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

Genetic switch for limbs and digits found in ancient fish

Before animals first walked on land, fish carried gene program for limbs

Genetic switch for limbs and digits found in ancient fish
2011-07-12
(Press-News.org) Genetic instructions for developing limbs and digits were present in primitive fish millions of years before their descendants first crawled on to land, researchers have discovered.

Genetic switches control the timing and location of gene activity. When a particular switch taken from fish DNA is placed into mouse embryos, the segment can activate genes in the developing limb region of embryos, University of Chicago researchers report in Proceedings of the National Academy of Sciences. The successful swap suggests that the recipe for limb development is conserved in species separated by 400 million years of evolution.

"The genetic switches that drive the expression of genes in the digits of mice are not only present in fish, but the fish sequence can actually activate the expression in mice," said Igor Schneider, PhD, postdoctoral researcher in the Department of Organismal Biology and Anatomy at the University of Chicago and lead author on the paper. "This tells us how the antecedents of the limb go back in time at every level, from fossils to genes."

The genetic hunt was inspired by a famous fossil find – the 2004 discovery of the transitional fossil Tiktaalik in the Canadian Arctic by a team led by Neil Shubin of the University of Chicago. A transitional species between fish and the four-legged tetrapods, Tiktaalik possessed fins containing a skeletal structure similar to the limbs of later land-dwelling animals.

Those similarities – particularly the wrist and hand-like compartments present in the fins of Tiktaalik and its peers – inspired a laboratory experiment to look at the homology, or shared physical and genetic traits, of fish and limbed animals.

"This is really a case where knowing something about the fossils and the morphology led us to think about genetic experiments," said Shubin, PhD, the Robert R. Bensley Professor of Organismal Biology and Anatomy and senior author of the study. "Tiktaalik and its cousins showed us that this limb compartment is not an utter novelty in tetrapods, as was thought for a long time. So an antecedent of that program must exist."

The research team compared a genetic switch region called CsB, known to regulate limb development in humans, with similar regions in mice, chickens, frogs, and two fish species: the zebrafish and the skate. Because the last common ancestor of all these species pre-dates Tiktaalik-like "fishapods," the comparison offered a glimpse at biology before animals made their first steps on land.

Schneider and colleagues compared the CsB regions from all five species and found that certain sequences were shared between the fish species and the tetrapods. The conservation allowed the researchers to try swapping switch sequences between species to see if they could still drive gene expression in the fin or limb. Remarkably, mouse CsB could turn on gene expression at the outer edge of the developing fin region of zebrafish, and both skate and zebrafish CsB were capable of activating gene expression in the wrist and proximal digits of the mouse limb.

"These sequences function in these organisms despite 400 million years of separation," Schneider said. "The homologies that are perhaps not evident by morphology – just comparing a hand and a fin – can be traced back to the genome, where you find that the regulatory regions that control the making of those structures are actually present and shared between these organisms."

The results contradict a previous finding that a developmental switch from pufferfish DNA was not capable of gene expression in the limbs of mice, suggesting that tetrapods evolved a novel developmental system. But the new experiments suggest that the genetic switch controlling limb development was in fact present deep in Earth's evolutionary tree.

"There previously was the idea that these switches had to be generated from scratch de novo, but no, they already existed, they were already there," said Marcelo Nobrega, MD, PhD, assistant professor of human genetics at the University of Chicago Medical Center and another author of the study. "Maybe the key was expressing a gene earlier or later or in a specific territory, but it was just a modification of a program that was already encoded in the genomes of fish almost half a billion years ago and remains there to this day."

"These new results are actually in line with both the fossil data and the expression data," Schneider said. "So now we can tell a story where the fossils and gene expression make sense in light of the genetic regulation."

Future experiments will focus more closely on how the gene regulation system functions, examining the differences between the segments in fish and tetrapods that control development of either a fin or a limb. Subtle changes in the timing or location of gene expression may produce the dramatic differences in anatomy that first allowed animal life on Earth to explore land.

"There is a whole universe of questions that are opened up by this discovery," Shubin said.



