The Knockdown of 12-lipoxygenase in Embryonic Zebrafish Causes Abnormal Development
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Transcript of The Knockdown of 12-lipoxygenase in Embryonic Zebrafish Causes Abnormal Development
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Amber BannonMentor: Maret Traber, PhD
The Knockdown of 12-lipoxygenase in Embryonic Zebrafish Causes Abnormal
Development
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Relevance 12-lipoxygenase may have a role in angiogenesis
Lipoxygenase plays important roles in inflammatory diseasesAtherosclerosisCancerOsteoporosis Diabetes
Kuhn and O’Donnell. Progress in lipid research 2006
Role in embryonic development has not yet been studied
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HypothesisWe believe 12-lipoxygenase is
necessary for normal embryonic development in zebrafish. Therefore, when it is knocked down, there will be an abnormal phenotype and altered gene expression.
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Zebrafish model Able to separate embryo from motherGenes are generally homologous to those
in humansRapid embryonic development
48 hpf12 hpf
*hpf = hours post fertilization
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Study designTreat embryos at the single cell stage
Inject with LOX morpholinoInject with control morpholino (random
oligomer)Non-injected control
Observe individual embryos over a 5 day period
Collect embryo samples for RNA extraction at 24 hpf and 48 hpf to analyze gene expression
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Morpholino injectionsShort anti-sense oligomers with high mRNA
binding affinity
Labeled with fluorescein tag to verify incorporation
Knock down protein expression by blocking exon/intron splice site
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EXON 1 INTRON EXON 2
EXON 1 EXON 2
PROTEIN
In normal cells…
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Morpholino injected…EXON 1 INTRON EXON 2MORPHOLIN
O
EXON 2EXON 1 INTRONMORPHOLINO
ABNORMAL PROTEIN
Confirmation of block by RT-PCR/gel electrophoresis
171bp
250bp
Control
Injected
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LOX knockdown malformations
LOX morpholino
injected
Control morpholino
injected
Noninjected control
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LOX morpholino injection increases the number of embryonic malformations
LOX
Cont
rol
Noni
njLO
XCo
ntro
l No
ninj
LOX
Cont
rol
Noni
nj
48hpf 72hpf 120hpf
02468
1012141618
Trial 1
MalformedDead
Num
ber
of fi
sh
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LOX morpholino injection increases the number of embryonic malformations
LOX
Cont
rol
Noni
njLO
XCo
ntro
l No
ninj
LOX
Cont
rol
Noni
nj
48hpf 96hpf 120hpf
05
10152025303540
Trial 2
MalformedDead
Num
ber
of fi
sh
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LOX morpholino injection increases the number of embryonic malformations
LOX
Cont
rol
Noni
njLO
XCo
ntro
l No
ninj
LOX
Cont
rol
Noni
njLO
XCo
ntro
l No
ninj
48hpf 72hpf 96hpf 120hpf
02468
1012141618
Trial 3
MalformedDead
Num
ber
of fi
sh
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Quantitative Reverse Transcriptase- Polymerase Chain Reaction (qRT-PCR)Utilizes reverse transcriptase to
synthesis cDNA from mRNAAmplifies and quantifies cDNA in real
timeThe number of copies of cDNA
measure the relative gene expressionUsing control and morpholino injected
samples we are able to determine changes in gene expression
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HPETE
PL-Arachidonic
LOX
PL-HPETE
GPx4 PLA2
PLA2
PL-HETE
GPx4
HETE
Proposed pathway for lipoxygenase activity
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12-lipoxygenase (12-LOX)Catalyzes the addition of oxygen to the 12th
carbon of arachidonic acid Produces hydroperoxides (HpETE) in
phospholipidsImportant role in normal biological functions
Byproducts cause the lipid-oxidation chain reaction
Arachidonic acid
OOH12-HpETE
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12-lipoxygenase
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HPETE
PL-Arachidonic
LOX
PL-HPETE
GPx4 PLA2
PLA2
PL-HETE
GPx4
HETE
Proposed pathway for lipoxygenase activity
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Gluatathione peroxidase 4 (GPx4)Catalyzes the reduction of the
hydroperoxides (HpETE) created by lipoxygenase
Produces hydroxy products (HETE)Important signaling molecule for normal
biological functionPhospholipid antioxidant that utilizes
glutathione and selenium
OOH12-HpETE
OH12-HETE
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Glutathione Peroxidase 4
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Phospholipase A2 (PLA2)Cleaves molecules from the phospholipid at
the sn-2 position
Produces HpETE and HETE from PL-HpETE and PL-HETE
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HPETE
PL-Arachidonic
LOX
PL-HPETE
GPx4 PLA2
PLA2
PL-HETE
GPx4
HETE
Proposed pathway for lipoxygenase activity
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Phospholipase A2
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ConclusionKnock down of 12-lipoxygenase expression
causes an abnormal phenotype in zebrafish embryos
There is a change in mRNA expression observed at 24 hpf
This change appears to be linked to the abnormal morphology seen in lipoxygenase knock down embryos
Lipoxygenase is necessary for normal embryogenesis in zebrafish
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What’s next?This project provides an essential stepping
stone for future research in the Traber lab on the molecular function of vitamin E in development
Knock down the other genes in the proposed pathway
Obtain vitamin E deficient fish and observe their development
Knock down LOX in vitamin E deficient fish
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AcknowledgementsMaret Traber, Ph.D.Traber labGalen MillerEd LabutRobert Tanguay, Ph.D.Tanguay LabKevin Ahern, Ph.D.Howard Hughes Medical InstituteCripps Scholarship Fund, College of Science