Male Frogs Turned Into Females By Pesticide Atrazine

Atrazine, one of the world's most widely used pesticides, wreaks havoc with the sex lives of adult male frogs, emasculating three-quarters of them and turning one in 10 into females, according to a new study by University of California, Berkeley, biologists.



The 75 percent that are chemically castrated are essentially "dead" because of their inability to reproduce in the wild, reports UC Berkeley's Tyrone B. Hayes, professor of integrative biology.



"These male frogs are missing testosterone and all the things that testosterone controls, including sperm. So their fertility is as low as 10 percent in some cases, and that is only if we isolate those animals and pair them with females," he said. "In an environment where they are competing with unexposed animals, they have zero chance of reproducing."



The 10 percent or more that turn from males into females - something not known to occur under natural conditions in amphibians - can successfully mate with male frogs but, because they are genetically male, all their offspring are male.



"When we grow these guys up, depending on the family, we will get anywhere from 10 to 50 percent females," Hayes said. "In a population, the genetically male females can decrease or wipe out a population just because they skew sex ratios so badly."



Though the experiments were performed on a common laboratory frog, the African clawed frog (Xenopus laevis), field studies indicate that atrazine, a potent endocrine disruptor, similarly affects frogs in the wild, and could possibly be one of the causes of amphibian declines around the globe, Hayes said.



Hayes and his UC Berkeley colleagues report their results in this week's online early edition of the journal Proceedings of the National Academy of Sciences. Last week, Hayes and colleagues published a review of pesticide's effects on amphibians in the Journal of Experimental Biology, concluding that atrazine is a likely contributor to worldwide amphibian declines.



"These kinds of problems, like sex-reversing animals skewing sex ratios, are much more dangerous than any chemical that would kill off a population of frogs," he said. "In exposed populations, it looks like there are frogs breeding but, in fact, the population is being very slowly degraded by the introduction of these altered animals."



Some 80 million pounds of the herbicide atrazine are applied annually in the United States on corn and sorghum to control weeds and increase crop yield, but such widespread use also makes atrazine the most common pesticide contaminant of ground and surface water, according to various studies.



More and more research, however, is showing that atrazine interferes with endocrine hormones, such as estrogen and testosterone - in fish, amphibians, birds, reptiles, laboratory rodents and even human cell lines at levels of parts per billion. Recent studies also found a possible link between human birth defects and low birth weight and atrazine exposure in the womb.
















As a result of these studies, the Environmental Protection Agency (EPA) is reviewing its regulations on use of the pesticide. Several states are considering banning atrazine, and six class action lawsuits have been filed seeking to eliminate its use. The European Union already bars the use of atrazine.



Hayes's studies in the early 2000s were the first to show that the hormonal effects of atrazine disrupt sexual development in amphibians. Working with the African clawed frog, Hayes and his colleagues showed in 2002 that tadpoles raised in atrazine-contaminated water become hermaphrodites - they develop both female (ovaries) and male (testes) gonads. This occurred at atrazine levels as low as 0.1 parts per billion (ppb), 30 times lower than levels allowed in drinking water by the EPA (3 ppb).



Subsequent studies showed that native leopard frogs (Rana pipiens) collected from atrazine-contaminated streams in the Midwest, including from areas up to 1,000 miles from where atrazine is applied, often had eggs in their testes. And many males had lower testosterone levels than normal females and smaller than normal voice boxes, presumably limiting their ability to call mates.



Hayes' research also established that many frogs in Midwestern streams contaminated by atrazine and other pesticides have compromised immune systems, leading to increased mortality from bacterial disease.



Those early studies were hampered by the inability to easily distinguish genetically male from genetically female frogs. Male frogs have two identical sex chromosomes (ZZ) while females have both a Z and a W - the opposite of XX female and XY male humans. But because all frog chromosomes look the same under a light microscope, it's not simple to distinguish male from female.



To overcome this, Hayes' colleague Roger Liu developed a line of all-male frogs so that the genetics would be unequivocal.



