Transcript Duchenne Muscular Dystrophy

Duchenne
Muscular
Dystrophy
- GENETICS The Cause and Cure
By: Chaz B
What Is Muscular Dystrophy?
Muscular Dystrophy is a group of inherited diseases in which the
muscles that control movement progressively weaken. In some
forms of this disease, the heart and other organs are also affected.
Muscular Dystrophy can occur at different ages of a persons life,
ranging from infancy to middle age or later.
There are nine major forms of muscular dystrophy. The type of the
disease is based in part on when in a person’s life muscular
dystrophy appears, but it also depends on the severity of muscle
weakness, which muscles are affected, the rate of symptom
progression, and the way the disease arises.
Duchenne Muscular Dystrophy
Duchenne muscular dystrophy (DMD)
was first described by the French
neurologist Dr. Guillaume Benjamin
Amand Duchenne in the 1860’s.
In DMD, boys begin to show signs of
muscle weakness as early as age 3. The
disease gradually weakens the voluntary
muscles, such as those in the arms, legs
and trunk. By the early teens or earlier,
the boy’s heart and respiratory muscles
also may be affected.
Though DMD affects boys almost
exclusively, in rare cases it can affect girls
as well. (X-linked recessive disease)
The Signs of DMD
The course of Duchenne Muscular Dystrophy is fairly predictable. Children
with the disorder are often late in learning to walk. In toddlers, parents
may notice enlarged calf muscles, or pseudohypertrophy.
A preschooler with DMD may seem clumsy and often fall. Parents also may
note that he has trouble getting up, climbing stairs or running.
By school age, the child may walk on his toes or the balls of his feet, with a
slightly rolling, unsteady gait. To try to keep his balance, the child will stick
his belly out and put his shoulders back. He may also have difficulty raising
his arms.
Many children with DMD lose the ability to walk some time between the
ages of 7 through 12. In the teen years, activities involving the arms, legs
or trunk may require assistance or mechanical support.
The Anatomy of Skeletal Muscle
The Anatomy of Skeletal Muscle
The Anatomy of Skeletal Muscle
DMD Genetic Analysis
The DMD gene is located on the short (p) arm of the X
chromosome at position 21.2.
More precisely, the DMD gene is located from base pair
31,137,344 to base pair 33,357,725 on the X
chromosome.
Cytogenetic Location: Xp21.2
Molecular Location on the X chromosome: base pairs
31,137,344 to 33,357,725
DMD Genetic Analysis
Exons are the portion of a gene which code for a protein,
and a single gene can consist of many exons separated by
stretches of DNA known as introns.
The dystrophin gene has a total of 79 exons. Mutation in
exons 45 through 52 result in either the production of a
functionless truncated protein or in the production of a
defective dystrophin protein that is quickly broken down,
rather than undergoing processing to yield a mature
functional dystrophin protein.
It is this absence of a functioning dystrophin protein that
results in the symptoms of DMD.
Possible Treatment?
The antisense oligomer AVI-4658 works by binding to and
blocking a specific sequence within exon 51 of the premessenger RNA.
This causes the splicing machinery to skip the affected
exons and yield a shortened dystrophin protein, missing a
segment within it, which nevertheless includes the key
functional portions at either end of the protein and thus
restores most of the dystrophin functionality.
The Muscular Dystrophy Campaign announced that the
antisense oligonucleotide drug AVI-4658 had performed
well in its second clinical trial in 19 boys with Duchenne
Muscular Dystrophy (DMD)
Possible Treatment?
Works Cited
"Dystrophin." Wikipedia, the Free Encyclopedia. Web. 28 Sept. 2011.
<http://en.wikipedia.org/wiki/Dystrophin>.
"Facts About Duchenne and Becker Muscular Dystrophies | MDA
Publications." Welcome to MDA | Muscular Dystrophy Association. Web.
19 Sept. 2011. <http://www.mdausa.org/publications/fa-dmdbmdwhat.html>.
Stout , Hilary. "Muscular Dystrophy Types & Causes of Each Form." WebMD Better Information. Better Health. Web. 19 Sept. 2011.
<http://www.webmd.com/parenting/understanding-muscular-dystrophybasics>.
http://speakingofresearch.com/tag/dmd/