Transposon persistence and control in germ cells.

Transposons, or 'jumping genes', are ubiquitous genomic elements with the dual capacity to drive evolutionary innovation and disrupt genome integrity through gene mutation and DNA damage. Their activity is particularly significant in germline cells, which transmit genetic material to the next generation. Transposon activity in these cells embodies a delicate balance: while limited transposon activity can introduce genetic diversity and drive evolution, unchecked mobilization risks DNA damage, sterility, and loss of fitness. As 'selfish genes', transposons have evolved strategies to ensure their propagation without jeopardizing host survival. This intricate relationship raises compelling questions about how transposon activity is regulated to sustain both genome stability and evolutionary potential. In this review, we explore recent advances in understanding the small RNA pathway that represses transposons in germ cells, the Piwi-interacting RNA pathway. Furthermore, we highlight how transposons creatively bypass repression. These findings illuminate the dynamic interplay between hosts and transposons, offering deeper insights into genome evolution and preservation.