Mammalian genomes are replete with millions of transposable elements that exist in various shapes and families. Although they provide an unvaluable source of genetic innovations over the course of evolution, the presence and activity of transposable elements constitute a permanent threat to the architecture and the function of the genome and can lead to pathological outcomes. Host genomes keep transposable elements in check through multilayered mechanisms of repression, which often act in a stage-, cell- and transposon-specific manner. 
Over the past years, our lab has developed several screens, in vivo and in cellula, to unravel more of these transposon controlling pathways, and address their impact on mammalian development and reproduction. This endeavour has allowed us to gain important insights into the role and diversification of DNA and RNA methylation-related pathways, and more recently, to novel chromatin-based modes of repression of transposable elements.