License: This is an open access protocol distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited
Protocol status: Working
We use this protocol and it's working
Created: February 10, 2021
Last Modified: May 14, 2023
Protocol Integer ID: 47152
Keywords: CUT&RUN, Nuclei, Frozen tissue
Abstract
Modified CUTANA™ ChIC/CUT&RUN Kit protocol using nuclei from brain tissue.
Add 1.8 mL of Pre-Wash Buffer per sample to a single conical tube labeled Wash Buffer
Add 72 µL μL of 25X protease inhibitor stock per sample to the Wash Buffer
Add 0.9 µL ul of 1M Spermindine per sample to the Wash Buffer
Room temperature
Transfer 1.4 mL of Wash Buffer per sample into a new conical tube labelled Cell Permeabilization Buffer
Add 2.8 µL of 5% digitonin to CP buffer
Store the remaining Cell Permeabilization Buffer at 4 °COvernight (for Day 2 use).
Transfer 100 µL per sample of Cell Permeabilization Buffer into a new tube labelled “Antibody Buffer”
Add 0.4 µL0.5 Molarity (M) EDTA per sample
Store final buffer on ice.
Section II - Bead Activation
Section II - Bead Activation
30m
30m
Gently resuspend the ConA Beads by pipetting.
Transfer 11 µL/sample to a 1.5 mL tube for batch processing.
*NOTE: Batch processing at this step is recommended to improve sample handling.
If a 1.5 mL tube magnet is not available, the beads can be processed individually (10 μL/ sample) in the provided 8-strip PCR tubes using a compatible 8-strip magnet.
Place the tube on a magnet until slurry clears and pipette to remove sup.
*IMPORTANT: For all steps involving magnetic racks, take care to avoid disturbing the immobilized beads with pipette tips.
To avoid drying the beads, immediately add 100 µL/sample cold Bead Activation Buffer.
Pipette gently to mix.
Place the tube on a magnet until slurry clears and pipette to remove sup.
Repeat previous step for total of two washes.
Resuspend beads in 11 µL/sample cold Bead Activation Buffer.
*NOTE: If not batch processing, use 10 μL/sample at this step. Proceed directly to Section III.
For each experimental condition, aliquot 10 µL/sample of activated bead slurry into separate 8-strip tubes.
Keep on ice until needed.
Tissue preparation and Sample Preparation: Nuclei
Tissue preparation and Sample Preparation: Nuclei
1h
1h
In the most sterile way possible, cut a small piece of tissue, around 50 mg, and leave it in the petri dish with a marking on the lid, in the dry ice. Weigh it and cut again if needed.
Make sure to use the ethanol to clean everything and be careful not to cut yourself.
Add 2 mL of 1X HB buffer into the dounce, which is sitting in the ice.
Place 20 mg frozen tissue into a pre-chilled 2 mL Dounce containing 2 mL cold 1x HB and let thaw for 00:05:00.
Dounce with “A” loose pestle until resistance goes away (~10 strokes).
Put the A pestle into the beaker of water
Dounce with “B” tight pestle for 20 strokes.
Put the B pestle into the beaker of water
Pour everything from the dounce into a 30 um MACS smartstrainer which is sitting on top of a labelled 50 mL falcon tube sitting in ice.
Resuspend cells in 105 µL /sample in RT Wash Buffer. Pipette to thoroughly resuspend.
Aliquot 100 µL washed cells to each 8-strip tube containing 10 µL of activated beads. Gently vortex or pipette to mix.
*NOTE: Beads are prone to clumping. If your beads are clumped, continue to vortex and/or pipette mix to ensure even resuspension.
Incubate cell-bead slurry on the platform rocker for 00:10:00 at Room temperature to adsorb cells to beads.
*NOTE: Count cells by Trypan staining prior to incubation with ConA beads. After incubation with ConA beads, check the sup to ensure most cells have adsorbed to the beads.
10m
I have been moving the tube to ice for 00:50:00 as an extra time incubation
50m
Sample Preparation: Cross-Linking (Optional)
Sample Preparation: Cross-Linking (Optional)
30m
30m
Labile targets or highly transient chromatin binding proteins may be improved by cross-linking
Transfer 500,000 cells or amount that you wish to use into a 1.5 mL lobind tube
Add formaldehyde directly to culture to achieve desired final concentration of formaldehyde.
(recommended 0.1%-1%)
I use 16% formaldehyde in 200 µL of nuclear extraction buffer, which requires 13.75 µL of formaldehyde.
