In the absence of forming a functional protein, intracellular molecules can still function as ncRNAs (Mattick & Makunin, 2006). ncRNAs make up a sizeable share of the transcriptional landscape (Carninci et al., 2005; ENCODE Project Consortium et al., 2012, 2007), but the precise function of many noncoding elements remains largely unknown. Defining the diverse biological roles carried out by multiple classes of ncRNAs is a burgeoning aspect of transcriptomics that will likely match or rival the large number and diversity represented by the proteome. Long noncoding RNAs (lncRNAs) represent one of the most abundant classes of nonprotein-coding RNAs in the brain (Jia et al., 2010; Ravasi et al., 2006). Similar to protein-coding transcripts, lncRNAs can be found within specific neuroanatomical regions (Belgard et al., 2011; Mercer, Dinger, Sunkin, Mehler, & Mattick, 2008). A study of human alcoholic brain tissue showed an increase in the expression of the lncRNA MALAT1 within multiple brain regions (Kryger, Fan, Wilce, & Jaquet, 2012). Overall expression of lncRNAs may be lower than protein-coding transcripts, but can be dynamically regulated in alcoholic brain tissue (Fig. 11.9).
