Svanhild Svanhild Nornes Nornes Morgan Newman Morgan Newman Michael Michael Lardelli Lardelli - - Uni. Of Adelaide Uni. Of Adelaide Using Using zebrafish zebrafish in human disease research: in human disease research: some advantages, disadvantages and ethical some advantages, disadvantages and ethical considerations. considerations. Giuseppe Giuseppe Verdile Verdile Ralph Martins Ralph Martins - - The The McCusker McCusker Foundation for Foundation for Alzheimer’s Alzheimer’s Disease Research Disease Research
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Using zebrafish zebrafish in human disease research: some advantages, disadvantages … · 2018-04-10 · Svanhild. Nornes Morgan Newman Michael Lardelli-Uni. Of Adelaide. Using zebrafish
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SvanhildSvanhild
NornesNornesMorgan NewmanMorgan NewmanMichael Michael LardelliLardelli
--Uni. Of AdelaideUni. Of Adelaide
Using Using zebrafishzebrafish in human disease research:in human disease research:some advantages, disadvantages and ethical some advantages, disadvantages and ethical
considerations.considerations.
Giuseppe Giuseppe VerdileVerdileRalph MartinsRalph Martins
--The The McCuskerMcCusker
Foundation for Foundation for Alzheimer’s Alzheimer’s Disease ResearchDisease Research
••
ZebrafishZebrafish
biology including advantagesbiology including advantages••
Screen for mutations that modify response to a compound
A zebrafish mutant strain lacking skin pigmentation, Casper, is useful in transplantation, tumorigenesis and metastasis studies etc.
(Created by Richard White, MD, PhD, a clinical fellow in the Stem Cell Program at Children's Hospital Boston, with others in the laboratory of Leonard Zon, MD. )
The embryo as a “test-cell”
Some advantages of testing molecular interactions in embryos rather than cultured cells :•
Normal gene expression background
•
Easy to perform complex manipulations of genetic state
•
Developmental phenotype indicates change in gene activity !
Zebrafish (Danio rerio) – Disadvantages
•
Non-mammalian physiology –
some drugs affecting zebrafish
do not affect mammals and vice-versa due to e.g. different rates of metabolism
•
Some anatomical differences from mammals
•
Non-placental –
testing drug interactions with placenta not possible
•
Great capacity for regeneration
Zebrafish (Danio rerio) – Ethical considerations
•
Pain –
Pain
perception by fish disputed.
Lynne Sneddon
et al. of Roslin
Institute found neurons responding appropriately to pain-inducing stimuli in fish. They also injected bee venom or acetic acid into lips of rainbow trout and observed behaviours they interpreted as experience of pain (rubbing lips onto stones, increased ventilation rate, rocking) which were greater than in controls. Morphine apparently acted as an analgesic.
James Rose of University of Wyoming was very critical of this study. Criticised Sneddon
et al.’s understanding of definition of “pain”
versus nociception, formulation of experiment (volume of toxin injected) and inconsistency in interpretation of results. He believes fish brain lacks structure for awareness of pain.
► Most prevalent form of dementia Australia 2004: 100,000 patients
► Complex molecular changes (not well understood)
► <5% of cases are familial (FAD) with an early onset and autosomal dominant inheritance
► >95% of cases are sporadic with a late onsetof > 65 years
Presenter
Presentation Notes
FAD-autosomal dominant inheritence pattern
Neuropathology of ADNeuropathology of AD►
Amyloid plaques Aggregates of the amyloid beta (Aβ) peptide
►
Neurofibrillary tangles (NFT)Aggregates of phosphorylated Tau
►
Extensive loss of neurons
NFTAmyloid plaque
http://www.alzheimer.med.br/goetz.htm
Presenter
Presentation Notes
Main features found in the hippocapmus region- memory region Neuronal loss attributed to astrocytes and microglia NT-Ach, Ser, Som, Glu
Genes Associated with ADGenes Associated with AD
►
Amyloid Precursor Protein (APP) Cleaved to release Aβ peptide
►
Presenilins
(PSEN) PSEN1 and PSEN2 essential for APP cleavage
►
Microtubule-Associated Protein Tau
(MAPT)NFTs contain aggregates of hyperphosphorylated Tau
►
APOEAllele 4 is a genetic risk factor for sporadic AD
Presenter
Presentation Notes
APP- cleaved to release A-beta PSEN- essential to the complex that cleaves APP Tau- hyperphosphorylated inhibiting its microtubule binding function APOE- a genetic risk factor for the development of AD, allele 4 is the specific variant associated with increased rsik
Three types of protein changeThree types of protein change due to gene mutationdue to gene mutation
normal
changed amino acid(“missense”)
internal deletion(e.g. splicing error)
Truncation(e.g. non-sense mutation or splicing error)
Two internal deletions in PSEN1We tried to recreate these in zebrafish
embryos
Failed attempt to create internal deletion still has VERY strong
PSEN1 loss phenotype!
Negative control (normal)
Phenotypic effects of injection of a morpholino designed to create an internal deletion in PSEN1
At 48 hours post fertilization:•
“Hydrocephalus”•
Pigmentation loss
Presenter
Presentation Notes
Need Picture
After much testing we found that our attempts to create After much testing we found that our attempts to create internal deletions had, instead, created small amounts of internal deletions had, instead, created small amounts of truncationstruncations
normal
changed amino acid(“missense”)
internal deletion(e.g. splicing error)
Truncation(e.g. non-sense mutation or splicing error)
Common (160+ in PSEN1)
Rare (2 in PSEN1)
Common (none
in PSEN1)
normal
changed amino acid(“missense”)
internal deletion(e.g. splicing error)
Truncation(e.g. non-sense mutation or splicing error)
Common (160+ in PSEN1)
Rare (2 in PSEN1)
Common (none
in PSEN1)
These mutations were once thought to have no function. We now know that they are so potent that they would kill any developing embryo –
Truncation in yellow region of PSEN1 protein creates very potent “dominant negative” forms
that interfere with normal PSEN1 protein
These observations could not have been made using cultured cells or mice
Could truncated PSEN1 protein contribute to Could truncated PSEN1 protein contribute to sporadic Alzheimersporadic Alzheimer’’s disease? s disease? We know thatWe know that::
•
PSEN1 is the
major site for mutations causing FAD.
•
Most FAD mutations in PSEN1 appear to dominantly reduce
protein activity. i.e. Reduced PSEN1 activity
causes Alzheimer’s disease.
•
Mechanisms are known that can cause protein truncation at low levels in ageing cells. Is decreased PSEN1 activity a “molecular common link”