Quench the fixation by adding 2.5 Molarity (M) glycine to a final concentration of 125 millimolar (mM)
In this case it would be 11 µL
600 rpm, 4°C, 00:03:00
Discard supernatant
Section IV - ANTIBODY BINDING
Section IV - ANTIBODY BINDING
18h
18h
If using a multi-channel pipette (recommended) place a multi-channel reagent reservoir on ice.
*IMPORTANT: If processing > 8 samples (more than 1 x 8-strip tube), for subsequent wash steps remove & replace sups for a single strip before processing the next strip. This avoids bead dry out during wash steps.
*NOTE: Multi-channel pipetting is highly recommended through the rest of the experiment. This helps to avoid bead dry out, improves yield, and increases experimental throughput.
Place the 8-strip tubes on an 8-strip tube magnet (high volume setting) until slurry clears.
Pipette to remove sup, taking care to avoid disturbing the immobilized beads with pipette tip.
Immediately add 50 µL cold Antibody Buffer to each sample and gently vortex and/or pipette mix to prevent beads from drying.
(Optional)
Add 2 µL SNAP-CUTANA K-MetStat Panel per 500,000 cells.
The samples designated for the positive (H3K4me3) and negative (IgG) control antibodies.
Add 0.5 µg antibody to each sample and gently vortex.
Incubate 8-strip tubes on rotator Overnight at 4 °C.
DAY 2 - Section IV - Antibody binding
DAY 2 - Section IV - Antibody binding
10m
10m
If using a multi-channel pipette (recommended) place a multi-channel reagent reservoir on ice.
Fill with Cell Permeabilization Buffer.
*IMPORTANT: If processing > 8 samples (more than 1 x 8-strip tube), for subsequent wash steps remove & replace sups for a single strip before processing the next strip. This avoids bead dry out during wash steps.
Place the 8-strip tubes on magnet until slurry clears. Pipette to remove sup.
*While beads are on magnet*, add 200 µL cold Cell Permeabilization Buffer directly onto beads.
Pipette to remove supernatant
Repeat previous step for total of two washes, without removing 8-strip tubes from the magnet.
Add 50 µL cold Cell Permeabilization Buffer to each sample.
Gently vortex and/or disperse clumps by thorough pipetting.
Section V - BINDING OF PAG-MNASE
Section V - BINDING OF PAG-MNASE
30m
30m
Add 2.5 µLpAG-MNase (20x stock) to each sample.
Gently vortex/pipette mix.
*NOTE: To evenly distribute enzyme across cells/nuclei, ensure beads are thoroughly
resuspended by gentle pipetting with a P200.
Incubate samples for 00:10:00 at Room temperature on the platform shaker
Return 8-strip tube to magnet.
Remove sup.
10m
*While beads are on magnet*, add 200 µL cold Cell Permeabilization Buffer directly onto beads.
Pipette to remove sup.
Repeat previous step for total of two washes without removing 8-strip tubes from the magnet.
Remove 8-strip tubes from the magnet.
Add 50 µL cold Cell Permeabilization Buffer to each sample.
Gently vortex and disperse clumps by pipetting.
Cover/ put away Cell Permeabilization Buffer for later use.
Section VI - TARGETED CHROMATIN DIGESTION AND RELEASE
Section VI - TARGETED CHROMATIN DIGESTION AND RELEASE
3h
3h
Place 8-strip tubes on ice.
Add 3 µLCalcium Chloride to each sample and gently vortex.
Ensure efficient digestion by making sure beads are thoroughly resuspended.
Gently pipette with a P200 if needed.
Incubate 8-strip tubes on rotator for 02:00:00 at 4 °C.
2h
Add 33 µLStop Buffer to each sample.
Gently vortex to mix.
Prior to first use, reconstitute E. coli Spike-in DNA in 200 µL DNase free water.
*IMPORTANT: Lyophilized DNA pellet is invisible to the eye.
Prior to opening, pellet DNA by quick spin in a benchtop microfuge.
After reconstitution, vortex tube on all sides to ensure complete resuspension.
Add 1-2 µLSpike-in DNA to each sample. Gently vortex to mix.
*NOTE: In general, aim for Spike-in DNA to comprise 0.5 – 5% (ideally closest to 1%) of total read counts in the sequencing data.
Therefore, while 0.5 ng is a good starting amount for both high (e.g. H3K27me3) and low (e.g. H3K4me3) abundance targets, this may need to be adjusted higher or lower depending on the antibody used, target of interest, total DNA yield, and sequencing results.
Incubate 8-strip tubes for 00:10:00at 37 °C in a thermocycler.
10m
(Optional - if Cross-Linking extra methodology only)
Place 8-strip tubes on magnet stand until slurry clears.
