|ASCB Visits Big Sky Country|
Stem Cell Researchers Meet in Bozeman
Numerous scientific meetings have been organized in recent years to highlight current research findings on sources of stem cells, demonstrating their multiand pluripotent nature and exploring potential therapeutic avenues for the treatment of disease. Why then have a meeting that focuses on signal transduction in stem cells? This question was answered in the opening keynote address by NIDDK Director Allen Spiegel in which he emphasized the high therapeutic potential of human stem cells, but also the need to more fully understand, at a basic level, the cell and molecular biology of stem cells to facilitate harnessing the full potential of these cells. While stem cells of human origin including human embryonic stem (ES) cells, hematopoietic stem cells and hepatic stem cells are the more obvious therapeutics, the meeting highlighted stem cell research ongoing in diverse organisms from fly to mouse to human. An underlying theme was the search for fundamental and conserved signal pathways that function to control stem cell growth, survival and fate.
A common feature of stem cells of diverse origin and type is self-renewal. A molecular understanding of the precise cues and the signal pathways that mediate self-renewal is key to harnessing the full potential of stem cells. The microenvironmental cues that dictate stem cell self-renewal in vivo is termed the stemcell niche and has been elegantly modeled in the Drosophila ovary by Haifan Lin of Duke. His presentation highlighted the piwi family of proteins which play an evolutionarily-conserved role in stem cell maintenance from plants to humans. Other presentations revealed advances in the cellular and molecular features of the hematopoietic stem cell niche comprised of a subset of N-cadherin positive osteoblasts residing at the bone surface (Linheng Li of the Stowers Institute). In the lung, a putative lung stem cell population positive for markers of both Type II and Clara cells reside in specific regions of the terminal bronchioles referred to as the bronchioalveolar junction that are implicated in airway renewal. Peter Donovan of Thomas Jefferson, Toru Nakano of Osaka University and Strat May of the University of Florida focused on identifying factors and signal pathways that are required for stem cell proliferation and survival using in vitro and in vivo approaches. Specific combinations of growth factors are required for proliferation and survival of embryonic germ (EG) cells including bFGF, LIF and c-Kit ligand. Also, Wnt proteins, secreted factors better known for their role in development and cancer, stimulate proliferation of hematopoietic stem cells (HSC).
Pathways downstream of these extracellular cues are being vigorously studied and components of the phosphatidylinositol 3kinase (PI3K) pathway including PTEN and Akt will be important for controlling survival and proliferation of stem cells similar to their role in non-stem cell systems. Distinct from most somatic cells, stem cells appear to possess unique cell cycle control mechanisms which account for their rapid rate of proliferation. Analysis of cyclin-dependent kinase (cdk) activity in mouse embryonic stem cells reveals novel cdk-cyclin complexes that are insensitive to the well defined cdk inhibitors and are largely constitutively active (Steve Dalton of the University of Georgia).
Besides self-renewal, stem cells are pluripotent and identification of the factors and signals that maintain this unique stem cell property is of high priority (Hans Schöler of the University of Pennsylvania). Recent findings were presented unveiling the key requirements for Nanog (Shinya Yamanaka of the Nara Institute), a homeobox transcription factor, and Foxd3 (Patricia Labosky of the University of Pennsylvania), a wingedhelix transcription factor, in ES cell functioning and early development of the epiblast. Esg1, a stem cell-specific protein with a less defined molecular function, was also identified as important in stem cell maintenance and early development (Tetsuya Tanaka of the NIH National Institute on Aging). Gene expression patterns in stem cells are also certainly controlled by the DNA methylation and chromatin acetylation status and will dictate pluripotency and developmental potential. Treating neural stem cells with inhibitors of DNA methylation and histone deacetylases increases their hematopoietic potential, supporting this notion (Albrecht Muller of the University of Wurzburg). In fact, this type of “re-programming” may account for the high failure rate of cloning by nuclear transfer. Ian Wilmut of the Roslin Institute suggested that identifying procedures to enhance the ability of the oocyte cytoplasm to remodel the chromatin of the transferred nucleus to achieve appropriate developmental regulation of gene expression is a priority.
—Lynn Heasley, University of Colorado Health Science Center
|Cell Biology in East Africa: Challenges and Satisfactions|
Former ASCB President J. Richard McIntosh was asked to describe his sabbatical work at Makerere University in Kampala, Uganda. He submitted the following report.
