A report of recent research progress in MS Summer/Fall 2002
In Search of the Genes for MS
by Sara M. Bernstein
Leena Peltonen grew up in a small town in Finland, where she decided to become a doctor at age 10 when her brother was diagnosed with childhood diabetes. She earned MD and PhD degrees and began studying the population of her homeland, identifying genes for Marfan syndrome (a disease that may occur in extremely tall people), hyperlipidemia and lactose intolerance. Now at the University of California, Los Angeles, she is among the tal-ented group of “detectives” focusing on the genes underlying MS with funding from the National MS Society.
In 1992, the Society began a major targeted research initiative to search for genes that make people susceptible to developing MS. Genes are segments of hereditary material that direct all activities of a cell. MS occurs too frequently in certain families to be accounted for simply by chance, but a single gene alone does not determine MS. Evidence suggests that MS is a multigenic disease, meaning that many separately inherited genes contribute to MS susceptibility, making the search more complex. Society-funded investigators are taking many approaches to finding MS genes, and are making exciting headway.
The MS DNA Bank
Stephen L. Hauser, MD (University of California, San Francisco) and his team are collecting and analyzing genetic material from people with MS and their families. So far, Hauser has banked material from hundreds of families, totaling thousands of individuals, and including approximately 1,000 people with MS. (For more on this effort and how to participate, see pages 3 and 9.) Based on analyses of the first 180 families, Hauser’s team is focusing on six regions that seem to have the greatest like-lihood of contributing to the risk of MS.
The team also is analyzing genes that may contribute to the clinical
severity of disease. For example, they reported that the gene for the immune
protein TGF-beta was associated with a mild course of
MS (Journal of Neuroimmunology, May 1, 2001). Hauser and colleagues also have found that early manifestations of MS in the optic nerve or spinal cord are shared by family members with MS, indicating that genetics influence the clinical expression of the disease (Brain, January 2002). Hauser has shared thousands of DNA samples with laboratories nationwide and all over the world, including Australia, France, and Scotland. The importance of his team’s gene library is reflected in a new, five-year Society grant for this project for $1.3 million, that began April 1, 2002.
Narrowing the Search
Putting together information from previous studies, Jonathan Haines, PhD (Vanderbilt University School of Medicine, Nashville) found that a region on chromosome 19 looked promising for containing a gene for MS. (Chromosomes are threadlike packages of genetic material within the cell.) Working with Hauser and Margaret Pericak-Vance, PhD (Duke University, Durham, NC), and funded by a Pilot Research Award, his team examined 137 families with two or more people with MS and 262 families with one person with MS. They analyzed eight “single nucleotide polymor-phisms,” or SNPs, on chromosome 19. SNPs are markers, or indicators that an MS gene may be nearby (see page 4). Haines and colleagues found that several markers occur more often in people with MS than in their relatives. This suggests that one of only a few genes in this region is involved in MS (Neurogenetics, October 2001).
The Immune Genes
Brian Weinshenker, MD (Mayo Clinic and Foundation, Rochester, MN) is focusing on genes that govern the immune system. His team is searching for genetic variations such as SNPs in people with MS, and determining whether these unique variations point to genes that influence MS susceptibility and progression.
Weinshenker’s team has confirmed previous studies that associated susceptibility to MS with the gene for CTLA4 – a molecule that stimulates immune cells (53 rd Annual Meeting of the American Academy of Neurology [AAN], April 2001, Abstract #P02.017). At this year’s AAN meeting, Weinshenker’s team reported that SNPs in the gene for the immune protein IL-4 may be related to MS susceptibility and severity (Abstract #P06.091).
