In September of 2004, HOPES team members Devon McGee and Agnieszka Milczarek visited the Laboratory of Stem Cell Biology and Pharmacology of Neurodegenerative Diseases, headed by Dr. Elena Cattaneo, at the University of Milan in Italy. HOPES would like to thank Dr. Cattaneo and the rest of the members of the lab for taking time out of their busy schedules to meet with us and share with us the philosophy behind their research. The following is the lab´s mission statement:
The ingenuity of mankind, often anonymous, has taught humanity to always make better use of water which runs ceaselessly… The mill is the processor of the river directing simplicity and chaos into a powerful and productive force. Our laboratory strives to remain a mill in constant operation.
Dr. Elena Cattaneo did her graduate work at the Massachusetts Institute of Technology in the lab of Professor R.D.G. McKay, where she became interested in neural stem cells and their potential therapeutic applications to neurodegenerative diseases. She decided to focus her studies on neural stem cells from a human brain structure called the striatum because she realized that “the striatum is at the center of many biophysiological events.” The striatum forms part of the basal ganglia, and is the part of the brain most affected in HD. (For more information on the basal ganglia and their role in HD, click here.) Remarkably, while at MIT, she was able to “immortalize” stem cells from the striatum and create a new cell line called ST14A. The cells exhibit quite accurately many of the properties of nerve cells from the striatum and can be engineered to express either normal or mutant huntingtin. (For more information about huntingtin, click here.) The cell line offers a great model of the Huntington´s disease and researchers around the world now use it in their labs.
Presently, Dr. Cattaneo works in the Department of Pharmacological Sciences and in the Center of Excellence on Neurodegenerative Diseases at the University of Milan, where she is a full professor of pharmaceutical biotechnology. Since 1995, she has collaborated on Coalition for the Cure, an international research group organized by the Huntington´s Disease Society of America. (For more information on the Huntington´s Disease Society of America, click here.) She has also collaborated on the Cure HD Initiative sponsored by the Hereditary Disease Foundation. Since 1988, she has been an investigator in the Italian Telethon Foundation. Dr. Cattaneo has received many awards and distinctions, including the “Le Scienze” Prize for Medicine and a medal from the president of Italy for her work on stem cells and HD. In addition, she coordinates a national program on stem cells and participates in Eurostemcell (www.eurostemcell.org), a group for research on stem cells funded by the European Union.
Dr. Cattaneo´s lab is comprised of senior scientists (similar to post doctoral fellows), junior scientists (similar to graduate students), and undergraduate students. Overall, there are about fifteen people working in the lab. Each member of the lab chooses and proposes his/her own research project to work on. Although the members of the lab have diverse research interests, the lab is unified in its quest to someday find a cure for HD. There are weekly lab meetings and each person is at least partially involved in all ongoing research projects.
Currently, the lab is focused on the mechanisms of neurodegeneration in Huntington´s disease, as well as neural stem cell biology and its potential application to HD and other neurodegenerative diseases. (For more information on stem cells and their potential to treat HD, click here.) The ultimate goals of the lab are to identify cellular pathways that might be suitable for therapeutic intervention and to find new methods for drug testing. While a majority of HD research is focused on the harmful effects of the mutant huntingtin protein, Dr. Cattaneo´s lab looks at the other side of the problem by examining the normal function of huntingtin protein. This is important because not much is known about how the huntingtin protein is supposed to work normally. By investigating the normal function, the researchers hope to find new ways of treating HD. Dr. Cattaneo´s research has revealed that normal huntingtin possesses a variety of anti-apoptotic capabilities, which means that it helps keep cells alive.
Thus, on the basis of Dr. Cattaneo´s work, the damaging effects of HD should be attributed not only to the toxic function of mutant huntingtin, but also to the loss of beneficial function of normal huntingtin. With this in mind, the lab hopes to completely make clear the physiological role of normal huntingtin and its mode of action in order to develop new ways to combat the disease. For example, once more is known about normal huntingtin, researchers can attempt to restore normal huntingtin function in people with HD, and this restoration of normal huntingtin function may significantly alleviate many HD symptoms.
