LAUSR

Development Mother's directions must be followed, even in the earliest stage of embryo development. The maternal genome is read up until a phase called the maternal-to-zygotic transition. At this point, which corresponds to the two-cell stage in mice, the embryonic genome takes over. Using single-cell analyses, Huang et al. examined the function of the maternal factor Stella. Widespread transcription changes result when Stella is eliminated. In particular, endogenous retroviruses such as MuERV-L that are normally active in the early embryo display impaired expression when Stella is knocked down in vivo. Hence, the normal activity of ancient viruses must be properly turned on for transitioning from maternal to zygotic control in development. eLife 10.7554/eLife.22345 (2017).