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Molecular Exam 2 > Special Topic: Cytoskeletal Protein Defects > Flashcards

Special Topic: Cytoskeletal Protein Defects Flashcards

1
Q

What is a hemolytic anemia?

A

result from abnormally shortened red blood cell lifespan

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2
Q

What is hereditary spherocytosis?

A

hemolytic anemia is characterized by spherical and fragile red blood cells that lyse and release hemoglobin

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3
Q

What are symptoms of heredity spherocytosis?

A

hemolysis, anemia, splenomegaly

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4
Q

What causes heredity spherocytosis?

A

mutations in genes for the erythrocyte membrane skeleton of red blood cells

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5
Q

What is the osmotic fragility test?

A
  • place few drops of blood into slightly hypotonic saline
  • Water rushes in by osmosis
  • normal cells will swell but not break
  • heredity spherocytosis cells will swell and break releasing hemoglobin due to being so fragile
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6
Q

What is the top EMS mutation for heredity spherocytosis?

A

spectrin/ankyrin defet

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7
Q

Nan ______ a mutation in cytoskeletal protein

A

is not

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8
Q

What is Nan a mutation for?

A

DNA binding protein called Kruppel like factor 1 or Klf1

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9
Q

What does Klf1 target?

A

EMS genes

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10
Q

What changes a WT mouse to a Nan mouse in Klf1 DNA binding motif?

A

glutamic acid to aspartic acid

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11
Q

What are treatments for heredity spherocytosis?

A

blood tranfusions
splenectomy- removal of spleen
increase RBC # and Hb

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12
Q

What are some characteristics of Duchenne Muscular dystrophy (DMD)?

A
  • severe, progressive muscle degeneration
  • loss of ability to walk
  • loss of cardiac and lung function
  • scoliosis
  • premature death
  • no cure
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13
Q

What is the treatment for DMD?

A

no actual treatment, just to improve quality of life

glucocorticoids slow decline in muscle strength but do not alter course of clinical disease

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14
Q

What causes death in DMD?

A

abnormal hearts and/or respiratory failure

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15
Q

DMD is ______ linked and _____

A

x; recessive

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16
Q

DMD defect present at birth but does not show symptoms until _____

A

about 3 years of age

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17
Q

What is the main function of the dystrophin protein?

A

provide structural stability to the muscle cell membrane during cycles of contraction and relaxation

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18
Q

What are the four functional domains of the dystrophin protein?

A

n-terminus
long spectrin like repeats domain
cysteine rich and c-terminus domain

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19
Q

What does the n-terminal of dystrophin bind to?

A

actin

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20
Q

What does the cys rich and c-terminal domains bind to?

A

dystroglycans and syntrophins

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21
Q

Where is dystrophin localized?

A

inner surface of muscle membrane

22
Q

Loss of dystrophin results in _____

A

destabilization of entire dystrophin-glycoprotein complex

23
Q

What is dystrophic myopathy?

A

progressive muscle degeneration with loss of functional muscle tissue over time with resulting weakness

24
Q

what is at an elevated level in DMD?

A

creatine kinase

25
Q

DMD causes necrosis of muscles fibers, occurs with

A

replacement of fat or connective tissue

26
Q

What is pseudohypertrophy?

A

replacement of muscle with adipose and fibrous connective tissue (enlarged calves)

27
Q

What is lordosis?

A

excessive inward curvature

28
Q

What is kyphosis?

A

upward back curvature outward

29
Q

What is a Gower maneuver?

A

due to weakened leg muscles, people with DMD will get on hands and renews then elevate the posterior then walk hands up legs

30
Q

What are CRDs?

A

complex repetitive discharges-abnormal spontaneous firing action potentials associated with membrane instability

31
Q

What are CRDs indicative of?

A

muscle membrane instability and muscle pathology

32
Q

What is Beck muscular dystrophy (BMD)?

A

milder form of duchenne
loss of walking at 16 years of age
muscle pain, dilated cardiomyopathy

33
Q

What leads to death in BMD?

A

increased workload on left ventricle leads to let ventricular enlargement, severity results in heart failure and death

34
Q

What is the incidence of DMD?

A

1/3 de novo mutations

2/3 familial

35
Q

What is the case of DMD vs BMD?

A

DMD: missing dystrophin protein to weaken muscle membrane
BMD: some dystrophin protein, abnormal quantity and size

36
Q

What type of mutation is DMD associated with?

A

frameshift mutations

37
Q

What type of mutation is BMD associated with?

A

in frame deletions

38
Q

What is a manifesting female carrier for DMD?

A 
mild form 
slightly elevated CK 
weaker muscles of back, arms, legs 
fatigue easily
heart problems/shortness of breath
39
Q

How do you diagnosis DMD?

A

EMG to measure muscle response to nervous stimulation
blood test: elevated creatine kinase levels
muscle biopsy
DNA gene deletion studies: PCR
quantitative dystrophin analysis: western blot

40
Q

How do you prenatal diagnose DMD?

A

fetal DNA: amniocentesis, chorionic villus sampling
molecular analysis: PCR
preimplantation genetics: remove single cell following IVF and see if they have bad gene

41
Q

What are some treatment strategies to DMD?

A

use of growth factors to make more muscles
use of gene therapy
strategy of exon skipping
strategy of nonsense (stop) codon read through

42
Q

What does myostatin do? What happens if you knock it out?

A

inhibits muscle growth.

if knocked out, it can lead to very large muscles

43
Q

What is the problem with replacing the dystrophin gene in gene therapy?

A

too large for adeno associated viruses

44
Q

What is the problem with microdystrophins for BMD treatment?

A

you can make a functional dystrophin protein and will generate protein with n terminus, some spectrin like repeats, and cya-rich and c-terminus
but issues with immunogenicity

45
Q

What is the issue with immunogenicity for microdystrophins?

A

T-cells mediated immunity against dystrophin proteins

46
Q

What is the problem with trying to treat DMD with exon skipping and skipping stop codon?

A

problems with immunogenicity

47
Q

What is eye dystrophin?

A

similar to muscle dystrophin but smaller in the eye

48
Q

What domains do eye dystrophin have?

A

spectrin, cys, c-terminus

and an actin binding site

49
Q

Would expression of Dp260 in muscle rescue DMD?

A

yes

50
Q

What happens when you use a natural isoform of dystrophin?

A

removes immunogenicity barrier

51
Q 
A 17 year old male exhibiting muscle weakness is examined for a dystrophinopathy. The patient is not restricted to a wheelchair but is easily fatigued. A western blot of protein, taken from a needle biopsy of muscle, shows 50% of the expected level of dystrophin protein which is slightly smaller than normal dystrophin. Multiplex PCR of exons from the dystrophin gene indicates a deletion from exon 50 to 51. What is the most likely diagnosis for this patient?
A. Duchenne muscular dystrophy 
B. Listeria infection
C. Hereditary Spherocytosis
D. Becker’s muscular dystrophy 
E. Cystic Fibrosis
A

D. Becker’s muscular dystrophy

Molecular Exam 2 (13 decks)

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