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pathophysiology > huntingtons disease > Flashcards

huntingtons disease Flashcards

1
Q

gene at play in Huntington disease

A

IT15 gene, HTT gene

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2
Q

the HTT gene generally has many

A

CAG repeats

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3
Q

in CAG repeats

A

repeats itself many times in a row in a gene

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4
Q

every healthy HTT gene has

A

a genotype with repeated HTT

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5
Q

CAG codes for what

A

amino acid glutamine

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6
Q

with more CAG repeats

A

the string of glutamines a protein is longer

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7
Q

too much CAG repeats leads to

A

a variety of cellular issues (especially in nerve cells)

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8
Q

examples of cellular issues cause by too many CAg repeats

A

issues with nerve signaling and mitcochondria

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9
Q

neurons with too many copies of glutamines

A

will malfunction and die

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10
Q

normally functioning HTT gene

A

10-35 CAG repeats

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11
Q

maybe Huntington HTT gene

A

36-39 CAG repeats

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12
Q

how many CAG repeats to get Huntington’s disease

A

40 or more

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13
Q

people with 27-35 CAG repeats

A

can’t get HT, children can inherit abnormal gene and develop HT

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14
Q

how could children get HT if parents did not have it

A

in meiosis, repeats are sometimes added or removed

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15
Q

the more CAG repeats the earlier

A

the earlier the Huntington disease starts

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16
Q

when proteins fold

A

sometimes there is a mistake

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17
Q

proteins are escorted by what

A

cellular proteins called a chaperone

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18
Q

what does the chaperone do

A

serves as quality control, making sure the protein is folded properly before guided to destination

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19
Q

if the protein does not appear to be folded correctly to the chaperone,

A

the chaperone calls for its destruction

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20
Q

how does the chaperone call for destruction

A

calls for the attachment of four or more signalling proteins to ubiquitin

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21
Q

adding four or more ubiquitin

A

polyubiquitination

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22
Q

any protein that has polyubiquinated

A

does not get escorted to its target site , it is taken to a proteasome

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23
Q

sole function of proteasome

A

shred proteins who carry polyubiquitination signal

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24
Q

after being the proteasome the peptides are

A

further broken down by other structures so the amino acids can be reused

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25
Q

peptides

A

short chains of amino acids

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26
Q

huntingtin

A

the protein HTT gene codes for

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27
Q

huntingtin carries

A

many glutamines in a row, (ecspecially mutant huntingtin)

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28
Q

one letter abbreviation for glutamine

A

Q

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29
Q

glutamine is….

A

polar (remember like attracts like)

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30
Q

the _____ region from one huntingtin is _______-__

A

the polyQ region from one huntingtin is chemically attracted to the polyQ region of another huntingtin

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31
Q

in many cases, huntingtin proteins or protein fragments from the polyQ region will

A

aggregate

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32
Q

aggregate

A

stick together

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33
Q

chaperones see aggregated huntingtin proteins as

A

misfolded, and try to ubiquinate them for destruction by proteasome

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34
Q

the aggregates of huntingtinm can sometimes

A

end up clogging a proteasome instead

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35
Q

how do aggregates clog proteasome

A

idk , relatively unknown

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36
Q

once proteasomes are clogged by aggregates

A

a positive feedback loop of aggregated huntingtin starts- they all start aggregating together

