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AUDE 5310 Embryology & Genetic Conditions > NOnsyndromic HL & Deafness > Flashcards

NOnsyndromic HL & Deafness Flashcards

1
Q

what is nonsyndromic hl

A

only hl is associated

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2
Q

how many genetic deafness is nonsyndromic

A

75-85%

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3
Q

DFN

A

deafness neurosensory

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4
Q

dominant conditions are identified by symbol

A

DFNA1

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5
Q

recessive conditions are identified by symbol

A

DFNB

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6
Q

DFNB1A =

A

connexin 26

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7
Q

DFNB1B =

A

connexin 26

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8
Q

what is the gene mutation of connexin 26

A

GJB2 gene mutation – Cx26
GJB6 gene mutation – Cx26

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9
Q

most common associated with nonsyndromic hl

A

GJB2 gene mutation – Cx26
GJB6 gene mutation – Cx26

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10
Q

what do modifier genes do for HL

A

modify severity of HL, making it worse or mild

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11
Q

how are modifier genes identified

A

with the primary AR or AD genes and explain intra-familial variability with identical mutations

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12
Q

why do we see differences in expressivity and penetrance with recessive disorders

A

modifier genes

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13
Q

what are transcription factors

A

proteins (excluding rna polymerase) involved in initiating and regulating trasncription of genes (DNA) to RNA

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14
Q

Which is the primary mode of congenital nonsyndromic deafness

A

recessive

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15
Q

what is the primary mod of later onset nonsyndromic deafness

A

dominant

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16
Q

Almost all of the autosomal dominant conditions show

A

post-lingual progressive hearing loss

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17
Q

post lingual

A

later on, after child has acquired the language

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18
Q

almost all AD conditions of HL start in high frequencies but differ in

A

age of onset
rate of progression
ultimate degree of HL
vestibular involvement

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19
Q

what is otosclerosis

A

specific to ossificatioin of footplate of the stapes and its ossification into the oval window

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20
Q

later onset, increased chances of it being

A

dominant

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21
Q

If otosclerosis inherited, then it is an

A

autosomal dominant disorder and exhibits incomplete penetrance

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22
Q

what is post-lingual

A
  • later on, after child has acquired the language
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23
Q

what is otosclerosis

A

ossification of the stapes footplatend its ossification into the oval window

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24
Q

Otosclerosis may look like it _________ even though they may have the gene

A

skips generations or members of the same generation

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25
Q

what most likely triggers otosclerosis

A

by a combination of genetic, environmental, hormonal, and/or other factors

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26
Q

when do we look at otosclerosis hormonal trigger?

A

when there is a gender difference

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27
Q

why is otosclerosis complex?

A

so many different genes and loci involved and most common is the OTSC gene

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28
Q

What is the site of lesion of otosclerosis

A

Starts around the otic capsule
only takes place at the otic capsule
after embryo structures are into place,no remodeling occurs following this development
so this happens post birth
usually once they are layed down, no new remodelig occurs but with this it does happen

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29
Q

Single most common cause of hearing loss in young adulthood

A

otosclerosis

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30
Q

In 50% of females, initial awareness or rapid acceleration of the hearing loss occurs during or immediately after

A

pregnancy

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31
Q

what can worsen otosclerosis

A

after menopause (because of change of hormones

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32
Q

who is most vulnerable population for otosclerosis?

A

young white females - we don’t know why

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33
Q

what is DFNA5

A

AD nonsyndromic progessive SNHL

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34
Q

what happens in DFNA5

A

Hearing loss is present in childhood and becomes worse as affected individuals grow older

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35
Q

is otosclerosis progressive

A

YES
Cna go from conducive to mixed
Usually doesn’t progress to deafness

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36
Q

> 50% of autosomal recessive nonsyndromic hearing loss is caused by

A

Connexin 26 (GJB2 gene) mutations

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36
Q

almost all recessive conditions are associated with

A

profound SNHL that is prelingual

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37
Q

what is connexin 26

A

protein found in cells throughout the body

38
Q

where can connexin 26 be found

A

The inner ear (including utricle & saccule - nonsensory epithelia)
Skin
Liver
Bladder
Placenta
Breast
Brain

39
Q

where in the ear are connexins found

A

not cochlear hair cells
in nonsensory epithelial cells and supporting cels

40
Q

what is the best management for connexin?

A

CI’s

41
Q

most common connexin disorders

A

26, 30

42
Q

what are the connexin proteins

A

connexin 26
connexin 30

43
Q

what are the connexin deafness genes

A

GJB

44
Q

What are DFNB1 & DFNB3

A

first and third recessive connexin deafness

45
Q

what is the protein product of GJB2

A

connexin 26

46
Q

what is the protein product of GJB6

A

Connexin 30

47
Q

what is the gene for connexin 26

A

GJB2

48
Q

what is the gene for connexin 30

A

GJB6

49
Q

What is connexin

A

inherited nonsyndromic hearing loss (mild to severe) and deafness usually congenital

50
Q

if a baby has connexin and isn’t diagnosed until age 2, is it still congenital

A

yes it can be

51
Q

98% connextin mutations are found

A

GJB2 (small gene with entire coding sequence in exon 2)

52
Q

associated with >50% of nonsyndromic SNHL

A

connexin 26 (GJB2)

53
Q

Mutations in the connexins are responsible for

A

diversity of diseases, including deafness and skin disorders

54
Q

if it is recessive and more common in certain populations?

