Gibson’s lab investigates the cellular and molecular mechanisms used by cells to assemble into layers or clusters during embryogenesis. Those tissues, comprised of densely packed cells known as epithelial cells, shape the body not only of simple creatures but also of mammals, where they line every body cavity from lung to intestine and form hormone- and milk-secreting glands. Unfortunately these cells have a dark side too- over 80% of human cancers, carcinomas, are of epithelial origin.
Image: Courtesy of Ashleigh Fritz, Stowers Institute for Medical Research
The Gibson lab has historically used the genetic powerhouse Drosophila to investigate the control of epithelial cell shape and proliferation during wing, leg and eye development. Breaking with tradition, their new study published in the May 15th, 2013 issue of Development, explains how developing sea anemone larvae construct an even more basic epithelial appendage, the tentacle. The paper charts how epithelial cell shape changes drive tentacle development and is also the first to identify candidate genes driving those changes. Most of all, by putting a new model organism representing one of the simplest animals center stage, the study illuminates some of the most fundamental principles animals use to construct a body.
Lacking even left-right symmetry, sea anemones are evolutionarily ancient. But during embryogenesis their larvae compensate for an uninspiring torso by sprouting tentacles from thickened epithelial buds surrounding their mouth. “Nematostella’s body is basically a bag of epithelium,” says Gibson. “And that simplicity makes it a great system for determining how epithelial cells act collectively to shape an appendage. Taking advantage of this fast, easy and cheap experimental system, we can quickly answer questions that give us deep insight into a process, at both the mechanistic and evolutionary levels.”
The all-Stowers study, led by first author Ashleigh Fritz, a graduate student at the University of Kansas School of Medicine working in the Gibson lab, began by imaging Nematostella larvae at the cellular level before, during, and immediately after “juvenile” tentacles sprang from their body. Freshly hatched Nematostella larvae are under intense pressure to get their tentacles up and running, as they use them to pull food toward their mouths. The question was, what kind of cellular reshuffling drove these survival-dependent changes in morphology?
“We thought tentacle outgrowth might be driven by cell proliferation,” says Fritz, noting that some of Nematostella’s freshwater cousins sprout appendages by constant cell division. “Instead, we observed that cells begin thickened and then thin out as tentacles elongate.” In other words, the process was driven not by cell duplication along a “tentacle axis” but rather by stretching a stockpile of cells.
Embryologists call the embryonic thickening of epithelial cells that provides raw material for a mature structure a placode. “Placodes have appeared over and over throughout evolution,” says Gibson, noting that placodes give rise to wings or eyes in flies and feathers and teeth in vertebrates. “Discovering that placodes are also utilized in animals as seemingly primitive as Nematostella shows how fundamental this strategy is in evolution.”
“Transcriptome analysis led us to identify novel tentacle markers,” says Fritz, referring to molecular probes used to define a particular cell type. “Also gene expression patterns that we and others have identified allowed us to construct the first-ever molecular model of how tentacles are patterned.”
In short, the study not only suggests universal principles underlying sculpting of epithelial structures from a placode, but also provides investigators with a toolkit to test whether specific genes drive the process.
An added bonus is that in 2007 a consortium of researchers sequenced the Nematostella genome and reported it to be more “human-like” in size and structure than that of Drosophila or another widely used model system, the nematode C. elegans. As a result, Gibson thinks that for many key questions, Nematostella may represent a better laboratory model than either.“The common ancestor of sea anemones, flies, and humans likely had a surprisingly complex genome,” he says, explaining that over millions of years of evolution flies and worms might have lost some genomic complexity. “As a result, these seemingly simple animals share some key genomic characteristics with humans and other vertebrates.”
In addition to Seidel and Paulson, Gibson lab postdoctoral fellow Aissam Ikmi, Ph.D., also contributed to the study.
The study was funded by the Stowers Institute for Medical Research and the Burroughs Wellcome Fund.
About the Stowers Institute for Medical Research
The Stowers Institute for Medical Research is a non-profit, basic biomedical research organization dedicated to improving human health by studying the fundamental processes of life. Jim Stowers, founder of American Century Investments, and his wife, Virginia, opened the Institute in 2000. Since then, the Institute has spent over 900 million dollars in pursuit of its mission.
Currently, the Institute is home to nearly 550 researchers and support personnel; over 20 independent research programs; and more than a dozen technology-development and core facilities.
Gina Kirchweger | Newswise
Cryo-electron microscopy achieves unprecedented resolution using new computational methods
24.03.2017 | DOE/Lawrence Berkeley National Laboratory
How cheetahs stay fit and healthy
24.03.2017 | Forschungsverbund Berlin e.V.
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...
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...
In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...
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...
Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to simulate these confined natural conditions in artificial vesicles for the first time. As reported in the academic journal Small, the results are offering better insight into the development of nanoreactors and artificial organelles.
Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to...
20.03.2017 | Event News
14.03.2017 | Event News
07.03.2017 | Event News
24.03.2017 | Materials Sciences
24.03.2017 | Physics and Astronomy
24.03.2017 | Physics and Astronomy