Research Updates
Gene Therapy Offers Hope for Congenital MD
A group of European scientists has shown that an innovative gene therapy
strategy holds promise for treating congenital muscular dystrophy (CMD) —
a group of muscular dystrophies that manifest at birth and cause a variable
degree of muscle weakness and wasting.
The most common form of CMD (called merosin-deficient CMD) is caused by
flaws in the laminin alpha2 gene, which encodes a protein that's part of a
larger protein complex called laminin. Laminin (sometimes called merosin)
normally serves as a linchpin in a protein scaffold that surrounds and supports
muscle cells, and when it's defective, the scaffold and the affected muscle
fall apart.
This type of CMD ranges in severity from mild to extreme. In the most severe
cases, affected individuals never gain the ability to walk, and die before age
30.
Theoretically, scientists could treat the disease by supplying an intact laminin
alpha2 gene. But the European scientists, led by Markus Ruegg at the University
of Basel in Switzerland, have shown that it might be more effective to supply
the gene for agrin, a protein that has similar functions to laminin alpha2.
 |
| In healthy muscle, laminin alpha2 provides a link between proteins outside the muscle cell and proteins on the inside, but in CMD, that link is destroyed. With gene therapy or a drug treatment, miniagrin could be used to reconnect the proteins. |
In the Sept. 20 issue of Nature, the group reported that a miniaturized version
of the agrin protein (called miniagrin) could substitute for laminin alpha2 and
thus largely prevent CMD in laminin alpha2-deficient mice.
The mice were genetically engineered to overproduce miniagrin. One day, people
with CMD might be treated with virally delivered miniagrin or a drug that
boosts the body's natural production of agrin, the group suggests.
These approaches would avoid potential immune reactions caused by giving the
laminin alpha2 protein to someone whose body has never seen it, they say.
The new study builds on previous MDA-supported research into gene therapy for Duchenne
muscular dystrophy, which is caused by a deficiency of the dystrophin
protein. Dystrophin-deficient mice are rescued from DMD when they're given
extra genes for one of two functionally similar proteins, utrophin or integrin.
MDA grantee Stephen Kaufman, who led the integrin studies at the University of
Illinois in Urbana, said the new study "adds to the potential for using
complementary genes to provide a remedy for the defective genes that cause
muscular dystrophy." Much work still needs to be done to develop this
complementary gene approach, he added.
With Aggressive Care, Nemaline Myopathy Often Has Good Prognosis
In the largest study of its kind to date, an MDA-funded research team has shown
that nemaline myopathy (NM) often follows a favorable course with time,
stabilizing in most cases and even improving in some.
NM causes muscle weakness and hypotonia (poor muscle tone), and is associated
with nemaline bodies, abnormal clumps of threadlike material that crowd
inside affected muscle cells. Despite those hallmark features, the disease
exists in many forms, ranging from severe congenital-onset (near birth) cases
to relatively mild adult-onset ones. It has been linked to mutations in several
genes.
Most studies on NM have examined just a handful of people, and with so many
variations, researchers have struggled to develop a clear picture of the
disease.
In the new study, MDA grantee Alan Beggs of Children's Hospital and Harvard
Medical School in Boston collaborated with researchers from the United States
and Australia to get a snapshot of the disease in 143 people. The study was
published in the September issue of Annals of Neurology.
In congenital-onset NM, there were often complications during pregnancy and
delivery, nearly all infants were hypotonic at birth, and some had significant
respiratory weakness. Many of them had feeding difficulties that required
gastrostomy (insertion of a feeding tube into the stomach). But despite those
dire beginnings, the majority of those babies survived, and some gained enough
strength to walk within the first few years of life.
In the most severe cases, respiratory failure at delivery led to death during
infancy. Infants who required respiratory support later in the first year of
life survived and remained ventilator-dependent. Other infants with respiratory
weakness and frequent respiratory infections improved with time; some went on
to require nighttime ventilation.
"The important point is that some apparently severe cases at birth later do
well, so aggressive postnatal management and supportive care are warranted,"
Beggs said.
Few people with childhood- and adult-onset NM experienced noticeable respiratory
weakness, none required gastrotomy, and only one child lost the ability to
walk. However, a significant number showed abnormal respiratory function in
laboratory tests, and a few died from respiratory disease.
