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BMS2002 > L07 > Flashcards

L07 Flashcards

1
Q

what is a phenotype

A

An observable physical properties of an organism

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2
Q

what are channelopathies

A

a group of disorders caused by dysfunction in ion channels

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3
Q

how are channelopathies explained

A

genetics

acquired

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4
Q

which disease has a monogenic channelopathy

A

cystic fibrosis

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5
Q

give an example for an idiopathic channelopathy

A

postoperative pain

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6
Q

give an example for acquired channelopathy

A

myasthenia gravis

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7
Q

what are the functions of cystic fibroses

A

Monogenic- arises from mutations in the CFTR gene.

Dysfunction in the influx of chloride ions (and water).

Leads to mucus accumulation and inflammation.

Subtypes functionally classified on the effect of the mutation on the channel.

Identified by genetic linkage

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8
Q

what happens in CF class 1

A

no creation of the protein (CFTR) from mRNA

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9
Q

what happens in CF class 2

A

CFTR is made but it fails to fold or get trafficked to the cell membrane

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10
Q

what happens in CF class 3

A

CFTR gating fails due to a mutation in the residues that control it

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11
Q

what happens in CF class 4

A

faulty CFTR is produced

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12
Q

what happens in CF class 5

A

insufficient quantities of CFTR

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13
Q

what happens in CF class 6

A

CFTR stability is reduced at the cell membrane

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14
Q

what are the methods of investigating genetic linkage

A

LINKAGE MAPPING

ASSOCIATION MAPPING

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15
Q

CF is Autosomal recessive

A

yes

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16
Q

what does 100% penetrance mean

A

Got the allele → Got the trait

17
Q

what gene encodes voltage gated Na channel subtype 1.7

A

SCN9A

18
Q

which genes encode which voltage gated Na channel subtype

A

SCN1A – 1.1

SCN2A – 1.2

SCN3A – 1.3

SCN4A – 1.4

SCN5A – 1.5

SCN8A – 1.6

SCN9A – 1.7

SCN10A – 1.8

SCN11A – 1.9

19
Q

which subunit of the voltage gated Na channel does SCN9A encode

A

alpha

20
Q

what is the effect of Nav1.7- on action potential

A

Contributes to the rising phase and amplifies subthreshold stimuli

21
Q

what are the features of Nav1.7-

A

Low activation threshold (vs other NaV channels)

Fast kinetics

TTX responsive

22
Q

SCN9A (Nav1.7) is highly expressed by sensory neurons of the Dorsal Root Ganglion DRG

A

yea

23
Q

what does Q10R MEAN

A

R substituted for Q

24
Q

what conditions are associated with SCN9A mutations

A

Paroxysmal extreme
pain disorder (PEPD)

(Primary) inherited erythromelalgia (IEM)

Small-fibre neuropathy

25
Q

what are the features of Inherited Erythromelalgia (IEM)

A

Mutation(s) in SCN9A (autosomal dominant)

Bilateral episodes of burning pain in feet & hands

Attacks triggered by exercise and/or heat

Onset in childhood and continued through adult life

26
Q

how do SCN9A mutations lead to IEM

A

First mutation L858H, located in the second domain (Yang et al 2004).

The mutations lower the activation threshold, allowing the mutant channels to open more easily in response to smaller depolarizations.

They slow or impair fast inactivation, resulting in prolonged channel opening times.

The mutations enhance the ramp response, causing larger currents in response to small, slow depolarizations.

Some mutations also impair slow inactivation, leading to increased channel availability.

The mutations shift the voltage-dependence of activation and inactivation, making the channel activate at more hyperpolarized potentials.

Increased excitability correlates with symptom severity

27
Q

what are the features of Paroxysmal extreme pain disorder

A

Mutation in SCN9A (autosomal dominant)

Severe pain in the rectal, ocular and mandibular areas

Attacks triggered by chewing and/or heat

Onset in childhood and continued through adult life

28
Q

how do SCN9A mutations cause PEDP

A

Lowered threshold for channel activation - the channel opens more easily in response to small depolarizations

Delayed channel inactivation - the channel stays open longer than usual

Enhanced response to repetitive stimulations - the channel recovers more quickly between activations

Altered voltage-dependence - the relationship between membrane voltage and channel opening is shifted

29
Q

what are the features of Complete insensitivity to pain (CIP)

A

Mutation in SCN9A (autosomal recessive)

Loss of all pain sensations

Tend to be non-sense mutations (within domains I & II) leading to a truncated protein

CIP patients often suffer major injuries as a result

30
Q

which disease is associated with enhanced activation of SCN9A

A

IEM

31
Q

which disease is associated with impaired activation of SCN9A

A

PEPD

32
Q

what are the autonomic effects of IEM and what are they caused by

A

cutaneous vasomotor abnormality

caused by sympathetic ganglion neuron being less excitable

33
Q

what are the autonomic effects of PEPD

A

skin flushing and watering of eyes and mouth

34
Q

what are the autonomic effects of CIP

A

there is non reported

35
Q

SNPs are studied to see if they are associated with a particular trait

A

yes

36
Q

which condition is associated with olfactory pathways

A

CIP

37
Q

how is anosmia caused in people with CIP

A

impaired signaling of olfactory sensory neuron

BMS2002 (14 decks)

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