Piwi-interacting RNAs (piRNAs) in animals: The story so far
Piwi-interacting RNAs (piRNAs) are small RNA molecules of between 24 to 31 nucleotides (nts) sequence and interact with Piwi subfamily proteins. These piRNAs play important regulatory roles in germline stem cell maintenance, epigenetic regulation, and transposition. Although the biogenesis pathways of piRNAs are not well understood but recent scientific advances have revealed some important aspects of their synthesis. Studies on regulatory mechanism of piRNAs are in their early stages. Yet, the current findings suggest that piRNA based regulation has direct implications on germline development and transposon silencing through heterochromatin formation or RNA destabilization. This review summarizes the knowledge about all aspects of piRNAs since its discovery.