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37
Q

Aggregation of huntingtin or its fragments

A

build up in large amounts, ecspecially in nerve cells

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38
Q

why does aggregation of huntingtin happen a lot in nerve cells

A

where HTT gene is expressed in the highest amounts, most huntingtin

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39
Q

aggregations have been observed in

A
  • nuclei

- cytoplasm

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40
Q

what usually aggregates in the nuclei

A

fragments

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41
Q

what usually aggregates in the cytoplasm

A

larger fragments and full proteins

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42
Q

aggregations eventually grow so large

A

that cells cannot properly send signals, build microtubules,etc

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43
Q

after large aggregations neruons will begin to

A

begin atrophy

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44
Q

atrophy

A

waste away

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45
Q

nerve death from Huntington begins

A

at various ages depending on the number of CAG repeats

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46
Q

how much of the brain is affected by huntington inclusions

A

the entire brain

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47
Q

what is the first region of the brain to see neuronal death

A

the striatum

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48
Q

more neuroanal death is seen

A

on the dorsal side

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49
Q

the dorsal side oversees

A

motor function

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50
Q

Huntington’s patients slowly lose

A

motor function, and eventually behavioral and cognitive function

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51
Q

other name for Guevedoces

A

5ARD

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52
Q

what happens around 6-8 weeks after fertilization

A

an embryo will decide what sex it will become

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53
Q

what forms first after fertilization

A

the internal genitalia

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54
Q

internal genitalia

A

gonads

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55
Q

what forms second after fertilization

A

tubes that connect the gonads to the external genitalia

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56
Q

what forms third after fertilization

A

the external genitalia

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57
Q

in early embryos, what distinct ridges of cells form

A

Wolffian duct, Mullerian duct

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58
Q

when does Wolffian duct and Mullerian duct form

A

a fter 5-6 weeks

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59
Q

the wolffian duct has the potential to turn into

A

a series of tubes that connect the male gonads to the penis- epididymis, vas deferens, seminal vesicle

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60
Q

males gonads

A

testes

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61
Q

the Mullerian duct has the potential to turn into

A

a series of tubes that connect the female gonads to the vagina

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62
Q

female gonads

A

ovaries

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63
Q

the ridges of the Wolffian Duct and Mullerian duct form near

A

undeveloped gonads, but also connect to the kidneys

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64
Q

gonads can turn into either

A

the etstes or ovaries

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65
Q

the decision of what the gonads turn into comes from

A

whether or not the SRY gene is expressed

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66
Q

SRY codes for

A

SRY protein

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67
Q

what is SRY protein

A

Sex-determining Region Y protein

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68
Q

SRY is on what chrosome

A

the Y chromosome

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69
Q

which gender expresses the SRY gene

A

biological males

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70
Q

SRY protein stimulates what

A

undifferentiated progenitor cells in the primitive gonads to “grow up”

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71
Q

SRY stimulates undifferentiated progenitor cells to grow up into what

A

into Leydig and Sertoli cells

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72
Q

where are Leydig and Sertoli cells found

A

the testes

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73
Q

after 6 to 7 weeks if gonad cells haven’t been hit with SRY….

A

they decide to grow into ovaries and develop into granulosa cells

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74
Q

Turner Syndrome Patients

A

also have ovaries

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75
Q

young Sertoli found are only found

A

only in the testes

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76
Q

young sertoli cells have the unique ability to

A

express a gene called teh AMH gene

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77
Q

where is the AMH gene found

A

on chromosome 19, NOT Y

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78
Q

AMH gene codes for

A

AMH

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79
Q

AMH is

A

Anti-Mullerian Hormone

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80
Q

AMH works to

A

stop the development of Mullerian duct

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81
Q

AMH makes the Mullerian duct

A

wither away into nothing

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82
Q

After AMH does its job, the Wolffian ducts then

A

then grow into the “male” tubes-epididymis, vas deferens, seminal vesicle

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83
Q

if AMH is not produced…..

A

the Wolffian ducts degrade and the Mullerian ducts grow into fallopian tubes and the uterus

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84
Q

what are steroids

A

a class of hormones that are ll synthesized from cholesterol

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85
Q

steroids are all

A

very close ins tructure

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86
Q

one steroid is often the

A

precursor of another

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87
Q

now that the gonads have developed,

A

embryos have either Leydig cells or granulosa cells

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88
Q

what mainly is produced by Leydig cells

A

androgens

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89
Q

what is mainly produced by granulosa cells

A

estrogens

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90
Q

testosterone is a direct precursor to

A

the estrogens

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91
Q

testosterone is also a precursor to

A

androgen DHT

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92
Q

DHT

A

dihydrotestosterone

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93
Q

by about 10 weeks

A

the internal anatomy has decided its fate, the external anatomy will begin to take place

