The sequences of the proteins that make up our bodies, along with information about when and where these proteins function, are encoded in the genomes of our cells. The genome can be considered our blueprint. However, about half of the genome is made up of transposons, self-reproducing sequences similar to viruses. Our research focuses on a mechanism known as PIWI-interacting RNA (piRNA) that animals have evolved to suppress these transposons.
piRNAs have sequences that are complementary to transposons, allowing them to precisely identify and repress “non-self” sequences within the genome. PiRNAs are particularly active in the germline, the region where germ cells are developed for transmission to the next generation. A key aspect of our research is to understand how piRNAs accurately distinguish non-self elements. We are interested in their function not only in relation to transposons, but also in the context of other non-self elements.
Our goal is to elucidate the mechanisms by which piRNAs distinguish between non-self and non-transposon elements. Through this understanding, we aim to develop innovative applications of piRNA technology.
Wolbachia, an intracellular symbiotic bacterium, commonly infects insects and is passed vertically from mother to offspring. Since piRNAs are present in wolbachia-infected cells and are passed on to the next generation, there may be a significant relationship between wolbachia and piRNAs. Our research aims to investigate how piRNAs contribute to the identification and control of endosymbionts and how they are influenced by these endosymbionts. This interaction has important implications for biological evolution and species conservation, and may provide new insights into the mechanisms of pathogen infection and host defense.
Our research has uncovered a novel phenomenon called piRNA self-organization. Self-organization is a process in which elements form large, ordered structures autonomously, without the supervision of the entire system. In this process, piRNAs are thought to interact and arrange themselves to efficiently repress targeted transposons. Thus, in this context, piRNAs are able to achieve an optimal arrangement for transposon repression without the need to know the complete sequence information of the transposon. This indicates a high degree of adaptability and autonomous function in piRNA-mediated gene regulation. This self-organization may allow piRNAs to adaptively bypass mutated transposon sequences while maintaining repression efficacy. We aim to elucidate the mechanisms behind this self-assembly and its implications for biological function.
piRNA clusters, specific genomic regions that serve as sources of piRNA production, are abundant in transposon fragment sequences. These clusters act as genomic reservoirs for transposons in need of repression. Notably, these regions show poor conservation across species, suggesting that they are dynamic sequences that evolve and disappear over time. Our goal is to elucidate the formation and maintenance of these clusters, with a particular focus on how a genome recognizes “non-self” elements.
Our approach integrates bioinformatics, where we collect and analyze mRNAs and piRNAs using large-scale sequencers and personal computers, with molecular biology to explain biological phenomena at the molecular level. Our research, which primarily uses insect cultured cells, also benefits from collaborations with various specialists working with different species of organisms. This multidisciplinary approach will help elucidate the relationship between piRNA and “non-self” elements in a variety of biological materials.