Weinshenker also presented exciting findings related to genetic factors
that might underlie some of the gender differences in MS, at the 2002 AAN
meeting. His team had previously found that a lower frequency of certain
variations that appear to cause in-creased production of interferon gamma
(an immune protein that incites inflammation in MS) in men may In Search
of MS Genes protect them from developing MS. Now, they have confirmed these
findings in three distinct populations from Minnesota, Ireland and Sardinia
(Abstract #S43.004). Further studies are underway to determine if this
gene explains the predilection of women to develop MS, in collaboration
with Clara Pelfrey, PhD (Cleveland Clinic Foundation), a Society grantee
who is exploring gender differences in the immune response in MS, and Koen
Vandenbroeck, MSc, PhD (Queen’s University of Belfast, UK), who also found
genetic differences by gender in the interferon gamma gene.
John Richert, MD (Georgetown University Medical Center, Washington, D.C.) had found that a key immune system gene called Sp3 was not activated in most people with MS. Sp3 is the gene for a “transcription factor” that turns on and off other genes in immune cells. Richert has obtained large regions of DNA from chromosome 7 that contain this gene, and is using this material to determine how the gene is controlled. So far, his team has shown that the protein that is coded for by the Sp3 gene is generated through highly unusual processes. Once these are clarified, the team can use this information to investigate how the gene’s activity might be modulated in MS.
Spanning the Globe
Groups who share the same ancestry are likely to have a greater number of similar genetic backgrounds than do more distantly related people, making it easier for scientists to pick out tiny variations linked to disease. Therefore, it should be easier to identify DNA abnormalities that may be responsible for MS in these populations.
Jorge Oksenberg, PhD (University of California, San Francisco), a collaborator of Stephen Hauser, MD, is collecting genetic material from a large number of families from different ethnic groups with at least one person who has MS. MS tends to affect people of Northern European heritage, and is less likely to occur in people from East Asia or in African Americans. Ten centers worldwide have provided samples from 754 families, including 756 individuals with MS and 1,117 unaffected family members. A large group of African-American patients and their families were recruited for enrollment into this study. Contrasting the genetic makeup of these groups may offer insight into genes that help cause – or help protect from – MS.
Oksenberg’s results so far demonstrate that genes not only influence who is at risk for MS, but also affect clinical features such as age of symptom onset, severity, progression and response to drugs. Oksenberg’s funding has recently been renewed through 2005 to extend these observations in populations from different ethnic backgrounds considered at low to medium risk for developing MS, particularly African Americans. More results from Oksenberg and colleagues are reported in “Microarray Technology: Expanding the Possibilities,” on page 7.
Leena Peltonen, MD, PhD (University of California, Los Angeles) and colleagues had performed a genome-wide scan (a scan of all genes in the human body) of Finnish families affected by MS. Four regions were detected as possible locations of genes for MS. With funding from the Society, Peltonen’s team narrowed down areas of interest on chromosomes 5 and 17. They also have recruited an additional 713 families for their studies. Peltonen recently was awarded a new research grant from the Society, and will focus her efforts on studying variations in chromosome 5 that may be indications of a gene for MS.
Tasmania has the highest prevalence of MS of any state or territory in Australia and has excellent genealogical records dating back to 1838. Both factors make it a superb place to study MS genes, according to Society grantee Trevor Kilpatrick, MBBS, PhD (The Royal Melbourne Hospital, Australia). Relatively few people settled the area, so Tasmanians may share genes that predispose them to MS. His team has collected data from more than 182 people with MS and 1,223 of their family members without MS. Kilpatrick and colleagues report progress in identifying segments of HLA genes (genes that dictate many of the body’s immune responses) in this population that may contribute to susceptibility to MS (The American Journal of Human Genetics, May 2002).
Expanding the Horizon
The recent completion of a draft of the human genome (all the genetic information in humans) provides these researchers with a wealth of information on existing genes and on variations in genetic material that may or may not be related to MS. Furthermore, new technologies also are expanding the horizons for genetics researchers (see page 7). These factors will surely speed up MS genetics efforts. But no search is possible without the participation of individuals with MS and their families. See page 9 to find out how you can help in the search for the genes underlying MS?
