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The molecular basis of muscular dystrophy

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Muscle weakness first affects feet, fronts of thighs, hips, belly, shoulders, and elbows. ... Symptoms - Generalized weakness and muscle wasting first affecting ... – PowerPoint PPT presentation

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Title: The molecular basis of muscular dystrophy


1
The molecular basis of muscular dystrophy(?????)
  • Wenya Hou
  • Xue Jing
  • Yitang Wang
  • Jiezhong Zhang

2
OUTLINE
  • INTRODUCTION
  • Duchenne muscular dystrophy (DMD)
  • Dysfelin
  • Therapeutic Approaches and perspective

3
  • a quarter of a million kids and adults are living
    with the disease, so chances are you may know
    someone who has it.

4
What is Muscular Dystrophy?
  • The muscular dystrophies (MD) are a group of more
    than 30 genetic diseases characterized by
    progressive weakness and degeneration of the
    skeletal muscles that control movement. Some
    forms of MD are seen in infancy or childhood,
    while others may not appear until middle age or
    later. Muscular dystrophies in general are a
    group of genetic, degenerative diseases primarily
    affecting voluntary muscles.

5
  • Healthy muscle tissue (left).
  • Muscular dystrophy (right).

6
HOW TO RECOGNIZE IF MUSCLE WEAKNESS IS CAUSED BY
MUSCULAR DYSTROPHY
  • Mostly affects boys (rarely girls).
  • Often brothers or male relatives have same
    problem.
  • First signs appear around ages 3 to 5 the child
    may seem awkward or clumsy, or he begins to walk
    'tiptoe' because he cannot put his feet flat.
    Runs strangely. Falls often.
  • Problem gets steadily worse over the next several
    years.

7
HOW TO RECOGNIZE IF MUSCLE WEAKNESS IS CAUSED BY
MUSCULAR DYSTROPHY
  • Muscle weakness first affects feet, fronts of
    thighs, hips, belly, shoulders, and elbows.
    Later, it affects hands, face, and neck muscles.
  • Most children become unable to walk by age 10.
  • May develop a severe curve of the spine.
  • Heart and breathing muscles also get weak. Child
    usually dies before age 20 from heart failure.

8
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9
There are probably nine types of muscular
dystrophy.
  • Duchenne muscular dystrophy (DMD)
  • Becker muscular dystrophy (BMD)
  • Emery-Dreifuss muscular dystrophy (EDMD)
  • Limb-girdle muscular dystrophy (LGMD)
  • Facioscapulohumeral muscular dystrophy (FSHD)
  • Myotonic (pronounced my-uh-tah-nick) dystrophy
    (MMD)
  • Oculopharyngeal Muscular Dystrophy (OPMD)
  • Distal Muscular Dystrophy (DD)
  • Congenital muscular dystrophy (CMD)

10
Duchenne muscular dystrophy (DMD)
  • Definition - One of nine types of muscular
    dystrophy, a group of genetic, degenerative
    diseases primarily affecting voluntary muscles.
  • Cause - An absence of dystrophin, a protein that
    helps keep muscle cells intact.

11
DMD
  • Onset - Early childhood - about 2 to 6 years.
  • Symptoms - Generalized weakness and muscle
    wasting first affecting the musclesof the hips,
    pelvic area, thighs and shoulders. Calves are
    often enlarged.
  • Progression - DMD eventually affects all
    voluntary muscles, and the heart and breathing
    muscles. Inheritance - X-linked recessive. DMD
    primarily affects boys, who inherit the disease
    through their mothers. Women can be carriers of
    DMD but usually exhibit no symptoms.

12
Becker muscular dystrophy (BMD)
  • is similar to DMD but often much less severe.
    There can be significant heart involvement.
    Progression - Disease progresses slowly and
    with variability. Most with BMD survive well into
    mid- to late adulthood.

13
Emery-Dreifuss muscular dystrophy (EDMD)
  • .Cause - Mutations in the genes that produce
    emerin, lamin A or lamin C, proteins in the
    membrane that surrounds the nucleus of each
    muscle cell.
  • Onset - Usually by 10 years of age.
  • Symptoms - Weakness and wasting of shoulder,
    upper arm and calf muscles joint stiffening
    fainting (because of cardiac abnormalities).
  • Progression - Disease usually progresses slowly.
    Cardiac complications are common and sometimes
    require a pacemaker.
  • Inheritance -Can be X-linked recessive, primarily
    affecting males, who inherit the disease through
    their mothers. Another type is autosomal
    dominant, meaning it can be inherited through
    either parent an autosomal recessive type occurs
    when a faulty gene is inherited from each parent.

