Pseudogenes: pseudo or real functional elements?

Pseudogenes are genomic remnants of ancient protein-coding genes which have lost their coding potentials through evolution. Although broadly existed, pseudogenes used to be considered as junk or relics of genomes which have not drawn enough attentions of biologists until recent years. With the broad applications of high-throughput experimental techniques, growing lines of evidence have strongly suggested that some pseudogenes possess special functions, including regulating parental gene expression and participating in the regulation of many biological processes. In this review, we summarize some basic features of pseudogenes and their functions in regulating development and diseases. All of these observations indicate that pseudogenes are not purely dead fossils of genomes, but warrant further exploration in their distribution, expression regulation and functions. A new nomenclature is desirable for the currently called 'pseudogenes' to better describe their functions.