Identification and characterization of human non-coding RNAs with tissue-specific expression

We have examined the expression profile of selected non-coding RNAs (ncRNAs) in 11 human tissues. Among 5489 full-length cDNA clones annotated as non-protein-coding transcripts in the H-Invitational database, we chose 150 clones for further analysis based on their gene structure and EST information. Expression profiling using quantitative RT-PCR and Northern blot hybridization revealed that the majority of the selected ncRNAs exhibited tissue specificity: 67% are predominantly expressed in a restricted subset of tissues. The absolute quantification of representative ncRNAs revealed that the majority of ncRNAs are expressed as low abundance transcripts. A comparative genomic analysis revealed that only 27% of the selected ncRNAs have mouse counterparts. Since the expression patterns of the human ncRNAs having no mouse counterparts remain to be similar to those of the mouse ncRNAs, the expression patterns of the selected ncRNAs may be conserved between human and mouse.