Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

New Insight into Primate Eye Evolution

20.05.2009
Researchers comparing the fetal development of the eye of the owl monkey with that of the capuchin monkey have found that only a minor difference in the timing of cell proliferation can explain the multiple anatomical differences in the two kinds of eyes.

The findings help scientists understand how a structure as complex as the eye could change gradually through evolution, yet remain functional.

The findings also offer a lesson in how seemingly simple genetic changes in the brain and nervous system could produce the multiple evolutionary changes seen in more advanced brains, without compromising function.

Analysis for this study was performed at St. Jude Children’s Research Hospital. The primates were housed at the Centro Nacional de Primates in Brazil. Contributing researchers at Cornell University and Universidade Federal do Pará, Brazil, approved all procedures. The researchers published their findings in the early online issue of Proceedings of the National Academy of Sciences.

“The molecular, cellular and genetic pathways that coordinate proliferation during development have been fine-tuned since the first multicellular organisms emerged millions of years ago,” said Michael Dyer, Ph.D., member of St. Jude Developmental Neurobiology and the paper’s first author. “When these pathways are deregulated during human development, one of the consequences is childhood cancer. Therefore, by studying how changes in the regulation of proliferation during development can lead to dramatic changes in form and function during evolution, we can gain a deeper understanding of these ancient pathways that lie at the heart of many pediatric cancers.”

The owl monkey’s eye has numerous adaptations to make it effective for nocturnal (active during the night) function. For example, it has a greater number of rod photoreceptor cells than the capuchin monkey, which is diurnal (active during the day). Rod cells are the most light-sensitive cells in the retina making them effective for nighttime vision. The owl monkey’s nocturnal retina is also larger and lacks a fovea, the central region of high-density cone photoreceptors that gives the diurnal eye high acuity and daytime color vision.

For both owl and capuchin monkeys, the specialized cell types in the eye all develop in the growing embryo from a single type of immature cell, called a retinal progenitor cell.

“These two species evolved about 15 million years ago from a common ancestor that had a diurnal eye,” Dyer said. “So, we believe that comparing how their eyes develop during embryonic growth could help us understand what evolutionary changes would be required to evolve from a diurnal to a nocturnal eye.”

The researchers hypothesized that only speeding up or slowing down the proliferation of the progenitor cells in the developing embryo might actually change the types of cells that they became. Thus, the evolutionary adaptation from diurnal to nocturnal eye might require no more than a modest genetic change that affected that timing.

Such a concept—that timing of cell proliferation might profoundly affect anatomy—has broader implications for understanding how the complex human brain evolved from simpler mammalian brains, Dyer said. In earlier comparative studies of the brains of more than 100 mammalian species, the study’s first author, Barbara Finlay, Ph.D., of Cornell University, Ithaca, New York, had found that those parts of the brain that are disproportionately larger in more complex brains develop last during embryonic growth.

“This finding suggested that changes in the growth of the brain during embryonic development could be a mechanism for evolutionary change,” Dyer said. “In other words, maybe the parts of the human brain that are bigger than in other mammals are bigger simply because the period of their growth is extended during fetal development.”

In their analysis, Dyer and his colleagues compared the timing of retinal progenitor cell proliferation into the different types of mature retinal cells in owl and capuchin monkey embryos. They found evidence that the extended period of progenitor cell proliferation in the owl monkey eye did, indeed, give rise to the different population of retinal cells that made the eye specially adapted for nocturnal vision.

They also found evidence that this extended period of proliferation also caused the size of the eye to be larger, which is necessary for the eye to accommodate the larger light-gathering and light-sensing structures necessary for nocturnal vision.

“The beauty of the evolutionary mechanism we have identified is that it enables the eye to almost toggle back and forth between a nocturnal and a diurnal structure,” Dyer said. “It is an elegant system that gives the eye a lot of flexibility in terms of specialization.”

More broadly, Dyer said, the finding offers support for the idea that important changes in brain structure can evolve via simple genetic changes that affect the timing of development of brain regions.

Other authors of this paper are Rodrigo Martins (St. Jude); Manoel da Silva Filho and Luiz Carlos Silveira (Universidade Federal do Pará, Brazil); Jose Augusto Muniz (Centro Nacional de Primatas, Brazil); and Constance Cepko (Harvard Medical School).

This research was supported in part by The National Science Foundation.

St. Jude Children’s Research Hospital
St. Jude Children’s Research Hospital is internationally recognized for its pioneering work in finding cures and saving children with cancer and other catastrophic diseases. Founded by late entertainer Danny Thomas and based in Memphis, Tenn., St. Jude freely shares its discoveries with scientific and medical communities around the world. No family ever pays for treatments not covered by insurance, and families without insurance are never asked to pay. St. Jude is financially supported by ALSAC, its fundraising organization. For more information, please visit www.stjude.org.

St. Jude Public Relations | EurekAlert!
Further information:
http://www.stjude.org

More articles from Life Sciences:

nachricht Transport of molecular motors into cilia
28.03.2017 | Aarhus University

nachricht Asian dust providing key nutrients for California's giant sequoias
28.03.2017 | University of California - Riverside

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: A Challenging European Research Project to Develop New Tiny Microscopes

The Institute of Semiconductor Technology and the Institute of Physical and Theoretical Chemistry, both members of the Laboratory for Emerging Nanometrology (LENA), at Technische Universität Braunschweig are partners in a new European research project entitled ChipScope, which aims to develop a completely new and extremely small optical microscope capable of observing the interior of living cells in real time. A consortium of 7 partners from 5 countries will tackle this issue with very ambitious objectives during a four-year research program.

To demonstrate the usefulness of this new scientific tool, at the end of the project the developed chip-sized microscope will be used to observe in real-time...

Im Focus: Giant Magnetic Fields in the Universe

Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.

The results will be published on March 22 in the journal „Astronomy & Astrophysics“.

Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...

Im Focus: Tracing down linear ubiquitination

Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.

Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...

Im Focus: Perovskite edges can be tuned for optoelectronic performance

Layered 2D material improves efficiency for solar cells and LEDs

In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...

Im Focus: Polymer-coated silicon nanosheets as alternative to graphene: A perfect team for nanoelectronics

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

International Land Use Symposium ILUS 2017: Call for Abstracts and Registration open

20.03.2017 | Event News

CONNECT 2017: International congress on connective tissue

14.03.2017 | Event News

ICTM Conference: Turbine Construction between Big Data and Additive Manufacturing

07.03.2017 | Event News

 
Latest News

Researchers shoot for success with simulations of laser pulse-material interactions

29.03.2017 | Materials Sciences

Igniting a solar flare in the corona with lower-atmosphere kindling

29.03.2017 | Physics and Astronomy

As sea level rises, much of Honolulu and Waikiki vulnerable to groundwater inundation

29.03.2017 | Earth Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>