Lecture 32 - Molecular basis of DMD

Question 1

The sacrolemma is the muscle ___

Answer 1

membrane

Question 2

_____links the sacroglycan complex/dystroglycan complex to the actin filaments

Answer 2

Drostrophin links the sacroglycan complex/dystroglycan complex to the actin filaments

Question 3

The dystrophin gene is on the _ chromosome 21

Answer 3

x chromosome - very large genes 1% of x chromosome

Question 4

mutations associated with ______cause DMD and BMD (becker muscular dystrophy)

Answer 4

mutations associated with dystrophin cause DMD and BMD (becker muscular dystrophy)

Question 5

What is the most common human MD?

Answer 5

Duchenne muscular dystrophy

Question 6

Isoforms exist as a result of an…

Answer 6

alternative promotor usage and splicing of pre-mRNA

Question 7

There are _ long isoforms of the dystrophin gene

Answer 7

4

skeletal, cardiac, smooth, brain

Question 8

What are the 4 domains of Dystrophin?

Answer 8

1) N-terminal “actin binding” domain
2) Middle “rod” domain
3) a cysteine-rich domain (constant in all isoforms)
4) A C-terminal end allowing assembly of the DAPC

Question 9

The most important bits are the ___ of the protein

Answer 9

ends

Question 10

The _____ ___determines whether you have a truncated (abnormal) protein, DMD, BMD

Answer 10

The reading frame determines whether you have a truncated (abnormal) protein, DMD, BMD

Question 11

silent mutations..

Answer 11

have no change in protein product

Question 12

nonsense mutations causes a…

Answer 12

premature stop codon

Question 13

15% of all gene mutations in DMD are ______

Answer 13

nonsense

Question 14

deletions account for __ of DMD cases (out of frame)

Answer 14

60%

Question 15

BMD will typically feature _-___ deletions

Answer 15

In-frame deletions

Question 16

_______ is a link of the internal cytoskeletion to the ECM

Answer 16

Dystrophin

Question 17

The ____links the actin cytoskeleton to the ECM

Answer 17

The CAPC links the actin cytoskeleton to the ECM

Question 18

Dytrophin has also been proposed to play a role in __ homeostasis

Answer 18

Dytrophin has also been proposed to play a role in Ca homeostasis

Question 19

True or False

In mdx mice and DMD patients, resting IC calcium levels are elevated in muscles

Answer 19

True

Activates inflammatory responses

Question 20

What are the consequences of membrane instability?

Answer 20

Calcium influx
apoptosis, necrosis
Inflammation Fibrosis

disrupted muscle architecture

clinical muscle weakness

Question 21

Deletions (65%) and duplications (5%) for DMD are detected by…

Answer 21

Deletions (65%) and duplications (5%) for DMD are detected by multiplex ligation dependent probe amplification analysis (MLPA)

Question 22

True or False

All people with DMD can be detected with MLPA

Answer 22

False

some patients have small duplications/deletions or point mutations - not detected by MLPA

Question 23

MLPA looks at ___ exons

Answer 23

all exons- unlike old PCR

Question 24

What are the characteristic findings in DMD (histology)

Answer 24

Variable fibre size

Hypercontracted (opaque) muscle fibres

Immature muscle fibre internal architecture

absent dystrophin

increased fibrosis and inflammatory cells within muscle

Question 25

Western blotting quantifies…

Answer 25

the amount of a protein in a specific tissue (determines size of protein) - useful for dystrophin