Silence The Gene, Save The Cell: RNA Interference As Promising Therapy For ALS

Scientists at the Ecole Polytechnique Fédérale de Lausanne (EPFL) in Switzerland have used RNA interference in transgenic mice to silence a mutated gene that causes inherited cases of amytrophic lateral sclerosis (ALS), substantially delaying both the onset and the progression rate of the fatal motor neuron disease. Their results will be published in the April issue of Nature Medicine, and in the journal's advanced online publication March 13.

In addition to silencing the mutated gene that causes ALS, the EPFL researchers were able to simultaneously deliver a normal version of the gene to motor neuron cells using a single delivery mechanism. "This is the first proof of principle in the human form of a disease of the nervous system in which you can silence the gene and at the same time produce another normal form of the protein," notes Patrick Aebischer, EPFL President and a co-author of the study.

ALS is a progressive neurological disease that attacks the motor neurons controlling muscles. Although its victims retain all their mental faculties, they experience gradual paralysis and eventually lose all motor function, becoming unable to speak, swallow or breathe. Known also as Lou Gehrig's disease, from the baseball player who succumbed to it, this harrowing disease has no cure and its pathogenesis is not very well understood.

An estimated 5,000 Americans are diagnosed with ALS every year, and most of these cases are "sporadic", with no identifiable cause. About 5-10% of ALS cases are inherited. Of these, 20% have been linked to any of more than 100 mutations in the gene that expresses the superoxide dismutase enzyme (SOD1).

These SOD1 mutations are "toxic gain-of-function mutations," meaning that the protein expressed by the mutated gene has, in addition to all its normal cellular functions, some additional function that makes it toxic to the cell. "Any mutation to the SOD1 gene is fatal to motor neuron cells," Aebischer notes. Recent research also indicates that mutant SOD1 gene expression in neighboring glial cells is also implicated in motor neuron death.

Lead author Cedric Raoul and colleagues targeted the cause of the disease by using RNA interference to silence the defective gene, preventing it from expressing the SOD1 protein.

RNA interference is part of a complex cellular housekeeping process that protects cells from invading viruses or other genetic threats. It works by interrupting messenger RNA as it transfers the genetic code for a protein from the nucleus to the site in the cell where the protein is synthesized.

To trigger RNA interference and silence a gene, short bits of double-stranded RNA are introduced in the cell, where they bind with matching sections of messenger RNA. The cell identifies the resulting messenger RNA strand as faulty and chops it up. As a result, the genetic blueprint isn't delivered and the protein never gets made.
"Gene silencing is an example of using "molecular scissors" at its most advanced level," Raoul explains.

Raoul and colleagues used RNA interference to reduce levels of mutant SOD1 protein in the spinal cords of transgenic ALS mice (mice bred to express the human SOD1 gene). Short strands of RNA that targeted multiple mutated and normal forms of the human SOD1 gene were delivered in a specially engineered lentivirus. Expression of the SOD1 protein was knocked down in the affected motor neurons and neighboring glial cells, and both the onset and the rate of progression of the disease in the treated mice were substantially reduced. In addition, the mice showed a significant improvement in neuromuscular function.
"This is the first demonstration of therapeutic efficacy in vivo of RNA interference-mediated gene silencing in an ALS model," notes Raoul.

Because the normal form of the SOD1 protein may be necessary for the survival or function of adult human motor neurons, the Swiss researchers designed a gene replacement technology that allows the knock-down of all mutant SOD1 forms while permitting the expression of a normal type SOD1 protein that is resistant to RNA interference-based silencing. Both these effects are expressed long-term via delivery by a single lentiviral vector.

Aebischer is optimistic about the future of gene silencing as a potential therapy, particularly in incurable progressive neurological diseases such as ALS. "I would not be surprised to see, in the next ten years, this technology used for treating diseases of the nervous system, particularly diseases that involve toxic gain-of-function, such as inherited forms of Parkinson's disease or Huntington's disease," notes Aebischer. "But it's important to note that the safety of delivering lentiviral vectors to the nervous system will have to be carefully examined prior to treating patients."

