Poly-A or Ribosomal RNA depletion

[NicoBxl]

Hi,

For RNA-seq experiment. Is it better to use poly-A or ribosomal RNA depletion library kit ? Is the sensitivity better in poly-A (for mRNA detection) ?

Thanks,

N.

[clissold]

Hi there,

I've tried many different kits to optimise this protocol and the most effective one to date is the Epicentre Ribozero kit.

Hope this helps.

[NicoBxl]

Do you have good correlation results with poly-a librairies ? And do you detect low expressed transcripts ?

[madseq]

Hi NicoBxl, I´m interested in your question too...

Everytime I use Ribozero, which is very effective at rRNA removal, I wonder how many mRNAs are being lost and if we are creating a lot of bias there. When we started using Ribozero we almost threw the first sample away because we thought that after rRNA removal we didn´t have RNAs anymore...

Anyone has done correlation studies?

[pmiguel]

If you have intact total RNA and no special interest in non-polyadenylated messages, then poly-A RNA purification is probably going to give you results more in line with what you expect. That is, expression profiles of the exons of the (mostly protein coding) genes of your organism.

If your RNA is not so intact, and/or you are interested in non-polyadenylated messages and/or just concerned that factors such as polyA tail length might bias your RNAseq data set -- then I would also recommend ribo-zero. But also, unless you know yourself to be a bench ninja, replace any step in the protocol calling for ethanol precipitation with a good column based approach instead. (E.g. zymo columns).

Let me just amplify that last point: ethanol precipitations of less than 1 ug of RNA or DNA should only be attempted by bench scientists with >10,000 hours of experience with non-kit-based molecular biology or those with access to extensive psychological (grief) counseling resources.

--
Phillip

[cascoamarillo]

This reminds me a paper I've recently read:

http://www.ncbi.nlm.nih.gov/pubmed/21737426

They compare poly-A selection, Ribominus and another RNA-SEQ kit (from Nugen).

btw; Phillip, I think you exaggerate a little with the bench hours and the ethanol precipitation

[protist]

There was a recent paper http://www.plosone.org/article/info:...l.pone.0027288 where they compared RiboZero & RiboMinus depeleted material to each other and to published polyA selected RNAseq data - take home message from their point of view was "We show for the first time, that ribo-depleted RNA-Seq produces reliable coding and non-coding gene expression data and is highly reproducible between different sequencing locations and when using different ribosomal RNA depletion strategies"

With the addition of a carrier - eg glycogen or linear polyacrylamide nucleic acid precipitation of amounts less than 1 ug is not that problematic. The main issue for students or the uninitiated is that the pellet especially when glycogen is used is very loose and care must be taken or it is easily sucked-up when removing the ethanol.

[ETHANol]

I was about to order a Ribo-zero kit since I will be working with some somewhat degraded RNA and saw Epicentre has a Ribo-Zero rRNA Removal Kit (human/mouse/rat) and a new Ribo-Zero Gold Kit (human/mouse/rat).

Is the new kit better like the marketing says?

BTW, I consider myself to be a full bench Ninja with permanently distorted pipeting thumbs from too many hours in the lab and resuspended endless invisible pellets, and I can say ethanol precipitation of less then 1 ug of nucleic acid without carrier or contaminant is not reliable. Use a spin column, that's what anybody that has taken a look at technology post 1990 would say.

[protist]

Can't comment on the Ribo-Zero gold kit but I would say that so far for us the RiboZero kits have lived up to the marketing hype. I have used their Gram Positive and Gram negative kits for Beasties whose rRNA depletion in the libraries was previously poor - as tested with MicrobeExpress and RiboMinus. For one of the organisms the rRNA depletion has gone from <30% to >80% when switching from RiboMinus to RiboZero Gram positive. The kits are more expensive but the extra reads and greater multiplexing capabilities we get make it worth it.

[pmiguel]

With the addition of a carrier - eg glycogen or linear polyacrylamide nucleic acid precipitation of amounts less than 1 ug is not that problematic. The main issue for students or the uninitiated is that the pellet especially when glycogen is used is very loose and care must be taken or it is easily sucked-up when removing the ethanol.

I think what you are trying to say is "you must become one with the pellet".

(BTW, I have seen at least one protocol that warns that glycogen was inhibitory to some down stream reaction. Also, I would worry that the glycogen was purified from some biological source and might contain RNA or DNA from that source...)

--
Phillip

[pmiguel]

I was about to order a Ribo-zero kit since I will be working with some somewhat degraded RNA and saw Epicentre has a Ribo-Zero rRNA Removal Kit (human/mouse/rat) and a new Ribo-Zero Gold Kit (human/mouse/rat).

Is the new kit better like the marketing says?

BTW, I consider myself to be a full bench Ninja with permanently distorted pipeting thumbs from too many hours in the lab and resuspended endless invisible pellets, and I can say ethanol precipitation of less then 1 ug of nucleic acid without carrier or contaminant is not reliable. Use a spin column, that's what anybody that has taken a look at technology post 1990 would say.

I thought the difference was that they added oligos to pull out mitochondrial rRNA as well.

--
Phillip

[rflrob]

I think what you are trying to say is "you must become one with the pellet".

(BTW, I have seen at least one protocol that warns that glycogen was inhibitory to some down stream reaction. Also, I would worry that the glycogen was purified from some biological source and might contain RNA or DNA from that source...)

--
Phillip

We use glycogen carrier in our lab for TRIzol purifying 10-100ng of RNA with some regularity, and this has worked well for Illumina RNA seq reagents from the last couple years (i.e. both the old RNA-seq and new TruSeq kits). At those levels, you are basically only seeing the pellet, but it's not too hard to use a Bioanalyzer with the Pico chips to see how well you've done.

[protist]

Phillip is correct they have added the extra mt rRNA removal to the gold kit.

With regard to the glycogen question we have always used Ambion (guaranteed DNA free) and hundreds of Euk/bac libraries later we have never seen contamination come through. However we did have a collaborator a couple of years back who used salmon sperm in their ChIP protocol & their first ChIPseq results were not pretty!

As in the main we are still doing 'home brew' strand specific libraries we routinely precipitate our fragmented RNA in the presence of glycogen and have had few problems. Recently for the bacterial libraries we have switched to Zymo RNA (5 ug) Clean&Concentrate columns at the fragmented RNA concentrating stage. We have also used them post the DNase-ing (25 ug variety) for some bacterial RNAs.

[NicoBxl]

With Ribo zero, is there a size selection step ?

[protist]

RiboZero is used to rRNA deplete total RNA - there is no size selection involved. Briefly, total RNA is mixed with microspheres & a rRNA removal solution which binds the rRNA and rRNA depleted material is eluted using centrifugation and columns provided in the kit.