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94
Q

what plays a major role in the process of external anatomy taking place

A

sex hromones

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95
Q

by 10 weeks the gonads have formed so……

A

now there are either Leydig or granulosa cells present

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96
Q

Leydig or Granulosa cells each make

A

a different type of steroid

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97
Q

the bundle of cells that will develop in the external genital have many

A

androgen receptors

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98
Q

testosterone can bind to and activate

A

bind to and activate androgen receptors

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99
Q

DHT is a far stronger

A

agonist of androgen receptors

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100
Q

because DHT is a strong agonist of androgen receptors

A

a small amount of DHT goes a long way in the formation fo a penis

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101
Q

enzyme that converts testosterone into the extra potent DHT is called

A

5a-reuctase

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102
Q

gene of 5a-reductase

A

SRD5A2

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103
Q

SRD5A2 is found

A

on the 2nd chromosome

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104
Q

SRD5A2 is NOT found where

A

on the Y chromosome

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105
Q

in people with guevedoces

A

each copy of SRD5A2 carries an amorphic mutation

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106
Q

when both copies of SRD5A2 carry an amorphic mutation

A

no DHT is ever produced in these people

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107
Q

people with guevendoces end up developing

A

ambiguous external genitalia that more closely resemble female genitalia than male

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108
Q

at the beginning the gonads

A

begin producing high amounts of sex hormones

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109
Q

remember that hormones

A

come from the gonads

110
Q

boys, even boys with guevedoces

A

have testes with Leydig cells inside, they will crank out large amounts of androgens at puberty

111
Q

in all males

A

DHT is not very biologically important in puberty or normal “male” activity

112
Q

the most important androgen in puberty

A

testosterone

113
Q

major processes that happen in puberty (males)

A

growth of the penis and testes

114
Q

the growth of the penis and testes is catalyzed by

A

testosterone

115
Q

during puberty in guevedoces

A

the previously small penis and scrotum begin to grow. sometimes they descend from the urogenital area

116
Q

for people with guevedoces, puberty

A

proceeds as if they were male

117
Q

long-term consequences of guevedoces

A
  • no breast development-muscle tone similar to other men of the same age
  • the ability to produce functioning sperm*
  • the ability to reproduce**
118
Q

people with guevedoces can only produce functioning sperm if

A

the testes descend (otherwise it is too hot)

119
Q

people with guevedoces can only reproduce if

A

the penis forms long enough for intercourse, or other transferring methods of sperm

120
Q

A person with XY chromosomes, but an amorphic mutation to the SRY gene

A

ovaries

, vagina

121
Q

person w/ XY chromosomes amorphic mutation to AMH gene

A

gonads: testes

fallopian tubes and uterus

122
Q

A person with XX chromosomes but a chromosomal translocation mutation where the SRY gene is present and active on their 1st chromosome

A

testes, penis

123
Q

maple syrup urine disease is

A

a rare autosomal disease

124
Q

MSUD is categorized as

A

metabolic and catabolic disorder

125
Q

two parts of metabolism

A

anabolism, catabolism

126
Q

anabolism

A

building molecules

127
Q

catabolism

A

breaking apart molecules

128
Q

in most cases symtoms of MAPUD begun

A

a few days after birth

129
Q

primary diagnostic symtom of MAPUD

A

urine with distinct sweet aroma, like maple syrup

130
Q

MUSD affects how many births

A

1 in 150,000

131
Q

because MSUD is recessive

A

both copies of a gene must be faulty

132
Q

the MSUD protein is a

A

trimer

133
Q

three genes that could be faulty in MSUD

A

one on chromosome 19
one on chromosome 6
one on chromosome 1

134
Q

msud gene on chromosome 19

A

BCKDHA

135
Q

BCKDHA makes what

A

E1-a protein

136
Q

MSUD geen on chromosome 6

A

E1-B protein

137
Q

musd gene on chromsome 1

A

DBT, makes E2 proteins

138
Q

E1-α, E1-β, and E2 come together to form

A

a trimeric enzyme

139
Q

what trimeric enzyme does E1-α, E1-β, and E2 form

A

branched-chain alpha-keto acid dehydrogenase

140
Q

important note for MSUD

A

does not follow dominant negative gene action

141
Q

it has been proposed that BCKD has

A

4 subunits, not 3

142
Q

BCKD

A

branched-chain alpha-keto acid dehydrogenase

143
Q

TO GET MUSD YOU MUST

A

inherit two faulty versions of the same chromosome

144
Q

_______ catalyzes an irreversible step of the breakdown of three “branched chain” amino acids

A

Branched-chain α-keto acid dehydrogenase

145
Q

what branched amino acids are catalyzed by Branched-chain α-keto acid dehydrogenase

A

valine, leucine, isoleucine

146
Q

the breakdown of the thee “branched chain” amino acids is a

A

3 step of 4 step process

147
Q

failure of BCKD leads to

A

excess amount of the three amino acids

148
Q

failure of BCKD also leads to excess byproduct…

A

alpha-keto acids

149
Q

keto-acids have

A

a before the name

150
Q

mostly, what are valine, leucine, isoleucine used

A

they are usually used to build the body’s own amino acids

151
Q

what chromosme is HTT

A

4th

152
Q

valine, leucine, isoleucine are brok en..

