Summary
A comprehensive SAGE (serial analysis of gene expression) library of purified human
platelets was established. Twenty-five thousand (25,000) tags were sequenced, and
after removal of mitochondrial tags, 12,609 (51%) non-mitochondrial-derived tags remained,
corresponding to 2,300 different transcripts with expression levels of up to 30,000
tags per million. This new, highly purified SAGE library of platelets is enriched
in specific transcripts.The complexity in terms of tag distribution is similar to
cells that are still able to replenish their mRNA pool by transcription.We show that
our SAGE data are consistent with recently published microarray data but show further
details of the platelet transcriptome, including (i) longer UTR regions and more stable
folding in the enriched mRNAs, (ii) biologically interesting new candidate mRNAs that
show regulatory elements, including elements for RNA stabilization or for translational
control, and (iii) significant enrichment of specific, highly transcribed mRNAs compared
to a battery of SAGE libraries from other tissues. Among several regulatory mRNA elements
known to be involved in mRNA localization and translational control, CPE elements
are in particular enriched in the platelet transcriptome. mRNAs previously reported
to be translationally regulated were found to be present in the library and were validated
by real-time PCR. Furthermore, specific molecular functions such as signal transduction
activity were found to be significantly enriched in the platelet transcriptome.These
findings emphasize the richness and diversity of the platelet transcriptome.
Keywords
Platelet - transcriptome - SAGE - signaling pathway - post-transcriptional regulation
- RNA element - gene ontology