Building a DNA Bank
A conversation with Dr. Stephen L. Hauser
Stephen L. Hauser, MD, directs a groundbreaking effort, supported by the National MS Society, to assemble DNA samples from people with MS and their families, and share them with researchers worldwide. A former Society-funded postdoctoral fellow and Harry Weaver Neuroscience Scholar, he chairs the Department of Neurology at the University of California, San Francisco.
How did you get interested in MS research?
“When I was in my second year at Harvard Medical School, my goal was to become a physician in Maine. Then I met a 27-year-old female patient who had a very aggressive form of MS, and I saw the devastation that this disease can cause. Caring for her was the most moving experience I had in medical school, and I decided to devote my career to fighting MS.”
From whom are your team members obtaining DNA?
“We’re focusing on three groups of people with MS and their parents and/or siblings: families with multiple members who have MS; families with only one member who has MS; and families of ethnic groups, such as African-Americans, who do not usually get MS. We now have a database of 2,700 people — 900 people with MS and about 1,800 family members. In addition to the DNA itself, we collect information about the people with MS–the onset of their disease, its progress, and types of symptoms. No one has ever assembled MS information from this many individuals. For researchers, this is priceless data."
Why is this DNA bank so important?
“Data such as this will help answer several questions: Are there genetic factors that determine whether a person with MS will have particular types of clinical problems? Is MS one problem or several problems? What genes influence how MS behaves clinically? And those are just a few of the areas that will benefit from the library.”
How will people use this information ten years from now?
“I don’t know—and that’s good news. The fields of genetics and proteomics now enjoy unbelievably rapid advances in technology. The beauty of this library is that it is useful today and it will be even more valuable the closer we get to solving the mysteries of MS. All of us who work on this project are profoundly grateful to National MS Society donors who have made it possible to pull this information together.”
Genetic Markers: Finding Needles in the Haystack
How do you find the gene – or in the case of MS, the genes – that confer susceptibility to disease? Basically, MS genetics researchers are looking for “genetic markers,” variations in genes that may contribute to MS. These markers are tiny needles in the haystack of the human genome, that is, all the genetic information necessary to build a human being.
Genes are units of heredity that are passed from parent to child, influencing personality, intelligence, physical appearance and other traits. Most of the 100 trillion cells in the human body contain the entire human genome, which comprises about 30,000 to 40,000 genes. These genes are packaged in chromosomes in the cell nucleus (Figure 1). Each person has 23 pairs of chromosomes, with one of each pair coming from each parent.
Within the gene, DNA (deoxyribonucleic acid) is the chemical that carries the instructions for making living things. DNA looks like a long ladder twisted into a helix, or coil. When uncoiled, the genome is about six feet long. The sides of the “ladder” are composed of sugar and phosphate molecules, and the “rungs” consist of nucleotide base pairs. These base pairs are made of four chemicals – adenine, thymine, guanine and cytosine. Adenine always pairs with thymine and guanine always pairs with cytosine.
The initial letters of these chemicals’ names – A, T, G, and C – are the “letters” of the DNA code. Each gene’s code combines the four chemicals in various ways, forming instructions, such as “ATCATCTTGGTGTT.” A chemical similar to DNA, ribonucleic acid (RNA), is a copy of these instructions that transports them from the nucleus of the cell to where the cell uses them to make the proteins that comprise the body and determine its function.
Mutations as “Markers”
A mutation in the genetic code – where base pairs are deleted, inserted or improperly “switched” – may result in susceptibility to disease. In some diseases, such as cystic fibrosis, three base pairs are missing in one gene – a relatively “simple” genetic error that results in a devastating disease. In MS and other “complex” genetic diseases, however, researchers believe that one gene does not “cause” disease, but that many genes are involved, increasing the predisposition or susceptibility to disease. (It will be necessary to understand how genes interact with environmental agents, such as viruses, diet and other factors to fully understand the cause of MS.) Researchers are looking for genetic markers for MS, that is, indications of such mutations, by tracing markers and their possible association with MS through generations of families.
