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high percentage of reads mapping to tRNA?
How do you interpret this? What does it mean for wet-lab side of things, does it inform any step that went right or wrong? This is for a total RNAseq minus rRNA experiment. 
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Hi seqtechno1,
Issues could be:
-Ribodepletion Kit used does not target tRNAs. If they are targeted then they will not be removed. Most kits use a pretty high (2.0x or above) bead cleanup, so even very small tRNAs would make it through the ribodepletion process. You could reduce the bead ratio so that tRNAs are removed but mRNA stays (assuming your mRNA is high enough quality to not be mixed in with the tRNAs.
-If this is the case, and most of your rRNA deleted RNA is tRNA, then when you go to do cDNA synthesis, most of your cDNA will be from tRNA, not your desired mRNA. Most RNASeq library prep kits will have various bead cleanups at various ratios. If you want, you try reducing the bead cleanup ratios at these steps as well to try and remove as much small cDNA products synthesized from small tRNA as possible.
These ideas will only work if your mRNA is go high enough quality to not be mixed in with tRNAs. IE if you are working with FFPE Total RNA, then its a lot harder to troubleshoot.
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Love this - good data definitely starts from good input, and poor input can only give relatively poor data. I particularly like the mention of Nanodrop/absorbance based methods for quantification. It's such a toss up if you'll get an accurate reading or what amounts to a randomly generated number, and a lot of library/sequencing related issues can be traced back to poor quant.07-01-2026, 11:43 AM
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I’m not a sequencing expert. I’m a purification scientist who uses NGS to evaluate workflows my group develops. With this perspective, we think about the sample first and the NGS workflow second. The sequencer is an exceptionally honest reporter, but it can only report on what you give it, so whether you get clean, interpretable data from an NGS workflow is largely determined before you begin.
Here are nine questions we think about, in roughly the order they matter, before...
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