discovery of new exploding star

What are they vaping? Study reveals alarming surge in adolescent vaping of THC, CBD, and synthetic cannabinoids

ECMWF - delivering forecasts over 10 times faster and cutting energy usage by 1000

Brazilian neuroscientist reveals how viral infections transform the brain through microscopic detective work

Turning social fragmentation into action through discovering relatedness

Cheese may really be giving you nightmares, scientists find

Study reveals most common medical emergencies in schools

Breathable yet protective: Next-gen medical textiles with micro/nano networks

Frequency-engineered MXene supercapacitors enable efficient pulse charging in TENG–SC hybrid systems

Developed an AI-based classification system for facial pigmented lesions

Achieving 20% efficiency in halogen-free organic solar cells via isomeric additive-mediated sequential processing

New book Terraglossia reclaims language, Country and culture

The most effective diabetes drugs don't reach enough patients yet

Breast cancer risk in younger women may be influenced by hormone therapy

Strategies for staying smoke-free after rehab

[Press-News.org] Slow-evolving elephant shark genome is first to be sequenced from cartilaginous fish
SF State biology professor publishes findings in the journal Nature