"Before, we knew we got fewer males than we should have, and we got hermaphrodites. Now, we have clearly shown that many of these animals are sex-reversed males," Hayes said. "We have animals that are females, in the sense that they behave like females: They have estrogen, lay eggs, they mate with other males. Atrazine has caused a hormonal imbalance that has made them develop into the wrong sex, in terms of their genetic constitution."



Coincidentally, another lab in 2008 discovered a sex-linked genetic marker in Xenopus, which has allowed Hayes to confirm the genetic sex of his frogs.



In Hayes' study, where 40 frogs lived for about three years after hatching in water with 2.5 ppb atrazine, about 10 percent of the frogs appeared to be resistant to the effects of the pesticide. In ongoing studies, Hayes is investigating whether this apparent resistance is inherited, as well as whether the sex-reversed males have more susceptible offspring.



Syngenta, which manufactures atrazine, disputes many of these studies, including Hayes', that show adverse effects of the presticide. But Hayes said that "when you have studies all over the world showing problems with atrazine in every vertebrate that has been looked at - fish, frogs, reptiles, birds, mammals - all of them can't be wrong."



"What people have to realize is that, just as with taking pharmaceuticals, they have to decide whether the benefits outweigh the costs," he said. "Not every frog or every human will be affected by atrazine, but do you want to take a chance, what with all the other things that we know atrazine does, not just to humans but to rodents and frogs and fish?"



Hayes' long-term studies of the effects of atrazine on frogs have been assisted by many UC Berkeley undergraduate students, including co-authors on the current paper: Vicky Khoury, Anne Narayan, Mariam Nazir, Andrew Park, Lillian Adame, Elton Chan, and graduate students Travis Brown, Daniel Buchholz, Sherrie Gallipeau and Theresa Stueve.



The work was funded by the Park Water Co., Mitch Kapor, Freada Klein, the Mitch Kapor Foundation, the David Foundation, the Cornell-Douglas Foundation, the Wallace Foundation, the UC Berkeley Class of '43 endowed chair and the Howard Hughes Biology Fellows Program.



Source:

Robert Sanders

University of California - Berkeley

Novel Evolutionary Tools For Studying Human Populations Using The X Chromosome

Research in the Department of Genetics at University of Leicester is well-known for its human population studies with the Y chromosome, including the relationship between the male surname and the Y chromosome, as well as a better understanding of the Viking settlement in the Northwest England.



Now a new research project using the X chromosome (present in one copy in men but two in women) will be the first readily applicable non sex-specific evolutionary tool to provide a more sex-balanced view in human population studies.



Although the Y chromosome is a better established evolutionary tool and has been used in many evolutionary studies, apart from ease of usage, it has a lot of limitations preventing it becoming the most evolutionary informative DNA segments in the Human genome.



Now as part of her doctoral studies, Holly Leung is investigating the potential of the X chromosome as another evolutionary informative segment in the human genome.



Holly said: "This may be the real key to solving many existing mysteries of human population evolution, for example the 'out of Africa' theory and the Neolithic expansion in Europe.



"The Y chromosome is the most common evolutionary tool we use in population studies but it doesn't mean that it is the most evolutionary informative DNA segment in the human genome.



"There are many limitations with the use of the Y chromosome which make it non-applicable to every evolutionary study because of its male specific lineage. It provides sex-biased information to the male and as a single genetic marker restricts the diversity of information source.



"The aim of my research is to produce and assess the usefulness of the evolutionary information provided by the X chromosome. It shares some properties with the Y chromosome, but provides an expanded view of human evolution because of its presence in males and females and the many independent genetic markers it contains."



Holly Leung is 24 years old, graduate from the BSc Medical Genetics in the University of Leicester in 2006. In the same year, she continues her study in the Department of Genetics doing PhD Genetics research as she discovered her interest in Evolutionary Genetics specifically in the study of evolutionary history of Human population.



The research is being presented to the public at the University of Leicester on Thursday 26th June. The Festival of Postgraduate Research introduces employers and the public to the next generation of innovators and cutting-edge researchers, and gives postgraduate researchers the opportunity to explain the real world implications of their research to a wide ranging audience.



