In recent years it has also become evident that the vast majority of the mammalian genome, and that of other complex organisms, is transcribed, apparently in a developmentally regulated manner, to produce large numbers of ncRNAs that are antisense, intergenic, interleaved, or overlapping with protein-coding genes [2]–[5]. In addition, there are increasing reports (Figure 1) of the functionality of individual ncRNAs in mammals (Table 1), other animals (see, e.g., [6]–[8]), plants (e.g., [9],[10]), and fungi (e.g., [11]), particularly in relation to developmental processes [12]. These include the involvement of ncRNAs in the regulation of the expression of homeotic genes [7],[13], oncogenes [14], and metabolic genes [15], as well as in the regulation of skeletal development [16], eye development [17], epithelial-to-mesenchymal transition [18], and subcellular structures [19]–[22], among many others (for reviews and additional examples, see [4], [12], [23]–[25]).
