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Old 10-31-2017, 11:05 PM   #1
Meyana
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Default NexteraXT Bionalayzer - undertagmentation?

Hi,

I am using the NexteraXT kit to prep mtDNA. I just did a test prep of some samples and had them run on a HS DNA Chip on the Bioanalyzer (see attachment).

I would like a second opinion on these. Does the libraries look undertagmentated?

(see past sample B, I screwed that one up...)
A: Following the procedure recommendations (1ng)
C: Half of the recommendations (0.5ng)
D: Quarter of the recommendations (0.25ng)

Also, quantifying the libraries by Qubit revealed them to be on the low end, just under 2nM with standard 12cycles PCR. Should I be concerned that the output of the prep is so low?

Thanks!
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File Type: pdf Bioanalyzer.pdf (1.15 MB, 54 views)

Last edited by Meyana; 11-01-2017 at 01:51 AM. Reason: Uploaded wrong file...
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Old 11-07-2017, 05:10 PM   #2
Meyana
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Would still appreciate any input
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Old 11-07-2017, 06:19 PM   #3
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Would you elaborate on the experiment aim because interpretation would depend on the final aim.

Edit: Are these post PCR libraries cleaned with beads?

Last edited by nucacidhunter; 11-07-2017 at 06:23 PM.
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Old 11-07-2017, 07:00 PM   #4
Meyana
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Quote:
Originally Posted by nucacidhunter View Post
Would you elaborate on the experiment aim because interpretation would depend on the final aim.

Edit: Are these post PCR libraries cleaned with beads?
The aim of the experiment is to identify mtDNA mutations (heteroplasmy). We willbe doing paired-end seq on the MiSeq. We will do around 5000X coverage to enable this.
Before prep I did an "enzymatic purification" to remove nDNA and only retain mtDNA from gDNA purified from mouse tissue.

These are post-PCR, AMPure purified libraries. Eluted in volume recommended by the protocol (and then 1/2 and 1/4 for samples C and D respectively, also using 1/2 and 1/4 beads for cleanup).
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Old 11-08-2017, 12:21 AM   #5
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I think that A is better because the other two show signs of low diversity library. For optimum read number you would need to quantify the library with qPCR and take the average size of area under 100-950 bp when calculating molar concentration.

You can change bead ratio to modify the size cut if you want to merge R1 and R2. If you do 2x300 cycles on current library A you probably will get around 30% merge.
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Old 11-08-2017, 04:41 PM   #6
Meyana
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Could you please elaborate on how you determine which of the libraries have lower diversity? Is it due to the "spiky" pattern?
(I am new to prep of samples, previously I just passed them on to another person in the lab, but I would like to know how to best assess the libraries).

Also, inherently my samples are very low complexity. Based on some quality checks of my protocol, I will estimate I have >95% mtDNA (compared to nDNA) in my sample before going into library prep. The mtDNA is only ~16kb. So no matter what, wouldn't this be considered a low complexity sample? And then it would make sense if the libraries show low complexity?

I am doing paired-end because I will be looking for mtDNA deletions which are very frequent in my model mouse system and may be important in disease symptom development. So as such, I will not merge R1 and R2.
I was thinking to use the v2 2x150bp kit.
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Old 11-08-2017, 06:32 PM   #7
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Spiky pattern is good indicator of ow diversity.

Your samples if tagmented randomly would produce around 15,000x15,000 fragments so it is not low diversity. PhiX is only 5.4 kb.

This library would be fine for sequencing.
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Old 11-08-2017, 08:37 PM   #8
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A and C looks good to me, D looks over-fragmented due to low starting mass.

B ? The size looks too large.

But I think you will have good data yield for A,C and D, may receive less data from B.
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Old 11-08-2017, 10:19 PM   #9
Meyana
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Thanks for the input from both of you!

nucacidhunter
For some of my samples I will not be able to input more than 500ng (at the max, working with very small brain tissue pieces) to the prep, which is why I was attempting to scale down the reaction. Do you think my output will suffer tremendously if I am to sequence something that looks like C or D?

GA-J
What makes you say D is over-fragmentated? When I compare to the NexteraXT manual and look at the examples provided by Illumima I would say all my libraries are a bit large...
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Old 11-09-2017, 01:53 AM   #10
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Quote:
Originally Posted by Meyana View Post
Thanks for the input from both of you!

nucacidhunter
For some of my samples I will not be able to input more than 500ng (at the max, working with very small brain tissue pieces) to the prep, which is why I was attempting to scale down the reaction. Do you think my output will suffer tremendously if I am to sequence something that looks like C or D?.
I guess you mean 500 pg and that should be fine. With your 16kb target and 5000x coverage you require 80Mb sequencing per sample. The required read number (2x150) would be ~267k plus some reads to cover off target regions.

D might be pushing it and you might get more duplicates but should not affect final results.
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