Source: Ecole Polytechnique Fédérale de Lausanne

First Mouse Model For Multiple System Atrophy Points To New Treatment Targets For Brain Diseases

A newly developed animal model for Multiple System Atrophy (MSA) – a collection of neurodegenerative disorders once thought to be three separate diseases – sheds new light on this little-studied brain disease, according to research from investigators at the University of Pennsylvania School of Medicine.

Virginia M.-Y. Lee, PhD, Director of Penn's Center for Neurodegenerative Disease Research, and colleagues demonstrated that the mice showed symptoms similar to human MSA. These include an accumulation of a protein called á-synuclein in oligodendrocytes – cells that produce the protective myelin sheath that covers axons. This protein accumulation disables oligodendrocytes, leading to a loss of the sheath on neurons and eventually nerve-cell malfunction and death. The mice also showed slowly progressive problems with their motor skills associated with the nerve-cell damage. Neurons are important in transmitting signals and in maintaining learning and memory.

"The uniqueness of this disease is that, unlike most of the neurodegenerative diseases, which affect neurons primarily and oligodendrocytes secondarily, this is the other way around," says Lee. In fact, there is growing evidence that non-neuronal cells also play a role in amyloid deposits in Alzheimer's disease and amyotrophic lateral sclerosis (ALS) mouse models. Lee and colleagues report their findings in the March 24, 2005 issue of Neuron.

MSA is so named because it affects multiple parts of the nervous system. Initially MSA was given three names, based on the symptoms physicians had observed. However, when they closely examined patients' pathology, the disorders seemed related, based on the á-synuclein proteins in cells. In the clinic, many patients with MSA present with symptoms similar to Parkinson's disease (PD), and MSA has been misdiagnosed as such.

Collectively, MSA now includes three related disorders characterized by their most prominent symptoms: olivopontocerebellar atrophy, which affects balance, coordination, and speech; striatonigral degeneration, the closest to Parkinson's disease because of slow movement and stiff muscles; and Shy-Drager syndrome, which involves altered bowel, bladder, and blood-pressure control. Other general symptoms include dizziness, impaired speech, breathing and swallowing difficulties, and blurred vision. Most patients develop dementia late in the course of the disease, which is usually diagnosed in people over 50.

Currently there is no specific drug to treat the myelin and nerve damage caused by the protein inclusions. Parkinson's disease drugs and others are used to alleviate early symptoms. "With this animal model, we now can plan tests of potential therapies for Multiple System Atrophy as part of our drug discovery program for Parkinson's disease, MSA, and related disorders," says Lee.

Source: University of Pennsylvania Medical Center

Selected examples of best practice in computational biology

1. A team of researchers from Case Western Reserve University (Cleveland, Ohio; http://www.csuohio.edu/mims/index.htm) is combining computational modeling with physiological experimentation to understand the relationship between metabolism of single human cells and organ and whole body metabolism. This work is yielding computer models of metabolism in liver, heart and brain that promote evidence-based methods for clinical decision support, including diagnosis and treatment [9].

2. An industrial team at United Devices, Inc. (Austin, Texas; http://ud.com/rescenter/ and http://ud.com/rescenter/files/ds_smallpox.pdf) developed technology for massive computational screening of lead drug compounds for drugs by accessing otherwise unused computer time in a global collaborative network of desktop computers. Recently they reported that this work yielded new compounds against a smallpox protein. This work will bring new drugs into animal and human testing cheaply and quickly, yielding more effective, less expensive drugs (United Devices, Inc. http://www-unix.gridforum.org/7_APM/LSG.htm; www.ud.com/rescenter/files/ds_smallpox.pdf.)

