Recommendations for mixing and diluting CRISPR gRNAs , mRNAs, and HDR oligo DNAs for mouse zygote injections.
Doug Mortlock Feb 2016
•A chart with the recommended final concentrations is found
on the TMESCSR website ( https://labnodes.vanderbilt.edu/resource/view/id/11363
) and is reproduced here.
•Sigma-Aldrich ships the RNAs at slightly higher
concentrations than shown below. Cas9
mRNA is provided at 500 ng/ul and gRNAs at 200 ng/ul.
•I do not further clean up or process the RNAs in any way
prior to dilution. However,
I do carefully re-precipitate the HDR oligos and resuspend them in sterile
RNAse-free water. This
can remove some contaminating non-DNA material that is sometimes present in
lyophilized oligos as shipped from the vendor.
1. To prepare
“N” injection days worth of injection mixture aliquotes, prepare N+1 tubes as
follows. Use clean, RNAse-free 1.5
ml microfuge tubes, sterile RNAse-free water, and RNAse-free arosol barrier
tips. Pre-rinse each tube by
adding 1 ml of the water, vortex, and dump out all the water. Spin down the
tubes briefly and remove any lingering dregs of water with a pipette tip. Place
all the tubes on ice.
2. Mix the
RNAs, water (and DNA oligo as needed) to create a mix with the correct final
concentrations of all reagents and volume that is equal to at least (N x 25) +
5 µl. Mix briefly by flicking the
tube gently (do NOT vortex).
3. Spin the
mixture at full speed in microfuge for 1 minute. This is to pellet any small
particulates – even if none are visible to the eye, before or after this step!
4. Drawing
from the top of the mixture volume, remove 25 µl and aliquot to one of the
tubes. Repeat for each
aliquot. There will be ~5 µl left
over. This hopefully has
concentrated any particulate material (that might clog injection needles) and
is discarded as a sacrifice to the CRISPR gods. Although it is NOT usually visibly apparent that there
are ANY particulates present, this step is added because it is TYPICAL for the
injection technicians to have needle-clogging problems with CRISPR
injections. This reduces embryo
survival. While this
pre-spin step may not always solve the problem it may help and is easy to do.
5. Clearly
label the aliquot tubes and bring them on ice to the transgenic core. They should be stored at -20˚ until injection date.
The chart below was culled from our TMESCSR recommendations as of Feb 2016. I know 'cause I wrote 'em.
Create the required mixture of components so that it has the final
concentrations shown below.
The "min volume to bring to Core" is specific to the Vanderbilt's core's preferences. So don't use this to argue with your core's staff about what is necessary. They get to decide that for themselves!
Experiment type
|
Final conc. Cas9 mRNA
|
Final conc. all gRNAs
|
Final conc. all ssDNA donor oligos
|
Buffer
|
Min. volume to bring to Core
|
Knockout experiment, RNA reagents only
|
100 ng/µl
|
50 ng/µl
|
-
|
Sterile, RNAse-free water
|
25 µl
PER INJECTION DAY
|
Knock-in experiment, RNA + ssDNA oligo(s)
|
100 ng/µl
|
50 ng/µl
|
200 ng/µl
|
Sterile, RNAse-free water
|
25 µl
PER INJECTION DAY
|
Requested
deviations from these concentrations will require consultation and approval
from the core manager. The
core staff may need to dilute the reagents more if injection problems arise
(e.g. clogging).
REQUIREMENTS FOR PURIFICATION:
• We
strongly suggest ssDNA oligos be re-precipitated before use to remove potential
contaminants from the vendor.
See TMESCSR website for this protocol.
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