Members of the research lab are also involved in the study of the biology of neural stem cells derived from the developing human brain. Neural stem cells seem promising because they are the developmental source of nerve cells. The number one problem in neurodegenerative diseases like HD is the death of nerve cells, which are usually unable to regenerate themselves. Neural stem cell transplantation may help restore nerve cells and may even prevent nerve cells from dying in the first place.
Neural stem cell therapy for neurodegenerative diseases is still a distant goal and many obstacles remain before it can be used as a treatment. One obstacle, for example, is that it is difficult to properly integrate neural stem cells into a recipient brain. Presently, Dr. Cattaneo´s lab is trying to identify the signals that instruct neural stem cells to undergo division and differentiate into nerve cells. Understanding the mechanisms that regulate nerve cell survival and differentiation will make it easier to develop ways to integrate neural stem cells into the brain. In addition to studying nerve cell division and differentiation, the lab is also producing cell and animal models of brain diseases for studies of cellular mechanisms and of drug efficacy.
HOPES members Devon McGee and Agnieszka Milczarek with Dr. Elena Cattaneo, center.
What´s special to Dr. Cattaneo about HD research?^
HD research involves a great deal of obligation to the HD community and this obligation is what drives Dr. Cattaneo and her coworkers to produce promising results in the lab. The lab often receives not only phone calls but also visits from individuals and families affected by HD, who bring assortments of jams and cookies and cakes to show their gratitude for the researchers´ work. Dr. Cattaneo and the other members of the lab recognize that it is important for the patients and their families to know that someone is constantly working on uncovering the mysteries of HD. For this exact reason, Cattaneo and some of the other researchers occasionally present their scientific results, in non-technical terms at the meetings of Italian associations for people with HD. This constant interaction between the researchers and individuals affected by HD has such a positive effect on the lab that the researchers become not only “driven by curiosity, but also by the desire to help patients.” All the researchers in the lab confess that they feel increased pressure to produce and publish results because they know that they are working for real patients – and this “healthy pressure,” as Dr. Cattaneo calls it, is one of the factors that make HD research so special.
Dr. Cattaneo also believes that HD research is extraordinary because of the close-knit HD research community that continues to develop around the world. Funding and support from associations such as the Hereditary Disease Foundation and the Huntington´s Disease Society of America (HDSA) in the United States and others in the European Union help bring together researchers who share one goal – to find a cure for HD – so that they can work as a team rather than compete with each other for results. Since 1997, the HDSA has coordinated “Coalition for the Cure,” which organizes researchers from almost twenty different laboratories and organizes them into five teams that work on different aspects of HD. Cattaneo says that coalitions such as these not only promote but also require sharing of unpublished results among research labs, which helps the coalition as a whole make progress as researchers build on each other´s ideas. Furthermore, labs that are part of such alliances have the advantage of sharing research materials such as useful genes or experimental mouse strains (for more information on animal models in HD research, click here), which speeds up the research, keeps costs down, and makes possible experiments that might not otherwise be possible. This type of sharing helps research labs circumvent financial and legal obstacles that might prevent them from obtaining materials developed by other research institutions.
On the one hand, being part of a scientific community that emphasizes sharing goes a long way to reduce competitive barriers commonly seen between labs working on similar projects. On the other hand, Cattaneo says it also adds pressure to be constantly productive. Researchers are expected to present new results at each of the annual or biannual meetings they must attend for each coalition or organization. Cattaneo admits that such expectations can add stress to her life, but being part of a community of researchers who have placed complete trust in each other and have vowed to work together for families affected by HD makes it worthwhile. She emphasizes that the formation of such a close-knit community could only have been possible with a disease like HD, because there has been historically much less interest in HD research than in diseases such as Alzheimer´s or Parkinson´s. (For more information on these diseases and how they compare to HD, click here.) Through her work on HD, Dr. Cattaneo has forged strong relationships with researchers from across the globe, including Drs. James Gusella and Marcy MacDonald at Massachusetts General Hospital, whom two other HOPES members visited in the summer of 2004. (For more information about the latter, click here.) In the process, Cattaneo´s obligation to patients has been complemented by the obligation she now feels to produce valuable results that she can share with fellow researchers.
