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8.3 Databases Results<br />

Figure 8.2: Internal organisation <strong>of</strong> the target prediction database <strong>of</strong> GenemiR.<br />

From top to bottom, the two conceptual workflows are consecutively displayed.<br />

Each <strong>of</strong> eight algorithms (circles) is represented by a different acronym:<br />

Diana-microT=DN-T; miRanda=MR; miRBase=MC;ElMMo=EM; PITA=PA; Pic-<br />

Tar=PT5/6; TargetscanS=TSS. MicroRNAs (diamonds) and target genes (squares)<br />

are assigned random labels for illustrative purposes.<br />

3. Gene symbols as determined by the HUGO Gene Nomenclature Commit-<br />

tee for [203] and the MGI Mouse Genome Informatics database resource<br />

for mouse [333].<br />

All expression datasets that the user wants to upload in the s<strong>of</strong>tware are re-<br />

ferred to as "external databases" because they are not part <strong>of</strong> the internal<br />

databases, they are user-defined and variable in size. Gene annotation data<br />

are derived from the Ensembl database [147], and a utility script is provided<br />

with the program to allow automatic updating <strong>of</strong> files, via the Ensembl Perl<br />

API, to reflect the latest annotation release <strong>of</strong> the human and mouse genomes.<br />

The internal databases <strong>of</strong> human and mouse microRNAs and gene identifiers<br />

for all annotated human and mouse genes are linked in a meaningful way by<br />

the algorithms that predict which <strong>of</strong> the microRNAs regulate which <strong>of</strong> the<br />

gens and, vice versa, which <strong>of</strong> the genes are regulated by which microRNAs.<br />

Thus, these linked databases consists <strong>of</strong> the union <strong>of</strong> prediction results gen-<br />

erated from the eight most widely used algorithms (considering PicTar 5-way<br />

and PicTar 6-way as separate algorithms) (Table 8.1), with the possibility <strong>of</strong><br />

increasing this number as new algorithms are produced with new sets <strong>of</strong> pre-<br />

dictions, thanks to the modular internal structure with which GenemiR was<br />

designed:<br />

1. PicTar [127,247] identifies putative microRNA targets in vertebrates, C.<br />

elegans and Drosophila, using the principle <strong>of</strong> cross-conservation. The<br />

two versions, PicTar 5-way and PicTar 6-way, refer to the number <strong>of</strong><br />

species in the comparison: 5-way includes human, chimp mouse, rat<br />

and dog genomes, and 6-way adds the chicken genome. PicTar employs<br />

206

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