Real-Time quantitative PCR: Choices and Decisions Dr Sandrine Javorschi-Miller R&D program Manager European Functional Genomic Seminar May 2005
Mar 26, 2015
Real-Time quantitative PCR:Choices and Decisions
Dr Sandrine Javorschi-MillerR&D program Manager
European Functional Genomic SeminarMay 2005
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Why using real-time PCR?
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Gene Expression Analysis Technologies
High-densityArrays
Real-time PCR
Nu
mb
er
of
sam
ple
s
Number of genes
1
10
100
>10,000
2-10 100-1000 >10,000
SAGE
Low-densityArrays
RPANorthern
To consider: Ratio samples / genes, needs for accuracy
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Comparison of Quantitative Assays (RNA/DNA):
Real-Time PCR
Amplicor/TMA NASBA
bDNA
XPLORE
Microarrays
RPA
Northern
100
101
102
103
104
105
106
107
108
108
107
106
105
104
103
102
101
100
Dynamic RangeSensitivity
NASBA: nucleic acid seq based amplification bDNA: branched DNA assay
Xplore: based on Invader technology
TMA: transcription mediated amplificationRPA: RNAse protection assay
Advantage: Real-Time PCR
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Real-time PCR in more details
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Phases of amplification
• Exponential phase• Plateau phase
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Exponential phase vs. plateau
• At some time or another, all reactions regardless of initial amount reach the same plateau!– Plateau is not quantitative– Exponential phase is quantitative
Cycles
Amplicon amount
Plateau information is not quantitative
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Before the Real-Time era: End-point PCR
• Examples of semi-quantitative PCR– End point analysis after reduce number of cycles (exponential
phase)• Not accurate• Not sensitive
– Competitive PCR• Time and reagent consuming
GOI (pg) 0 0.1 1 10?
PCR condition 95oC for 2 min# of cycles 30
95oC for 15 sec 62oC for 30 sec 72oC for 30 sec
End Point is at best semi-quantitative
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Choices and Decisions
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One Step or Two Step RT-PCR?
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One Step or Two Step RT-PCR?
RNAOne Step RT-PCR
(One tube)Two Step RT-PCR
(Two tubes)
Amplicon Amplicon
cDNA
GS primersOligo dT
Random Primers(GS Primers)
1 target
1 amplicon
X targets
X amplicons
Target pool
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Two-Step RT-PCR• Separate conditions for cDNA
synthesis & PCR• Flexible choice of primers• Ideal for quantification of
multiple genes from a limited number of RNA samples
One-Step RT-PCR• Highly defined conditions to
support RT and Taq• Requires gene specific primer• Ideal for quantification of 1 or 2
messages from a large number of RNA samples
One Step or Two Step RT-PCR?
Perfect for:- Lot of samples- Small amount of targets
Perfect for:- Few samples- Large amount of targets
Two-step RT-PCR is more convenient and cost effective
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Which Reverse Transcriptase?
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RNAse H reduced Thermostable
ReverseTranscriptase:
SuperScript III ™ RT
• No RNA template degradation > Higher cDNA yield– Improved sensitivity
• Reduced 5’ / 3’ bias due to mispriming– Increased reliability
• Greater percentage of full-length cDNA– complete sequence representation
• Improved thermostability– high temperature cDNA synthesis– relaxes secondary structure– improved primer specificity
• Consistent cDNA synthesis efficiency– wide template diversity– wide range of template amount
What RT enzyme?
Good Reverse transcriptase is essential!
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B-Actin TaqMan primers (RNA concentrations from 100ng to 0.1pg)
1.00E-01
1.00E+00
1.00E+01
0 5 10 15 20 25 30 35 40
Cycle
Nor
mal
ized
Flu
ores
cenc
e
Company A one step kitSSIII one step qRT-PCR
SuperScript™ III Platinum® One-Step RT-PCR
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Which Polymerase?
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Antibody Hot Start
- Fast activation
- Maximum activity in early cycles
Hot Start
- Increased specificity
- Reduced artifacts (less Primer Dimers)
Which Taq polymerase?
Platinum® Taq DNA Polymerase
Hot Start Taq is a must!
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PLATINUM® Taq automatic hot start
PCR Assembly
InactiveTaq DNA Polymerase
Fully ActiveTaq DNA Polymerase
Temperature CyclingInitial TemplateDenaturation
94oC, 30s - 3 min
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UDG or no UDG?
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Carry-over protection/comparison
Uracil DNA Glycosylase DecontaminationDone by Nested PCR with pCR2.1 Plasmid
0 5 10 15 20 25 30 35 40 45 50
Cycle Number
I-with UDG I-without UDG Q-with UDG Q-without UDG
20 cycles, ~1,000,000 fold difference
DNA Amplicon with dUTP
Mix with UDG and dUTP
XAmplicon with dUTP
Not all UDG kits are built equal!