Figure 1. All of the information it takes to “build” a human
being — 30,000 to
40,000 genes, that is — are packaged within most cells in the body, in the form of
“DNA” (deoxyribonucleic acid). DNA is a six-foot ladder coiled within the cell,
and packaged into chromosomes. Variations in the nucleotide base pairs – the
chemicals that comprise the “rungs” of this ladder – serve as markers for re-searchers.
By identifying these tiny variations, geneticists can speed up their
search for genes that make people susceptible to diseases such as MS.
There are several types of markers, and one that is becoming more useful to MS genetics researchers is the single nucleotide polymorphism (SNP). This variation occurs when just one nucleotide base replaces another, for example, an “A” replaces a “T.”
Each person’s genetic material contains about three million SNPs, most of which are not responsible for diseases, but the ones located near genes associated with disease will also be linked with the disease. Researchers are tracing SNPs that are inherited by people with MS, because these may be signposts for nearby genes that contribute to this disease. Occasionally, an SNP itself may cause disease.
“When we collect genetic material from people, we extract genes from cells in their blood,” explains Brian Weinshenker, MD (Mayo Clinic and Foundation, Rochester, MN). “We detect SNPs by amplifying genes a million-fold with a chemical reaction, called PCR (polymerase chain reaction), and putting pieces of these genes in certain types of gel. We visualize the DNA material with one of a variety of techniques, typically labeling with a radioactive chemical. We watch how the fragments of DNA move in the gel in order to see if there is some variation in the genetic material from people with MS.”
“SNPs have several advantages over other markers,” adds Jonathan Haines, PhD (Vanderbilt University School of Medicine, Nashville). “There are three million of them – more than other markers – and we can identify them more easily due to advances in genetics technology.”
Haines and Weinshenker’s studies (see page 2) have been expedited by the nearly complete Human Genome Project, an international effort to map the entire sequence of genetic material in humans, including SNPs. “Thanks to this effort, we now know more than half of the SNPs in humans,” says Weinshenker. “We have used this information to streamline our activities; we need less time to discover SNPs so we have more time to test these variations in people with multiple sclerosis.”
Clinical Trials — 2002
Now available on the National MS Society Web site:
Agents in Clinical Trials for MS — A comprehensive chart listing agents in current, planned or recently completed studies in people with MS. Includes a glossary. An expanded version for healthcare professionals is available.
Trials Recruiting Patients — A list of ongoing studies around the country that are recruiting subjects, indexed by state.
Clinical Trial Resources — Links to other opportunities to participate.
Check it out at:
Microarray Technology: Expanding the Possibilities
To find the genes for MS, researchers have to comb through genetic material taken from thousands of people. In recent years, this task has been eased somewhat with the development of microarray technology, also known as “gene-chip” technology.
Microarray technology uses a robot to precisely apply DNA (the chemical that carries the instructions for making living things, see page 4) to glass slides. Researchers then attach fluorescent labels to cDNA, which are complementary copies of these instructions which bind to a specific DNA strand on the slides. A laser scans the slides and records the brightness of the fluorescent signal. This brightness reveals how much of a specific DNA fragment is present, and how active it is.
Small Chips: Big Advances
The two great advantages of microarrays are that this technology can be used to analyze tens of thousands of genes at once, and does so using a chip that is the width of two small fingers. Several Society-funded grantees are taking advantage of this new technology, with exciting results.
Lawrence Steinman, MD (Stanford University, California), along with Society-funded grantee Jorge Oksenberg, PhD (University of California, San Francisco) and colleagues at Albert Einstein College of Medicine, New York, compared genes from brain lesions (areas of myelin damage) in four people with MS to tissue from people without MS. They found that several genes were more active in people with MS, including genes for inflammatory proteins in the immune system. Other genes were less active, including genes associated with nerve cells and myelin, the coating that insulates nerve fibers. Different genes were active in lesions with ongoing inflammation, and in those without inflammatory activity (Nature Medicine, May 2002).
