Alzheimer's disease

Question 1

Features of AD

Answer 1

1. Memory impairment due to neuronal loss
2. Decrease of Ach levels
3. Increased glutamate excitotoxicity
4. Proteotoxic stress

Question 2

Major AD risk factors

Answer 2

1. Age
2. APOE (2-3 fold increase with one allele)

Question 3

AD and amyloid

Answer 3

Characterised by deposition of amyloid beta peptide in extracellular compartment of the brain (ebwteen nerve cells) ion the form of amyloid plaques.

Secondary pathological changes occur in the neuronal cytoplasm, with accumulation of abnormally phosphorylated form of microtubule-associated protein tau.

This makes AD a secondary tauopathy.

Question 4

Population frequencies of predominant APOE alleles:

Answer 4

o e2: 8.4%
o e3: 77.9%
o e4: 13.7%

o With 58.5% of the AD population being at least heterozygous for APOE 4.

Question 5

1. siRNAs as therapeutic strategy for AD: ADVANTAGES and LIMITATIONS

Answer 5

siRNAs - small interfering RNA.

ADVANTAGES: siRNA is a powerful tool for modulating gene expression through gene silencing. AI driven design, chemical modifications for better stability

LIMITATIONS: potential high off-target effects, unfavorable immune response, instability of naked siRNA, nuclease susceptibility and a need to develop a suitable delivery system

Question 6

What have population studies shown about APOE

Answer 6

Population studies have shown that an inheritance of the apolipoprotein E (APOE) variant APOE4 allele increases the risk of developing AD, whereas APOE2 homozygotes are protected from late-onset AD

Question 7

2 route of viral delivery

Answer 7

1. intracisternal
2. intraventricular (protein)

Question 8

Outcome of viral gene therapy study (Rosenberg et al., 2018)

Answer 8

The data demonstrated that while all three routes are capable of mediating ApoE2 expression in AD relevant regions, intracisternal delivery of AAVrh.

10hAPOE2-HA safely mediated wide distribution of ApoE2 with the least invasive surgical intervention, thus providing the optimal strategy to deliver vector-mediated human APOE2 to the CNS.

Question 9

Viral vectors in AD

Answer 9

FOR AD viral vectors have been developed, e.g. recombinant adeno-associated viral vector (rAAV) and the HIV-derived lentiviral vector.

In these vectors, the viral genes for self-replication and, in the case of rAAV, incorporation of genetic material into chromosomal DNA, have been deleted.

Question 10

AAVrh.10-APOE2 : target type and mechanism of action

Answer 10

1. APOE
2. Viral delivery of APOE2

Question 11

AAVrh.10-APOE2: advantages and disadvantages

Answer 11

+ Single administration
+ Targeted delivery

• delivery issues
• do not cross BBB
• need invasive intrathecal injection

Question 12

IONIS-MAPTRx: target type and mechanism of action

Answer 12

Tau
ASO, binds tau mRNA and inhibits translation

Question 13

IONIS-MAPTRx: advantages and disadvantages

Answer 13

+ easy manufacture
+ can target at any site

• cytotoxicity
• requires chemical modifications

Question 14

miRNAs: target type and mechanism of action

Answer 14

multiple targets
miRNA mimic of ASOs

Question 15

miRNA: advantages and disadvantages

Answer 15

+ Simultaneous targeting of multiple AD-related pathways

• cannot be used to target 1 specific mRNA.

Question 16

siRNA: target type and mechanism of action

Answer 16

BACE1, Tau, and other targets.
BBB-penetrating synthetic siRNAs.

Question 17

difference between siRNA- and miRNA-based therapeutic agents

Answer 17

siRNA: one specific target, act by mRNA cleavage by endonucleolytic capacity
miRNA: multiple context-specific targets, and usually act by translational repression

Question 18

siRNAs for AD therapy : study by Zhou et al

Answer 18

causes Glut1 overexpressed on luminal membrane.

• intracisternal route was the best route.

Question 19

What are MIRs

Answer 19

mammalian-wide interspersed repeat
- repress tau translation by competing for ribosomal RNA pairing with the MAPT mRNA

Question 20

What are NATs

Answer 20

natural antisense transcripts
- regulate epigenetic state, transcription, RNA stability or translation of overlapping egnes.

Question 21

what is MAPT-AS1

Answer 21

brain-enriched NAT that is
conserved in primates and contains an embedded MIR.

Question 22

Increased expression of the NAT-MIR (MAPT-AS1)

Answer 22

represses neuronal tau levels and is negatively correlated with tau pathology.

Question 23

MAPT-AS1 - transcripts and expression during differentiation

Answer 23

MAPT-AS1 alternatively spliced transcripts share a common 3’end exon

MAPT-AS1 and MAPT expression INCREASES during neuronal differentiation.

Question 24

tau repression is mediated by:

Answer 24

a MIR element
5’ AS pairing region complementary to MAPT 5’UTR.

Question 25

MIR 7-mer motifs

Answer 25

these mediate tau translational repression

Question 26

active translation - MAPT-AS1

Answer 26

two 7-mer motifs in MAPT IRES mediate abse-pariing with complementary motifs in the 18S rRNA, facilitating recruitment of 40S ribosomal subunit

Question 27

repressed translation

Answer 27

tNAT1 binds to MAPT IRES via region of complementarity and competes with/blocks IRES binding to 18s rRNA.

Question 28

ASO - MAPT

Answer 28

chemically modified ASO can be designed to target specific degradation of MAPT mRNA.