I write from Kampala, Uganda, where I have worked for seven of the last twelve months at Makerere University in the School of Veterinary Medicine. My host, George Lubega, heads the Department of Parasitology and Microbiology, where he specializes in nematode and trypanosome infections of farm animals and people. Upon his return from Ph.D. and postdoctoral training at McGill, George started a Lab for Molecular Biology. I joined this group to pursue their discovery that trypanosome tubulin injected into laboratory mice grants protection against subsequent trypanosome infection. This result is, of course, surprising, because it is not obvious how antibodies raised against a cytoplasmic protein could affect host-pathogen interactions. The experiments from Lubega’s group are, however, quite convincing1. Protection is effective against several strains of Trypanosoma brucei, and even against other species of African trypanosomes, so the protecting antigen is not one of the “Variable Surface Glycoproteins,” which are the immunedominant antigen on the parasite’s surface. It is these that change so frequently during a normal infection that the host’s immune response is ineffective.
The possibility that protection comes purified tubulin has been made unlikely by Lubega’s findings that rabbit antibodies raised against either very pure trypanosome tubulin or against a synthetic polypeptide that corresponds to the 12 Cterminal amino acids from trypanosome btubulin will kill trypanosomes grown in culture2. I found these results sufficiently convincing and interesting to make me want to help figure out what is going on. Thanks to support from the University of Colorado and a Fulbright Research Fellowship, I have taken a halfyear’s leave, spread over a full calendar year and divided as four 1-2 month stints. This rather ungainly organization has allowed me both to keep in touch with my lab in Boulder and to spend enough time in Kampala to work where the parasites and their hosts are available for convenient study.
My life in Kampala has been extraordinarily pleasant, thanks to several aspects of this year’s leave. My wife Marjorie was able to take a leave from the History Department at Colorado and has enjoyed the hospitality of the Department of Women and Gender Studies at Makerere. There she has taught in the graduate program and studied the roles of women in Uganda’s market economy, viewed from both historical and anthropological perspectives. Marjorie and her collaborator, Grace Bantebya, the Chair of WGS, have organized the activities of several research assistants to obtain interviews with about 140 women who work in various sectors of Uganda’s economy, including highflying business executives, market vendors, nurses, teachers, and manual laborers. The research has taken Marjorie over much of Uganda, including a weekend in a village, where she was the first “mzungu” (white person) ever to have stayed the night. Our living circumstances could hardly have been nicer: a spacious apartment in a block of rebuilt flats right on campus and an easy walk from our departments. The view from our back windows is lined by lush trees: avocado, nut and lime. These filter the morning sun and help keep the flat cool, although the temperatures in Kampala are quite moderate: 70–80o F both day and night, thanks to its 3,000+ foot elevation and proximity to Lake Victoria, which is almost as big as Lake Superior. Makerere University is on a hill at the edge of Kampala, which reduces both air pollution and the population of mosquitoes, a serious issue in a country where malaria is endemic. More interesting local fauna includes flocks of Marabou storks with six-foot wingspans and beaks to match, egrets, pied crows, hawks, buzzards and ibises with iridescent wings. Our trees have even sported the occasional monkey.
We have felt blessed by not having to take public transportation from a more distant dwelling; traffic in Kampala, like most cities in the developing world, is both heavy and aggressive. We have also been able to walk to a local market for shopping at stalls where women sell produce from the surrounding countryside. Shopping at large supermarkets can usually be done with the help of “matatu taxis,” which are minibuses that hawk their destination, wait until they are filled, then tear off through traffic, leaving off and picking up passengers on demand at some risk to the life and limb of all. Our diet has included delicious midday dinners, cooked in university cafeterias (beans, chicken, beef, local fish, liver, “matooke”, which resembles plantain, rice, and “posho”, a stiff cornmeal porridge). Our suppers at home have been assembled mainly from beans, a delicious variety of greens, avocados, tomatoes, and cucumbers with pineapples, mangos, papayas, and passion fruit for dessert.
