Myopathies Flashcards

1
Q

What is a myopathy?

A

Muscle disease

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2
Q

What is sarcopenia?

A

Loss of muscle mass with age

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3
Q

What are satellite cells?

A

Stem cells present in the muscle between the sarcolemma and basal lamina.

Involved in remodelling, repair and growth of muscle

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4
Q

What are the features of skeletal muscle?

A

sarcomere -> myofibrils -> muscle fibres

Multinucleated cells

Fibres are surrounded by cell membrane called the sarcolemma

Sarcolemma further surrounded by basal lamina

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5
Q

Why can muscle fibres not divide?

A

They contain post-mitotic nuclei

So satellite cells are the only ones contributing to remodelling of muscle

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6
Q

What is muscular dystrophy?

A

A group of 8 inherited disorders each characterised by the gene mutation that leads to a change in protein expression

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7
Q

What is congenital MD?

A

A combination of the 7 MDs

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8
Q

What is the appearance of normal muscle?

A

Muscle fibres are polyglonal, similar in size and tightly packed

Sarcolemmal nuclei

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9
Q

What is the appearance of MD muscle?

A

Muscle fibres vary in shape

More nuclei, found in center of the muscle fibres

Basophilic

Fibrosis and adipose tissue

Infiltration of inflammatory cells causes necrotic tissue

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10
Q

What are possible defective genes that can lead to MD?

A

Dystrophin - found under muscle fibres
Emerin/ lamin - found in envelope surrounding nucleus
Sarcoglycans - cross the muscle fiber membrane

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11
Q

What is Duchenne Muscular dystrophy?

A

Inherited, X-linked disorder caused by a mutation in the gene coding for dystrophin

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12
Q

How does DMD progress?

A

Muscle fibres are weak and break easily

This triggers a cycle of degradation and regeneration

The regeneration of muscle tissue cannot keep up with degradation so eventually the muscle fibres are replaced with adipose and fibrotic tissue

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13
Q

What is the dystrophin gene?

A

A mutation in this causes DMD

One of the largest genes in the human body

79 exons
0.02% of the muscle fibre weight

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14
Q

What is the dystrophin-associated complex?

A

Dystrophin is a part of a complex called the dystrophin-associated glycoprotein molecule

Associated with many proteins found:
Intracellularly
Extracellularly
Freely

A defect in any of the genes coding for the parts of this complex leads to MD

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15
Q

Is there a cure for MD?

A

No

There are currently lots of scientific research and clinical trials

Mdx mouse - model for DMD

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16
Q

What are potential treatments for MD?

A

Restoration of missing or defective proteins
Replacement of dystrophin with similar proteins
Prevent death of muscle fibres
Enhance repair and regeneration
Prevent inflammation or fibrosis

17
Q

What are methods to restore missing or defective proteins?

A

Stem cell therapy
Exon skipping - skip mutated genes
Genome editing
Stem cells - restore defective proteins

18
Q

How can you enhance repair and regeneration in the muscle?

A

Improve the number of satellite cells in the muscle

19
Q

What protein can we replace dystrophin with?

A

Utrophin

Found in nerve terminals and developing muscle