Transfer supernatants containing DNA to new 8-strip tubes
Reverse cross-links by adding 0.8 µL 10% SDS and 1 µL of 20 µg/µL Proteinase K to each reaction.
Mix by vortexing
Overnight55 °C
in a thermocycler
Quick spin in benchtop microfuge.
Place 8-strip tubes on a magnet stand until slurry clears.
Transfer sups containing CUT&RUN enriched DNA to 1.5 mL tubes and discard ConA Beads.
Section VII - DNA PURIFICATION
Section VII - DNA PURIFICATION
30m
30m
Add 420 µLDNA Binding Buffer to each sample.
Mix well by vortexing.
For every sample, place a DNA Cleanup Column into a DNA Collection Tube.
Load each sample onto a column and label the top.
Centrifuge for 16.000 x g, 00:00:30Room temperature
Discard the flow-through.
Place the collection tube back on to the column.
*NOTE: A vacuum manifold can be used in place of centrifugation.
For each step, add the indicated buffer, turn the vacuum on, and allow the solution to pass through the column before turning the vacuum off.
30s
Prior to first use, add 20 mL ≥ 95% ethanol to DNA Wash Buffer.
Section VII (continued)
Section VII (continued)
SECTION VII: DNA PURIFICATION (~30 MIN), CONTINUED
Add 200 µLDNA Wash Buffer to each sample column
Centrifuge for16.000 x g, 00:00:30 , Room temperature
Discard the flow-through.
Place the collection tube back on to the column.
30s
Repeat for a total of two washes.
Discard the flow-through.
Centrifuge one additional time for 16.000 x g, 00:00:30 to completely dry the column.
30s
Transfer column to a clean pre-labeled 1.5 mL lobind tube, ensuring the column does not come into contact with the flow-through.
Elute DNA by adding 12 µLDNA Elution Buffer, taking care to ensure the buffer is added to the center of the column rather than the wall.
Tap the column + collection tube on the benchtop to ensure all droplets are absorbed onto the resin.
*NOTE: 12 μL is recommended, however DNA can be eluted in 6 – 20 μL volumes depending on anticipated yield and desired final concentration.
Larger elution volumes, longer incubation times, and/or multiple rounds of elution may improve DNA yield. However, sample concentration will be reduced with larger total elution volume.
Let sit00:05:00, then centrifuge for 16.000 x g, 00:01:00, RT.
6m
Vortex eluted material and use 1 µL to quantify the CUT&RUN-enriched DNA using the Qubit fluorometer as per the manufacturer’s instructions.
See Quality Control Checks section for typical DNA yields.
CUT&RUN DNA can be stored at -20 °C for future processing.
Section VIII - Library Preparation
Section VIII - Library Preparation
18m
18m
1) End Prep
Starting Material: 500 pg–1 µg fragmented DNA. We recommend that DNA be sheared in 1X TE
If the DNA volume post shearing is less than 50 µL, add 1X TE to a final volume of 50 µL
Alternatively, samples can be diluted with 10 millimolar (mM) Tris-HCl, pH 8.0 or 0.1X TE.
NEBNext End Prep
Add the following components to a sterile nuclease-free tube:
A
B
Reagent
Amount
NEBNext Ultra II End Prep Enzyme Mix
7 ul
NEBNext Ultra II End Prep Reaction Buffer
3 ul
DNA
50 ul
Volume
60 ul
End Prep Reaction
Set a 100 µL or 200 µL pipette to 50 µL and then pipette the entire volume up and down at least 10 times to mix thoroughly.
Perform a quick spin to collect all liquid from the sides of the tube.
Note: It is important to mix well. The presence of a small amount of bubbles will not interfere with performance.
Place in a thermocycler, with the heated lid set to ≥ 75 °C, and run the following program:
A
B
Time
Temperature
30 minutes
20°
30 minutes
65°
Hold
4°
End Prep Incubation
If necessary, samples can be stored at –20°C; however, a slight loss in yield (~20%) may be observed. We recommend continuing with adaptor ligation before stopping.
Serapure purification
- Add 1.8X Speed beads to samples (108 µL beads to 60 µL reaction)
- Flick to mix
- Incubate for 00:10:00 at room temperature
- Use the magnet to collect the DNA-beads
- Discard supernatant
- Wash with 70% ethanol
- Dry at 37 °C for 00:03:00
- Elute with 20 µL TE buffer
- Incubate for 00:05:00 at room temperature
- Use the magnet to collect the DNA-beads
- Collect supernatant into a new tube
18m
Universal Adapter ligation
Add the following components directly to the End Prep Reaction Mixture: