Notably, some studies of gene expression in the brain based on sequencing technologies reported a high proportion of transcripts from introns and intergenic repeats— portions of the gene not coding for protein—including a subfamily of Alu-elements (a short stretch of biochemically distinctly recognizable DNA), in the transcriptome of brain tissue (Faulkner, Kimura, Daub, Wani, & Plessy, 2009; Xu, et al., 2010). Thus, we would expect an especially high level of enrichment of regulatory elements, such as transcriptional and translational factors, microRNAs and so forth. It was shown that the set of non-coding long and short RNAs (lncRNA and miRNA, respectively) is also highly enriched in the transcriptome of the brain (Chodroff, et al., 2010; Kuss & Chen, 2008; Ponjavic, Oliver, Lunter, & Ponting, 2009; Schonrock, et al., 2010; St Laurent, Faghihi, & Wahlestedt, 2009). A complex orchestra of these non-coding RNAs, which have important structural and regulatory functions as transcriptional and posttranscriptional regulators of gene expression (Amaral, Clark, Gascoigne, Dinger, & Mattick, 2011; Landgraf, et al., 2007), is expressed in the brain, where ncRNA play key roles in neuronal differentiation,