Beggs emphasized that these findings should sound a warning for all people with
NM to watch for respiratory complications, especially at night.
"Formal sleep studies on all patients are important to establish who may be at
risk [for nighttime respiratory problems]. Abnormal findings should be followed
up every few years, during significant changes in health, and prior to
surgery," he said.
SMA Drug Search Gains Ground
Scientists have reported progress toward developing a drug treatment for spinal
muscular atrophy (SMA) — a life-threatening disease that kills
muscle-controlling nerve cells (motor neurons) in the spinal cord.
Nearly all cases of SMA are caused by flaws in the SMN1 gene, which encodes a
protein called survival motor neuron (SMN). Everyone has a "backup" SMN
gene called SMN2, but it produces very low levels of active SMN protein — not
enough to fully substitute for SMN1.
 |
| Two genes — SMN1 and SMN2 — produce the essential SMN protein, but SMN2 makes a shortened version predominantly. Hence, a deficiency of SMN1 causes SMA. Researchers hope to treat SMA using a drug to boost the level of full-length protein from SMN2. |
The key difference between SMN1 and SMN2 lies in the way cells handle RNA (the
intermediate between genes and proteins). Two years ago, MDA grantees Christian
Lorson of Arizona State University in Tempe and Elliot Androphy of New England
Medical Center in Boston showed that an essential piece of SMN2 RNA is normally
removed, creating a shortened (and mostly nonfunctional) SMN protein.
Still, people with SMA who happen to have extra copies of the SMN2 gene develop
a less severe form of the disease (SMA type 2 or 3), and in mice, a genetically
engineered boost of SMN2 can eliminate the disease.
Inspired by those observations, the San Diego-based biotechnology company Aurora
Biosciences is screening millions of chemicals to find drugs that might
jump-start SMN2 (see Quest, vol. 8, no. 4, "Fast-Track
Pharmacy: Fishing for Drugs"). In the meantime, Lorson, Androphy and
two other research teams have reported some promising "hits" in smaller
screens.
In their MDA-funded screen, Lorson, Androphy and their team attached the SMN2
gene to the gene for jellyfish green fluorescent protein (GFP), and injected
the fused SMN2-GFP gene into cells in a petri dish. That allowed them to use a
simple color change — from no color to bright green — to identify chemicals
that stimulated the cells to make full-length SMN2. In the November issue of
Gene Therapy, they report that the mineral sodium vanadate turned the cells
green, and also increased the level of full-length SMN2 in cells derived from
SMA patients.
The other two groups conducted similar screens, starting with cells from SMA
patients.
One group found that the antibiotic and anti-cancer drug aclarubicin increased
the amount of full-length SMN2. The group, led by Arthur Burghes of Ohio State
University in Columbus, presented its findings at the American Society of Human
Genetics meeting held in San Diego in October. With support from MDA, Burghes
created the mouse model of SMA in the late 1990s.
The other group found similar results with sodium butyrate — a drug that's been
used to treat certain kinds of anemia. When tested on mice, the drug appeared
to lessen the severity of SMA, and improved survival in those with mild disease
signs similar to SMA types 2 and 3. The group, led by Hung Li of Kaohsiung
Medical University in Taiwan, published its findings in the Aug. 14 issue of
the Proceedings of the National Academy of Sciences.
Despite the promising results, it's doubtful that any of the chemicals can be
used to treat SMA. Sodium vanadate is toxic, Lorson said. And although
aclarubicin and sodium butyrate have been used to treat other diseases, it's
unclear whether they'll have beneficial effects on SMA. They, too, may turn out
to be toxic at the doses needed.
At this point, Burghes said, "I would say absolutely do not take aclarubicin. In
my view, butyrate has not been tested rigorously enough in animals and there is
no evidence it works in humans [with SMA]."
Still, these small screens offer an encouraging look ahead at Aurora's large
screen. "These are great 'proof of principle' experiments in the sense that now
we know there are chemicals that can modulate the RNA processing of SMN2,"
Lorson said.
