Biological mechanisms affected by the Piwi-pi-RNA pathways

Genome instability, triggered by irrevocable DNA mutations, is fundamental to cellulair aging [2]. However, some cell types could resist aging. Researchers defined in this study the concept of “aging-resistant cells”. This would be cells that do not experience aging and constitute a tissue that could result in a line of “immortal” cells. In these age-resistant cells, the whole genome seems preserved throughout the life of the subject. Therefore, the tissue itself does not experience aging, and does not deteriorate with time. Without genome instabilities, it remains capable of proliferating and surviving [2].

This seems to originate from one biological mechanism: the Piwi-piRNA pathway (“P-element-induced wimpy testis in drosophila” – Piwi-interacting noncoding RNA). It is a gene-regulating pathway, where non-coding ARNs, ARNpis, interact with Piwi proteins. Piwi proteins are originally know for repressing stem cell differentiation and maintain genomic stability in the germinal line. This “molecular machine” seems to be responsible for the processes that maintain genetic material integrity [2]. It works mostly in aging-resistant cells, by repressing the activity of genetically mobile elements, the transposable elements.

It is active in germinal cells as well as in the primary phases of embryo development. This study also shows that outside of the germinal line, the Piwi-piRNA pathway is active in all types of somatic cells that don’t show signs of aging. These cells can be found in many organisms: with somatic stem cells in poriferans (“sponges”), medusas, planarias, sea slugs, drosophiles and in some mammals [2].