Makerere was the first university in East Africa, and for many years the best. During the troubled times of the rule of recentlydeceased Idi Amin, this university, like many of Uganda’s institutions, fell on hard times. (The runs of journals in cell biology start with impressive coverage in the 1960s but stop cold in the late 1970s-early ‘80s.) The university is now rebuilding, but it must do so under a government that has made the difficult but reasonable decision to invest in the literacy of children, rather than higher education. Already they are coming close to the goal of “Universal Primary Education,” including girls; this presages important cultural changes in the near future. Most university students must, however, now pay fees. Classes are often large (up to several hundred students/classroom), and they meet both late into weekday nights and through much of the day on Saturday. Faculty salaries are usually insufficient to keep a family, so many univ e r s i t y teachers have additional jobs. Books and supplies are scarce, so lectures contain much material that is delivered slowly and must be learned by rote. Facilities for laboratory teaching are also limited. While the university library includes books, newspapers, and computers with internet connections, the latter are often slow and fickle; MedLine searches are time consuming, and downloading papers is glacial. Most current money for periodicals is going into online subscriptions, but the resources are not sufficient to get up-to-date issues of Nature, Journal of Cell Biology, Science, or Cell. In spite of these difficulties, the educational level of the faculty is high and many of the students are exceptionally bright and keen to learn.
Makerere’s School of Veterinary Medicine is an impressive part of an impressive institution. Its principal focus is on the farm animals of Uganda. Its secondary interest is the indigenous wild animals, which include an impressive subset of Africa’s game. A Bachelor’s degree in Veterinary Medicine is designed to train a student who already has an extensive secondary school education in science (like England, Uganda still has “A-level” exams, which are commonly more advanced than the standards imposed by most American high schools). After a period of hands-on fieldwork, graduates have sufficient training to become practicing vets. There is also a post-graduate program that offers specialized training in various kinds of veterinary research. The Master’s Degree (M.Sc.) includes both course work and a thesis.
The Molecular Biology Lab was established by Lubega upon his return from training in Montreal. With support from the university and the World Health Organization, Lubega has assembled a real molecular lab, complete with plenty of space and all the hardware one needs for most experiments with recombinant DNA. With advanced planning, one can get all essential supplies. Thus, when money is available, experiments are limited only by one’s imagination; indeed, this is one of the three or four best setup labs in Uganda. Everything is, however, quite expensive, because transportation costs must be added to catalogue prices, and sometimes there is an import tariff as well. Complex equipment is even more of a problem, because the nearest service engineer is generally thousands of miles away. Moreover, the university’s infrastructure does not include stable electric power or running hot water. On top of this, dollars or pounds sterling are hard to come by, so there is a premium on keeping experiments as simple as possible.
The lab includes undergraduates, M.Sc. and Ph.D. research students, some technicians, and a visiting English parasitologist who is supported by the Wellcome Trust. Lubega is very busy, since he is Head of Department as well as the principal lecturer in the molecular M.Sc. program. Thus, the more senior research students often play the role of mentor to the younger ones, much as happens in an American lab, although there are no post docs here to help the pedagogic mix. I have felt at home in this lab since my arrival. Lubega assigned me about six feet of bench, and he designated a small room for light microscopy. There I have set up the ancient but honorable Zeiss microscope that I brought as a gift from the University of Colorado to Makerere. Since it includes a film camera and all the traditional optics, I hoped that it would allow us to visualize trypanosome under the influence of cytotoxic antibodies.
Shortly after my arrival in September, I got promising images of cultured trypanosome with both phase and fluorescence optics. Building largely on work from Keith Gull’s lab, I developed a method for getting small numbers of blood-form trypanosomes fixed and attached to glass coverslips, so they could be processed for immunofluorescence. I also gave a set of about 30 lectures on cell biology to the M.Sc. students, relying heavily on the 1995 edition of Alberts et al., which the Taylor and Francis Group was kind enough to contribute.
I then worked with Donasian Ochola, the most senior of Lubega’s research students interested in trypanosomes; we confirmed the cytotoxic effects of the old tubulin antibodies on T. brucei growing in culture. Shortly thereafter, David Kateete succeeded with efficient bacterial expression of the T. brucei’s genes for aand b-tubulin, so 100 mg quantitites of protein could be purified for immunization of rabbits, either as separate proteins or as a-b mixtures. These antibodies have now been obtained as second and third bleeds and the sera prepared for examination. The rabbit that was immunized most aggressively is now producing cytotoxic antibodies, laying to rest the fear that the published effect was due to a contaminating trypanosome protein. Moreover, the cytotoxicity is blocked by absorption of the antibody with recombinant tubulin, so we have gained confidence that this surprising phenomenon is reproducible and reliable. Now we are working to understand the killing by following the antibodies into the cells and looking for characteristic pathologies at death. We have also prepared affinity columns with which to purify both the antibodies and native trypanosome tubulin. Some monoclonal antibodies raised in Gull’s lab against trypanosome cytoskeletal components are also under study. Thus, what started as an exciting but implausible phenomenon is blossoming into an investigation that might lead to an effective and economical vaccine against sleeping sickness.