Drug Helps Preserve Bone for Corticosteroid Users
The risk of fracturing bones, particularly the vertebrae in the spine, is high
in patients taking corticosteroids, such as prednisone (Deltasone, Orasone) and
prednisone-related medications. Corticosteroids, also known as glucocorticoids,
are often prescribed for myasthenia gravis, Lambert-Eaton syndrome,
dermatomyositis and polymyositis. They're also sometimes used in inclusion-body
myositis and Duchenne muscular dystrophy.
A recent study conducted under the auspices of Procter & Gamble and Aventis
Pharmaceuticals targeted 500 men and women ages 18 to 85 taking corticosteroids
and found the drug Actonel to be effective in preserving bone. The study,
released at a meeting of the American College of Gastro-enterology in October,
found that Actonel (generic name risedronate) reduced the number of vertebral
fractures in patients taking it by 70 percent compared to the fracture number
in those taking a placebo. All study subjects were given calcium supplements,
and some also received vitamin D.
The study estimates that up to 50 percent of those taking more than 7.5
milligrams a day of prednisone or the equivalent for a similar drug will
experience bone fractures because of osteoporosis (see "Sticks
and Stones Break Fragile Bones").
The study found that Actonel was generally well tolerated, but the drug can't be
used by patients who can't stand or sit upright for at least 30 minutes. Severe
irritation of the esophagus can result from lying down after taking Actonel.
The drug also can't be taken by those with severe kidney impairment or certain
types of bone disorders other than osteoporosis.
Multicenter Study to Test Albuterol, Oxandrolone in FSH Dystrophy
A new, multicenter study to test two medications in 160 people with facioscapulohumeral
muscular dystrophy (FSHD) is recruiting participants.
 |
| John Kissel |
The study follows the publication of the results of an earlier trial of
albuterol (brand name Proventil and others), a beta-adrenergic agonist,
which was found to increase muscle bulk and grip strength. The study, an
MDA-supported, one-year trial of 90 people with FSHD, was published in the Oct.
23 issue of Neurology (also see Quest, vol. 7, no. 4, "Research
Updates").
Oxandrolone (Oxandrin) is an anabolic (tissue-building) steroid, a synthetic
compound resembling the male hormone testosterone. It's now used to treat
involuntary weight loss associated with severe illness, protein breakdown
associated with corticosteroid drugs and bone pain associated with
osteoporosis.
The new trial is designed to test the hypothesis that albuterol taken on a
precise dosing schedule (given one month on and one month off), alone or
combined with oxandrolone, may cause increases in muscle strength, function or
bulk in FSHD. The investigators will also measure various biochemical changes,
if such should occur.
The study will take place at Ohio State University Medical Center in Columbus;
the University of Rochester Medical Center in Rochester, N.Y.; Brigham and
Women's Hospital/ Harvard University in Boston; the University of Texas
Southwestern Medical Center in Dallas; the University of Kansas Medical Center
in Kansas City; the University of Texas Health Science Center at San Antonio;
Montreal (Quebec, Canada) Neurological Institute; and Kings Regional
Neuroscience Center in London, England. Trial participants must be able to make
regular visits to one of these centers.
"We hope that the design and large size of the study will answer definitively
the question of whether anabolic agents represent viable treatment options in
FSHD and other forms of muscular dystrophy," said neurologist John Kissel,
co-director of the MDA clinic at OSU, who is on the study team.
For more information or to inquire about participation in the study, contact
Karen Downing at OSU's Department of Neurology at (614) 293-6813 or downing.42@osu.edu.
Newly Found Genes for Muscle Atrophy May Be Clues in ALS, SMA, CMT
A team of scientists based at Regeneron Pharmaceuticals in Tarry-town, N.Y., has
found two genes whose normal function appears to be to accelerate muscle
atrophy — a process of muscle breakdown that occurs as a consequence of disuse,
injury, aging, and certain neuromuscular diseases.
The findings might yield insights into treatments for amyotrophic lateral
sclerosis (ALS), spinal muscular atrophy (SMA) and Charcot-Marie-Tooth
disease (CMT), says Louis Kunkel, an MDA grantee and geneticist at
Children's Hospital of Boston.
In ALS and SMA, the death of muscle-controlling nerve cells (motor neurons) in
the spinal cord causes severe atrophy of voluntary muscles throughout the body.