INFORMATION:

The paper, "Appendage expression driven by the Hoxd global control region is an ancient gnathostome feature," will be published online the week of July 11 by the Proceedings of the National Academy of Sciences. In addition to Shubin, Schneider, and Nobrega, authors include Ivy Aneas and Andrew R. Gehrke of the University of Chicago, and Randall D. Dahn of Mount Desert Island Biological Lab.

Funding for the research was provided by the American Heart Association and the University of Chicago Biological Sciences Division.

[Attachments] See images for this press release:
Genetic switch for limbs and digits found in ancient fish

ELSE PRESS RELEASES FROM THIS DATE:

A classic instinct -- salt appetite -- is linked to drug addiction

A classic instinct -- salt appetite -- is linked to drug addiction
2011-07-12
Durham, N.C., U.S. and Melbourne, Australia -- A team of Duke University Medical Center and Australian scientists has found that addictive drugs may have hijacked the same nerve cells and connections in the brain that serve a powerful, ancient instinct: the appetite for salt. Their rodent research shows how certain genes are regulated in a part of the brain that controls the equilibrium of salt, water, energy, reproduction and other rhythms – the hypothalamus. The scientists found that the gene patterns activated by stimulating an instinctive behavior, salt appetite, ...

Landscape change leads to increased insecticide use in the Midwest

2011-07-12
MADISON - The continued growth of cropland and loss of natural habitat have increasingly simplified agricultural landscapes in the Midwest. A Great Lakes Bioenergy Research Center (GLBRC) study concluded that this simplification is associated with increased crop pest abundance and insecticide use, consequences that could be tempered by perennial bioenergy crops. While the relationship between landscape simplification, crop pest pressure, and insecticide use has been suggested before, it has not been well supported by empirical evidence. This study, published online in ...

Regional system to cool cardiac arrest patients improves outcomes

2011-07-12
A broad, regional system to lower the temperature of resuscitated cardiac arrest patients at a centrally-located hospital improved outcomes, according to a study in Circulation: Journal of the American Heart Association. Cooling treatment, or therapeutic hypothermia, is effective yet underused, researchers said. A network of first responders, EMS departments and more than 30 independent hospitals within 200 miles of Minneapolis, Minn., and Abbott Northwestern Hospital collaborated to implement the protocol. "We've shown that a fully integrated system of care, from ...

Obstructive sleep apnea linked to blood vessel abnormalities

2011-07-12
Obstructive sleep apnea may cause changes in blood vessel function that reduces blood supply to the heart in people who are otherwise healthy, according to new research reported in Hypertension: Journal of the American Heart Association. However, treatment with 26 weeks of continuous positive airway pressure (CPAP) improved study participants' blood supply and function. Obstructive sleep apnea, which causes periodic pauses in breathing during sleep, affects about 15 million adults in the United States, according to the American Heart Association. The sleep disorder ...

Nearly all patients with high-grade bladder cancer do not receive guideline-recommended care

2011-07-12
A study at UCLA's Jonsson Comprehensive Cancer Center found that nearly all patients with high-grade, non-invasive bladder cancer are not receiving the guideline-recommended care that would best protect them from recurrence, a finding that researchers characterized as alarming. In fact, out of the 4,545 bladder cancer patients included in the study, only one received the comprehensive care recommended by the American Urology Association and the National Comprehensive Cancer Network. Receiving the recommended comprehensive care for high-grade bladder cancer is critical ...

Do-it-yourself brain repair following stroke

2011-07-12
Stroke is a leading cause of long-term disability and death in the United States. A team of researchers — led by Gregory Bix, at Texas A&M College of Medicine, College Station — has identified a way to exploit one of the brain's self-repair mechanisms to protect nerve cells and enhance brain repair in rodent models of stroke. The authors suggest that this approach could provide a nontoxic treatment for stroke. The most common form of stroke (ischemic stroke) occurs when a blood vessel that brings oxygen and nutrients to the brain becomes clogged, for example with a blood ...

PXR: A stepping stone from environmental chemical to cancer?

2011-07-12
Several chemicals that can accumulate to high levels in our body (for example BPA and some pesticides) have been recently linked to an increased risk of cancer and/or impaired responsiveness to anticancer drugs. A team of researchers, led by Sridhar Mani, at Albert Einstein College of Medicine, New York, has now identified a potential mechanistic link between environmental exposure to these foreign chemicals (xenogens) and cancer drug therapy response and survival. PXR is one protein by which cells (including tumor cells) can sense xenogens. In their study, Mani and colleagues ...