According to Dr. Cattaneo, to be conceptualized correctly, HD must be seen as a cascade in which every single disease event leads to more events that cause further dysfunction and damage (see Figure AH-0.) In some way, HD researchers are lucky because they have a definite single starting point of the disease: a CAG expansion in the Huntington gene. Cattaneo agrees that the genetic nature of HD makes it easier to research than other neurodegenerative diseases, which can have varying genetic and environmental causes. However, the disease cascade has yet to be completely figured out, and Cattaneo stresses that it will be important not only to find a majority of the disease events, but also to arrange them in the correct temporal order; that is, to figure out when each dysfunction occurs, what causes it, and what other dysfunctions it causes itself. As is evident from Figure AH-0, this will not be an easy task.
Researchers in Dr. Cattaneo´s lab are already working on putting together the schematic cascade, but Cattaneo says that the work is difficult since “every result leads to more experimentation.” With every new mechanism she and the researchers discover, there is more they need to find out about its causes and effects. Cattaneo says that often, “your brain goes faster than your hands,” and while she or her colleagues may form hypotheses and ideas rapidly, the funding and time may not allow for immediate experimentation to follow up on those ideas. However, one researcher in the lab, Chiara Zuccato, was recently very successful in figuring out a very important aspect of the disease cascade. After learning that normal huntingtin protein increases the amounts of brain-derived neurotrophic factor (BDNF) in nerve cells, she set out to find the mechanism by which it does so. Zuccato found that normal huntingtin increases the production of BDNF by indirectly inhibiting a molecule called NRSE, which normally prevents the production of BDNF (this finding will be explained in more detail in a later section).
Because BDNF is a protective growth factor in the brain and is depleted in the nerve cells of people with HD, researchers in Dr. Cattaneo´s lab are now focusing their energies on the functions of normal huntingtin and what prevents it from performing these functions in people with HD. This approach is different from the classic research approach that has typically focused only on mutant huntingtin. However, mutant and normal huntingtin may be linked earlier on in the disease cascade and Cattaneo´s lab is now on a quest to figure out how mutant huntingtin´s toxicity could cause normal huntingtin´s loss of function in HD.
Unfortunately, BDNF production is only one of many cellular processes that are disturbed in HD, and Cattaneo says real progress will be made when researchers are finally able to link together all the dysfunctions in a cause-and-effect relationship. Transcriptional dysregulation is a major disease mechanism in HD that affects the production of proteins needed by nerve cells (one of these is BDNF, mentioned above). Mitochondrial dysfunction, which causes abnormalities in energy metabolism, is another major disease mechanism. (For more information on problems with energy metabolism in HD, click here.) As of now, researchers only understand bits and pieces of each of these major mechanisms, and Cattaneo believes that mapping out precisely what events lead to these dysfunctions will be crucial in understanding HD and developing a cure.
Because HD involves a complicated cascade of events, Dr. Cattaneo believes that an effective cure will actually involve a combination of treatments. She is very hopeful about the use of new techniques such as RNA interference, which attack the disease as close as possible to the beginning of the cascade by “silencing” the mutant Huntington gene. However, Cattaneo doesn´t think that such techniques will ever be able to fully block the production of the mutant huntingtin protein. (For more information on RNA interference, click here.) Cattaneo says that “a cure with only one strategy is not realistic; to battle HD you need a more global approach.” In the future, she believes that the most successful therapy, which could turn into a cure, will involve different types of treatments at different stages of the disease. According to Cattaneo, these treatments will ideally begin before the onset of symptoms and change accordingly as the disease progresses from the nerve cell dysfunction stage to the nerve cell death stage. Future treatment of HD may include:
- Stage I: Early treatment with RNA interference to prevent expression of mutant huntingtin; continues throughout the following stages.
- Stage II: Dysfunction of nerve cells combated by drugs that prevent toxic functions of mutant huntingtin and drugs that restore the functions of normal huntingtin.
- Stage III: Nerve cell death combated by cell replacement therapy (possibly with the use of stem cells) as well as protective strategies involving therapy with growth factors such as BDNF.
Dr. Cattaneo believes that for patients, “a cure is anything that gives them more time,” and she hopes that a treatment regimen like the one outlined above could postpone and decrease the symptoms of the disease to such an extent that it could in fact be considered an effective cure.