In CMT, damage to the peripheral nerves that carry signals from the spinal cord
to muscles causes a milder atrophy of muscles in the extremities.
In the new study, Sue Bodine and her colleagues at Regeneron induced atrophy of
a leg muscle in rats by three separate methods: severing the nerve to the
muscle (denervation), immobilizing the leg or preventing the leg from bearing
weight. Then, they extracted genetic material from the atrophied muscles and
looked for genes that weren't "turned on" in normal muscles.
In all three models of atrophy, they found two genes — MuRF1 and MAFbx — that
were upregulated (activated).
To test the roles of MuRF1 and MAFbx in muscle atrophy, they deleted each of the
genes in two different groups of mice. Both strains of mutant mice were
resistant to the muscle atrophy caused by denervation. The researchers also
were able to trigger signs of atrophy by delivering the MAFbx gene to muscle
cells.
The results were published in the Oct. 26 issue of Science.
The MuRF1 and MAFbx genes both encode "ubiquitin ligases," a family of proteins
that mark other proteins for destruction. Finding drugs that block the activity
of MuRF1 and MAFbx might be an effective way to prevent muscle atrophy, Bodine
and her group suggest.
Kunkel, who's using "gene chip" technology to search for genes that modify the
course of muscular dystrophy, says that such drugs "might alleviate some of the
symptoms and make the quality of life better for people with motor neuron
diseases [like ALS and SMA] and peripheral nerve disorders [like CMT]."
However, it's not yet known whether MuRF1 and MAFbx contribute to the muscle
atrophy that occurs in those diseases, he says.
Coenzyme Q10 May Help in Friedreich's Ataxia, Mitochondrial Disease
Coenzyme Q10, a dietary supplement that's available over the counter, has "come
of age" with respect to its ability to alleviate symptoms in people with Friedreich's
ataxia, some other forms of ataxia that are apparently directly related
to a lack of coenzyme Q10, and perhaps in some mitochondrial disorders of muscle,
says Salvatore DiMauro, a neurologist and MDA grantee who specializes in
mitochondrial diseases at Columbia-Presbyterian Medical Center in New York.
Coenzyme Q10 — or coQ10 — is part of the energy-producing machinery of the
mitochondria (subunits in cells) and also acts as an antioxidant, combating
dangerous free radicals that can destroy cell membranes and other structures.
 |
| Salvatore DiMauro |
DiMauro attended the Fifth European Meeting on Mitochondrial Pathology in
Venice, Italy, in September, and was particularly impressed with a presentation
by Raffaele Lodi of the University of Bologna (Italy) and Oxford University
(England). Lodi, DiMauro says, "presented a study using coQ10 that showed a
remarkably good result in patients with Friedreich's ataxia that may connect
with our own research." Lodi's studies, using nuclear magnetic resonance images
of the brain and muscle, showed a decline in lactic acid [a metabolic byproduct
that's undesirable in excess] and an improvement in ATP stores [a measure of
stored molecular energy] in skeletal muscle and in the brain with coQ10.
DiMauro reports that clinical measures of functional improvement in Friedreich's
ataxia were also found with coQ10 therapy.
He notes that he and other researchers have seen several patients with a genetic deficiency
of coQ10 benefit from using the substance. Testing for such a
deficiency is complex and requires a specialized medical center laboratory, he
says.
Another group for which coQ10 supplementation might be helpful is those with
mitochondrial disorders, DiMauro says. In particular, he says, patients with MELAS,
MERRF and Kearns-Sayre mitochondrial disorders have been studied
by Japanese researchers and found to have some (though not major) deficiencies
in their coQ10 levels. "Whether that's enough to justify using coQ10, I'm not
certain," DiMauro says, but he believes it's probably worth trying.
DiMauro's group prescribes 600 to 1,000 milligrams a day of coenzyme Q10 divided
into three doses and recommends that people take the pills with meals. He also
endorses using a liquid form of coQ10.
DiMauro recommends that people with neuromuscular disorders consult with their
own doctors before taking a supplement, but he also says that coQ10, at least
in the recommended doses, hasn't caused any problems. "The good thing is, so
far there have been absolutely no side effects. It seems to be a totally
harmless compound, even in patients who went up to three grams [3,000
milligrams] a day on their own," he says.  |