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Which Detection system?
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• dsDNA specific stains– Ethidium bromide (used in first experiments)– SYBR Green I (most widely used today)
• Probe-Based Systems (unlabeled primers plus probes)– TaqMan and TaqMan MGB probe system (5’ nuclease assay)– Dual Probe System, uses FRET between probes hybridized side by side to the
amplicon– Molecular Beacon probe (hairpin probe, quencher and fluorophore are
separated when hybridized to the amplicon)– Epoch probe (second structure probe, quencher and fluorophore are
separated when hybridized to the amplicon)
• Primer/oligo labeled systems– Amplifluor: hairpin primer with fluorophore and quencher– LUX™: primer with one fluorophore and no quencher, proprietary to
Invitrogen
Detection chemistry?
Decision, Decision…
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Detection chemistry?
TaqMan®
Quantiprobe®
SYBR Green I®
Amplifluor™
Q
Q
LUX™
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Which detection system?
- Multiplexing
- High Specificity
- High Sensitivity
Probe based
or
LUX™ primers
- Monoplexing- Cost saving- Fast initial screening
Sybr Green I®
A detection system for every applications!
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LUXTM (Light Upon eXtension)
The fluorescent intensity is modulated due to the proximity of the fluorophore to specific primary & secondary structures of the oligonucleotide. The design rules have been incorporated into the LUX Designer™. The labeled primer exhibits low fluorescence but incorporation during PCR produces a large increase in fluorescence
LUX™
Light Upon eXtension!
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Quenching effect
• The fluorogenic LUX primer has an attached fluorophore at the
3’end and a short sequence tail on the 5’ end that is
complementary to the 3’end of the primer. The resulting hairpin hairpin
secondarysecondary structure structure provides optimal quenching of the attached
fluorophore.
• The quenching of fluorescence in duplex (ds DNA) is provided by
the terminal dG-dC or dC-dG base pairthe terminal dG-dC or dC-dG base pair when the dye is attached to
a thymidine / cytosine within three nucleotides from the 3΄-end.
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Competitive Audit Data
• Certified LUX primers were compared to TaqMan® Gene Expression Assays from ABI and QuantiTect Gene Expression Assays from QIAGEN using Platinum Super-Mix UDG (1X ROX).– Standard curve generated from ten-fold serial dilutions of ORF clone
(107 –102 copies).ABI 7700
PCR Efficiency: 93%R2:0.998
PCR Efficiency: 92%R2:0.999
Quantitect IL6
PCR Efficiency: 94%R2:0.996
LUX IL6 TaqMan IL6
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Comparison of LUX™ to TaqManComparison of LUX™ to TaqMan
LUX™ sensitivity advantages
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Melting curve analysis
Method:
1. Real-time PCR2. After amplification: 60°C to 95°C (slow ramp)3. Fluorescence signal is recorded continuously during the slow temperature ramp4. Melting curve : Fluorescence signal vs. Temperature5. Melting curve is converted to melting peaks by plotting –dF/dT vs Temperature
LUX™ Built-in control feature!
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0
0.05
0.1
0.15
0.2
0 5 10 15 20 25 30 35 40 45 50Cycle
No
rm.F
luo
ro.
Sample 1
Sample 2
Sample 3
Positive Control
NTC
NTC
0
0.2
0.4
0.6
0.8
60 65 70 75 80 85 90 95Temperature
-dF
/dT
Sample 1
Sample 2
Sample 3
Positive Control
NTC
NTC
Fast control of the PCR product specificity without:- opening the tube and - running a gel
Provides accurate real time assessment of quality:
- eliminates risk of false positives
- reduces risk of contamination
Specificity – Melting Curve
Advantages LUX™ versus TaqMan®
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Advantages LUX™ versus TaqMan®
Alexa 546
TET
FAM
All detectors
Triplex amplification using standard protocol:
- 10,000 copies of Gene X are amplified using a LUX primer set labeled with Alexa Fluor 546- 1,000 copies of Gene Z are amplified using a LUX primer set labeled with TET - 100 copies of Gene Y are amplified using a LUX primer set labeled with FAM
Excitation (nm)
Emission (nm)
FAM 492 517
JOE 520 548
TET 521 536
HEX 533 550
Alexa Fluor 546 554 570
Data from Molecular Probes spectra
Easy multiplexing!
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Simple Primer Design with the new D-LUX™ Designer
Advantages LUX™ versus TaqMan®
www.invitrogen.com/dluxdesigner
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3 Choices to access LUX™ primers
Scientific project
D-LUX™ Designer Self Service
Certified LUX™ primers- HSKG
-Virus /Bacteria- Human genes
EvoQuest™ LUX™ Custom Service
Flexibility!