A

apart for energy in certain instances

153
Q

what instances are valine, leucine, isoleucine broken down

A
  • starvation/fasting
  • fighting illness
  • body consumed too much protein
154
Q

almost all pieces of the breakdown of valine, leucine, isoleucine

A

end of falling into the Krebs cycle

155
Q

what is the Krebs cycle

A

the complex process in which a cell produces energy from glucose

156
Q

since pieces of breakdown of valine, leucine, isoleucine join…

A

join cycle late, means they dont generate as much energy as the sugar

157
Q

Krebs cycle is responsible for

A

for energy production of cells

158
Q

what are the krebs cycle pieces that come from the keto acids

A

Acetyl-CoA, Succinyl-CoA

159
Q

when valine, isoleucine and their alpha-keto acids accrue in the bloodstream…

A

they move into cells

160
Q

when valine, isoleucine and their alpha-keto acids accrue in the bloodstream and move into cells

A

it is toxic for cells, ecspecially nerve cells

161
Q

when the amino acids and their alpha-keto acids move into cells, why is it toxic?

A

three amino acids and keto acids block entry of other amino acids into the brain (much like in PKU)

162
Q

having too much of the three amino acids and not enough of the rest leads to

A

temporary mental retardation, impaired motor control, seizures

163
Q

the extra byproducts (keto acids) are someties broken down to

A

to form sotolon

164
Q

what is sotolon

A

a small chemical that smells strongly of maple syrupor fenugreek

165
Q

how is sotolon excreted

A

through urine

166
Q

amino acid breakdown is almost completely carried out where

A

in the mitochondria of liver cells

167
Q

1 of the cures for MSUD

A

complete liver transplant `

168
Q

why can a complete liver transplant cure MSUD

A

the new transplant cells do not carry the mutation, and can produce E1-a, E1-b, and E2 correctly

169
Q

before a liver transplant, people w/ MSUD must

A

closely monitor their diets to avoid protein

170
Q

why must ppl w/ MSUD closely monitor their diets to avoid protein before a liver transplant

A

they should have just enough valine, leucine, and isoleucine to produce their proteins

171
Q

ppl w/ MSUD undergoing a liver transplant must also

A

avoid going into starvation mode, usually eat MSUD diet powder

172
Q

why avoid going into starvation mode (MSUD transplant)

A

so the body dosen’t break down protein for energy, it must stay in first gear and break down carbohydrates constantly

173
Q

classifications of MSUD

A

Acute MSUD, Intermediate MSUD, Intermittent MSUD

174
Q

Acute MSUD

A

two amorphic or severe hypomorphic mutations inherited for any one of the pieces f the trimer

175
Q

In acute MSUD symptoms are

A

present almost immediately after birth and results in death within the first few months of life unless treated immediately

176
Q

severe hypomorphic

A

less than 8% function

177
Q

intermediate MSUD

A

one piece of the trimer receives two hypomorphic (8-15% function) mutations.

178
Q

in intermediate MSUD, function of the trimer

A

is slow, but still work `

179
Q

in intermediate MSUD, symptoms begin

A

in childhood, but when depends on how hypomorphic and patients diet

180
Q

phosphorylation

A

adding a phosphate group to the R-chain

181
Q

phosphorylations generally turn proteins

A

on or off

182
Q

phosphorylations are almost always

A

reversible

183
Q

kinase

A

an enzyme that adds a phosphate group

184
Q

phosphatase

A

enzyme that removes a phosphate group

185
Q

kinase and phosphate can both be

A

on or off switch

186
Q

less extreme forms of MSUD exist

A

in mutations of 2 other genes BCKDK and BCKDP `

187
Q

BCKDK does what

A

codes for BCKD kinase

188
Q

what does BCKD kinase do

A

adds a PO4 to the -3 to BCKD

189
Q

BCKDP does what

A

codes for BCKD phosphatase

190
Q

what does BCKD phosphatase do

A

removes a PO4 to the -3 from BCKD

191
Q

in the liver,

A

BCKDK gene is expressed in cells at very low rates compared to other cells

192
Q

Why does BCKDK code for the off switch (remember it is expressed at low rates)

