Entering edit mode
Peter Glaus
▴
70
@peter-glaus-5589
Last seen 10.3 years ago
Hi Dave,
regarding BitSeq's non-uniform read distribution model. BitSeq learns
two separate bias models for sense and anti-sense reads so these reads
are being distinguished.
Kind regards,
Peter.
On 29/01/13 09:19, Dave Gerrard wrote:
> Hi Peter,
> Thanks for your reply. A lot of 'conventional' cDNA protocols
created
> double-stranded DNA, from which the orginal strand information was
> lost but some RNA based library protocols retain the strandedness
(see
> http://biology.stackexchange.com/questions/1958/difference-between-
strand-specific-and-not-strand-specific-rna-seq-data
> ). The difference would matter most when you have overlapping
> transcritps (common in small genomes) or you have no clue about
> transcription strand (ncRNAs with no poly-A).
>
> However, given that I am working on poly-A extracted RNAs from the
> sparse human genome, and BitSeq's mapping strategy, it's not too bad
> an assumption that the coding strand was the source.
>
> The reason I asked was because Cufflinks refuses to do non-uniform
> distribution without strand information (according to the manual).
> From you answer, it sound's like BitSeq infers the strand from the
> mapping direction (which is what I want) but does it then do
something
> different for reads that map in the anti-sense direction?
>
> Dave
>
>
> On 27 January 2013 20:37, Peter Glaus <glaus@cs.man.ac.uk> <mailto:glaus@cs.man.ac.uk>> wrote:
>
> Hi Dave,
> as far as I understand the RNA-seq protocols, the "endedness" of
> reads is determined depending on whether they were generated in
> first-strand synthesis or second-strand synthesis.
>
> Either way, this can be also determined based on transcripts
> "strandedness" (in our case known from annotation) and read
being
> aligned to sense or anti-sense strand of the transcript. So
BitSeq
> tries to determine end for each read and it is safe to use the
> non-uniform model.
>
> If you want to make sure that everything runs OK you can use
> verbose flag to get more information and check the number of
reads
> that are reported in the pre-processing part and watch for any
> unexpected warnings.
>
> Regards,
> Peter.
>
>
>
> On 01/25/2013 12:02 PM, Dave Gerrard wrote:
>> I have RNAseq data generated from poly-A capture RNAs. There
>> appears to be a strong 3' bias to the mapped reads but the
>> library prep was NOT strand specifc. I would like to correct
for
>> the positional bias in the mapped reads and Bitseq has a
>> 'uniform' parameter which can be set to 'FALSE' if reads are
not
>> uniform. Please can you tell me if this requires 'stranded'
>> mapped read information (as per the cufflinks manual) or
whether
>> It will work without knowing the source strand?
>>
>> Thanks,
>> Dave Gerrard
>> --
>> david.gerrard@manchester.ac.uk
>> <mailto:david.gerrard@manchester.ac.uk>
>>
>> Bioinformatics | The University of Manchester | Michael Smith
>> Building | Room B.1079 | Oxford Road | Manchester | M13 9PT
>> T: 0161 275 5737
>>
>> http://personalpages.manchester.ac.uk/staff/David.Gerrard/
>
>
>
>
> --
> david.gerrard@manchester.ac.uk
<mailto:david.gerrard@manchester.ac.uk>
>
> Bioinformatics | The University of Manchester | Michael Smith
Building
> | Room B.1079 | Oxford Road | Manchester | M13 9PT
> T: 0161 275 5737
>
> http://personalpages.manchester.ac.uk/staff/David.Gerrard/
[[alternative HTML version deleted]]