Abstract :
Mammalian genomes encode numerous non-protein-coding RNAs (ncRNAs) including microRNAs and natural antisense transcripts. Functional validation studies indicate that ncRNAs are involved in regulation of various normal cellular pathways and a range of essential biological processes. Deregulations of ncRNAs are also documented in variety of human complex disorders including cardiovascular and hematopoietic disorders. This review provides an overview of different ncRNA classes and summarizes recent reports regarding involvement of ncRNAs in cardiovascular and hematopoietic disorders.
The human genome sequencing projects revealed that the human genome contains over 3 billion DNA base pairs, but only 20,000–25,000 protein-coding genes. In fact, only about 1.2% of the genome codes for proteins.1 Surprisingly, the number of human genes seems to be almost equal to lower mammals like rodents, and less than a factor of two greater than that of many much simpler organisms, such as the roundworm and the fruit fly. On the other hand, recent studies have revealed that eukaryotic genomes are almost entirely transcribed,2,3 generating an enormous number of non-protein-coding RNAs (ncRNAs).4-6 Thus there may be a vast reservoir of biologically meaningful ncRNAs that greatly exceed the 1.2% of the genome that corresponds to conventional protein coding genes.7,8 Several classes of functional ncRNAs have been identified in recent years. Text box-1 provides a list of mammalian RNA species and various categories of ncRNAs. Natural antisense transcripts and microRNAs are two prominent and complex classes of ncRNAs.1
