Lysosomal catabolic activity governs the exit of the murine totipotent 2-cell state by silencing early-embryonic retrotransposons [CUT&Tag]

During the development in mouse early embryos, a subset of retrotransposons and genes are transiently expressed in the totipotent 2-cell embryos. These 2-cell-embryo-asscoiated (referred to as 2C) transcripts rapidly shut down their expression beyond the late 2-cell stage of embryos, and this timely shutdown governs the embryo to exit from the 2-cell stage. However, mechanisms regulating this wave of shutdown are not fully understood. In this study, we established a novel connection between lysosomal catabolic activity and 2C transcripts in regulating the exit of totipotent 2-cell state by using both in vitro 2-cell-like cells model and mouse embryos. Our results showed that the activation of lysosomal catabolism in mouse embryos governed the embryo to exit from the 2-cell state by suppressing the expression of 2C transcripts. Mechanistically, we found that lysosomal catabolic activity modulated 2C transcripts by inactivating transcriptional factors Tfe3/Tfeb and abolishing their transcriptional activation on 2C retrotransposons, MERVL/MT2-Mm. Collectively, our study elucidates the function of lysosomal activity in orchestrating transcriptomic landscape and early development in mouse embryos and reveals an unanticipated layer of transcriptional control on early-embryonic retrotransposons from lysosomal signaling.