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  • Mapping to miRBase

    Hi guys,

    How to do the mapping to miRBase to identify human miRNAs?

    1. At first you should download 2 fasta files from the website: http://www.mirbase.org/ftp.shtml (and merge them into one file):
    hairpin.fa Fasta format sequences of all miRNA hairpins
    mature.fa Fasta format sequences of all mature miRNA sequences

    3. Then, you should generate gtf for Bowtie 1 (if you want to use specifically Bowtie 1) or gff for Htseq (based on the downloaded fasta files).

    I did the analysis this way, but I received very strange results (for example mir-8689, mir-7689 - I mean miRNAs with very high numbers) instead of what I was expecting (mir9, mir31, etc.- miRNAs with much smaller numbers).

    Do you know maybe what I could do wrongly?

    Thanks for your answer in advance!

  • #2
    Hi Caroline,

    What I do is download the sequences from miRBase and then change all 'U' to 'T' and then create the index with bowtie-build and then align.

    Could it be that because you are not changing U to T you only get hits for miRNAs with no Us?

    Cheers,
    sergio

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    • #3
      Hello Sergio,

      Thanks so much! I have just tried your approach! You are right! It is working!

      Best wishes,
      Caroline

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