JCI online early table of contents: July 11, 2011

2011-07-12
EDITOR'S PICK: Do-it-yourself brain repair following stroke Stroke is a leading cause of long-term disability and death in the United States. A team of researchers — led by Gregory Bix, at Texas A&M College of Medicine, College Station — has identified a way to exploit one of the brain's self-repair mechanisms to protect nerve cells and enhance brain repair in rodent models of stroke. The authors suggest that this approach could provide a nontoxic treatment for stroke. The most common form of stroke (ischemic stroke) occurs when a blood vessel that brings oxygen and ...

Vitamin D insufficiency prevalent among psoriatic arthritis suffers

2011-07-12
New research reports a high prevalence of vitamin D insufficiency and deficiency among patients with psoriatic arthritis. Seasonal variation in vitamin D levels was not observed in patients in southern or northern locations. The findings published today in Arthritis Care & Research, a journal of the American College of Rheumatology (ACR), also show no association between disease activity and vitamin D level. Psoriasis is a common chronic skin disorder, likely caused by an autoimmune response, and is characterized by red scaly patches on the surface of the skin. When ...

SUMO defeats protein aggregates that typify Parkinson’s disease

SUMO defeats protein aggregates that typify Parkinson’s disease
2011-07-12
A small protein called SUMO might prevent the protein aggregations that typify Parkinson's disease (PD), according to a new study in the July 11, 2011, issue of The Journal of Cell Biology (www.jcb.org). Insoluble protein clusters are the hallmarks of several neurodegenerative diseases. In PD, neurons harbor insoluble clumps of the protein alpha-synuclein. What triggers these protein pileups remains obscure. A possible clue for PD came when researchers overexpressed alpha-synuclein in human kidney cells and found that the protein was modified by the addition of the small, ...

LAST 30 PRESS RELEASES:

UC stroke experts discuss current and future use of AI tools in research and treatment

The Southern Ocean’s low-salinity water locked away CO2 for decades, but...

OHSU researchers develop functional eggs from human skin cells

Most users cannot identify AI bias, even in training data

Hurricane outages: Analysis details the where, and who, of increased future power cuts

Craters on surface of melanoma cells found to serve as sites for tumor killing

Research Spotlight: Mapping overlooked challenges in stroke recovery

Geographic and temporal patterns of screening for breast, cervical, and colorectal cancer in the US

Cannabis laws and opioid use among commercially insured patients with cancer diagnoses

Research Spotlight: Surprising gene mutation in brain’s immune cells linked to increased Alzheimer’s risk

Missing molecule may explain Down syndrome

Donor diabetes and 1-year Descemet membrane endothelial keratoplasty success rate

Endothelial cell loss 1 year after successful DMEK in the diabetes endothelial keratoplasty study

Overactive Runx1 gene triggers early disc degeneration linked to aging

NYU Langone Health chair of ophthalmology, Dr. Kathryn Colby, honored with Castroviejo Medal at AAO 2025

Chemotherapy combination boosts overall survival in patients with EGFR-mutant non-small cell lung cancer

FAU’s Queen Conch Lab receives prestigious international award

Post-traumatic vasospasm: An overlooked threat after brain injury

Scientists smash record in stacking semiconductor transistors for large-area electronics

Large language models prioritize helpfulness over accuracy in medical contexts

In a surprising discovery, scientists find tiny loops in the genomes of dividing cells

Printing technique could vastly improve the environmental impact of digital displays

‘Skinny fat’ linked to silent artery damage, McMaster study reveals

Sulfated yeast rises to the challenge facing rare earth metals

Global analysis reveals how biochar supercharges composting and cuts greenhouse gases

Blocking a cellular switch could prevent lung-scarring disease

Planet formation depends on when it happens: UNLV model shows why

Deep sleep supports memory via brain fluid and neural rhythms

Biochar and iron additives show promise for reviving degraded peatlands and locking away carbon

Cancer cells reactivate embryo-like gene editors to fuel growth

[Press-News.org] Genetic switch for limbs and digits found in ancient fish
Before animals first walked on land, fish carried gene program for limbs