More information about the Festival of Postgraduate Research is available at: le.ac.uk/gradschool/festival



UNIVERSITY OF LEICESTER




Founded in 1921, the University of Leicester has 19,000 students from 136 countries. Teaching in 18 subject areas has been graded Excellent by the Quality Assurance Agency- including 14 successive scores - a consistent run of success matched by just one other UK University. Leicester is world renowned for the invention of DNA Fingerprinting by Professor Sir Alec Jeffreys and houses Europe's biggest academic Space Research Centre. 90% of staff are actively engaged in high quality research and 13 subject areas have been awarded the highest rating of 5* and 5 for research quality, demonstrating excellence at an international level. The University's research grant income places it among the top 20 UK research universities. The University employs over 3,000 people, has an annual turnover of ВЈ184m, covers an estate of 94 hectares and is engaged in a ВЈ300m investment programme- among the biggest of any UK university.



Source:

le.ac.uk

2007 Class Of Distinguished Young Scholars In Medical Research Announced By W.M. Keck Foundation

The W.M. Keck Foundation, a leading supporter of high-impact medical research, science and engineering, has announced the 2007 class of grant recipients under its Distinguished Young Scholars in Medical Research Program.



Robert A. Day, Chairman and Chief Executive Officer said: "Now in its ninth year, our Young Scholars program is designed to give the nation's most promising young scientists the resources they need to pursue potentially breakthrough research projects in biomedicine. We are very pleased to support this group of Young Scholars who clearly exhibit extraordinary promise for future research and academic leadership."



Under the program, each grant recipient's sponsoring institution receives an award of up to $1 million to support the scientist's research activities for a period of up to five years, as well as to enable the institution to purchase necessary equipment and resources to facilitate the scientist's ongoing study. It is hoped that the investment in the Keck Scholars will greatly benefit society for generations to come with continued advances in understanding -- and combating -- the fundamental mechanisms of human disease.



The Young Scholars Program was initiated in 1999 and has awarded grants totalling nearly $45 million to date. Each grant applicant must be nominated by his or her research institution and then evaluated by the Foundation's Medical Research Board and a Scientific Advisory Committee and unanimously approved by the Foundation's Board of Directors. Nominations are accepted on an invitation-only basis.



The 2007 class of Distinguished Young Scholars is:



* Job Dekker, Ph.D., Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School -- Dr. Dekker has developed a system to study the complex way in which chromosomes are regulated. By comparing cancer and normal cells, the research has the potential to uncover defects in chromosome regulation that cause malignancy, which may lead to advances in combating cancerous cells in the body.



* Wallace Marshall, Ph.D., Department of Biochemistry, University of California, San Francisco -- Dr Marshall investigates how cilia, the hair-like projections that move substances over a cell, are involved as key factors in debilitating human diseases. By studying blue-green algae, Dr. Marshall's research may lead to new insights into human ciliary disorders, such as polycystic kidney disease and retinal degeneration.



* Amy Wagers, Ph.D., Harvard Stem Cell Institute, Section on Developmental and Stem Cell Biology at Joslin Diabetes Center, Harvard Medical School -- Dr. Wagers investigates the decline with age in the body's ability to maintain homeostatic cell replacement and to regenerate cells after injury. Building on previous research of the relationship between the age of stem cells and their ability to regenerate themselves, Dr. Wagers hopes to discover a method to slow down or reverse the natural process of aging, which may potentially lead to advances in treating age-related illnesses, such as diabetes, immune deficiencies, muscle weakness, and cancer.
















* Xander Wehrens, M.D., Ph.D., Department of Molecular Physiology & Biophysics, Baylor College of Medicine -- Dr. Wehrens hopes to define the mechanisms of specialized protein complexes in excitable cells, such as heart muscle. His research has the potential to explain the underlying causes of certain types of heart failure and cardiomyopathy.



* Jennifer Zallen, Ph.D., Developmental Biology Program, Memorial Sloan-Kettering Cancer Center -- Dr. Zallen's work on the nature of three-dimensional Rosetta cell structures combines molecular genetics, live imaging, and quantitative statistical analysis. Her study of a fruit fly's cell structure may be applied to other organisms' cell structures, with the potential to develop approaches to analyze cell behavior and structure in living embryos.



The Foundation's Board of Directors has unanimously approved the recommendations made by the Scientific Advisory Committee.