However, because potential drugs will be used to combat the disease at different time points in different individuals, the researchers will need biomarkers. Biomarkers are biological indicators that can be measured in patients to determine the severity of disease and to show whether drugs are effective in specific stages of the disease. Measuring the severity of symptoms is not sufficient because symptoms can vary so widely between patients and between stages of the disease. A possible biomarker that the Cattaneo lab is considering using is the level and activity of the A2A receptor, a receptor molecule that is expressed by nerve cells in the striatum and becomes more active in the presence of mutant huntingtin. Another possibility involves measuring levels of BDNF, which can also be used to track the progression and severity of the disease.
Dr. Cattaneo´s lab tries to simultaneously identify drug targets as they learn about new disease mechanisms. She stresses that successful drug development cannot happen without a deep understanding of the disease mechanism that the drug is meant to attack. Therefore, she believes that studies on compounds such as nutritional supplements and their effects in people with HD are not as promising at they may seem since most of the studies are conducted without an understanding of how the supplements exert their effects. An understanding of the disease mechanism is essential to picking drug targets – molecules that the drug will act on to alter some pathway – that will be both effective and safe. The drug must act early enough in the pathway to successfully stop the disease cascade, but it must also be specific enough so that it does not cause significant side effects.
Dr. Cattaneo´s lab has contributed to significant breakthroughs in HD research. Prior to the research done by the Cattaneo lab, it was assumed that since the HD allele gives rise to mutant huntingtin, mutant huntingtin must be toxic to nerve cells and it must be the only reason that nerve cells die. Indeed, numerous studies support this notion. However, Dr. Cattaneo´s lab showed that mutant huntingtin is not the only reason that nerve cells die. In fact, it may be only half the reason. Whereas earlier research had simply disregarded normal huntingtin´s role in the HD disease process, the Cattaneo lab found that normal huntingtin is actually crucial to nerve cell survival in the brain. They have found that individuals with the HD allele experience nerve cell death not only because their cells produce toxic mutant huntingtin, but also because the normal huntingtin they produce loses its normal functions.
Dr. Cattaneo and two other members of her lab, Dorotea Rigamonti and Chiara Zuccato, are leading experts in the field of normal huntingtin function. They have amassed a remarkable amount of evidence supporting the notion that normal huntingtin is, in fact, beneficial to nerve cells. They began their research in this area by first inserting extra copies of either normal huntingtin protein or mutant huntingtin protein into nerve cells grown in culture dishes in the lab. In 2000, they reported that nerve cells overproducing normal huntingtin can survive even when deprived of key growth factors or when subjected to other conditions that would normally cause them to die. Furthermore, they found that normal huntingtin appears to keep nerve cells alive by stopping the cascade of events that usually leads to apoptosis, or programmed cell death. They therefore concluded that normal huntingtin serves as a kind of protein “lifesaver” for nerve cells.
Other researchers, such as Scott Zeitlin of Columbia University in the USA, have confirmed these findings by creating knockout mice that express neither mutant huntingtin nor normal huntingtin. In such cases, the mice develop severe brain damage. In this instance, the brain damage can be explained not by mutant huntingtin (because it isn´t present), but by the absence of normal huntingtin (which also is not present). Interrupting huntingtin production at various points in the mice´s lives also leads to apoptosis. Remarkably, mice lacking normal huntingtin display very similar neurological symptoms to mice that express mutant huntingtin, suggesting that the absence of normal huntingtin and the presence of mutant huntingtin might be different sides of the same coin.
Lab members Evangelia Papadimou, Erika Reitano, and Alessia Tarditi, left to right.
The discovery of the importance of normal huntingtin function was a significant contribution to the field of HD research. However, it does not explain why nerve cells in the striatum are targeted preferentially in HD. The huntingtin protein is produced in many cells throughout the body. Since normal huntingtin does not function correctly in people with HD, and since it is present in all types of cells, scientists were puzzled by the fact that only nerve cells in the striatum were seriously affected by the disease. Intrigued by this question, Zuccato and her colleagues undertook an examination of brain-derived neurotrophic factor (BDNF). As discussed above, BDNF is a growth factor that is known to be crucial to the development and survival of nerve cells in the striatum. It is usually produced in the cell bodies of nerve cells in the cortex and then travels to the striatum along fibers that connect the two brain regions. With this is mind, the researchers hypothesized that there might be a connection between BDNF and huntingtin. Amazingly, they found that normal huntingtin stimulates the production of BDNF in nerve cells grown in lab culture dishes. Specifically, huntingtin seems to indirectly activate the “on” switch, or promoter, of the gene that encodes BDNF. When this gene is turned on, it prompts nerve cells to make more BDNF. Normal huntingtin enables the gene to be turned on by inhibiting a molecule called NRSE, which normally turns the gene off. Contrarily, mutant huntingtin does not inhibit NRSE, which means that NRSE stays around and keeps the gene turned off so that no BDNF can be produced. Zuccato and her colleagues confirmed this link between huntingtin and BDNF by carrying out experiments involving genetically engineered mice. They found that mice overproducing normal huntingtin have elevated amounts of BDNF in their brains, whereas mice with mutant huntingtin have lower than normal levels of BDNF in their brains.
