One gene for pea pod color generates green pods while a variant of that gene gives rise to the yellow-pod phenotype, a feature that helped Gregor Mendel, the 19th century Austrian priest and scientist, first describe genetic inheritance. However, many modern-day geneticists are focused on the strange ability of some genes to be expressed spontaneously in either of two possible ways.
In order to better understand this phenomenon of epigenetic multistability, a major complication for Mendelian genetics, scientists at UC San Diego grew virtual bacterial cells in a computer experiment. They created a two-phenotype model system programmed to grow in ways that matched natural growth. In a deceptively simple experiment, they then recorded the degree to which the two phenotypes varied over time in individual cells, and then repeated the experiment over and over. They reported in the Nov. 19 online edition of Proceedings of the National Academy of Sciences (PNAS) that variability due to epigenetic multistability is larger and persists much longer than they had expected.
While the phenomenon is yet to be discovered in the human genome, the new results suggest that researchers studying bacteria should carefully design their experiments to measure variability due to epigenetic multistability. Even in human cells, multistability may play a role in genes can alternate between “on” and “off” settings.
“Scientists studying bacteria have simply not had the tools to understand phenotypic variability,” said Ting Lu, lead author of the study who was a physics graduate student in the lab of bioengineering professor Jeff Hasty. (Lu is currently a postdoctoral fellow at Princeton University.) “We’ve arrived at a theoretical framework that allows experimenters to measure the ephemeral nature of epigenetics.”
Epigenetic multistability may be vital to cells that are outwardly different, but genetically identical. Only one of the two phenotypes might thrive in a given environmental condition; however, the less advantageous phenotype could come in handy if the environmental conditions unexpectedly changed. By having both phenotypes, the chances would be better that the best one will be present when needed.
Researchers in many labs recently have demonstrated that gene expression can be surprisingly random. The framework established in the UCSD study evaluates how such noisy gene expression affects the properties of developing cellular colonies, such as the progression of bacterial infections or the growth of a population of cancerous cells.
The PNAS paper also documented that the time it takes for a population of cells to reach a stable variance depends on the initial growth conditions and how easily those conditions support cell growth.
“Different results can emerge depending on how cells are grown,” said Jeff Hasty, a professor of bioengineering at UCSD and senior author of the paper. “Our results should allow all researchers studying bacteria to better understand the variability they routinely see from one experiment to the next."
This work is supported by the National Institutes of Health.
Source: UCSD
Related stories:
Herbicide-resistant grape could revitalize Midwest wine industry
An herbicide that is effective at killing broadleaf weeds in corn, but also annihilated most of the grapes in Illinois and other Midwestern states, may finally have a worthy contender. Researchers at the University of Illinois have developed a new grape called Improved Chancellor which is resistant to the popular herbicide 2, 4-D.
Researchers continue to find genes for type 1 diabetes
Genetics researchers have identified two novel gene locations that raise the risk of type 1 diabetes. As they continue to reveal pieces of the complicated genetic puzzle for this disease, the researchers expect to improve predictive tests and devise preventive strategies.
Iowa State University researcher developed forerunner of Nobel research in 1986
This year's Nobel Prize for chemistry was given to researchers for their work on illuminating living cells that enables scientists and researchers to study how genes, proteins, and entire cells operate.
Scientists discover cause of weakness in marine animal hybrids
Scientists at Scripps Institution of Oceanography at UC San Diego have shown for the first time that a genetic malfunction found in marine crustaceans called copepods likely explains why populations of animals that diverge and eventually reconnect produce weak "hybrid" offspring.
Doctors warn patients of HPV link to oral cancer
Ten years ago, most of Dr. Brian Nussenbaum's oral cancer patients were men over 60 who used tobacco and drank heavily. Today, his patients with oral cancer look different. And so does the risky behavior that seems to be leading to their cancer.
Discovering a new life form in the hot springs of Yellowstone
Geysers, mud pots, steam vents and hot springs in the region now known as Yellowstone National Park awed American Indians and early European explorers. Now, two million tourists visit the park in northwestern Wyoming each year to watch wildlife and view the spectacular scenery. Scientists home in on the hot springs, exploring their ecology and plumbing their scalding waters in search of highly adapted, heretofore-undiscovered microorganisms.
Scientists trace molecular origin of proportional development
When it comes to embryo formation in the lowly fruit fly, a little molecular messiness actually leads to enhanced developmental precision, according to a study in the Oct. 14
Developmental Cell from Cincinnati Children's Hospital Medical Center.
Embryonic heart exhibits impressive regenerative capacity
A new study demonstrates that the embryonic mouse heart has an astounding capacity to regenerate, a phenomenon previously observed only in non-mammalian species. The research, published by Cell Press in the October 14th issue of the journal
Developmental Cell, describes the previously unrecognized potential of the embryonic heart to replace diseased tissue through compensatory proliferation of healthy cells.