Based in Los Angeles, the W.M. Keck Foundation was established in 1954 by the late W.M. Keck, founder of the Superior Oil Company. The Foundation's grant making is focused primarily on pioneering efforts in the areas of medical research, science and engineering. The Foundation also maintains a Southern California grant program that provides support in the areas of civic and community services with a special emphasis on children and youth.



For more information about the W.M. Keck Foundation and the Young scholars program, please visit the Foundation's web site at wmkeck/programs/scholars.html.



Source: Louise Weston

W. M. Keck Foundation

Cancer Biologist Dario Altieri To Lead The Wistar Institute Cancer Center

The Wistar Institute announces that cancer biologist Dario C. Altieri, M.D., has been appointed director of Wistar's Cancer Center, a National Cancer Institute-designated Cancer Center since 1972. Altieri will also take on the role of the Institute's Chief Scientific Officer and professor in the Wistar Molecular and Cellular Oncogenesis Program.


Altieri will join Wistar full-time in September from his previous appointment as professor and chair of the Department of Cancer Biology at the University of Massachusetts Medical School.


The Wistar Institute recruited Altieri after an extensive search for a cancer biologist to lead the scientific faculty of the Wistar Cancer Center. Current Cancer Center Director Russel E. Kaufman, M.D., steps away from his Wistar Cancer Center leadership position to focus on his role as president and CEO of The Wistar Institute.


"The Wistar Institute Cancer Center recently achieved a very successful NCI review and renewal of its Cancer Center Support Grant, and now is the ideal time to pass on the leadership," Kaufman said. "Dario Altieri has the experience and intellect we desired in a candidate to further our progress in both basic cancer science and our ongoing efforts in translating scientific discovery into practical therapies to prevent and cure cancer."


"Throughout his career, he has shown excellent leadership and a remarkable ability to recruit top-notch scientific talent, capabilities that we plan to utilize in earnest as we expand our research faculty," Kaufman added.


At Wistar, Altieri will continue his laboratory's successful research program on the mechanisms that underlie how tumor cells survive and proliferate in cancer. In particular, his laboratory is interested in how tumor cells evade the normal processes that cause cells with genetic faults to self-destruct. Understanding these mechanisms could provide new therapeutic targets and novel approaches for virtually every type of human cancer. To date, his research has resulted in nine patents and over 160 scientific articles.


Born in Milan, Italy, and educated at the University of Milan School of Medicine, Altieri became a practicing clinician at the university, where he would later earn a postgraduate specialty degree in clinical and experimental hematology. In 1987, he joined the Scripps Clinic and Research Foundation in La Jolla, Calif., first as a research fellow and later as a member of the faculty.


In 1994, Altieri became an associate professor at the Yale University School of Medicine, was named professor in 1999, and served in that role for some time before being recruited as the founding chair of the Department of Cancer Biology at the University of Massachusetts.


Altieri is also an accomplished scientific citizen of the international cancer research community. He is currently on the editorial board of seven scientific publications and a reviewer for 16 such journals. As a mentor, he has guided the careers of over 40 men and women, from undergraduates to postdoctoral fellows. In 2005, he co-founded both the National Cancer Biology Training Consortium, an effort to promote scientific excellence in the next generation of cancer researchers, and the Pancreatic Cancer Alliance, an all-volunteer patient advocacy organization devoted to supporting the efforts of pancreatic cancer research.


Source:

Wistar Institute

Brain Tumor Growth Linked To Lowered Expression Of Hundreds Of Immune Function Genes

A new study links progression of a lethal type of brain tumor with reduced expression of more than 600 immune system genes, suggesting how complex the immune response is to the cancer and the resulting difficulty in targeting specific immune system proteins for treatment.


Previous research found that people with allergies were less likely to be diagnosed with this type of brain cancer, called glioblastoma multiforme. However, it was not clear whether allergies reduce brain tumor risk or whether the growing tumor "cures" allergies.


To further explore the relationship between these two conditions, scientists examined almost 1,000 genes associated with allergies, immunity and inflammation to learn how they were affected once these tumors were present in the brain.