The lab´s studies are both enlightening and intriguing because the findings do not necessarily conform to previous hypotheses about the disease. They reveal the true complexity of the disorder. In addition to generating mutant huntingtin which is thought to interfere with several crucial cellular proteins and systems, HD also somehow deprives the brain of normal huntingtin – which would otherwise turn on the gene for the growth factor BDNF and protect nerve cells from apoptosis. As mentioned previously, Cattaneo´s lab believes that mutant huntingtin´s toxicity and normal huntingtin´s loss of function may be related. In fact, another group of researchers has recently shown in genetically engineered mice that mutant huntingtin can destroy normal huntingtin. It is also clear that normal huntingtin interacts with the brain in complex ways and there are many aspects of huntingtin that need to be further explored. As Dr. Cattaneo noted, “Much additional research must be completed before these findings can help patients, and we want to be clear that this is not a cure. But we are optimistic that our work will help guide the development of new therapies, such as drugs to replace or boost the activity of normal huntingtin, or to increase levels of another brain protein.”
By more clearly exposing the complexities of HD, Dr. Cattaneo´s lab has opened the door for the production of better treatments for the disease. Many of the drugs currently available only alleviate some of the symptoms of HD and can have serious side effects. Furthermore, the drugs often treat one symptom only to make another symptom worse. For example, doctors often prescribe sedatives to control involuntary movements, but these drugs also decrease levels of the neurotransmitter dopamine in the brain, worsening the patient´s depressive symptoms.
As a result of the findings of Dr. Cattaneo´s lab, several more innovative treatments for HD are currently being tested, such as replacing the damaged nerve cells with transplants of fetal tissue or injecting neurotrophic factors such as BDNF into the striatum. The use of fetal tissues is very controversial and raises many ethical questions, but the preliminary results do look promising. Researchers at the School of Medicine in Creteil, France have transplanted fetal nerve cells into the striata of five people with HD. Three of the people improved significantly in terms of motor and intellectual function. Currently, clinical trials with a larger number of patients are being conducted.
Obstacles and Challenges^
Although Dr. Cattaneo certainly enjoys the rewards of being a part of an HD research team, she emphasizes that she and her coworkers face numerous obstacles. The intense pressure and time constraints that accompany HD research force the researchers to live demanding and hectic lifestyles. Because the lab is part of an HD coalition that meets every six months, as well as other organizations that meet regularly, the Cattaneo lab is expected to maintain constant progress. The labs in the coalition are the best in the world and Dr. Cattaneo said she feels pressure to live up to high expectations. She confesses that she is usually unable to sleep the night before coalition meetings because the excitement and pressure are great.
In order to be able to report new results every six months, members of the lab cannot afford to waste any time. They generally arrive at the lab at 8:30 am and leave between 9:00 pm and 11:00 pm. If they leave at 6 pm, they consider it a half-day. Furthermore, they do not take weekends off. As researcher Chiara Zuccato put it, “There are twenty-four hours in a day – I need to sleep about seven hours and it takes over an hour to get to and from work. For pretty much the rest of the day, I´m in the lab.” Dr. Cattaneo has two children and it is very hard for her to spend so much time away from them. Luckily, it is an Italian way of life to have support from the family and her mother-in-law helps take care of the children.
Many people are not able to handle the pace of this lifestyle, and it is not uncommon for researchers to leave the lab after a year or two. Ironically, Dr. Cattaneo enjoys her work so much that it is hard for her to be away from the lab. The last time she took a vacation she got up very early every morning before her family woke up to check her e-mail and maintain correspondence with the lab.
