Myopathies Flashcards
What is a myopathy?
Muscle disease
What is sarcopenia?
Loss of muscle mass with age
What are satellite cells?
Stem cells present in the muscle between the sarcolemma and basal lamina.
Involved in remodelling, repair and growth of muscle
What are the features of skeletal muscle?
sarcomere -> myofibrils -> muscle fibres
Multinucleated cells
Fibres are surrounded by cell membrane called the sarcolemma
Sarcolemma further surrounded by basal lamina
Why can muscle fibres not divide?
They contain post-mitotic nuclei
So satellite cells are the only ones contributing to remodelling of muscle
What is muscular dystrophy?
A group of 8 inherited disorders each characterised by the gene mutation that leads to a change in protein expression
What is congenital MD?
A combination of the 7 MDs
What is the appearance of normal muscle?
Muscle fibres are polyglonal, similar in size and tightly packed
Sarcolemmal nuclei
What is the appearance of MD muscle?
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
What are possible defective genes that can lead to MD?
Dystrophin - found under muscle fibres
Emerin/ lamin - found in envelope surrounding nucleus
Sarcoglycans - cross the muscle fiber membrane
What is Duchenne Muscular dystrophy?
Inherited, X-linked disorder caused by a mutation in the gene coding for dystrophin
How does DMD progress?
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
What is the dystrophin gene?
A mutation in this causes DMD
One of the largest genes in the human body
79 exons
0.02% of the muscle fibre weight
What is the dystrophin-associated complex?
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
Is there a cure for MD?
No
There are currently lots of scientific research and clinical trials
Mdx mouse - model for DMD