The researchers expected to see that allergy gene function was low in brain tumor tissue, which would be consistent with the known immune system suppression that is associated with these tumors.


What they found was a surprise: Allergy genes were not the only immune function genes suppressed during tumor growth. Instead, in almost 70 percent of the 919 genes examined, the genes' activity was decreased as the brain tumors progressed.


"This result provides evidence that there is a relationship between glioblastoma and allergies specifically, high tumor aggressiveness is associated with low allergy-related gene function," said Judith Schwartzbaum, lead author of the study and an associate professor of epidemiology at Ohio State University. "But it still does not tell us whether allergies inhibit tumor growth or tumors block allergies."


The findings also show that immune function in the brain continues to change as these tumors grow.


"As the tumor progresses, the majority of the immune-function genes express themselves at lower levels," Schwartzbaum said. "So we know that with progression there is less immune function, but we don't know which came first, the lowered immune function or the cancer."


The cause of this kind of cancer remains unknown, and there is no cure. The complexity of the immune response to this tumor suggests that it will be difficult to identify key immune function proteins that inhibit tumor growth. Schwartzbaum said that in addition to using information about the immune system to treat tumors, researchers must also study the immune system to find ways to prevent these aggressive tumors.


The study is published in a recent issue of the journal Neuro-Oncology.


Glioblastomas constitute up to 60 percent of adult primary brain tumors in the United States, affecting an estimated 3 in 100,000 people. Patients who undergo surgery, radiation and chemotherapy survive on average for about one year, with fewer than a quarter of patients surviving up to two years and fewer than 10 percent surviving up to five years.


The researchers used publicly available data from genetic analysis of 142 brain tumor tissue samples collected from patients with glioblastoma multiforme tumors as part of the National Cancer Institute's The Cancer Genome Atlas project.















The scientists used levels of expression of the CD133 gene as an indicator of tumor progression. Previous studies had suggested that activation of this gene is related to tumor aggression and a poor clinical outcome.


With these data, Schwartzbaum and colleagues then plotted expression of immune function genes against levels of CD133 expression in these tumors.


Gene expression refers to the switching on or activation of genes. Schwartzbaum and her colleagues analyzed mRNA expression data in their study; mRNA synthesis is the first step in gene expression and may lead to creation of functional proteins.


The analysis showed that higher levels of CD133 expression were associated with lower levels of immune function gene expression in 69 percent of the genes examined.


There were, however, immune function genes whose expression increased with CD133 expression, including a cytokine gene called interleukin-17 that is linked to inflammation, and a gene related to suppression of immune function called NCAM-1.


The genes whose function was lowered with tumor progression included most of those associated with allergies, as well as, paradoxically, many of those that counteract allergy genes. In another surprising finding, many genes known to suppress immune function were also expressed at lower levels as the tumor progressed.


"That was a surprise because you'd think that genes that suppress the immune system would be more active in these tumors, which may be lethal, in part, because they are immunosuppressive. But we didn't see that," Schwartzbaum said.


Schwartzbaum is planning to focus her subsequent research on the end products of genetic activation, immune function proteins or cytokines.


She plans to analyze 1,200 samples from the Janus Serum Bank in Norway, which were collected on average 10 years before brain tumor diagnosis, to find out whether the presence of certain cytokines in those samples might offer clues that will help identify people at high risk for brain tumor development.


This work was supported by the National Cancer Institute and the Neurosciences Signature Program in the Ohio State College of Medicine.


Schwartzbaum conducted the research with Kun Huang and Jianhua Yu of Ohio State's Comprehensive Cancer Center; Sean Lawler and E. Antonio Chiocca of Ohio State's Department of Neurological Surgery; and Bo Ding of the Institute of Environmental Medicine at the Karolinska Institutet in Stockholm, where Schwartzbaum is a visiting researcher.


Source: Ohio State University

New Test For Safer Biomedical Research Results

In cancer research, as in most other biomedical sciences, they are playing a key role: living cells, kept in sterile plastic containers with red culture media populating incubators in laboratories around the world. But do researchers always know what is really living in their culture dishes? Under the microscope, different cell lines are almost impossible to distinguish from each other. When these important research objects stop growing without apparent reason - is it because of the manipulations by the scientists or because of an invisible viral or bacterial infection?



