RxPG News Feed for RxPG News

Medical Research Health Special Topics World
  Home
 
   Health
 Aging
 Asian Health
 Events
 Fitness
 Food & Nutrition
 Happiness
 Men's Health
 Mental Health
 Occupational Health
 Parenting
 Public Health
 Sleep Hygiene
 Women's Health
 
   Healthcare
 Africa
 Australia
 Canada Healthcare
 China Healthcare
 India Healthcare
 New Zealand
 South Africa
 UK
 USA
 World Healthcare
 
 Latest Research
 Aging
 Alternative Medicine
 Anaethesia
 Biochemistry
 Biotechnology
 Cancer
 Cardiology
 Clinical Trials
 Cytology
 Dental
 Dermatology
 Embryology
 Endocrinology
 ENT
 Environment
 Epidemiology
 Gastroenterology
 Genetics
 Gynaecology
 Haematology
 Immunology
 Infectious Diseases
 Medicine
 Metabolism
 Microbiology
 Musculoskeletal
 Nephrology
 Neurosciences
 Obstetrics
 Ophthalmology
 Orthopedics
 Paediatrics
 Pathology
 Pharmacology
 Physiology
 Physiotherapy
 Psychiatry
 Radiology
 Rheumatology
 Sports Medicine
 Surgery
 Toxicology
 Urology
 
   Medical News
 Awards & Prizes
 Epidemics
 Launch
 Opinion
 Professionals
 
   Special Topics
 Ethics
 Euthanasia
 Evolution
 Feature
 Odd Medical News
 Climate

Last Updated: Feb 19, 2013 - 1:22:36 AM
Research Article
Latest Research Channel

subscribe to Latest Research newsletter
Latest Research

   EMAIL   |   PRINT
Evolutionary biologists urged to adapt their research methods

Feb 15, 2013 - 5:00:00 AM
This multi-dimensional approach allowed Yokoyama's lab in 2009 to identify the scabbardfish as the first fish known to have switched from ultraviolet vision to violet vision. And Yokoyama pinpointed exactly how the scabbardfish made the switch, by deleting an amino acid molecule at site 86 in the chain of amino acids in the opsin gene.

 
[RxPG] To truly understand the mechanisms of natural selection, evolutionary biologists need to shift their focus from present-day molecules to synthesized, ancestral ones, says Shozo Yokoyama, a biologist at Emory University.

Yokoyama will present evidence for why evolutionary biology needs to make this shift at 1:30 pm on Friday, February 15, during the American Academy of Arts and Sciences (AAAS) annual meeting in Boston.

This is not just an evolutionary biology problem, it's a science problem, says Yokoyama, a leading expert in the natural selection of color vision. If you want to understand the mechanisms of an adaptive phenotype, the function of a gene and how that function changes, you have to look back in time. That is the secret. Studying ancestral molecules will give us a better understanding of genes that could be applied to medicine and other areas of science.

For years, positive Darwinian selection has been studied almost exclusively using comparative sequence analysis of present-day molecules, Yokoyama notes. This approach has been fueled by increasingly fast and cheap genome sequencing techniques. But the faster, easier route, he says, is not necessarily the best one if you want to arrive at a true, quantitative result.

If you only study present-day molecules, you're only getting part of the picture, and that picture is often wrong, he says.

Yokoyama has spent two decades teasing out secrets of the adaptive evolution of vision in fish and other vertebrates.

Five classes of opsin genes encode visual pigments and are responsible for dim-light and color vision. Fish provide clues for how environmental factors can lead to vision changes, since the available light at various ocean depths is well quantified. The common vertebrate ancestor, for example, possessed ultraviolet vision, which is suited to both shallow water and land.

As the environment of a species sinks deeper in the ocean, or rises closer to the surface and moves to land, bits and pieces of the opsin genes change and vision adapts, Yokoyama says. I'm interested in exactly how that happens at the molecular level.

Molecular biologists can take DNA from an animal, isolate and clone its opsin genes, then use in vitro assays to construct a specific visual pigment. The pigment can be manipulated by changing the positions of the amino acids, in order to study the regulation of the gene's function.

In 1990, for example, Yokoyama identified the three specific amino acid changes that switch the human red pigment into a green pigment.

A few years later, another group of researchers confirmed Yokoyama's findings, but found that the three changes only worked in one direction. In order to reverse the process, and turn the green pigment back to red, it took seven changes.

They discovered this weird quirk that didn't make sense, Yokoyama says. Why wouldn't it take the same number of changes to go in either direction? That question was interesting to me.

He spent 10 years researching and pondering the question before he realized the key problem: The experiments were conducted on present-day molecules.

When the earliest mammalian ancestors appeared 100 million years ago, they had only the red pigment. Around 30 million years ago, the gene for the red pigment duplicated itself in some primates. One of these duplicated red pigments then acquired sensitivity to the color green, turning into a green pigment.

At the point that the three changes in amino acids occurred in this pigment, other mutations were happening as well, Yokoyama says. You have to understand the original interactions of all of the amino acids in the pigment, which means you have to look at the ancestral molecules. That's the trick.

In other words, just as changes in an animal's external environment drive natural selection, so do changes in the animal's molecular environment.

Statistical analysis allows Yokoyama and his collaborators to travel back in time and estimate the sequences for ancestral molecules. It's a lot of work, he says. We don't have a clear picture of every intermediate species. We have to do a step-by-step retracing, screening for noise in the results at each step, before we can construct a reliable evolutionary tree.

In 2008, Yokoyama led an effort to construct the most extensive evolutionary tree for dim-light vision, including animals from eels to humans. At key branches of the tree, Yokoyama's lab engineered ancestral gene functions, in order to connect changes in the living environment to the molecular changes.

The lengthy process of synthesizing ancestral proteins and pigments and conducting experiments on them combines microbiology with painstaking techniques of theoretical computation, biophysics, quantum chemistry and genetic engineering.

This multi-dimensional approach allowed Yokoyama's lab in 2009 to identify the scabbardfish as the first fish known to have switched from ultraviolet vision to violet vision. And Yokoyama pinpointed exactly how the scabbardfish made the switch, by deleting an amino acid molecule at site 86 in the chain of amino acids in the opsin gene.

Experimenting on ancestral molecules is the key to getting a correct answer to problems of natural selection, but there are very few examples of that being done in evolutionary biology, Yokoyama says.



Related Latest Research News
Moderate to severe psoriasis linked to chronic kidney disease, say experts
Licensing deal marks coming of age for University of Washington, University of Alabama-Birmingham
Simple blood or urine test to identify blinding disease
Physician job satisfaction driven by quality of patient care
Book explores undiscovered economics of everyday life
Gene and stem cell therapy combination could aid wound healing
Solving the internet capacity crunch
Breathing new life into preterm baby research
Perceptions of the role of the state shape water services provision
UltraHaptics -- it's magic in the air

Subscribe to Latest Research Newsletter

Enter your email address:


 Feedback
For any corrections of factual information, to contact the editors or to send any medical news or health news press releases, use feedback form

Top of Page

 
Contact us

RxPG Online

Nerve

 

    Full Text RSS

© All rights reserved by RxPG Medical Solutions Private Limited (India)