MuERV-L Gag protein (green) in 2-cell embryos: Wild-type on left and Stella knockout on right (extract from Fig. 3G).
Stella modulates transcriptional and endogenous retrovirus programs during maternal-to-zygotic transition
Huang Y et al. (2017) Elife pii: e22345. doi: 10.7554/eLife.22345. [Epub ahead of print]
Digest from the paper
When a sperm cell fertilizes an egg cell, this creates a single-cell embryo called a zygote that will go on to divide repeatedly throughout development. The zygote inherits the contents of the egg including many important proteins that initially control how the embryo develops. In mice, the embryo takes over control of development once the zygote has divided to form a two-cell embryo. This transition of control destroys the maternally inherited proteins, activates the embryonic genome and a subset of DNA sequences called transposable elements that evolved from virus DNA.
One of the proteins inherited from the egg cell is called Stella. Embryos that lack Stella die within the first few cell divisions, which suggests that the protein is needed during the earliest stages of development. However, it is not clear what Stella's role in the early embryo is.
Huang, Kim et al. decided to investigate how Stella might affect the genes that are switched on during development by using a technique called RNA-seq to study egg cells and early embryos from mice. Two-cell embryos that lacked Stella could not activate a number of genes that produce proteins that are critical for development and a group of transposable elements called endogenous retroviruses. In particular, a lack of Stella significantly reduced the activity of an endogenous retrovirus called MuERV-L.
Further experiments showed that MuERV-L is needed for normal embryonic development, and so suggests that transposable elements play important roles in this process. Future studies will aim to explore these roles in more detail. It will also be important to identify the genes that Stella targets in embryos, and to investigate the roles that similar maternally inherited proteins play in early embryonic development.
Read more about research in the Surani lab.