Contaminations with other cell lines or pathogenic agents are a common and well-known problem. Often they are the reason why cell experiments fail to produce useable or reproducible results. Even worse, laboratory staff can get infected with dangerous pathogens from a cell culture.



To make those important cell culture experiments safer, DKFZ researchers Dr. Markus Schmitt and Dr. Michael Pawlita have developed a test which is able to identify 37 different cell contaminations in a single run. The researchers have tested the system in over 700 samples from different research labs and have now published their results.



The method called "Multiplex cell Contamination Test" (McCT) detects not only wide-spread viruses but also a number of mycoplasmas, which are considered the major contaminators of cell cultures. In addition, the test checks the cells for their origin. Thus, if dog genetic material is found in what are supposed to be monkey cells, then a contamination of the cell culture is obvious. The test also includes detection of commonly used standard cell lines. Contamination with the fast-growing cancer cell line HeLa, for example, is a dreaded source of false results.



Pawlita and Schmitt found contaminations in a high percentage of cell samples. Twenty-two percent of tested cultures were contaminated with one of the various types of the parasitic bacterium called mycoplasma. "What we noticed about the results," says Markus Schmitt, "was that contaminations were frequent in some laboratories, while others sent in cultures that were constantly clean. Thus, care in laboratory work seems to play an important role."



The test is highly specific and needs no more than ten copies of foreign DNA in the cell sample to be positive. This is a sensitivity which is comparable to or even higher than those of previously available commercial mycoplasma tests. McCT results are reproducible to 99.6 percent. The method is based on multiplication of specific DNA sequences by polymerase chain reaction and subsequent detection of the multiplied DNA regions. A special advantage of the new test is that it can be carried out on a high-throughput basis. The DKFZ researchers can manage up to 1,000 tests per week.



Markus Schmitt und Michael Pawlita: High-throughput detection and multiplex identification of cell contaminations. Nucleic Acids Research 2009, DOI: 10.1093/nar/gkp581



Source:
Dr. Sibylle Kohlstädt


Helmholtz Association of German Research Centres

Scientists Use RNA To Reprogram One Cell Type Into Another

For the past decade, researchers have tried to tweak cells at the gene and nucleus level to reprogram their identity. Now, working on the idea that the signature of a cell is defined by molecules called messenger RNAs, which contain the chemical blueprint for how to make a protein, researchers at the University of Pennsylvania School of Medicine, School of Arts and Sciences and School of Engineering have found another way to change one cell type into another.


By simply flooding one cell type, a nerve cell, with the an abundance of a specific type of messenger RNA (mRNA) from another cell type, the investigators changed a neuron into an astrocyte-like cell, a star-shaped brain cell that helps to maintain the blood-brain barrier, regulates the chemical environment around cells, responds to injury, and releases regulatory substances.


James Eberwine, PhD, Elmer Holmes Bobst Professor of Pharmacology, Junhyong Kim, PhD, Edmund J. and Louise W. Kahn Term Endowed Professor of Biology and first author Jai-Yoon Sul, PhD, Assistant Professor of Pharmacology, and colleagues report their findings online this week in the Proceedings of the National Academy of Sciences. This approach offers the possibility for a new type of cell-based therapy for neurodegenerative and other diseases.


"In some ways, this is akin to what a virus does," explains Eberwine, "When a virus infects a cell it affects the host cell genome and the RNAs that it can make." By putting the RNA of one cell type, in the correct amounts, into another cell type, we were able to change its function."


"This research overturns the notion that all cells are permanently hardwired with little ability to change their physiology," notes Sul.


"What's new about this approach is that we didn't have to make the host cell pluripotent, that is the ability to develop into any of three major tissue types, we can directly convert from one cell type to another, without the intermediate step," explains Eberwine. The scientists put in an excess of astrocyte messenger RNAs into the neuron cell body using phototransfection, a method they created a few years ago that creates temporary pores in the cell membrane. "The RNA population was then diffused into the cell and the host cell did the rest," adds Eberwine.


