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  • emolinari
    Member
    • May 2013
    • 47

    #1

    low TopHat mapping!!!

    Hi guys,

    another problem to solve. I am running TopHat on some human cells samples I have submitted to our facility for RNAseq. The bioanalyzer values were great (all above RIN 8.5) and thus a library based exclusively on ribo depletion has been created.
    I have multiplexed 4 samples in a lane (75bp, single-end) and obtained roughly 50 mil reads for each sample.
    This is my TopHat summary:

    Reads kept by tophat2 for mapping: 48777778
    Reads discarded by tophat2: 321249

    Number of unique reads that mapped: 5922988
    Percentage of unique reads that mapped: 12.06%

    I have used transcriptome for Tophat2...but I cannot understand why such a low mapping percentage (not the same across the samples, ranges across 12-40%).
    Do you have any idea???
    Other groups in our lab (doing polyA selection, on same cells, using same RNAseq pipeline) map almost 90% of the reads.

    Help me please!!!
    Thanks
    Manu

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