“The authors show the ideal application of microarray technology and
compare acute and silent lesions and find pronounced differences in the
tissue,” comment Stephen M. Tompkins, PhD, and Stephen D. Miller, PhD (Northwestern
University Medical School, Evanston, IL) in an editorial accompanying the
published study. “The data may enable scientists to tailor therapeutic
strategies to stages and/or forms of MS.”
|“We can collect exponentially more in-formation from a single MS
lesion than was previously possible.”
- Stephen M. Tompkins, PhD, and Stephen D. Miller, PhD
Steinman and Oksenberg, along with Society-funded fellows Sergio Baranzini, PhD (University of California, San Francisco), Christopher Lock, PhD, and Rosetta Pedotti, MD (Stanford University, California) used microarrays and other technologies to create “gene libraries” from the brain tissue of people with MS, and to determine which genes appeared most frequently (Science, November 2001).
They found that osteopontin — a gene involved in bone formation that may also participate in inflammation — appeared often. The researchers then determined, in an MS-like disease in mice, that osteopontin was most prominent in areas of myelin damage during active disease, but not during remission. In mice lacking osteopontin, symptoms were significantly less severe and the percent-age of remissions much higher. Osteopontin may influence the occurrence of relapses and remissions in MS, and may be a target for MS therapies.
In an effort related to the Society’s targeted investigation of gender differences in MS, Halina Offner, PhD, and Society-funded fellow Agata Matejuk, PhD (Oregon Health Sciences University, Portland) attempted to identify immune-related genes affected by treatment with the female sex hormone estrogen. Using microarray technology, they screened more than 12,000 genes from mice treated with estrogen. Estrogen treatment affected 18 immune system proteins – some known culprits and some previously unsus-pected (Endocrinology, January 2002).
In other ongoing studies, John Bright, PhD (Vanderbilt University, Nashville) and Brian Popko, PhD (University of Chicago) are both using microarrays to look at genes involved in the development of myelin-making cells. Data from these studies may be used to design treatments to promote myelin repair in MS.
“Now, with the advent of gene microarray technology, we can collect exponentially more information from a single MS lesion than was previously possible,” comment Tompkins and Miller in their editorial, adding that they hope to see the results of microarray studies correlated with data from basic studies and clinical trials. “The association of all these types of information is invaluable to scientists studying MS,” they conclude.
It’s Your Turn
Individuals with MS and their family members are a vital part of genetics research. Researchers need genetic material from thousands of people to complete the studies we have described. The more samples available, the greater the chance of identifying the genes that contribute to MS.
Who Can Participate?
The MS DNA Bank at the University of California, San Francisco (see pages 1,3), is looking for information from families with one person with MS (simplex families), and those with more than one person with MS (multiplex). In a simplex family, the parents are required to participate. If this is not possible, an unaffected sibling can serve as a substitute. Unaffected siblings and the spouse can participate as well. In multiplex families, participants must include two siblings with MS, their parents (if possible) and unaffected siblings. If extended family (e.g., cousins) members have MS, they and other relatives are usually asked to participate.
Different populations are being studied to learn why some ethnic groups develop MS at higher rates than others. Families of African-American heritage are encouraged to participate.
People with infectious disorders (e.g., HIV, chronic hepatitis) are not eligible.
What is Involved?
Participants will be asked to:
˜ fill out a questionnaire describing their families
˜ sign a form to release medical records (only people with MS)
˜ read and sign a consent form
˜ donate a blood sample (approximately five tablespoons)
If you are interested in participating, please contact:
MS DNA Bank
Department of Neurology
University of California at San Francisco
513 Parnassus Avenue, Box 0435
San Francisco, CA 94143-0435
On the National MS Society Web Site…
Clinical trials — a chart of agents under study and a list of trials
How Are Grants Funded? — a detailed explanation
New Research — summaries of recently funded projects
Research Fact Sheet — fast facts about MS research
Bulletins — the latest news about MS research and treatment
Research Highlights — newsletter of research progress