"We liken the differentiated cells to ecological communities, forests and meadows," notes Kim. "Each have similar organisms but have settled on particular characteristics that we recognize as distinct. And, just as ecological communities can be nudged from one type to another, we thought we could nudge differentiated cells from one type to another through the use of the RNA population. So, we like to think of cells as an ecological community of molecules, with dynamic molecular interactions producing a larger system-level cell function similar to how organism interactions generate forests and meadows.


The approach they used, called Transcriptome induced phenotype remodeling, or TIPeR, is distinct from the induced pluripotent stem cell (iPS) approach in that host cells do not have to be dedifferentiated to a pluripotent state and then redifferentiated with growth factors to the destination cell type. This work is more similar to the prior nuclear transfer work in which the nucleus of one cell is transferred into another cell where upon the transferred nucleus then directs the cell to change phenotype based upon the RNAs that are made.















TIPeR uses RNA populations to direct the DNA in the host nucleus to change the cell's RNA populations to that of the destination cell type, which in turn changes the phenotype of the cell.


There are about 100,000 mRNA molecules in a neuron at any one time. The researchers transferred nearly double that: About 200,000 astrocyte mRNAs were transferred into the neuron, effectively dampening the neuron mRNA's ability to be translated and made into protein.


Essentially the team extracted and produced mRNA from an astrocyte, then used phototransfection to create pores in the neuron cell membrane to flood it with an excess of astrocyte mRNAs, which reside in the neuron host cell cytoplasm. Because there are now so many astrocyte mRNAs versus neuron mRNAs, they take over like a virus and the astrocyte mRNAs are translated into astrocyte proteins in the cytoplasm. These astrocyte proteins then influence gene expression in the host nucleus so that astrocyte genes are turned on and astrocyte cell-enriched proteins are made.


To track the change from a neuron to an astrocyte, the team looked at the RNA profile, shape, and physiology of the new cell. "For now, these are astrocyte-like cells," says Eberwine. "While the cells don't look like neurons any longer, they don't have the mature star-like astrocyte shape, but rather look like immature astrocytes. The new cell expresses astrocyte proteins and has an astrocyte-like physiology. We start to see changes within a week and they are stable over the life of the primary cell culture."


These studies were enabled through the collaboration of a number of investigators spanning multiple disciplines including David Meaney from Bioengineering, Vijay Kumar and David Cappelleri from Mechanical Engineering and Junhyong Kim and Miler Lee from Biology. The additional Pharmacology Department contributors include Chia-wen Wu, Fanyi Zeng, Jeanine Jochems, Tae Kyung Kim, Tiina Peritz, Peter Buckley and Minsun Kim.


Future studies are envisioned towards the generation of distinct cell types and dissection of the core set of RNAs responsible for the generation of particular cellular phenotypes.


This work was funded by grants from the W. M. Keck Foundation, the National Institutes of Health, and the State of Pennsylvania.


PENN Medicine is a $3.6 billion enterprise dedicated to the related missions of medical education, biomedical research, and excellence in patient care. PENN Medicine consists of the University of Pennsylvania School of Medicine (founded in 1765 as the nation's first medical school) and the University of Pennsylvania Health System.


Penn's School of Medicine is currently ranked #4 in the nation in U.S.News & World Report's survey of top research-oriented medical schools; and, according to most recent data from the National Institutes of Health, received over $379 million in NIH research funds in the 2006 fiscal year. Supporting 1,700 fulltime faculty and 700 students, the School of Medicine is recognized worldwide for its superior education and training of the next generation of physician-scientists and leaders of academic medicine.


The University of Pennsylvania Health System (UPHS) includes its flagship hospital, the Hospital of the University of Pennsylvania, rated one of the nation's top ten "Honor Roll" hospitals by U.S.News & World Report; Pennsylvania Hospital, the nation's first hospital; and Penn Presbyterian Medical Center. In addition UPHS includes a primary-care provider network; a faculty practice plan; home care, hospice, and nursing home; three multispecialty satellite facilities; as well as the Penn Medicine at Rittenhouse campus, which offers comprehensive inpatient rehabilitation facilities and outpatient services in multiple specialties.


Source: University of Pennsylvania School of Medicine