Piwi-interaction RNAs (piRNAs) have long been an area of confusion. However now new research suggests these abundant molecules may form part of the organisms search engine, capable of querying the entire history of a cells genetic past. These molecules may have the task of detecting and silencing foreign, viral, RNA.
In Caenorhabditis elegans it was found that inserted foreign genes were often silenced, however some were not. When the worms were genetically modified to lack the piwi protein, consequently silencing would no longer occur. Therefore it appears that PiRNA is acting to silence inserted genes within C. elegans.
PiRNAs do not have memory built into their sequence, rather PiRNAs are epigenetic and allow mismatch pairing. Therefore piRNAs are able to scan and potentially recognise all sequences that have ever been expressed within the genome. Silencing can only occur when a sequence has not been seen before. Importantly piRNAs are not fixed to the one-generation they are passed down through the germ lineand are transmitted to both egg and sperm.
However why were not all inserted sequences silenced? This apparent flexibility appears to provide an adaptive advantage to the organism. Allowing new genetic variations to occur brings with it the potential to adapt and become more successful.
PiRNA, like sRNAs, are proving to be remarkable complex and exciting area of research. PiRNAs offer an exciting avenue for newpersonalised medicine research. The ability to construct piRNAs, which are able silence specific human genes, could be a major tool in the fight against disease. Maybe they could be used to treat genetic diseases such Huntington’s. In overly simple terms a piRNA could be designed to silence the extended part of the HTT gene, therefore preventing the disease. The utilisation of the apparent piRNA ‘search engine’ could be used by scientist to find certain genes within the genome. Identification of certain genes would determine the besttreatment options for the patient.
Have you heard of piRNA? What are your opinions upon this topic? Is it a exciting avenue for the future? Or just another interesting idea which wont lead to anything?