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  • Problems displaying SAM file in IGV

    Hi,

    I am starting to play around with some NGS data and am trying to display a SAM file (e coli reads aligned to the genome) in Intergrative Genome Viewer. When I load the file no reads appear. Has anyone else experienced anyhting like this? I have imported the correct genome and checked that genome name agrees between files etc.

    Any help would be appreciated!

    Gavin

  • #2
    Problem resolved!

    I don't even want to admit what was happening

    Comment


    • #3
      Dear Gavin,
      I have also experienced this problem. Could you tell me how you fixed it? No doubt it is something simple that I have overlooked.

      Comment


      • #4
        I thought I had fixed it but it turns out I was wrong.

        I have absolutely no idea what the issue is at all

        Comment


        • #5
          The IGV developer is a really nice guy (despite an insertional mutation in his surname :-) and is a member here; if you send him a good test case & description you are likely to get a response.

          Comment


          • #6
            Lol.

            I can provide my SAM and genome file if you can give me an e-mail address?

            I just can't get the alignments to display.

            Comment


            • #7
              Did you try zooming in? I've found it won't display if you've got high coverage and you're zoomed out far due to memory constraints.
              Mendelian Disorder: A blogshare of random useful information for general public consumption. [Blog]
              Breakway: A Program to Identify Structural Variations in Genomic Data [Website] [Forum Post]
              Projects: U87MG whole genome sequence [Website] [Paper]

              Comment


              • #8
                igv-help (at) broadinstitute.org is the address to get assistance

                Comment


                • #9
                  Originally posted by gavin.oliver View Post
                  I thought I had fixed it but it turns out I was wrong.

                  I have absolutely no idea what the issue is at all
                  Reduce your input file ((s|b)am I assume) to a one alignment. Load it and
                  check if it shows up. If the alignment does no show up try to change the
                  chrm string format. The chrm string has to match to whatever contig header
                  string is used in the reference you use. That was my main problem when
                  I started using IGV.

                  Ultimately the IGV mailing list is your friend.
                  -drd

                  Comment


                  • #10
                    I have sent the SAM and genome files to the igv-help address. All the fixes mentioned on this thread I have already attempted (or tried to).

                    Comment


                    • #11
                      Let us know what the problem was when you find out.
                      -drd

                      Comment


                      • #12
                        Hi Gavin,

                        Did you end up getting a response from the guys at IGV or end up solving the problem? I seem to be experiencing the same issues. Thanks

                        Comment


                        • #13
                          Unfortunately not!

                          Comment


                          • #14
                            Hi Gavin,
                            did you try to view the alignment using an other third part tool ?
                            If I suggest you that, it is because I had the same problem with my SAM files, and this problem reproduced with other tools.
                            In my case, SAM files were converted from illumina export files using script export2sam.pl script. illumina pipeline reports file name of the sequence matched and not the fasta header of the sequence matched, whereas viewers use the header.
                            So, as you could anderstand if the name of the reference sequence and the name of sequence matched are not the same, softwares (IGV or others) consider that there are not reads mapped to the reference.
                            I don't know if you are in same case, but you could verify if field RNAME in SAM file seems ok.

                            Jennifer

                            Comment


                            • #15
                              Hi Jennifer,

                              To be honest I haven't pursued the problem any further. Shifting priorities in my job means that I haven't been spending any time on NGS of late. It is something I may have to revisit in the future but for the time-being my hands are tied!

                              Sorry I can't be more help.

                              Gavin

                              Comment

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