14
Limb-girdle muscular dystrophy (LGMD)
  • Definition - One of nine types of muscular
    dystrophy, a group of genetic, degenerative
    diseases primarily affecting voluntary muscles.
  • Cause - A mutation in any of at least 15
    different genes that affect proteins necessary
    for muscle function.
  • Onset -Childhood to adulthood.
  • Symptoms - Weakness and wasting first affecting
    the muscles around the shoulders and hips (limb
    girdles).
  • Progression - Usually progresses slowly, with
    cardiopulmonary complications sometimes occurring
    in later stages of the disease.
  • Inheritance - Some types are autosomal dominant,
    meaning LGMD is inherited from one parent. Other
    types are autosomal recessive and occur when a
    faulty gene is inherited from each parent.

15
Facioscapulohumeral muscular dystrophy (FSHD)
  • Definition - One of nine types of muscular
    dystrophy, a group of genetic, degenerative
    diseases primarily affecting voluntary muscles.
  • Cause - A missing piece of DNA on chromosome 4.
  • Onset - Usually by age 20.
  • Symptoms - Weakness and wasting of the muscles
    around the eyes and mouth, and of the shoulders,
    upper arms and lower legs initially, with later
    weakness of abdominal muscles and sometimes hip
    muscles.
  • Progression - Progresses slowly with some periods
    of rapid deterioration. Disease may span many
    decad

16
Myotonic (pronounced my-uh-tah-nick) dystrophy
(MMD)
  • Definition - One of nine types of muscular
    dystrophy, a group of genetic, degenerative
    diseases primarily affecting voluntary muscles.
  • Cause - A repeated section of DNA on either
    chromosome 19 or chromosome 3.
  • Onset - Congenital form appears at birth. More
    common form may begin in teen or adult years.
  • Symptoms - Generalized weakness and muscle
    wasting first affecting the face, lower legs,
    forearms, hands and neck, with delayed relaxation
    of muscles after contraction common. Other
    symptoms involve the gastrointestinal system,
    vision, heart or respiration. Learning
    disabilities occur in some cases. Congenital
    myotonic dystrophy is the more severe form.
  • Progression - Progression is slow, sometimes
    spanning 50 to 60 years.
  • Inheritance - Autosomal dominant the disease may
    be inherited through either the father or the
    mother.

17
Oculopharyngeal Muscular Dystrophy (OPMD)
  • Definition - One of nine types of muscular
    dystrophy, a group of genetic, degenerative
    diseases primarily affecting voluntary muscles.
  • Cause - A faulty gene for poly(A)-binding protein
    nuclear 1 (PABPN1), which is suspected to lead to
    production of extra chemical material that causes
    formation of clumps in the muscle cells.
  • Onset - Usually not until the 40s or 50s.
  • Symptoms - OPMD first causes weakness of the
    muscles of the eyelids and throat weakness of
    facial and limb muscles often occurs later.
    Swallowing problems and difficulty keeping the
    eyes open are common problems.
  • Progression - Slow.

18
Distal Muscular Dystrophy (DD)
  • Definition - A class of muscular dystrophies that
    primarily affect distal muscles, which are those
    of the lower arms, hands, lower legs and feet.
    Muscular dystrophies in general are a group of
    genetic, degenerative diseases primarily
    affecting voluntary muscles.
  • Cause - A mutation in any of at least eight genes
    that affect proteins necessary to the function of
    muscles.
  • Onset - childhood to adulthood
  • Symptoms - Weakness and wasting of muscles of the
    hands, forearms and lower legs.
  • Progression - Slow progression not
    life-threatening.
  • Inheritance - May be autosomal dominant, meaning
    a faulty gene is inherited from one parent or
    autosomal recessive, occurring when a faulty gene
    is inherited from each parent.

19
Congenital muscular dystrophy (CMD)
  • Definition - A class of muscular dystrophies that
    show themselves at or near birth. Muscular
    dystrophies in general are a group of genetic,
    degenerative diseases primarily affecting
    voluntary muscles.
  • Cause - Genetic mutations affecting some of the
    proteins necessary for muscles and sometimes for
    the eyes and/ or brain.
  • Onset - At or near birth.
  • Symptoms - Generalized muscle weakness with
    possible joint stiffness or looseness. Depending
    on the type, CMD may involve spinal curvature,
    respiratory insufficiency, mental retardation or
    learning disabilities, eye defects or seizures.
  • Progression - Varies with type many are slowly
    progressive some shorten life span.
  • Inheritance - Autosomal recessive or autosomal
    dominant these diseases are sometimes inherited
    through both parents and sometimes inherited from
    one parent . They can also occur spontaneously
    because of a newly developed genetic flaw
    (mutation).

20
Duchenne muscular dystrophy (DMD)
21
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24
  • ERM family

Spectrin family
e.dystrophin
?
muscular dystrophy
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