A

founder effect = consanguinity which is why we see it so much in the deaf communities

55
Q

most frequent cause of AR deafness

A

mutations of the connexins

56
Q

what is a gap junction

A

when two cells are very close, and they come together and through the ion channels, the ions are exchanged

57
Q

what happens if connexin intercellular communication is mutated

A

If they are mutated, they will not open and close, then the gap junctio nis defected and K+ ions cannot go in or out (cannot regulate potassium or calcium ions)
Clinically results in deafness or severe to profound SNHL

58
Q

what makes up a connexin

A

6 individual connexins

59
Q

describe mendelians second mendelia law of independent assortment

A

one gene transmitted is not influenced by other genes on that chromosome unless they are very close
alleles of different genes assort independently of one another during gamete formation

60
Q

what is an example of when mendelian law of independent assortment doesn’t hold tru

A

connexin deafness
Because they are so closely linked to each other, when an individual has a specific type of mutation in GJB6, it can influence the expression of the GJB2 gene
As a result, individuals can have hearing loss when they have two mutations in the GJB2 gene or two mutations in the GJB6 gene, or one mutation in each of these genes

61
Q

if there are two mutations in the GJB gene, chance of passing GJB2 or 6 to offspring rises

A

from 50% to 100%

62
Q

very common for GJB2 & GJB6 to be transmitted ______

A

together

63
Q

what is the mode of transmission of connexin?

A

AR

64
Q

List the several connexin proteins that are involved in human deafness

A

Cx26 (DFNB1/DFNA3) (most common)
Cx30 (GJB6-DFNA3; also common)
Cx32 (DFN or DFNX, X-linked Charcot-Marie-Tooth Disease)

65
Q

what is a deletion mutation

A

one base is deleted in the nucleotide

66
Q

single most common mutation in Caucasians and Asians with Connexin 26

A

35delG

67
Q

35delG mutation arises from

A

deletion - frameshift mutation

68
Q

35delG causes

A

truncated proteins

69
Q

How do connexin 26 present themselves?

A

congenital, recessive, bilateral
Born with a hearing loss
small % will lose hl soon after birth
mild to profound (depending on genotype)
most of the cases will progress so why we have to watch them

70
Q

what are other connexin phenotypes

A

Skin diseases and deafness and GJB2 mutations

71
Q

why are we concerned with skin issues?

A

treatment is CI’s because they have nothing else going on like cognitive impairment etc., but if they have skin issues and put the processor on it will rub on the skin and cause it to bleed, more likely to get infected
May not be candidates for it then because of this skin implication
What would you do to provide auditory input? They will fxn as deaf individuals, like sign lanaguage

72
Q

what is an xlinked nonsyndromic HL

A

x linked congenital stapes fixation with perilymph gusher

73
Q

what is the difference between congenital stapes fixation with perilymph gusher and otosclerosis

A

they are born with it fixated into the oval window
it is congenital
otosclerosis is developed over time

74
Q

what is x linked congenital stapes fixation with perilymph gusher

A

mixed hl
increase in hl if surgery is performed
can be progressive
females have milder symptoms

75
Q

why would hl increase if surgery occurs with x linked congenital stapes fixation with perilymph gusher

A

When you remove the footplate, the perilymph will gush out
Instead of correctible hearing loss with HA’s, there is a severe SNHL that may not be fixed with HA’s

76
Q

what is x linked congenital stapes fixation with perilymph gusher commonly misdiagnosed as

A

otosclerosis

77
Q

what is an example of mitorchondrial nonsyndromic HL

A

Aminoglycoside-induced ototoxicity

78
Q

what is an Irreversible but preventable hearing loss

A

Aminoglycoside-induced ototoxicity

79
Q

Mechanism of ototoxicity of aminoglycosides is due to

A

interference with the production of ATP in the mitochondria of cochlear hair cells

80
Q

Patients may have sudden onset ________ when exposed to aminoglycosides, which is generally not progressive

A

severe/profound SNHL

81
Q

is Aminoglycoside-induced ototoxicity dose dependent?

A

NO
they are not dose dependent

82
Q

what is not dose dependent

A

can take one or two doses and see the effects

83
Q

what is dose dependent

A

can take it a lot before seeing any issues

84
Q

what are the 3 categories of genetic disease

A

complex genetic disorders
monogenic diseases
environmental diseases

85
Q

what are complex diseases

A

caused in part by the environment and in part by genes as well as by an interaction between the two

86
Q

what is monogenic disease

A

primarily caused by genes
The environment only plays a minor role

87
Q

what is environmental diseases

A

primarily caused by the environment
Genes can play a minor role such as to determine a person’s susceptibility to being infected by certain infectious agents

88
Q

risk of single genetic variance that results in increased risk

A

mendelian disease

89
Q

a lot of variants are needed and the additive effect of a lot of variants cause the disorder

A

complex genetics

90
Q

why is there no clear inheritance pattern for complex genetics

A

becuase there are several different variants responsible for the disease

91
Q

what are many complex genetic diseases are due to

A

single nucleotide polymorphisms (SNPs)

92
Q

what is an example of complex diseases

A

age related hearing loss

93
Q

give an example of age related hl

A

Most 20-year-olds do not have a hearing loss but at least 50% of 70-year-olds do
There also is a difference between the best and worst hearing 70-year-olds
this is caused by genes and the environment

AUDE 5310 Embryology & Genetic Conditions (18 decks)

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