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Other convenient formats?
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Cells Direct kit
No RNA isolation step required.
The cDNA synthesis is performed by SuperScript™ III RNase H- RT.
DNase treatment eliminates genomic DNA so you can be confident that results are due to cDNA amplification.
Cell Lysis
DNase Treatment
cDNA Synthesis
Application: qPCR
All done in 1
tube!
From cells to cDNA in ONE TUBE!
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From 1 cell to 10,000 cells without NAP!
Cells Direct kit
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RTS kits
Proprietary Polymer Mix
Optimized PCR SuperMix
Temperature-controlled Lyophilization
Packaging
Vialing
Complete Cycle within 3 days
Shelf-life = 1 year
Room Temperature Stable
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Standard Curve RTS one step y = -3.548(x) + 37.1
R2 = 0.998
10
15
20
25
30
35
40
1.00E+00 1.00E+01 1.00E+02 1.00E+03 1.00E+04 1.00E+05 1.00E+06Starting Concentration
Cyc
le T
hre
sh
old
Standard Curve aqueous (SuperScript III one step)y = -3.505(x) + 36.8
R2 = 0.999
10
15
20
25
30
35
40
1.00E+00 1.00E+01 1.00E+02 1.00E+03 1.00E+04 1.00E+05 1.00E+06Starting Concentration
Cyc
le T
hre
sh
old
RTS and regular mixes have equal performances
RTS kits
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What mix for what instrument?
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Invitrogen qPCR Reagent Selection Guide
SYBR Green Detection Fluorescent Probes/Primers(LUX™, TaqMan®, etc.)
ABI 7000, 7700, 7900
Roche LightCycle
r
Any Instrumen
t
ABI 7000, 7700, 7900
Roche LightCycle
r
Any Instrument
DNA or
cDNA
Platinum SYBR Green
qPCR SuperMix-
UDG w/ROX
Platinum SYBR Green
qPCR SuperMix-
UDG w/BSA
Platinum SYBR Green
qPCR SuperMix-
UDG
Platinum Quantitative
PCR SuperMix-
UDG w/ROX
Platinum Quantitative
PCR SuperMix-
UDG
Platinum Quantitative
PCR SuperMix-
UDG
RNA, 1-
Step
SuperScript III Platinum SYBR Green
One-Step qRT-PCR Kit
w/ROX
SuperScript III Platinum SYBR Green
One-Step qRT-PCR Kit
w/BSA
SuperScript III Platinum SYBR Green
One-Step qRT-PCR Kit
SuperScript III Platinum One-Step
qRT-PCR Kit w/ROX
SuperScript III Platinum One-Step
qRT-PCR Kit
SuperScript III Platinum One-Step
qRT-PCR Kit
RNA, 2-
Step
SuperScript III Platinum SYBR Green
Two-Step qRT-PCR Kit
w/ROX
SuperScript III Platinum SYBR Green
Two-Step qRT-PCR Kit
w/BSA
SuperScript III Platinum SYBR Green
Two-Step qRT-PCR Kit
SuperScript III Platinum Two-Step
qRT-PCR Kit w/ROX
SuperScript III Platinum Two-Step
qRT-PCR Kit
SuperScript III Platinum Two-Step
qRT-PCR Kit
A solution for each problem!
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SYBR Green LC qPCR versus Roche qPCR
HPRT primers were used with plasmid standards from 1x107 to 1x101 copies. Invitrogen SYBR Green LC (blue) quantified all 7 logs with a slope of –3.644 and an R-value of -1.00. No template controls (NTC’s) were negative with the SYBR LC kit. Roche’s FastStart DNA Master Plus (green) quantified 5 of 7 logs with a slope of –3.700 and an R-value of -1.00. The NTCs along with the last two dilutions showed contamination.
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What method of quantitation?
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What Method and When
http://www.gene-quantification.de/strategy.html
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Absolute quantitation
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Relative Quantitation: ΔΔCt Method
CtGOIs – Ctnorm
s = ΔCtSample
CtGOIc – Ctnorm
c = ΔCtCalibrator
ΔCtSample – ΔCtCalibrator = ΔΔCt
Fold Induction = 2- ΔΔCt
GOI = Gene of InterestNorm = Normalizer (Housekeeping) gene
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Where to find more info?
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Invitrogen qPCR Central
www.invitrogen.com/qpcr
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Invitrogen qPCR Central
www.invitrogen.com/qpcr
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Invitrogen multidisplinary qPCR group
• R&D qPCR group in Carlsbad, CA• Enzymologists in Carlsbad, CA• Chemists from Molecular Probes in Eugene, OR• Custom Primer manufacturing facility in Frederick, MA• EvoQuest service group in Carlsbad, CA• And more…
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The end
www.invitrogen.com/qpcr