Lecture 4- Multiple Sclerosis Flashcards

1
Q

multiple sclerosis

A

most common CNS demyelinating disease- accumulating disability

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2
Q

epidemiology of MS

A

~23 000 cases in australia (1:1000)

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3
Q

onset of MS

A

most commonly in early adulthood (25-40yrs)

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4
Q

subtypes of MS

A
relapsing-remitting (60%)
secondary progressive (30%)- followup to relapsing remitting
primary progressive (10%)- w/o relapsing remitting
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5
Q

describe MS progression

A

CNS inflammation–>demyelination–> remyelination–> progressive neurodegeneration

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6
Q

inflammatory phase

A

immune cells led by T-cell mediated autoimmunity cross BBB, have reaction against myelin (target ODs)

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7
Q

demyelination and remyelination of axons

A

after inflammatory phase- OD progenitor cell make new myelin

process continues until pool of progenitor cells depleted

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8
Q

progressive neurodegeneration

A

failure for new myelin synthesis

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9
Q

periventricular plaques

A

95% of MS patients

white spots on MRI- water filled holes in brain due to demyelination and cell death in white matter tract

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10
Q

more common in which gender?

A

females 2-3 times fold

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11
Q

more common in which ethnicity?

A

north european ancestry

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12
Q

environmental risk factors

A

EBV, sunlight/vitD

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13
Q

treatments

A

are disease modifying; modulate course of disease and slow it down
e.g. Ocrelizumab- humanized anti-CD20 mAb

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14
Q

coding and non coding DNA in genome

A

1% protein coding; rest non-coding DNA

non coding- important in gene regulation

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15
Q

SNPs

A

most common known genetic variation
can be used as genetic markers in mapping
usually bi-allelic- both alleles of a gene

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16
Q

GWAS

A

compare SNP allele frequencies between groups of individuals e.g. cases and controls across genome
statistically significant difference in allele frequencies implies SNP in close genomic proximity to causal genetic locus
- diseases from families not applicable
- applicable to genetically complex common diseases

17
Q

why is identifying genes from GWAS hits hard?

A
  • top GWAS SNPs do not reside in genes, only 5% in protein coding regions
  • tend to be found in regulatory regions which influence gene regulatory sites
18
Q

SNPs effect on predisposition of gene

A

small effects to predisposition on its own

- lots together increase genetic burden and predisposition

19
Q

ANZgene

A

GWAS identified two MS susceptibility genes

20
Q

the two MS susceptibility genes identified by ANZgene GWAS

A

CD40 and CYP27B1

21
Q

HLA (DR2) association with MS

A

interaction with T cell receptor

22
Q

why did we use GWAS?

A

family based genetic studies not successful in identifying highly penetrant genetic mutations

23
Q

GWAS results

A

false positive associations really high, therefore replication very important
validation cohort important

24
Q

CD40

A

associated with susceptibility to MS
chr 20q13
involved in Ag presentation
member of TNF receptor family

25
function of CD40
Ag presentation - important regulatory of cellular and humoral immunity - co stimulatory molecule expressed on Ag presenting cells - CD40-CD40L binding expressed on surface of activated CD4 helper T cells, activates APCs
26
CYP27B1 gene
associated with MS chr 12q13-14 involved in vitD synthesis
27
function of CYP27B1 gene
involved in vitD synthesis - provides instructions for making vitD enzyme (hydroxylase) which converts vitD to active form, regulates calcium metabolism and and immune system via VDR
28
MS risk
mainly driven by genes with immune function; dysregulation
29
what triggers onset of MS?
unclear- combination of genetic and environmental
30
major genetic risk locus
HLA complex
31
MS loci identified so far?
explain 25% of variance in risk | 1/3rd of loci associated with other autoimmune diseases
32
genetic associations for MS phenotype?
no genetic basis for clinical heterogeneity i.e. subtypes
33
NGS
detection and analysis of known (SNPs) and unknown pathogenic mutations
34
targeted DNA sequencing
specific genomic regions
35
whole exome sequencing
only protein coding regions
36
whole genome sequencing
all protein coding and non coding regions | e.g. look for particular mutations that has allowed neurons to survive as long as it has
37
targeted RNA sequencing
specific gene transcripts
38
whole genome RNA sequencing
entire transcriptome