You may wonder how Marjorie and I were able to set up such an interesting and rewarding experience. The process was a combination of serendipity and persistence. Our son works in development economics, and he pointed us towards Uganda as a place with sufficient infrastructure and political stability to make a research year practical. Over the years we have hosted several African visitors to the US and learned from them about the strengths and problems of different cities and institutions. We surfed the web to see who was publishing what from where, and both of us found promising possibilities in Kampala. We then set up a two-week visit to Uganda (at our own expense) to meet our potential hosts and explore specific research projects. Finally, we applied for support from Fulbright, which provided us with some cash and useful training for living in sub-Saharan Africa, as well as connections with the American Embassy, which proved useful in transporting research tools and materials.
This year has provided a valuable test of what it might be like to pursue scientific work in the developing world after my “retirement.” While coping with slow computer lines, unstable electricity, limited research resources, and the hassles of living in a poor country are chores that require flexibility and perseverance, the benefits that my wife and I have enjoyed from the friendships, the diversity of life, and the possibility of making a little progress on something that might actually help with a world health problem have far outweighed these costs.
The ASCB is grateful to the following members who have recently given gifts to support Society activities:
|George Beadle An Uncommon Farmer
Paul Berg and Maxine Singer CSHL Press, © 2003, 383 pp., illus., index Hardcover, $35, ISBN 0-87969-688-5
Written by Nobel Laureate Paul Berg of Stanford University and President Emerita of the Carnegie Institution Maxine Singer, George Beadle, An Uncommon Farmer, explores the life a Nebraska farm boy who grew up to become an intellectual powerhouse in genetics and molecular biology.
George Beadle was a towering scientific figure whose work from the 1930s to 1960 marked the transition from classical genetics to the molecular era. Among other distinctions, he made the pivotal, Nobel Prize-winning discovery with Edward Tatum that the role of genes is to specify proteins. From 1946 to 1960 he led the Caltech Biology Division, rebuilding it to a powerhouse in molecular biology, and afterwards became a successful President of the University of Chicago.
How to Win the Nobel Prize - An Unexpected Life in Science
In 1989, J. Michael Bishop along with Harold Varmus were awarded the Nobel Prize for their discovery that normal genes under certain conditions can cause cancer. In this book, Bishop tells how he and Varmus made their momentous discovery. More than a lively account of the making of a brilliant scientist, it is the story of the long and ongoing struggles to control infectious diseases and to find and attack the causes of cancer.
How to Win the Nobel Prize affords the pleasure of hearing about science from a brilliant practitioner who is a humanist at heart. Bishop’s perspective will be valued by anyone interested in biomedical research and in the past, present, and future of the battle against cancer.
|Members In The News|
Tony Hyman of the Max Planck Institute of Molecular Cell Biology & Genetics, an ASCB member since 1996, won the 2003 European Molecular Biology Organization (EMBO) Gold Medal.
Story Landis, an ASCB member since 1976, has been appointed Director of the NIH National Institutes of Neurological Disorders and Strokes, effective September 1.
|Grants & Opportunities|
NIAID Fellowships. The National Institute of Allergy and Infectious Diseases is accepting applications for biodefense training and development researchers in the areas of prevention, detection, diagnosis and treatment of diseases caused by potential bioterrorism agents. Support includes grants, fellowships and career development awards.
NIH Loan Repayment Programs. The National Institutes of Health Loan Repayment Programs offer up to $35,000 per year to repay student loans of scientists, physicians, dentists, and other health professionals willing to commit to a career in clinical, pediatric, health disparities or contraception and infertility research. Applicants must have doctorate and be able to commit at least 50% of their time for two years conducting qualified research. Apply before December 31.
MARC Grants. The NIGMS Minority Access to Research Careers is accepting applications for predoctoral fellowships. Application deadline is April 5 and December 5 of each year.
Postdoctoral Researcher. Two positions available immediately to study signal transduction pathways regulating neuronal functional and structural plasticity. The goal of this work is to relate biochemistry regulatory mechanisms to physiological effects in adults brain tissue. The candidate must have a Ph.D. and should have experience in either biochemistry or neuronal electrophysiology. Work will be performed at The University of Texas Southwestern Medical Center, a leading research institution. One position is limited to a US citizen or permanent resident. Interested candidates should send their C.Vs and contact information of three references to James A. Bibb, Ph.D., UT Southwestern is an equal opportunity, affirmative action employer.