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  • cassiemin
    Junior Member
    • Mar 2017
    • 1

    #1

    human contamination for mouse RNAseq samples

    I'm working on data analysis of mouse RNAseq samples now. The library was prepared by Nugen Universal Plus mRNA-seq kit, sequenced by Illumina HiSeq 2500, single end 50bp. I mapped the reads to mm10 reference and the mapping rate was low for some samples. I checked the unmapped reads and found it can be mapped to the human genome. I summarized commands and the mapping rate as follows.

    STAR --genomeDir /path/to/Mus_musculus.GRCm38_dir --readFilesIn /path/to/read1 --outFileNamePrefix /path/to/output/dir/prefix --outSAMtype BAM SortedByCoordinate Unsorted --outFilterType BySJout --outFilterMultimapNmax 20 --alignSJoverhangMin 8 --alignSJDBoverhangMin 1 --outFilterMismatchNmax 999 --outFilterMismatchNoverReadLmax 0.04 --alignIntronMin 20 --alignIntronMax 100000 --alignMatesGapMax 100000

    STAR --genomeDir /path/to/ENSEMBL.homo_sapiens_dir --readFilesIn /path/to/read1 --outFileNamePrefix /path/to/output/dir/prefix --outSAMtype BAM SortedByCoordinate Unsorted --outFilterType BySJout --outFilterMultimapNmax 20 --alignSJoverhangMin 8 --alignSJDBoverhangMin 1 --outFilterMismatchNmax 999 --outFilterMismatchNoverReadLmax 0.04 --alignIntronMin 20 --alignIntronMax 100000 --alignMatesGapMax 100000


    Sample mouse_mapping_rate human_mapping_rate
    mouse_sample1 28.63% 71.87%
    mouse_sample2 72.53% 41.21%
    mouse_sample3 75.03% 37.65%
    mouse_sample4 50.51% 55.50%
    mouse_sample5 68.56% 43.18%
    mouse_sample6 3.30% 90.45%
    mouse_sample7 75.45% 39.63%
    mouse_sample8 69.98% 42.84%
    mouse_sample9 33.56% 69.02%
    mouse_sample10 23.53% 78.36%
    mouse_sample11 54.74% 54.65%
    mouse_sample12 58.27% 50.32%
    mouse_sample13 50.98% 56.36%
    mouse_sample14 77.27% 37.42%
    mouse_sample15 48.44% 57.53%
    mouse_sample16 58.93% 50.21%
    mouse_sample17 78.94% 36.84%
    mouse_sample18 65.56% 44.09%

    My questions are:
    Could anyone know what's the overlap rate between the mouse and human transcriptome?
    Whether can human contamination interfere with the analysis of mouse data?
    Thanks a lot.
    Last edited by cassiemin; 06-20-2018, 12:05 PM.
  • GenoMax
    Senior Member
    • Feb 2008
    • 7142

    #2
    Use bbsplit.sh from BBMap to separate human and mouse reads as shown in this thread.

    SeqAnswers thread page for BBsplit can be found here.

    Comment

    • cmbetts
      Senior Member
      • Jun 2012
      • 120

      #3
      Have you verified with your sequencing provider that they gave you the right data back? I've previously had a vender return another user's data to me. Luckily, we had used a custom protocol and it was immediately obvious something was up.
      Also, check the source of your samples. One time I bought human liver FFPE that turned out to align to rat...

      Comment

      • sosocute
        Junior Member
        • Sep 2019
        • 1

        #4
        Did you ever figure out the source of contamination?

        Comment

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