A

the liver is the main site of branched-chain amino acid breakdown» we want this enzyme ON in the liver - so the OFF switch will be expressed at low rates here» its the off switch`

193
Q

BCKDP – when it suffers a hypomrphic mutation

A
  • similar symptoms to intermittent MSUD

- when the liver needs to turn on all of its inactive copies of BCDK, it can’t

194
Q

what happens when inactive copies of BCDK can’t be turned on

A

leucine, isoleucine, valine and their keto-acids build up in the body, leading to a short period of MSUD symptoms

195
Q

after a period of time with inactive BCKD

A

liver cells produce completely new BCDK trimers that aren’t off yet, patient returns to normal

196
Q

BCKD phosphatase turns

A

BCKD on

197
Q

BCKD kinase turns

A

BCKD off

198
Q

when BCKDK suffers a hypomorphic mutation

A

opposite of MSUD

199
Q

opposite of MSUD

A

instead of BCDK not working it works too much

200
Q

result of opposite of MSUD

A

branched chain amino acids are broken down instead of being used to build proteins

201
Q

big symptom of opposite of MSUD

A

cachexia

202
Q

what is cachexia

A

“wasting away”

the loss of muscle mass and/or the failure to add new muscle mass

203
Q

Intermittent MSUD

A

Like intermediate, trainer functions at 15+ % efficiency

204
Q

Intermittent MSUD symptoms

A

Episodes rare, life can be normal w a proper diet. Episodes often accompany infections

205
Q

Angelman syndrome defined by

A

mental impairment, excessively happy demeanor, jerky movements, sleep disturbance

206
Q

what jerky movements in angelman are common

A

hand flapping

207
Q

how many ppl are affected by angelman

A

1 in 20,000 live births

208
Q

does Angelman SYndrome present the same phenotype in its patients

A

yes

209
Q

the multiple mechanisms for angelman phenotype

A

imprinting and deletion
imprinting errors
uniparental disomy

210
Q

genetic imprinting

A

when one copy of a gene is “turned off” after it is inherited

211
Q

genetic imprinting is usually caused by

A

methylation

212
Q

methylation

A

additon of methyl group -CH3 o a gene

213
Q

the methyl group in genetic imprinting does what

A

blocks transcription from happening> DNA never becomes RNA>never makes protein

214
Q

(imprinting) for many genes, either the mother’s chromosome or the father’s chromosome is

A

systematically silenced

215
Q

what is a gene always silenced in sperm, not in eggs

A

UBE3A

216
Q

where is UBE3A located on

A

on the 15th chromosome

217
Q

UBE3A codes for

A

protein E6-AP

218
Q

E6-AP is involved in what

A

the ubiquitination process

219
Q

what is ubiquitination process

A

cell’s way of targeting and destroying certain proteins

220
Q

since the father’s copy of UBE3A is always silenced,

A

the mother’s copy becomes extremely important

221
Q

in about 75% of cases of Angelman

A

a chromosomal deletion mutation leads to the complete deletion of this gene in the egg

222
Q

if there is a deletion of UBE3A in the egg

A

since the father’s copy is silenced the baby will have no functioning copies of E6-AP

223
Q

UBE3A gene is located very close to

A

P gene (causes type 2 albinism)

224
Q

since UBE3A is so close to P gene

A

chromosomal deletion mutation will affect both genes» albinism more common in people with Angelman

225
Q

what percentage of Angelman is an imprinting error

A

20%

226
Q

what is the imprinting error that causes Angelman

A

the mother’s copy of the gene is methylated w/ the fathers

227
Q

result of imprinting error

A

both copies are off, phenotypes look the same as if mom’s gene is missing

228
Q

rare cases of Angelman syndrome

A

caused by uniparental disomy

229
Q

uniparental disomy is

A

rare condition where . zygote inherits two copies of a chromosome from one parent and no copies from another