3. A team from the University of Connecticut in Storrs, Connecticut (http://www.cbit.uchc.edu/index.html) formed the National Resource for Cell Analysis and Modeling, a nationally accessible computational environment for modeling cell functions. This environment speeds the pace of research at the cellular level by permitting researchers to readily put experimental biochemical data in the context of a computational model of a cell to understand how individual biochemical reactions give rise to coordinated functions at the pathway and cellular level [10].

4. A team from Johns Hopkins University (http://www.bme.jhu.edu/labs/levchenko) is using Monte Carlo modeling to predict biochemical signaling pathways in heart muscle cells. By using the computer-driven random walk to simulate diffusion of signaling molecules in the cell, it is possible to model cellular behavior in great detail, and thus provide a more detailed view of cell signaling. Cell signaling relates to basic and clinical research [11].

5. A team from Indiana University (http://www.indiana.edu/neurosci/sporns.html and
http://www.indiana.edu/cortex/robots.html) is developing an autonomous computational robot with learning capabilities similar to the human brain. This research is aimed at understanding principles of brain function and also at understanding brain function to build automated intelligent systems and robots that can serve human needs [12].

6. A team based at Massachusetts General Hospital/Harvard Medical School is studying malignant brain tumors as self-organizing and adaptive biosystems. Their Tumor Complexity Modeling Project (TCMP) uses methods from various disciplines, such as tumor biology, bioengineering, materials science, mathematical biology, nonlinear physics as well as computational and complex systems science. The immediate aim of TCMP is to develop novel experimental, computational, mathematical and theoretical tumor models. The ultimate goal is to develop virtual treatment planning devices and strategies for malignant brain tumors (http://btc.mgh.harvard.edu/TumorModeling/)

From Trends in Biotechnology Volume 23, Issue 3 , March 2005, Pages 113-117

The artist as neuroscientist

When a flat picture is viewed from different angles, the 3D scene can still be perceived without jarring distortions.


Vuilleumier et al. found that the blurry, fearful face on the right activated the amygdala more than the sharply detailed or unfiltered versions.

The neuroscience of art
Paintings and drawings are a 40,000-year record of experiments in visual neuroscience, exploring how depth and structure can best be conveyed in an artificial medium. Artists are driven by a desire for impact and economy: thousands of years of trial and error have revealed effective techniques that bend the laws of physics without penalty. We can look at their work to find a naive physics that uncovers deep and ancient insights into the workings of our brain. Discrepancies between the real world and the world depicted by artists reveal as much about the brain within us as the artist reveals about the world around us.

From www.nature.com/nature/focus/arts/index.html

Profiles in Science Web site

PAPERS OF DNA PIONEER AND NOBEL LAUREATE FRANCIS CRICK
ADDED TO NATIONAL LIBRARY OF MEDICINE'S PROFILES IN SCIENCE
WEB SITE

BETHESDA, MARYLAND - The National Library of Medicine, a
part of the National Institutes of Health, is proud to
present an extensive selection from the papers of one of
the twentieth century's greatest scientists, Francis Crick,
on its Profiles in Science Web site.

This latest collection on Profiles in Science represents a
close collaboration between the National Library of
Medicine and the Wellcome Library for the History and
Understanding of Medicine in London, which holds the Crick
papers. The Crick collection brings to 14 the number of
notable researchers and public health officials whose
personal and professional records are featured on Profiles.
The site is located at <http://www.profiles.nlm.nih.gov>.

The name of Francis Crick (1916-2004) is inextricably
linked to the discovery of the double helix of
deoxyribonucleic acid (DNA) in 1953, considered the most
significant advance in biology since Darwin's theory of
evolution. The insights of Crick, and his collaborator,
James D. Watson, into the structure of DNA and into the
genetic code made possible a new understanding of heredity
at the molecular level.

"Major current advances in science and biotechnology, such
as genetic engineering, the mapping of the human genome,
and genetic fingerprinting, all have their origins in
Crick's inspired work," said Donald A.B. Lindberg, M.D.,
director of the National Library of Medicine. "The double
helix has not only reshaped biology, it has become a
cultural icon, represented in sculpture, visual art,
jewelry, and toys."