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How to demultiplex dual-index NextSeq data for random index 2?

Hi all,

I have a question here and I could not find any sufficient information about this. Hope someone is able to help.

I have a set of NextSeq data sequenced pair-end, dual-indexed whereby the index2 is a 8bp random index. The cycle run is 76, 8, 8 and 76 for R1, I1, I2, R2 respectively.

I wanted to demultiplex my reads according to sample by index 1 then from there, demultiplex the reads in each sample by index 2.

I tried various options as described below but to no avail, could anyone please help me out?

Options tried:

1) bcl2fastq using --use-bases-mask Y, I8, I8, Y and sample sheet containing info on I2 as NNNNNNNN

--- with this I got all my reads as Undetermined reads and I could not separate them by index 1

2) bcl2fastq using --use-bases-mask Y, I8, Y8, Y and sample sheet does not contain info on I2

--- I was hoping this could work but all i got for R2 (which I presume would be my index 2 in this case) are all Ns

Please advice on how I can demultiplex my reads by 1st index then 2nd index. Thank you very much.

next-gen sequencing

Did you ever find a way to do this ?

How many unique indexes do you expect in second position?

Index_2 has 4 unique indexes as 4 samples are Dual index and 4 have a single index.

Thanks Genomax , i tried both post's suggestions and still not working for me. I'll explore more thanks.

Can you tell us what is not working and we can try to help?

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