230
Q

two forms of uniparental disomy

A

uniparental isodisomy

uniparental heterodisomy

231
Q

uniparental isodisomy

A

when a person inherits the SAME chromosome from a parent twice

232
Q

what cases would uniparental isodisomy happen

A

where a person would have a monosomy but undergoes a monosomy rescue

233
Q

what is a monosomy rescue

A

the single chromosome is duplicated

234
Q

a person who underwent a monosomy rescue will have

A

46 chromosomes, but 2 identical copies of the same one

235
Q

uniparental heterodisomy occurs when

A

there would be a trisomy but the zygote undergoes trisomy rescue

236
Q

trisomy rescue

A

one copy of the tripled chromosome discarded

237
Q

in how many cases of trisomy rescue will the embryo be normal

A

2/3

238
Q

in _____ cases of trisomy rescue___

A

1/3 cases, the embryo could inherit two copies of one parent’s chromosomes

239
Q

uniparental disomy can be the cause of AS when

A

-a person inherits 2 copies of father’s 15th chromosme, none from mom

240
Q

when 2 copies of father’s 15th chromosome inherited

A

both copies of father’s UBE3A gene silenced by methylation,&raquo_space;> AS phenotype

241
Q

AS rember

A

3 unique genotypes lead to same phenotype

242
Q

albinism

A

lack of pigment melanin

243
Q

two main types of albinism

A
  • oculocutaneous albinism

- ocular albinism

244
Q

oculocutaneous albinism

A

affects skin, hair , eyes

245
Q

ocular albinism

A

eyes only

246
Q

people w/ oculocutaneous albinism have ..

A

extremely fair skin, white-blonde hair, light blue eyes

247
Q

melanocytes do what

A

produce black pigment melanin that makes skin look dark

248
Q

melanocytes produce more melanin in response to

A

more sunlight exposure

249
Q

melanocytes package small amounts of melanin into

A

vessels called melanosomes

250
Q

melanosomes are passed on tp

A

superficial keratinocytes

251
Q

what does melanin do

A

absorbs UV rays from sun that can give u cancer

252
Q

skin color is determined by what

A

fatctor of number f melanosomes, how active melanocytes are

253
Q

what does NOT determine skin color

A

number of melanocytes

254
Q

A melanocyte generally ha

A

ling projections called dendrite that reach to more superficial layers

255
Q

dendrites of melancyte,…

A

passes melanosomes into outer cells

256
Q

albinism often causes

A

red eyes, ,

257
Q

albinism red eyes…

A

because w/ a total lack of pigment blood vessels in your can be seen, sensitive too sun

258
Q

what type of disorder is albinism

A

recessive

259
Q

most common mutation for oculocutaneous albinism comes in on

A

TYR gene on chromosome 11

260
Q

TYR gene codes for

A

enzyme tyrosinase

261
Q

two types type 1 of albinism

A

Type 1A: Amorphic mutation in TYR

Type 1B: Hypomorphic mutation in TYR

262
Q

types of type 1 of albinism look

A

same at birth, usally type 1b is more dirty blonde

263
Q

tyrosinase is

A

an enzyme that catalyzes an important step in the synthesis of melanin from tyrosine

264
Q

without tyrosinase

A

melanin’s precursor can’t be mDE, MELNIN CAN’T BE MADE EITHER

265
Q

melanin’s precursor `

A

dopquinone

266
Q

type 2 oculocutaneous albinism

A

comes from a deficiency in a transport protein found in the membrane of melanocytes

267
Q

the transport protein in the membrane of melanocytes

A

allows other proteins like tyrosinase to pass into the melanocyte from other cells, causing more melanin to be prduced inside

268
Q

gene for the transport protein in membrane of melanocyte

A

P gene, found on 15th chromosme

269
Q

the other types of albinism come from

A

mutations in other enzymes in the melanin synthesis pathway , not as common

270
Q

the other types of albinism can also come from

A

issues w transportation in melanocytes, storing melanin correctly etc

271
Q

ho many different genotypes of albinism have been seen

A

ho many different genotypes of albinism have been seen

272
Q

htt is found on

A

chromosome 4 :)

pathophysiology (24 decks)

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