The long noncoding RNAs are often expressed at low abundance, about 1/10 of the median mRNA level as surveyed in GENCODE [1].

Many lncRNAs are detected at only a few copies per cell by quantitative RNA FISH (Fig. 1, top left).

However, the importance of low abandence lncRNAs should not be dismissed or underestimated. To the contrary, lncRNAs often functionally operate at low copy numbers, by mechanisms such as tethering the nascently transcribed lncRNAs to recruit chromatin modifier/remodelers to modify local chromatin active state, or spliceosomes to facilitate ongoing transcription, or acting as enhancer RNAs to activate gene transcription (Fig.1 right).

Therefore, the accurate profiling of lncRNAs even at low abundance is essential for lncRNA research. and it‘s one of the three major benefits for LncRNA profiling using Arraystar lncRNA microarrays.

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Figure 1. lncRNA at low copy number shown by RNA FISH (left) can cis-regulate the target gene (right).

References
1. Cabili M.N. et al. (2015) "Localization and abundance analysis of human lncRNAs at single-cell and single-molecule resolution." Genome Biol. 16:20 [PMID: 25630241].