A big obstacle in Italian academia is the lack of available jobs. Currently, the government is attempting to abolish assistant professorships. If this happens, even individuals with many qualifications will not be able to find positions within academic settings. An individual could be highly prolific for fifteen years and make significant research discoveries and still not be able to advance in the field. This situation in the US would be equivalent to post doctoral students never being able to become professors. Dr. Cattaneo sees this lack of job positions as an obstacle because it will be even harder to recruit new people into her lab.
Because the lab uses stem cells and there are numerous ethical issues surrounding stem cells, it has encountered a few obstacles in the form of religious and political interference. (For a concise discussion on stem cell ethics, click here.) However, members of the lab believe that this problem is a result of the public being misinformed. They believe that once the public better understands stem cell research this issue will no longer be an obstacle.
Another obstacle arises when the researchers must decide whether they should devote to making an old experiment more complete or whether they should devote time to starting a new experiment. On one hand, they want the experiment to be completely thorough. On the other hand, their minds are racing with new ideas and they want to start new experiments. This situation is worsened by the fact that it is difficult for the researchers to satisfy both their curiosities and their own expectations. In one instance, Zuccato had already written and submitted a paper about an experiment when she realized that there was something missing. Despite having a ton of other things to do, she immediately stopped submission of the paper and decided to redo the entire experiment with added conditions to make it more thorough. Thus, for researchers, it is a constant struggle to balance thoroughness with productivity.
Surprisingly, Dr. Cattaneo explains that money is not normally a major obstacle for her lab, because it is supported by many sources, including the University of Milan, the European community, and many American foundations. Happily, for at least the next four years, there is adequate funding. Dr. Cattaneo is very thankful for this: she points out that “research always begets new research,” and funding is crucial for exploring new possibilities.
Between their work on normal huntingtin function, mutant huntingtin function, and the development of stem cells into useful nerve cell models, the members of the Cattaneo lab will have their hands full for many years to come. Dr. Cattaneo knows that she and her fellow lab members will continue working their twelve hour days in hopes of finding new treatments for HD. As Cattaneo puts it, in Italy, the researcher´s reward “is not monetary; it is a dot on a gel” – that is, a single dot showing the successful results of an experiment. For Cattaneo, helping young enthusiastic researchers get started in the field is almost as rewarding. Dr. Cattaneo reminds us that “science has no guarantees but one: that researchers will keep working.” She encourages people affected by HD to learn about the research efforts going on around the world, and she hopes that the knowledge that “someone is thinking about this [disease] every minute of every day” can be comforting and reassuring.
For further reading^
- To find out more about the Cattaneo lab, please visit its website at http://users.unimi.it/DPS/struttura.php?id=10.
- For more information about the Huntington´s Disease Society of America and their Coalition for the Cure, visit the HDSA website at www.hdsa.org.
- Cattaneo E., Rigamonti D. Goffredo D. and Zuccato C. (2001) Loss of normal huntingtin function: new developments in Huntington´s disease research. Trends in Neurosciences, 24:3, 182-187.
This article is fairly easy to read. It succinctly summarizes the background of HD as well as the various hypotheses about its molecular pathology.
- Rossi F. and Cattaneo E. (2002) Neural stem cell therapy for neurological diseases: dreams and reality. Nature Reviews Neuroscience, 3, 401-409.
This is a very in-depth article about the therapeutic potential of neural stem cell therapy. It also explains all of the obstacles that must be overcome before neural stem cell therapy can become a viable treatment.
- Zuccato C. et al. (2001) Loss of huntingtin-mediated BDNF gene transcription in Huntington´s disease. Science, 293, 493-496.
This is a technical article that describes how the beneficial activity of huntingtin is lost in people with HD and how this leads to decreased production of BDNF.
- Zuccato C., Tartari T., Crotti C., Goffredo D., Valenza M., Conti L., Cataudella T., Leavitt B. R., Hayden M. R.,Timmusk T., Rigamonti D. and Cattaneo E. (2003) Huntingtin interacts with REST/NRSF to modulate the transcription of NRSE-controlled neuronal genes. Nature Genetics, 35: 76-83.
This article is very technical. It describes in detail how normal huntingtin increases transcription of BDNF by silencing NRSE.
– A. Milczarek and D. McGee, 04/29/05