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  • Too much "no feature" counts??

    Hello,
    I’m having some issues analysing RNASeq data on Chipster. I have single-end rna samples (brain) sequenced on a illumina NextSeq platform from rattus norvergicus.
    When i run the TopHat (Rattus6.0.83/fr-firststrand/20 hits allowed per read/…) i obtain:

    Reads:
    Input : 29084606
    Mapped : 27577865 (94.8% of input)
    of these: 1284892 ( 4.7%) have multiple alignments (17957 have>20)
    94.8% overall read mapping rate.

    When running the HTSeq (Rattus6.0.83/"reverse"/no paired end/chromosome names in the BAM "1"/ union / exon / gene_id) for counting the reads per gene i found a lot of no_feature reads.

    __no_feature 7413760
    __ambiguous 111934
    __too_low_aQual 0
    __not_aligned 0
    __alignment_not_unique 4203664

    Is it normal?

    Then in the differential expression using the DESeq2 i get extremely few or even no significant padj values. Only get 12 signicant padj values even compairing MALES VH and FEMALES VH which seems quite shocking to us.
    I’m i doing something wrong?
    Thank you very much in advance for the help.

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